Move libjbig into its own directory

git-svn-id: http://svn.code.sf.net/p/netpbm/code/trunk@2205 9d0c8265-081b-0410-96cb-a4ca84ce46f8

1 files changed, 2905 insertions, 0 deletions

diff --git a/converter/other/jbig/libjbig/jbig.c b/converter/other/jbig/libjbig/jbig.c
new file mode 100644
index 00000000..90295d8b
--- /dev/null
+++ b/converter/other/jbig/libjbig/jbig.c
@@ -0,0 +1,2905 @@
+/*
+ *  Portable Free JBIG image compression library
+ *
+ *  Markus Kuhn -- mkuhn@acm.org
+ *
+ *  $Id: jbig.c,v 1.12 2000-04-08 11:42:18+01 mgk25 Rel $
+ *
+ *  This module implements a portable standard C encoder and decoder
+ *  using the JBIG lossless bi-level image compression algorithm as
+ *  specified in International Standard ISO 11544:1993 or equivalently
+ *  as specified in ITU-T Recommendation T.82. See the file jbig.doc
+ *  for usage instructions and application examples.
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; if not, write to the Free Software
+ *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ * 
+ *  If you want to use this program under different license conditions,
+ *  then contact the author for an arrangement.
+ *
+ *  It is possible that certain products which can be built using this
+ *  software module might form inventions protected by patent rights in
+ *  some countries (e.g., by patents about arithmetic coding algorithms
+ *  owned by IBM and AT&T in the USA). Provision of this software by the
+ *  author does NOT include any licences for any patents. In those
+ *  countries where a patent licence is required for certain applications
+ *  of this software module, you will have to obtain such a licence
+ *  yourself.
+ */
+
+#ifdef DEBUG
+#include <stdio.h>
+#endif
+
+#include <stdlib.h>
+#include <assert.h>
+
+#include "jbig.h"
+
+
+/* optional export of arithmetic coder functions for test purposes */
+#ifdef TEST_CODEC
+#define ARITH
+#define ARITH_INL
+#else
+#define ARITH      static
+#ifdef __GNUC__
+#define ARITH_INL  static __inline__
+#else
+#define ARITH_INL  static
+#endif
+#endif
+
+#define MX_MAX  23     /* maximal supported mx offset for
+			* adaptive template in the encoder */
+
+#define TPB2CX  0x195  /* contexts for TP special pixels */
+#define TPB3CX  0x0e5
+#define TPDCX   0xc3f
+
+/* marker codes */
+#define MARKER_STUFF    0x00
+#define MARKER_RESERVE  0x01
+#define MARKER_SDNORM   0x02
+#define MARKER_SDRST    0x03
+#define MARKER_ABORT    0x04
+#define MARKER_NEWLEN   0x05
+#define MARKER_ATMOVE   0x06
+#define MARKER_COMMENT  0x07
+#define MARKER_ESC      0xff
+
+/* loop array indices */
+#define STRIPE  0
+#define LAYER   1
+#define PLANE   2
+
+/* special jbg_buf pointers (instead of NULL) */
+#define SDE_DONE ((struct jbg_buf *) -1)
+#define SDE_TODO ((struct jbg_buf *) 0)
+
+/* object code version id */
+
+const char jbg_version[] = 
+" JBIG-KIT " JBG_VERSION " -- Markus Kuhn -- "
+"$Id: jbig.c,v 1.12 2000-04-08 11:42:18+01 mgk25 Rel $ ";
+
+/*
+ * the following array specifies for each combination of the 3
+ * ordering bits, which ii[] variable represents which dimension
+ * of s->sde.
+ */
+static const int index[8][3] = {
+  { 2, 1, 0 },    /* no ordering bit set */
+  { -1, -1, -1},  /* SMID -> illegal combination */
+  { 2, 0, 1 },    /* ILEAVE */
+  { 1, 0, 2 },    /* SMID + ILEAVE */
+  { 0, 2, 1 },    /* SEQ */
+  { 1, 2, 0 },    /* SEQ + SMID */
+  { 0, 1, 2 },    /* SEQ + ILEAVE */
+  { -1, -1, -1 }  /* SEQ + SMID + ILEAVE -> illegal combination */
+};
+
+
+/*
+ * Array [language][message] with text string error messages that correspond
+ * to return values from public functions in this library.
+ */
+#define NEMSG         9  /* number of error codes */
+#define NEMSG_LANG    3  /* number of supported languages */
+static const char *errmsg[NEMSG_LANG][NEMSG] = {
+  /* English (JBG_EN) */
+  {
+    "Everything is ok",                                     /* JBG_EOK */
+    "Reached specified maximum size",                       /* JBG_EOK_INTR */
+    "Unexpected end of data",                               /* JBG_EAGAIN */
+    "Not enough memory available",                          /* JBG_ENOMEM */
+    "ABORT marker found",                                   /* JBG_EABORT */
+    "Unknown marker segment encountered",                   /* JBG_EMARKER */
+    "Incremental BIE does not fit to previous one",         /* JBG_ENOCONT */
+    "Invalid data encountered",                             /* JBG_EINVAL */
+    "Unimplemented features used"                           /* JBG_EIMPL */
+  },
+  /* German (JBG_DE_8859_1) */
+  {
+    "Kein Problem aufgetreten",                             /* JBG_EOK */
+    "Angegebene maximale Bildgr\366\337e erreicht",         /* JBG_EOK_INTR */
+    "Unerwartetes Ende der Daten",                          /* JBG_EAGAIN */
+    "Nicht gen\374gend Speicher vorhanden",                 /* JBG_ENOMEM */
+    "Es wurde eine Abbruch-Sequenz gefunden",               /* JBG_EABORT */
+    "Eine unbekannte Markierungssequenz wurde gefunden",    /* JBG_EMARKER */
+    "Neue Daten passen nicht zu vorangegangenen Daten",     /* JBG_ENOCONT */
+    "Es wurden ung\374ltige Daten gefunden",                /* JBG_EINVAL */
+    "Noch nicht implementierte Optionen wurden benutzt"     /* JBG_EIMPL */
+  },
+  /* German (JBG_DE_UTF_8) */
+  {
+    "Kein Problem aufgetreten",                             /* JBG_EOK */
+    "Angegebene maximale Bildgr\303\266\303\237e erreicht", /* JBG_EOK_INTR */
+    "Unerwartetes Ende der Daten",                          /* JBG_EAGAIN */
+    "Nicht gen\303\274gend Speicher vorhanden",             /* JBG_ENOMEM */
+    "Es wurde eine Abbruch-Sequenz gefunden",               /* JBG_EABORT */
+    "Eine unbekannte Markierungssequenz wurde gefunden",    /* JBG_EMARKER */
+    "Neue Daten passen nicht zu vorangegangenen Daten",     /* JBG_ENOCONT */
+    "Es wurden ung\303\274ltige Daten gefunden",            /* JBG_EINVAL */
+    "Noch nicht implementierte Optionen wurden benutzt"     /* JBG_EIMPL */
+  }
+};
+
+
+
+/*
+ * The following three functions are the only places in this code, were
+ * C library memory management functions are called. The whole JBIG
+ * library has been designed in order to allow multi-threaded
+ * execution. no static or global variables are used, so all fuctions
+ * are fully reentrant. However if you want to use this multi-thread
+ * capability and your malloc, realloc and free are not reentrant,
+ * then simply add the necessary semaphores or mutex primitives below.
+ */
+
+static void *checked_malloc(size_t size)
+{
+  void *p;
+  
+  p = malloc(size);
+  /* Full manual exception handling is ugly here for performance
+   * reasons. If an adequate handling of lack of memory is required,
+   * then use C++ and throw a C++ exception here. */
+  if (!p)
+    abort();
+
+#if 0
+  fprintf(stderr, "%p = malloc(%ld)\n", p, (long) size);
+#endif
+
+  return p;
+}
+
+
+static void *checked_realloc(void *ptr, size_t size)
+{
+  void *p;
+
+  p = realloc(ptr, size);
+  /* Full manual exception handling is ugly here for performance
+   * reasons. If an adequate handling of lack of memory is required,
+   * then use C++ and throw a C++ exception here. */
+  if (!p)
+    abort();
+
+#if 0
+  fprintf(stderr, "%p = realloc(%p, %ld)\n", p, ptr, (long) size);
+#endif
+
+  return p;
+}
+
+
+static void checked_free(void *ptr)
+{
+  free(ptr);
+
+#if 0
+  fprintf(stderr, "free(%p)\n", ptr);
+#endif
+
+}
+
+
+
+/*
+ * The next functions implement the arithmedic encoder and decoder
+ * required for JBIG. The same algorithm is also used in the arithmetic
+ * variant of JPEG.
+ */
+
+#ifdef DEBUG
+static long encoded_pixels = 0;
+#endif
+
+ARITH void arith_encode_init(struct jbg_arenc_state *s, int reuse_st)
+{
+  int i;
+  
+  if (!reuse_st)
+    for (i = 0; i < 4096; s->st[i++] = 0);
+  s->c = 0;
+  s->a = 0x10000L;
+  s->sc = 0;
+  s->ct = 11;
+  s->buffer = -1;    /* empty */
+  
+  return;
+}
+
+
+ARITH void arith_encode_flush(struct jbg_arenc_state *s)
+{
+  unsigned long temp;
+
+#ifdef DEBUG
+  fprintf(stderr, "  encoded pixels = %ld, a = %05lx, c = %08lx\n",
+	  encoded_pixels, s->a, s->c);
+#endif
+
+  /* find the s->c in the coding interval with the largest
+   * number of trailing zero bits */
+  if ((temp = (s->a - 1 + s->c) & 0xffff0000L) < s->c)
+    s->c = temp + 0x8000;
+  else
+    s->c = temp;
+  /* send remaining bytes to output */
+  s->c <<= s->ct;
+  if (s->c & 0xf8000000L) {
+    /* one final overflow has to be handled */
+    if (s->buffer >= 0) {
+      s->byte_out(s->buffer + 1, s->file);
+      if (s->buffer + 1 == MARKER_ESC)
+	s->byte_out(MARKER_STUFF, s->file);
+    }
+    /* output 0x00 bytes only when more non-0x00 will follow */
+    if (s->c & 0x7fff800L)
+      for (; s->sc; --s->sc)
+	s->byte_out(0x00, s->file);
+  } else {
+    if (s->buffer >= 0)
+      s->byte_out(s->buffer, s->file); 
+    /* T.82 figure 30 says buffer+1 for the above line! Typo? */
+    for (; s->sc; --s->sc) {
+      s->byte_out(0xff, s->file);
+      s->byte_out(MARKER_STUFF, s->file);
+    }
+  }
+  /* output final bytes only if they are not 0x00 */
+  if (s->c & 0x7fff800L) {
+    s->byte_out((s->c >> 19) & 0xff, s->file);
+    if (((s->c >> 19) & 0xff) == MARKER_ESC)
+      s->byte_out(MARKER_STUFF, s->file);
+    if (s->c & 0x7f800L) {
+      s->byte_out((s->c >> 11) & 0xff, s->file);
+      if (((s->c >> 11) & 0xff) == MARKER_ESC)
+	s->byte_out(MARKER_STUFF, s->file);
+    }
+  }
+
+  return;
+}
+
+
+ARITH_INL void arith_encode(struct jbg_arenc_state *s, int cx, int pix) 
+{
+  extern short jbg_lsz[];
+  extern unsigned char jbg_nmps[], jbg_nlps[];
+  register unsigned lsz, ss;
+  register unsigned char *st;
+  long temp;
+
+#ifdef DEBUG
+  ++encoded_pixels;
+#endif
+
+  assert(cx >= 0 && cx < 4096);
+  st = s->st + cx;
+  ss = *st & 0x7f;
+  assert(ss < 113);
+  lsz = jbg_lsz[ss];
+
+#if 0
+  fprintf(stderr, "pix = %d, cx = %d, mps = %d, st = %3d, lsz = 0x%04x, "
+	  "a = 0x%05lx, c = 0x%08lx, ct = %2d, buf = 0x%02x\n",
+	  pix, cx, !!(s->st[cx] & 0x80), ss, lsz, s->a, s->c, s->ct,
+	  s->buffer);
+#endif
+
+  if (((pix << 7) ^ s->st[cx]) & 0x80) {
+    /* encode the less probable symbol */
+    if ((s->a -= lsz) >= lsz) {
+      /* If the interval size (lsz) for the less probable symbol (LPS)
+       * is larger than the interval size for the MPS, then exchange
+       * the two symbols for coding efficiency, otherwise code the LPS
+       * as usual: */
+      s->c += s->a;
+      s->a = lsz;
+    }
+    /* Check whether MPS/LPS exchange is necessary
+     * and chose next probability estimator status */
+    *st &= 0x80;
+    *st ^= jbg_nlps[ss];
+  } else {
+    /* encode the more probable symbol */
+    if ((s->a -= lsz) & 0xffff8000L)
+      return;   /* A >= 0x8000 -> ready, no renormalization required */
+    if (s->a < lsz) {
+      /* If the interval size (lsz) for the less probable symbol (LPS)
+       * is larger than the interval size for the MPS, then exchange
+       * the two symbols for coding efficiency: */
+      s->c += s->a;
+      s->a = lsz;
+    }
+    /* chose next probability estimator status */
+    *st &= 0x80;
+    *st |= jbg_nmps[ss];
+  }
+
+  /* renormalization of coding interval */
+  do {
+    s->a <<= 1;
+    s->c <<= 1;
+    --s->ct;
+    if (s->ct == 0) {
+      /* another byte is ready for output */
+      temp = s->c >> 19;
+      if (temp & 0xffffff00L) {
+	/* handle overflow over all buffered 0xff bytes */
+	if (s->buffer >= 0) {
+	  ++s->buffer;
+	  s->byte_out(s->buffer, s->file);
+	  if (s->buffer == MARKER_ESC)
+	    s->byte_out(MARKER_STUFF, s->file);
+	}
+	for (; s->sc; --s->sc)
+	  s->byte_out(0x00, s->file);
+	s->buffer = temp & 0xff;  /* new output byte, might overflow later */
+	assert(s->buffer != 0xff);
+	/* can s->buffer really never become 0xff here? */
+      } else if (temp == 0xff) {
+	/* buffer 0xff byte (which might overflow later) */
+	++s->sc;
+      } else {
+	/* output all buffered 0xff bytes, they will not overflow any more */
+	if (s->buffer >= 0)
+	  s->byte_out(s->buffer, s->file);
+	for (; s->sc; --s->sc) {
+	  s->byte_out(0xff, s->file);
+	  s->byte_out(MARKER_STUFF, s->file);
+	}
+	s->buffer = temp;   /* buffer new output byte (can still overflow) */
+      }
+      s->c &= 0x7ffffL;
+      s->ct = 8;
+    }
+  } while (s->a < 0x8000);
+ 
+  return;
+}
+
+
+ARITH void arith_decode_init(struct jbg_ardec_state *s, int reuse_st)
+{
+  int i;
+  
+  if (!reuse_st)
+    for (i = 0; i < 4096; s->st[i++] = 0);
+  s->c = 0;
+  s->a = 1;
+  s->ct = 0;
+  s->result = JBG_OK;
+  s->startup = 1;
+  return;
+}
+
+
+ARITH_INL int arith_decode(struct jbg_ardec_state *s, int cx)
+{
+  extern short jbg_lsz[];
+  extern unsigned char jbg_nmps[], jbg_nlps[];
+  register unsigned lsz, ss;
+  register unsigned char *st;
+  int pix;
+
+  /* renormalization */
+  while (s->a < 0x8000 || s->startup) {
+    if (s->ct < 1 && s->result != JBG_READY) {
+      /* first we have to move a new byte into s->c */
+      if (s->pscd_ptr >= s->pscd_end) {
+	s->result = JBG_MORE;
+	return -1;
+      }
+      if (*s->pscd_ptr == 0xff) 
+	if (s->pscd_ptr + 1 >= s->pscd_end) {
+	  s->result = JBG_MARKER;
+	  return -1;
+	} else {
+	  if (*(s->pscd_ptr + 1) == MARKER_STUFF) {
+	    s->c |= 0xffL << (8 - s->ct);
+	    s->ct += 8;
+	    s->pscd_ptr += 2;
+	    s->result = JBG_OK;
+	  } else
+	    s->result = JBG_READY;
+	}
+      else {
+	s->c |= (long)*(s->pscd_ptr++) << (8 - s->ct);
+	s->ct += 8;
+	s->result = JBG_OK;
+      }
+    }
+    s->c <<= 1;
+    s->a <<= 1;
+    --s->ct;
+    if (s->a == 0x10000L)
+      s->startup = 0;
+  }
+
+  st = s->st + cx;
+  ss = *st & 0x7f;
+  assert(ss < 113);
+  lsz = jbg_lsz[ss];
+
+#if 0
+  fprintf(stderr, "cx = %d, mps = %d, st = %3d, lsz = 0x%04x, a = 0x%05lx, "
+	  "c = 0x%08lx, ct = %2d\n",
+	  cx, !!(s->st[cx] & 0x80), ss, lsz, s->a, s->c, s->ct);
+#endif
+
+  if ((s->c >> 16) < (s->a -= lsz))
+    if (s->a & 0xffff8000L)
+      return *st >> 7;
+    else {
+      /* MPS_EXCHANGE */
+      if (s->a < lsz) {
+	pix = 1 - (*st >> 7);
+	/* Check whether MPS/LPS exchange is necessary
+	 * and chose next probability estimator status */
+	*st &= 0x80;
+	*st ^= jbg_nlps[ss];
+      } else {
+	pix = *st >> 7;
+	*st &= 0x80;
+	*st |= jbg_nmps[ss];
+      }
+    }
+  else {
+    /* LPS_EXCHANGE */
+    if (s->a < lsz) {
+      s->c -= s->a << 16;
+      s->a = lsz;
+      pix = *st >> 7;
+      *st &= 0x80;
+      *st |= jbg_nmps[ss];
+    } else {
+      s->c -= s->a << 16;
+      s->a = lsz;
+      pix = 1 - (*st >> 7);
+      /* Check whether MPS/LPS exchange is necessary
+       * and chose next probability estimator status */
+      *st &= 0x80;
+      *st ^= jbg_nlps[ss];
+    }
+  }
+
+  return pix;
+}
+
+
+
+/*
+ * Memory management for buffers which are used for temporarily
+ * storing SDEs by the encoder.
+ *
+ * The following functions manage a set of struct jbg_buf storage
+ * containers were each can keep JBG_BUFSIZE bytes. The jbg_buf
+ * containers can be linked to form linear double-chained lists for
+ * which a number of operations are provided. Blocks which are
+ * tempoarily not used any more are returned to a freelist which each
+ * encoder keeps. Only the destructor of the encoder actually returns
+ * the block via checked_free() to the stdlib memory management.
+ */
+
+
+/*
+ * Allocate a new buffer block and initialize it. Try to get it from
+ * the free_list, and if it is empty, call checked_malloc().
+ */
+static struct jbg_buf *jbg_buf_init(struct jbg_buf **free_list)
+{
+  struct jbg_buf *new_block;
+  
+  /* Test whether a block from the free list is available */
+  if (*free_list) {
+    new_block = *free_list;
+    *free_list = new_block->next;
+  } else {
+    /* request a new memory block */
+    new_block = (struct jbg_buf *) checked_malloc(sizeof(struct jbg_buf));
+  }
+  new_block->len = 0;
+  new_block->next = NULL;
+  new_block->previous = NULL;
+  new_block->last = new_block;
+  new_block->free_list = free_list;
+
+  return new_block;
+}
+
+
+/*
+ * Return an entire free_list to the memory management of stdlib.
+ * This is only done by jbg_enc_free().
+ */
+static void jbg_buf_free(struct jbg_buf **free_list)
+{
+  struct jbg_buf *tmp;
+  
+  while (*free_list) {
+    tmp = (*free_list)->next;
+    checked_free(*free_list);
+    *free_list = tmp;
+  }
+  
+  return;
+}
+
+
+/*
+ * Append a single byte to a single list that starts with the block
+ * *(struct jbg_buf *) head. The type of *head is void here in order to
+ * keep the interface of the arithmetic encoder gereric, which uses this
+ * function as a call-back function in order to deliver single bytes
+ * for a PSCD.
+ */
+static void jbg_buf_write(int b, void *head)
+{
+  struct jbg_buf *now;
+
+  now = ((struct jbg_buf *) head)->last;
+  if (now->len < JBG_BUFSIZE - 1) {
+    now->d[now->len++] = b;
+    return;
+  }
+  now->next = jbg_buf_init(((struct jbg_buf *) head)->free_list);
+  now->next->previous = now;
+  now->next->d[now->next->len++] = b;
+  ((struct jbg_buf *) head)->last = now->next;
+
+  return;
+}
+
+
+/*
+ * Remove any trailing zero bytes from the end of a linked jbg_buf list,
+ * however make sure that no zero byte is removed which directly
+ * follows a 0xff byte (i.e., keep MARKER_ESC MARKER_STUFF sequences
+ * intact). This function is used to remove any redundant final zero
+ * bytes from a PSCD.
+ */
+static void jbg_buf_remove_zeros(struct jbg_buf *head)
+{
+  struct jbg_buf *last;
+
+  while (1) {
+    /* remove trailing 0x00 in last block of list until this block is empty */
+    last = head->last;
+    while (last->len && last->d[last->len - 1] == 0)
+      last->len--;
+    /* if block became really empty, remove it in case it is not the
+     * only remaining block and then loop to next block */
+    if (last->previous && !last->len) {
+      head->last->next = *head->free_list;
+      *head->free_list = head->last;
+      head->last = last->previous;
+      head->last->next = NULL;
+    } else
+      break;
+  }
+
+  /*
+   * If the final non-zero byte is 0xff (MARKER_ESC), then we just have
+   * removed a MARKER_STUFF and we will append it again now in order
+   * to preserve PSCD status of byte stream.
+   */
+  if (head->last->len && head->last->d[head->last->len - 1] == MARKER_ESC)
+    jbg_buf_write(MARKER_STUFF, head);
+ 
+  return;
+}
+
+
+/*
+ * The jbg_buf list which starts with block *new_prefix is concatenated
+ * with the list which starts with block **start and *start will then point
+ * to the first block of the new list.
+ */
+static void jbg_buf_prefix(struct jbg_buf *new_prefix, struct jbg_buf **start)
+{
+  new_prefix->last->next = *start;
+  new_prefix->last->next->previous = new_prefix->last;
+  new_prefix->last = new_prefix->last->next->last;
+  *start = new_prefix;
+  
+  return;
+}
+
+
+/*
+ * Send the contents of a jbg_buf list that starts with block **head to
+ * the call back function data_out and return the blocks of the jbg_buf
+ * list to the freelist from which these jbg_buf blocks have been taken.
+ * After the call, *head == NULL.
+ */
+static void jbg_buf_output(struct jbg_buf **head,
+			void (*data_out)(unsigned char *start,
+					 size_t len, void *file),
+			void *file)
+{
+  struct jbg_buf *tmp;
+  
+  while (*head) {
+    data_out((*head)->d, (*head)->len, file);
+    tmp = (*head)->next;
+    (*head)->next = *(*head)->free_list;
+    *(*head)->free_list = *head;
+    *head = tmp;
+  }
+  
+  return;
+}
+
+
+/*
+ * Calculate y = ceil(x/2) applied n times. This function is used to
+ * determine the number of pixels per row or column after n resolution
+ * reductions. E.g. X[d-1] = jbg_ceil_half(X[d], 1) and X[0] =
+ * jbg_ceil_half(X[d], d) as defined in clause 6.2.3 of T.82.
+ */
+unsigned long jbg_ceil_half(unsigned long x, int n)
+{
+  unsigned long mask;
+  
+  mask = (1UL << n) - 1;     /* the lowest n bits are 1 here */
+  return (x >> n) + ((mask & x) != 0);
+}
+
+
+/*
+ * Initialize the status struct for the encoder.
+ */
+void jbg_enc_init(struct jbg_enc_state *s, unsigned long x, unsigned long y,
+                  int planes, unsigned char **p,
+                  void (*data_out)(unsigned char *start, size_t len,
+				   void *file),
+		  void *file)
+{
+  unsigned long l, lx;
+  int i;
+  size_t bufsize;
+
+  extern char jbg_resred[], jbg_dptable[];
+
+  s->xd = x;
+  s->yd = y;
+  s->planes = planes;
+  s->data_out = data_out;
+  s->file = file;
+
+  s->d = 0;
+  s->dl = 0;
+  s->dh = s->d;
+  s->l0 = jbg_ceil_half(s->yd, s->d) / 35;   /* 35 stripes/image */
+  while ((s->l0 << s->d) > 128)              /* but <= 128 lines/stripe */
+    --s->l0;
+  if (s->l0 < 2) s->l0 = 2;
+  s->mx = 8;
+  s->my = 0;
+  s->order = JBG_ILEAVE | JBG_SMID;
+  s->options = JBG_TPBON | JBG_TPDON | JBG_DPON;
+  s->dppriv = jbg_dptable;
+  s->res_tab = jbg_resred;
+  
+  s->highres = checked_malloc(planes * sizeof(int));
+  s->lhp[0] = p;
+  s->lhp[1] = checked_malloc(planes * sizeof(unsigned char *));
+  bufsize = ((jbg_ceil_half(x, 1) + 7) / 8) * jbg_ceil_half(y, 1);
+  for (i = 0; i < planes; i++) {
+    s->highres[i] = 0;
+    s->lhp[1][i] = checked_malloc(sizeof(unsigned char) * bufsize);
+  }
+  
+  s->free_list = NULL;
+  s->s = (struct jbg_arenc_state *) 
+    checked_malloc(s->planes * sizeof(struct jbg_arenc_state));
+  s->tx = (int *) checked_malloc(s->planes * sizeof(int));
+  lx = jbg_ceil_half(x, 1);
+  s->tp = (char *) checked_malloc(lx * sizeof(char));
+  for (l = 0; l < lx; s->tp[l++] = 2);
+  s->sde = NULL;
+
+  return;
+}
+
+
+/*
+ * This function selects the number of differential layers based on
+ * the maximum size requested for the lowest resolution layer. If
+ * possible, a number of differential layers is selected, which will
+ * keep the size of the lowest resolution layer below or equal to the
+ * given width x and height y. However not more than 6 differential
+ * resolution layers will be used. In addition, a reasonable value for
+ * l0 (height of one stripe in the lowest resolution layer) is
+ * selected, which obeys the recommended limitations for l0 in annex A
+ * and C of the JBIG standard. The selected number of resolution layers
+ * is returned. 
+ */
+int jbg_enc_lrlmax(struct jbg_enc_state *s, unsigned long x, 
+		   unsigned long y)
+{
+  for (s->d = 0; s->d < 6; s->d++)
+    if (jbg_ceil_half(s->xd, s->d) <= x && jbg_ceil_half(s->yd, s->d) <= y)
+      break;
+  s->dl = 0;
+  s->dh = s->d;
+
+  s->l0 = jbg_ceil_half(s->yd, s->d) / 35;  /* 35 stripes/image */
+  while ((s->l0 << s->d) > 128)             /* but <= 128 lines/stripe */
+    --s->l0;
+  if (s->l0 < 2) s->l0 = 2;
+
+  return s->d;
+}
+
+
+/*
+ * As an alternative to jbg_enc_lrlmax(), the following function allows
+ * to specify the number of layers directly. The stripe height and layer
+ * range is also adjusted automatically here.
+ */
+void jbg_enc_layers(struct jbg_enc_state *s, int d)
+{
+  if (d < 0 || d > 255)
+    return;
+  s->d  = d;
+  s->dl = 0;
+  s->dh = s->d;
+
+  s->l0 = jbg_ceil_half(s->yd, s->d) / 35;  /* 35 stripes/image */
+  while ((s->l0 << s->d) > 128)             /* but <= 128 lines/stripe */
+    --s->l0;
+  if (s->l0 < 2) s->l0 = 2;
+
+  return;
+}
+
+
+/*
+ * Specify the highest and lowest resolution layers which will be
+ * written to the output file. Call this function not before
+ * jbg_enc_layers() or jbg_enc_lrlmax(), because these two functions
+ * reset the lowest and highest resolution layer to default values.
+ * Negative values are ignored. The total number of layers is returned.
+ */
+int jbg_enc_lrange(struct jbg_enc_state *s, int dl, int dh)
+{
+  if (dl >= 0     && dl <= s->d) s->dl = dl;
+  if (dh >= s->dl && dh <= s->d) s->dh = dh;
+
+  return s->d;
+}
+
+
+/*
+ * The following function allows to specify the bits describing the
+ * options of the format as well as the maximum AT movement window and
+ * the number of layer 0 lines per stripes.
+ */
+void jbg_enc_options(struct jbg_enc_state *s, int order, int options,
+		     long l0, int mx, int my)
+{
+  if (order >= 0 && order <= 0x0f) s->order = order;
+  if (options >= 0) s->options = options;
+  if (l0 >= 0) s->l0 = l0;
+  if (mx >= 0 && my < 128) s->mx = mx;
+  if (my >= 0 && my < 256) s->my = my;
+
+  return;
+}
+
+
+/*
+ * This function actually does all the tricky work involved in producing
+ * a SDE, which is stored in the appropriate s->sde[][][] element
+ * for later output in the correct order.
+ */
+static void encode_sde(struct jbg_enc_state *s,
+		       long stripe, int layer, int plane)
+{
+  unsigned char *hp, *lp1, *lp2, *p0, *p1, *q1, *q2;
+  unsigned long hl, ll, hx, hy, lx, ly, hbpl, lbpl;
+  unsigned long line_h0 = 0, line_h1 = 0;
+  unsigned long line_h2, line_h3, line_l1, line_l2, line_l3;
+  struct jbg_arenc_state *se;
+  unsigned long i, j, y;
+  unsigned t;
+  int ltp, ltp_old, cx;
+  unsigned long c_all, c[MX_MAX + 1], cmin, cmax, clmin, clmax;
+  int tmax, at_determined;
+  int new_tx;
+  long new_tx_line = -1;
+  struct jbg_buf *new_jbg_buf;
+
+#ifdef DEBUG
+  static long tp_lines, tp_exceptions, tp_pixels, dp_pixels;
+  static long encoded_pixels;
+#endif
+
+  /* return immediately if this stripe has already been encoded */
+  if (s->sde[stripe][layer][plane] != SDE_TODO)
+    return;
+
+#ifdef DEBUG
+  if (stripe == 0)
+    tp_lines = tp_exceptions = tp_pixels = dp_pixels = encoded_pixels = 0;
+  fprintf(stderr, "encode_sde: s/d/p = %2ld/%2d/%2d\n",
+	  stripe, layer, plane);
+#endif
+
+  /* number of lines per stripe in highres image */
+  hl = s->l0 << layer;
+  /* number of lines per stripe in lowres image */
+  ll = hl >> 1;
+  /* current line number in highres image */
+  y = stripe * hl;
+  /* number of pixels in highres image */
+  hx = jbg_ceil_half(s->xd, s->d - layer);
+  hy = jbg_ceil_half(s->yd, s->d - layer);
+  /* number of pixels in lowres image */
+  lx = jbg_ceil_half(hx, 1);
+  ly = jbg_ceil_half(hy, 1);
+  /* bytes per line in highres and lowres image */
+  hbpl = (hx + 7) / 8;
+  lbpl = (lx + 7) / 8;
+  /* pointer to first image byte of highres stripe */
+  hp = s->lhp[s->highres[plane]][plane] + stripe * hl * hbpl;
+  lp2 = s->lhp[1 - s->highres[plane]][plane] + stripe * ll * lbpl;
+  lp1 = lp2 + lbpl;
+  
+  /* initialize arithmetic encoder */
+  se = s->s + plane;
+  arith_encode_init(se, stripe != 0);
+  s->sde[stripe][layer][plane] = jbg_buf_init(&s->free_list);
+  se->byte_out = jbg_buf_write;
+  se->file = s->sde[stripe][layer][plane];
+
+  /* initialize adaptive template movement algorithm */
+  c_all = 0;
+  for (t = 0; t <= s->mx; t++)
+    c[t] = 0;
+  if (stripe == 0)
+    s->tx[plane] = 0;
+  new_tx = -1;
+  at_determined = 0;  /* we haven't yet decided the template move */
+  if (s->mx == 0)
+    at_determined = 1;
+
+  /* initialize typical prediction */
+  ltp = 0;
+  if (stripe == 0)
+    ltp_old = 0;
+  else {
+    ltp_old = 1;
+    p1 = hp - hbpl;
+    if (y > 1) {
+      q1 = p1 - hbpl;
+      while (p1 < hp && (ltp_old = (*p1++ == *q1++)) != 0);
+    } else
+      while (p1 < hp && (ltp_old = (*p1++ == 0)) != 0);
+  }
+
+  if (layer == 0) {
+
+    /*
+     *  Encode lowest resolution layer
+     */
+
+    for (i = 0; i < hl && y < hy; i++, y++) {
+
+      /* check whether it is worth to perform an ATMOVE */
+      if (!at_determined && c_all > 2048) {
+	cmin = clmin = 0xffffffffL;
+	cmax = clmax = 0;
+	tmax = 0;
+	for (t = (s->options & JBG_LRLTWO) ? 5 : 3; t <= s->mx; t++) {
+	  if (c[t] > cmax) cmax = c[t];
+	  if (c[t] < cmin) cmin = c[t];
+	  if (c[t] > c[tmax]) tmax = t;
+	}
+	clmin = (c[0] < cmin) ? c[0] : cmin;
+	clmax = (c[0] > cmax) ? c[0] : cmax;
+	if (c_all - cmax < (c_all >> 3) &&
+	    cmax - c[s->tx[plane]] > c_all - cmax &&
+	    cmax - c[s->tx[plane]] > (c_all >> 4) &&
+	    /*                     ^ T.82 says here < !!! Typo ? */
+	    cmax - (c_all - c[s->tx[plane]]) > c_all - cmax &&
+	    cmax - (c_all - c[s->tx[plane]]) > (c_all >> 4) &&
+	    cmax - cmin > (c_all >> 2) &&
+	    (s->tx[plane] || clmax - clmin > (c_all >> 3))) {
+	  /* we have decided to perform an ATMOVE */
+	  new_tx = tmax;
+	  if (!(s->options & JBG_DELAY_AT)) {
+	    new_tx_line = i;
+	    s->tx[plane] = new_tx;
+	  }
+	}
+	at_determined = 1;
+      }
+      
+      /* typical prediction */
+      if (s->options & JBG_TPBON) {
+	ltp = 1;
+	p1 = hp;
+	if (y > 0) {
+	  q1 = hp - hbpl;
+	  while (q1 < hp && (ltp = (*p1++ == *q1++)) != 0);
+	} else
+	  while (p1 < hp + hbpl && (ltp = (*p1++ == 0)) != 0);
+	arith_encode(se, (s->options & JBG_LRLTWO) ? TPB2CX : TPB3CX,
+		     ltp == ltp_old);
+#ifdef DEBUG
+	tp_lines += ltp;
+#endif
+	ltp_old = ltp;
+	if (ltp) {
+	  /* skip next line */
+	  hp += hbpl;
+	  continue;
+	}
+      }
+
+      /*
+       * Layout of the variables line_h1, line_h2, line_h3, which contain
+       * as bits the neighbour pixels of the currently coded pixel X:
+       *
+       *          76543210765432107654321076543210     line_h3
+       *          76543210765432107654321076543210     line_h2
+       *  76543210765432107654321X76543210             line_h1
+       */
+      
+      line_h1 = line_h2 = line_h3 = 0;
+      if (y > 0) line_h2 = (long)*(hp - hbpl) << 8;
+      if (y > 1) line_h3 = (long)*(hp - hbpl - hbpl) << 8;
+      
+      /* encode line */
+      for (j = 0; j < hx; hp++) {
+	line_h1 |= *hp;
+	if (j < hbpl * 8 - 8 && y > 0) {
+	  line_h2 |= *(hp - hbpl + 1);
+	  if (y > 1)
+	    line_h3 |= *(hp - hbpl - hbpl + 1);
+	}
+	if (s->options & JBG_LRLTWO) {
+	  /* two line template */
+	  do {
+	    line_h1 <<= 1;  line_h2 <<= 1;  line_h3 <<= 1;
+	    if (s->tx[plane])
+	      arith_encode(se, (((line_h2 >> 10) & 0x3e0) |
+				((line_h1 >> (4 + s->tx[plane])) & 0x010) |
+				((line_h1 >>  9) & 0x00f)),
+			   (line_h1 >> 8) & 1);
+	    else
+	      arith_encode(se, (((line_h2 >> 10) & 0x3f0) |
+				((line_h1 >>  9) & 0x00f)),
+			   (line_h1 >> 8) & 1);
+#ifdef DEBUG
+	    encoded_pixels++;
+#endif
+	    /* statistics for adaptive template changes */
+	    if (!at_determined && j >= s->mx && j < hx-2) {
+	      c[0] += !(((line_h2 >> 6) ^ line_h1) & 0x100);
+	      for (t = 5; t <= s->mx; t++)
+		c[t] += !(((line_h1 >> t) ^ line_h1) & 0x100);
+	      ++c_all;
+	    }
+	  } while (++j & 7 && j < hx);
+	} else {
+	  /* three line template */
+	  do {
+	    line_h1 <<= 1;  line_h2 <<= 1;  line_h3 <<= 1;
+	    if (s->tx[plane]) 
+	      arith_encode(se, (((line_h3 >>  8) & 0x380) |
+				((line_h2 >> 12) & 0x078) |
+				((line_h1 >> (6 + s->tx[plane])) & 0x004) |
+				((line_h1 >>  9) & 0x003)),
+			   (line_h1 >> 8) & 1);
+	    else
+	      arith_encode(se, (((line_h3 >>  8) & 0x380) |
+				((line_h2 >> 12) & 0x07c) |
+				((line_h1 >>  9) & 0x003)),
+			   (line_h1 >> 8) & 1);
+#ifdef DEBUG
+	    encoded_pixels++;
+#endif
+	    /* statistics for adaptive template changes */
+	    if (!at_determined && j >= s->mx && j < hx-2) {
+	      c[0] += !(((line_h2 >> 6) ^ line_h1) & 0x100);
+	      for (t = 3; t <= s->mx; t++)
+		c[t] += !(((line_h1 >> t) ^ line_h1) & 0x100);
+	      ++c_all;
+	    }
+	  } while (++j & 7 && j < hx);
+	} /* if (s->options & JBG_LRLTWO) */
+      } /* for (j = ...) */
+    } /* for (i = ...) */
+
+  } else {
+
+    /*
+     *  Encode differential layer
+     */
+    
+    for (i = 0; i < hl && y < hy; i++, y++) {
+
+      /* check whether it is worth to perform an ATMOVE */
+      if (!at_determined && c_all > 2048) {
+	cmin = clmin = 0xffffffffL;
+	cmax = clmax = 0;
+	tmax = 0;
+	for (t = 3; t <= s->mx; t++) {
+	  if (c[t] > cmax) cmax = c[t];
+	  if (c[t] < cmin) cmin = c[t];
+	  if (c[t] > c[tmax]) tmax = t;
+	}
+	clmin = (c[0] < cmin) ? c[0] : cmin;
+	clmax = (c[0] > cmax) ? c[0] : cmax;
+	if (c_all - cmax < (c_all >> 3) &&
+	    cmax - c[s->tx[plane]] > c_all - cmax &&
+	    cmax - c[s->tx[plane]] > (c_all >> 4) &&
+	    /*                     ^ T.82 says here < !!! Typo ? */
+	    cmax - (c_all - c[s->tx[plane]]) > c_all - cmax &&
+	    cmax - (c_all - c[s->tx[plane]]) > (c_all >> 4) &&
+	    cmax - cmin > (c_all >> 2) &&
+	    (s->tx[plane] || clmax - clmin > (c_all >> 3))) {
+	  /* we have decided to perform an ATMOVE */
+	  new_tx = tmax;
+	  if (!(s->options & JBG_DELAY_AT)) {
+	    new_tx_line = i;
+	    s->tx[plane] = new_tx;
+	  }
+#ifdef DEBUG
+	  fprintf(stderr, "ATMOVE: line=%ld, tx=%d, c_all=%ld\n",
+		  i, new_tx, c_all);
+#endif
+	}
+	at_determined = 1;
+      }
+      
+      if ((i >> 1) >= ll - 1 || (y >> 1) >= ly - 1)
+	lp1 = lp2;
+
+      /* typical prediction */
+      if (s->options & JBG_TPDON && (i & 1) == 0) {
+	q1 = lp1; q2 = lp2;
+	p0 = p1 = hp;
+	if (i < hl - 1 && y < hy - 1)
+	  p0 = hp + hbpl;
+	if (y > 1)
+	  line_l3 = (long)*(q2 - lbpl) << 8;
+	else
+	  line_l3 = 0;
+	line_l2 = (long)*q2 << 8;
+	line_l1 = (long)*q1 << 8;
+	ltp = 1;
+	for (j = 0; j < lx && ltp; q1++, q2++) {
+	  if (j < lbpl * 8 - 8) {
+	    if (y > 1)
+	      line_l3 |= *(q2 - lbpl + 1);
+	    line_l2 |= *(q2 + 1);
+	    line_l1 |= *(q1 + 1);
+	  }
+	  do {
+	    if ((j >> 2) < hbpl) {
+	      line_h1 = *(p1++);
+	      line_h0 = *(p0++);
+	    }
+	    do {
+	      line_l3 <<= 1;
+	      line_l2 <<= 1;
+	      line_l1 <<= 1;
+	      line_h1 <<= 2;
+	      line_h0 <<= 2;
+	      cx = (((line_l3 >> 15) & 0x007) |
+		    ((line_l2 >> 12) & 0x038) |
+		    ((line_l1 >> 9)  & 0x1c0));
+	      if (cx == 0x000)
+		if ((line_h1 & 0x300) == 0 && (line_h0 & 0x300) == 0)
+		  s->tp[j] = 0;
+		else {
+		  ltp = 0;
+#ifdef DEBUG
+		  tp_exceptions++;
+#endif
+		}
+	      else if (cx == 0x1ff)
+		if ((line_h1 & 0x300) == 0x300 && (line_h0 & 0x300) == 0x300)
+		  s->tp[j] = 1;
+		else {
+		  ltp = 0;
+#ifdef DEBUG
+		  tp_exceptions++;
+#endif
+		}
+	      else
+		s->tp[j] = 2;
+	    } while (++j & 3 && j < lx);
+	  } while (j & 7 && j < lx);
+	} /* for (j = ...) */
+	arith_encode(se, TPDCX, !ltp);
+#ifdef DEBUG
+	tp_lines += ltp;
+#endif
+      }
+
+
+      /*
+       * Layout of the variables line_h1, line_h2, line_h3, which contain
+       * as bits the high resolution neighbour pixels of the currently coded
+       * highres pixel X:
+       *
+       *            76543210 76543210 76543210 76543210     line_h3
+       *            76543210 76543210 76543210 76543210     line_h2
+       *   76543210 76543210 7654321X 76543210              line_h1
+       *
+       * Layout of the variables line_l1, line_l2, line_l3, which contain
+       * the low resolution pixels near the currently coded pixel as bits.
+       * The lowres pixel in which the currently coded highres pixel is
+       * located is marked as Y:
+       *
+       *            76543210 76543210 76543210 76543210     line_l3
+       *            76543210 7654321Y 76543210 76543210     line_l2
+       *            76543210 76543210 76543210 76543210     line_l1
+       */
+      
+
+      line_h1 = line_h2 = line_h3 = line_l1 = line_l2 = line_l3 = 0;
+      if (y > 0) line_h2 = (long)*(hp - hbpl) << 8;
+      if (y > 1) {
+	line_h3 = (long)*(hp - hbpl - hbpl) << 8;
+	line_l3 = (long)*(lp2 - lbpl) << 8;
+      }
+      line_l2 = (long)*lp2 << 8;
+      line_l1 = (long)*lp1 << 8;
+      
+      /* encode line */
+      for (j = 0; j < hx; lp1++, lp2++) {
+	if ((j >> 1) < lbpl * 8 - 8) {
+	  if (y > 1)
+	    line_l3 |= *(lp2 - lbpl + 1);
+	  line_l2 |= *(lp2 + 1);
+	  line_l1 |= *(lp1 + 1);
+	}
+	do {
+
+	  assert(hp - (s->lhp[s->highres[plane]][plane] +
+		       (stripe * hl + i) * hbpl)
+		 == (ptrdiff_t) j >> 3);
+
+	  assert(lp2 - (s->lhp[1-s->highres[plane]][plane] +
+			(stripe * ll + (i>>1)) * lbpl)
+		 == (ptrdiff_t) j >> 4);
+
+	  line_h1 |= *(hp++);
+	  if (j < hbpl * 8 - 8) {
+	    if (y > 0) {
+	      line_h2 |= *(hp - hbpl);
+	      if (y > 1)
+		line_h3 |= *(hp - hbpl - hbpl);
+	    }
+	  }
+	  do {
+	    line_l1 <<= 1;  line_l2 <<= 1;  line_l3 <<= 1;
+	    if (ltp && s->tp[j >> 1] < 2) {
+	      /* pixel are typical and have not to be encoded */
+	      line_h1 <<= 2;  line_h2 <<= 2;  line_h3 <<= 2;
+#ifdef DEBUG
+	      do {
+		++tp_pixels;
+	      } while (++j & 1 && j < hx);
+#else
+	      j += 2;
+#endif
+	    } else
+	      do {
+		line_h1 <<= 1;  line_h2 <<= 1;  line_h3 <<= 1;
+
+		/* deterministic prediction */
+		if (s->options & JBG_DPON) {
+		  if ((y & 1) == 0) {
+		    if ((j & 1) == 0) {
+		      /* phase 0 */
+		      if (s->dppriv[((line_l3 >> 16) & 0x003) |
+				    ((line_l2 >> 14) & 0x00c) |
+				    ((line_h1 >> 5)  & 0x010) |
+				    ((line_h2 >> 10) & 0x0e0)] < 2) {
+#ifdef DEBUG
+			++dp_pixels;
+#endif
+			continue;
+		      }
+		    } else {
+		      /* phase 1 */
+		      if (s->dppriv[(((line_l3 >> 16) & 0x003) |
+				     ((line_l2 >> 14) & 0x00c) |
+				     ((line_h1 >> 5)  & 0x030) |
+				     ((line_h2 >> 10) & 0x1c0)) + 256] < 2) {
+#ifdef DEBUG
+			++dp_pixels;
+#endif
+			continue;
+		      }
+		    }
+		  } else {
+		    if ((j & 1) == 0) {
+		      /* phase 2 */
+		      if (s->dppriv[(((line_l3 >> 16) & 0x003) |
+				     ((line_l2 >> 14) & 0x00c) |
+				     ((line_h1 >> 5)  & 0x010) |
+				     ((line_h2 >> 10) & 0x0e0) |
+				     ((line_h3 >> 7) & 0x700)) + 768] < 2) {
+#ifdef DEBUG
+			++dp_pixels;
+#endif
+			continue;
+		      }
+		    } else {
+		      /* phase 3 */
+		      if (s->dppriv[(((line_l3 >> 16) & 0x003) |
+				     ((line_l2 >> 14) & 0x00c) |
+				     ((line_h1 >> 5)  & 0x030) |
+				     ((line_h2 >> 10) & 0x1c0) |
+				     ((line_h3 >> 7)  & 0xe00)) + 2816] < 2) {
+#ifdef DEBUG
+			++dp_pixels;
+#endif
+			continue;
+		      }
+		    }	
+		  }	
+		}
+
+		/* determine context */
+		if (s->tx[plane])
+		  cx = (((line_h1 >> 9)  & 0x003) |
+			((line_h1 >> (4 + s->tx[plane])) & 0x010) |
+			((line_h2 >> 13) & 0x00c) |
+			((line_h3 >> 11) & 0x020));
+		else
+		  cx = (((line_h1 >> 9)  & 0x003) |
+			((line_h2 >> 13) & 0x01c) |
+			((line_h3 >> 11) & 0x020));
+		if (j & 1)
+		  cx |= (((line_l2 >> 9)  & 0x0c0) |
+			 ((line_l1 >> 7)  & 0x300)) | (1UL << 10);
+		else
+		  cx |= (((line_l2 >> 10) & 0x0c0) |
+			 ((line_l1 >> 8)  & 0x300));
+		cx |= (y & 1) << 11;
+
+		arith_encode(se, cx, (line_h1 >> 8) & 1);
+#ifdef DEBUG
+		encoded_pixels++;
+#endif
+		
+		/* statistics for adaptive template changes */
+		if (!at_determined && j >= s->mx) {
+		  c[0] += !(((line_h2 >> 6) ^ line_h1) & 0x100);
+		  for (t = 3; t <= s->mx; t++)
+		    c[t] += !(((line_h1 >> t) ^ line_h1) & 0x100);
+		  ++c_all;
+		}
+		
+	      } while (++j & 1 && j < hx);
+	  } while (j & 7 && j < hx);
+	} while (j & 15 && j < hx);
+      } /* for (j = ...) */
+
+      /* low resolution pixels are used twice */
+      if ((i & 1) == 0) {
+	lp1 -= lbpl;
+	lp2 -= lbpl;
+      }
+      
+    } /* for (i = ...) */
+  }
+  
+  arith_encode_flush(se);
+  jbg_buf_remove_zeros(s->sde[stripe][layer][plane]);
+  jbg_buf_write(MARKER_ESC, s->sde[stripe][layer][plane]);
+  jbg_buf_write(MARKER_SDNORM, s->sde[stripe][layer][plane]);
+
+  /* add ATMOVE */
+  if (new_tx != -1) {
+    if (s->options & JBG_DELAY_AT) {
+      /* ATMOVE will become active at the first line of the next stripe */
+      s->tx[plane] = new_tx;
+      jbg_buf_write(MARKER_ESC, s->sde[stripe][layer][plane]);
+      jbg_buf_write(MARKER_ATMOVE, s->sde[stripe][layer][plane]);
+      jbg_buf_write(0, s->sde[stripe][layer][plane]);
+      jbg_buf_write(0, s->sde[stripe][layer][plane]);
+      jbg_buf_write(0, s->sde[stripe][layer][plane]);
+      jbg_buf_write(0, s->sde[stripe][layer][plane]);
+      jbg_buf_write(s->tx[plane], s->sde[stripe][layer][plane]);
+      jbg_buf_write(0, s->sde[stripe][layer][plane]);
+    } else {
+      /* ATMOVE has already become active during this stripe
+       * => we have to prefix the SDE data with an ATMOVE marker */
+      new_jbg_buf = jbg_buf_init(&s->free_list);
+      jbg_buf_write(MARKER_ESC, new_jbg_buf);
+      jbg_buf_write(MARKER_ATMOVE, new_jbg_buf);
+      jbg_buf_write((new_tx_line >> 24) & 0xff, new_jbg_buf);
+      jbg_buf_write((new_tx_line >> 16) & 0xff, new_jbg_buf);
+      jbg_buf_write((new_tx_line >> 8) & 0xff, new_jbg_buf);
+      jbg_buf_write(new_tx_line & 0xff, new_jbg_buf);
+      jbg_buf_write(new_tx, new_jbg_buf);
+      jbg_buf_write(0, new_jbg_buf);
+      jbg_buf_prefix(new_jbg_buf, &s->sde[stripe][layer][plane]);
+    }
+  }
+
+#if 0
+  if (stripe == s->stripes - 1)
+    fprintf(stderr, "tp_lines = %ld, tp_exceptions = %ld, tp_pixels = %ld, "
+	    "dp_pixels = %ld, encoded_pixels = %ld\n",
+	    tp_lines, tp_exceptions, tp_pixels, dp_pixels, encoded_pixels);
+#endif
+
+  return;
+}
+
+
+/*
+ * Create the next lower resolution version of an image
+ */
+static void resolution_reduction(struct jbg_enc_state *s, int plane,
+				 int higher_layer)
+{
+  unsigned long hx, hy, lx, ly, hbpl, lbpl;
+  unsigned char *hp1, *hp2, *hp3, *lp;
+  unsigned long line_h1, line_h2, line_h3, line_l2;
+  unsigned long i, j;
+  int pix, k, l;
+
+  /* number of pixels in highres image */
+  hx = jbg_ceil_half(s->xd, s->d - higher_layer);
+  hy = jbg_ceil_half(s->yd, s->d - higher_layer);
+  /* number of pixels in lowres image */
+  lx = jbg_ceil_half(hx, 1);
+  ly = jbg_ceil_half(hy, 1);
+  /* bytes per line in highres and lowres image */
+  hbpl = (hx + 7) / 8;
+  lbpl = (lx + 7) / 8;
+  /* pointers to first image bytes */
+  hp2 = s->lhp[s->highres[plane]][plane];
+  hp1 = hp2 + hbpl;
+  hp3 = hp2 - hbpl;
+  lp = s->lhp[1 - s->highres[plane]][plane];
+  
+#ifdef DEBUG
+  fprintf(stderr, "resolution_reduction: plane = %d, higher_layer = %d\n",
+	  plane, higher_layer);
+#endif
+
+  /*
+   * Layout of the variables line_h1, line_h2, line_h3, which contain
+   * as bits the high resolution neighbour pixels of the currently coded
+   * lowres pixel /\:
+   *              \/
+   *
+   *   76543210 76543210 76543210 76543210     line_h3
+   *   76543210 76543210 765432/\ 76543210     line_h2
+   *   76543210 76543210 765432\/ 76543210     line_h1
+   *
+   * Layout of the variable line_l2, which contains the low resolution
+   * pixels near the currently coded pixel as bits. The lowres pixel
+   * which is currently coded is marked as X:
+   *
+   *   76543210 76543210 76543210 76543210     line_l2
+   *                            X
+   */
+      
+  for (i = 0; i < ly; i++) {
+    if (2*i + 1 >= hy)
+      hp1 = hp2;
+    pix = 0;
+    line_h1 = line_h2 = line_h3 = line_l2 = 0;
+    for (j = 0; j < lbpl * 8; j += 8) {
+      *lp = 0;
+      line_l2 |= i ? lp[-lbpl] : 0;
+      for (k = 0; k < 8 && j + k < lx; k += 4) {
+	if (((j + k) >> 2) < hbpl) {
+	  line_h3 |= i ? *hp3 : 0;
+	  ++hp3;
+	  line_h2 |= *(hp2++);
+	  line_h1 |= *(hp1++);
+	}
+	for (l = 0; l < 4 && j + k + l < lx; l++) {
+	  line_h3 <<= 2;
+	  line_h2 <<= 2;
+	  line_h1 <<= 2;
+	  line_l2 <<= 1;
+	  pix = s->res_tab[((line_h1 >> 8) & 0x007) |
+			   ((line_h2 >> 5) & 0x038) |
+			   ((line_h3 >> 2) & 0x1c0) |
+			   (pix << 9) | ((line_l2 << 2) & 0xc00)];
+	  *lp = (*lp << 1) | pix;
+	}
+      }
+      ++lp;
+    }
+    *(lp - 1) <<= lbpl * 8 - lx;
+    hp1 += hbpl;
+    hp2 += hbpl;
+    hp3 += hbpl;
+  }
+
+#ifdef DEBUG
+  {
+    FILE *f;
+    char fn[50];
+    
+    sprintf(fn, "dbg_d=%02d.pbm", higher_layer - 1);
+    f = fopen(fn, "wb");
+    fprintf(f, "P4\n%lu %lu\n", lx, ly);
+    fwrite(s->lhp[1 - s->highres[plane]][plane], 1, lbpl * ly, f);
+    fclose(f);
+  }
+#endif
+
+  return;
+}
+
+
+/* 
+ * This function is called inside the three loops of jbg_enc_out() in
+ * order to write the next SDE. It has first to generate the required
+ * SDE and all SDEs which have to be encoded before this SDE can be
+ * created. The problem here is that if we want to output a lower
+ * resolution layer, we have to allpy the resolution reduction
+ * algorithm in order to get it. As we try to safe as much memory as
+ * possible, the resolution reduction will overwrite previous higher
+ * resolution bitmaps. Consequently, we have to encode and buffer SDEs
+ * which depend on higher resolution layers before we can start the
+ * resolution reduction. All this logic about which SDE has to be
+ * encoded before resolution reduction is allowed is handled here.
+ * This approach might be a little bit more complex than alternative
+ * ways to do it, but it allows us to do the encoding with the minimal
+ * possible amount of temporary memory.
+ */
+static void output_sde(struct jbg_enc_state *s,
+		       unsigned long stripe, int layer, int plane)
+{
+  int lfcl;     /* lowest fully coded layer */
+  long i;
+  unsigned long u;
+  
+  assert(s->sde[stripe][layer][plane] != SDE_DONE);
+
+  if (s->sde[stripe][layer][plane] != SDE_TODO) {
+#ifdef DEBUG
+    fprintf(stderr, "writing SDE: s/d/p = %2lu/%2d/%2d\n",
+	    stripe, layer, plane);
+#endif
+    jbg_buf_output(&s->sde[stripe][layer][plane], s->data_out, s->file);
+    s->sde[stripe][layer][plane] = SDE_DONE;
+    return;
+  }
+
+  /* Determine the smallest resolution layer in this plane for which
+   * not yet all stripes have been encoded into SDEs. This layer will
+   * have to be completely coded, before we can apply the next
+   * resolution reduction step. */
+  lfcl = 0;
+  for (i = s->d; i >= 0; i--)
+    if (s->sde[s->stripes - 1][i][plane] == SDE_TODO) {
+      lfcl = i + 1;
+      break;
+    }
+  if (lfcl > s->d && s->d > 0 && stripe == 0) {
+    /* perform the first resolution reduction */
+    resolution_reduction(s, plane, s->d);
+  }
+  /* In case HITOLO is not used, we have to encode and store the higher
+   * resolution layers first, although we do not need them right now. */
+  while (lfcl - 1 > layer) {
+    for (u = 0; u < s->stripes; u++)
+      encode_sde(s, u, lfcl - 1, plane);
+    --lfcl;
+    s->highres[plane] ^= 1;
+    if (lfcl > 1)
+      resolution_reduction(s, plane, lfcl - 1);
+  }
+  
+  encode_sde(s, stripe, layer, plane);
+
+#ifdef DEBUG
+  fprintf(stderr, "writing SDE: s/d/p = %2lu/%2d/%2d\n", stripe, layer, plane);
+#endif
+  jbg_buf_output(&s->sde[stripe][layer][plane], s->data_out, s->file);
+  s->sde[stripe][layer][plane] = SDE_DONE;
+  
+  if (stripe == s->stripes - 1 && layer > 0 &&
+      s->sde[0][layer-1][plane] == SDE_TODO) {
+    s->highres[plane] ^= 1;
+    if (layer > 1)
+      resolution_reduction(s, plane, layer - 1);
+  }
+  
+  return;
+}
+
+
+/*
+ * Convert the table which controls the deterministic prediction
+ * process from the internal format into the representation required
+ * for the 1728 byte long DPTABLE element of a BIH.
+ *
+ * The bit order of the DPTABLE format (see also ITU-T T.82 figure 13) is
+ *
+ * high res:   4  5  6     low res:  0  1
+ *             7  8  9               2  3
+ *            10 11 12
+ *
+ * were 4 table entries are packed into one byte, while we here use
+ * internally an unpacked 6912 byte long table indexed by the following
+ * bit order:
+ *
+ * high res:   7  6  5     high res:   8  7  6     low res:  1  0
+ * (phase 0)   4  .  .     (phase 1)   5  4  .               3  2
+ *             .  .  .                 .  .  .
+ *
+ * high res:  10  9  8     high res:  11 10  9
+ * (phase 2)   7  6  5     (phase 3)   8  7  6
+ *             4  .  .                 5  4  .
+ */
+void jbg_int2dppriv(unsigned char *dptable, const char *internal)
+{
+  int i, j, k;
+  int trans0[ 8] = { 1, 0, 3, 2, 7, 6, 5, 4 };
+  int trans1[ 9] = { 1, 0, 3, 2, 8, 7, 6, 5, 4 };
+  int trans2[11] = { 1, 0, 3, 2, 10, 9, 8, 7, 6, 5, 4 };
+  int trans3[12] = { 1, 0, 3, 2, 11, 10, 9, 8, 7, 6, 5, 4 };
+  
+  for (i = 0; i < 1728; dptable[i++] = 0);
+
+#define FILL_TABLE1(offset, len, trans) \
+  for (i = 0; i < len; i++) { \
+    k = 0; \
+    for (j = 0; j < 8; j++) \
+      k |= ((i >> j) & 1) << trans[j]; \
+    dptable[(i + offset) >> 2] |= \
+      (internal[k + offset] & 3) << ((3 - (i&3)) << 1); \
+  }
+
+  FILL_TABLE1(   0,  256, trans0);
+  FILL_TABLE1( 256,  512, trans1);
+  FILL_TABLE1( 768, 2048, trans2);
+  FILL_TABLE1(2816, 4096, trans3);
+
+  return;
+}
+
+
+/*
+ * Convert the table which controls the deterministic prediction
+ * process from the 1728 byte long DPTABLE format into the 6912 byte long
+ * internal format.
+ */
+void jbg_dppriv2int(char *internal, const unsigned char *dptable)
+{
+  int i, j, k;
+  int trans0[ 8] = { 1, 0, 3, 2, 7, 6, 5, 4 };
+  int trans1[ 9] = { 1, 0, 3, 2, 8, 7, 6, 5, 4 };
+  int trans2[11] = { 1, 0, 3, 2, 10, 9, 8, 7, 6, 5, 4 };
+  int trans3[12] = { 1, 0, 3, 2, 11, 10, 9, 8, 7, 6, 5, 4 };
+  
+#define FILL_TABLE2(offset, len, trans) \
+  for (i = 0; i < len; i++) { \
+    k = 0; \
+    for (j = 0; j < 8; j++) \
+      k |= ((i >> j) & 1) << trans[j]; \
+    internal[k + offset] = \
+      (dptable[(i + offset) >> 2] >> ((3 - (i & 3)) << 1)) & 3; \
+  }
+
+  FILL_TABLE2(   0,  256, trans0);
+  FILL_TABLE2( 256,  512, trans1);
+  FILL_TABLE2( 768, 2048, trans2);
+  FILL_TABLE2(2816, 4096, trans3);
+
+  return;
+}
+
+
+/*
+ * Encode one full BIE and pass the generated data to the specified
+ * call-back function
+ */
+void jbg_enc_out(struct jbg_enc_state *s)
+{
+  long bpl;
+  unsigned char bih[20];
+  unsigned long xd, yd, y;
+  long ii[3], is[3], ie[3];    /* generic variables for the 3 nested loops */ 
+  unsigned long stripe;
+  int layer, plane;
+  int order;
+  unsigned char dpbuf[1728];
+  extern char jbg_dptable[];
+
+  /* some sanity checks */
+  s->order &= JBG_HITOLO | JBG_SEQ | JBG_ILEAVE | JBG_SMID;
+  order = s->order & (JBG_SEQ | JBG_ILEAVE | JBG_SMID);
+  if (index[order][0] < 0)
+    s->order = order = JBG_SMID | JBG_ILEAVE;
+  if (s->options & JBG_DPON && s->dppriv != jbg_dptable)
+    s->options |= JBG_DPPRIV;
+  if (s->mx > MX_MAX)
+    s->mx = MX_MAX;
+  s->my = 0;
+  if (s->mx && s->mx < ((s->options & JBG_LRLTWO) ? 5U : 3U))
+    s->mx = 0;
+  if (s->d > 255 || s->d < 0 || s->dh > s->d || s->dh < 0 ||
+      s->dl < 0 || s->dl > s->dh || s->planes < 0 || s->planes > 255)
+    return;
+
+  /* ensure correct zero padding of bitmap at the final byte of each line */
+  if (s->xd & 7) {
+    bpl = (s->xd + 7) / 8;     /* bytes per line */
+    for (plane = 0; plane < s->planes; plane++)
+      for (y = 0; y < s->yd; y++)
+	s->lhp[0][plane][y * bpl + bpl - 1] &= ~((1 << (8 - (s->xd & 7))) - 1);
+  }
+
+  /* calculate number of stripes that will be required */
+  s->stripes = ((s->yd >> s->d) + 
+		((((1UL << s->d) - 1) & s->xd) != 0) + s->l0 - 1) / s->l0;
+
+  /* allocate buffers for SDE pointers */
+  if (s->sde == NULL) {
+    s->sde = (struct jbg_buf ****)
+      checked_malloc(s->stripes * sizeof(struct jbg_buf ***));
+    for (stripe = 0; stripe < s->stripes; stripe++) {
+      s->sde[stripe] = (struct jbg_buf ***)
+	checked_malloc((s->d + 1) * sizeof(struct jbg_buf **));
+      for (layer = 0; layer < s->d + 1; layer++) {
+	s->sde[stripe][layer] = (struct jbg_buf **)
+	  checked_malloc(s->planes * sizeof(struct jbg_buf *));
+	for (plane = 0; plane < s->planes; plane++)
+	  s->sde[stripe][layer][plane] = SDE_TODO;
+      }
+    }
+  }
+
+  /* output BIH */
+  bih[0] = s->dl;
+  bih[1] = s->dh;
+  bih[2] = s->planes;
+  bih[3] = 0;
+  xd = jbg_ceil_half(s->xd, s->d - s->dh);
+  yd = jbg_ceil_half(s->yd, s->d - s->dh);
+  bih[4] = xd >> 24;
+  bih[5] = (xd >> 16) & 0xff;
+  bih[6] = (xd >> 8) & 0xff;
+  bih[7] = xd & 0xff;
+  bih[8] = yd >> 24;
+  bih[9] = (yd >> 16) & 0xff;
+  bih[10] = (yd >> 8) & 0xff;
+  bih[11] = yd & 0xff;
+  bih[12] = s->l0 >> 24;
+  bih[13] = (s->l0 >> 16) & 0xff;
+  bih[14] = (s->l0 >> 8) & 0xff;
+  bih[15] = s->l0 & 0xff;
+  bih[16] = s->mx;
+  bih[17] = s->my;
+  bih[18] = s->order;
+  bih[19] = s->options & 0x7f;
+  s->data_out(bih, 20, s->file);
+  if ((s->options & (JBG_DPON | JBG_DPPRIV | JBG_DPLAST)) ==
+      (JBG_DPON | JBG_DPPRIV)) {
+    /* write private table */
+    jbg_int2dppriv(dpbuf, s->dppriv);
+    s->data_out(dpbuf, 1728, s->file);
+  }
+
+#if 0
+  /*
+   * Encode everything first. This is a simple-minded alternative to
+   * all the tricky on-demand encoding logic in output_sde() for
+   * debugging purposes.
+   */
+  for (layer = s->dh; layer >= s->dl; layer--) {
+    for (plane = 0; plane < s->planes; plane++) {
+      if (layer > 0)
+	resolution_reduction(s, plane, layer);
+      for (stripe = 0; stripe < s->stripes; stripe++)
+	encode_sde(s, stripe, layer, plane);
+      s->highres[plane] ^= 1;
+    }
+  }
+#endif
+
+  /*
+   * Generic loops over all SDEs. Which loop represents layer, plane and
+   * stripe depends on the option flags.
+   */
+
+  /* start and end value vor each loop */
+  is[index[order][STRIPE]] = 0;
+  ie[index[order][STRIPE]] = s->stripes - 1;
+  is[index[order][LAYER]] = s->dl;
+  ie[index[order][LAYER]] = s->dh;
+  is[index[order][PLANE]] = 0;
+  ie[index[order][PLANE]] = s->planes - 1;
+
+  for (ii[0] = is[0]; ii[0] <= ie[0]; ii[0]++)
+    for (ii[1] = is[1]; ii[1] <= ie[1]; ii[1]++)
+      for (ii[2] = is[2]; ii[2] <= ie[2]; ii[2]++) {
+	
+	stripe = ii[index[order][STRIPE]];
+	if (s->order & JBG_HITOLO)
+	  layer = s->dh - (ii[index[order][LAYER]] - s->dl);
+	else
+	  layer = ii[index[order][LAYER]];
+	plane = ii[index[order][PLANE]];
+
+	output_sde(s, stripe, layer, plane);
+
+      }
+
+  return;
+}
+
+
+void jbg_enc_free(struct jbg_enc_state *s)
+{
+  unsigned long stripe;
+  int layer, plane;
+
+#ifdef DEBUG
+  fprintf(stderr, "jbg_enc_free(%p)\n", s);
+#endif
+
+  /* clear buffers for SDEs */
+  if (s->sde) {
+    for (stripe = 0; stripe < s->stripes; stripe++) {
+      for (layer = 0; layer < s->d + 1; layer++) {
+	for (plane = 0; plane < s->planes; plane++)
+	  if (s->sde[stripe][layer][plane] != SDE_DONE &&
+	      s->sde[stripe][layer][plane] != SDE_TODO)
+	    jbg_buf_free(&s->sde[stripe][layer][plane]);
+	checked_free(s->sde[stripe][layer]);
+      }
+      checked_free(s->sde[stripe]);
+    }
+    checked_free(s->sde);
+  }
+
+  /* clear free_list */
+  jbg_buf_free(&s->free_list);
+
+  /* clear memory for arithmetic encoder states */
+  checked_free(s->s);
+
+  /* clear memory for differential-layer typical prediction buffer */
+  checked_free(s->tp);
+
+  /* clear memory for adaptive template pixel offsets */
+  checked_free(s->tx);
+
+  /* clear lowres image buffers */
+  if (s->lhp[1]) {
+    for (plane = 0; plane < s->planes; plane++)
+      checked_free(s->lhp[1][plane]);
+    checked_free(s->lhp[1]);
+  }
+
+  return;
+}
+
+
+/*
+ * Convert the error codes used by jbg_dec_in() into a string
+ * written in the selected language and character set.
+ */
+const char *jbg_strerror(int errnum, int language)
+{
+  if (errnum < 0 || errnum >= NEMSG)
+    return "Unknown error code passed to jbg_strerror()";
+  if (language < 0 || language >= NEMSG_LANG)
+    return "Unknown language code passed to jbg_strerror()";
+
+  return errmsg[language][errnum];
+}
+
+
+/*
+ * The constructor for a decoder 
+ */
+void jbg_dec_init(struct jbg_dec_state *s)
+{
+  s->order = 0;
+  s->d = -1;
+  s->bie_len = 0;
+  s->buf_len = 0;
+  s->dppriv = NULL;
+  s->xmax = 4294967295UL;
+  s->ymax = 4294967295UL;
+  s->dmax = 256;
+  s->s = NULL;
+
+  return;
+}
+
+
+/*
+ * Specify a maximum image size for the decoder. If the JBIG file has
+ * the order bit ILEAVE, but not the bit SEQ set, then the decoder
+ * will abort to decode after the image has reached the maximal
+ * resolution layer which is still not wider than xmax or higher than
+ * ymax.
+ */
+void jbg_dec_maxsize(struct jbg_dec_state *s, unsigned long xmax,
+		     unsigned long ymax)
+{
+  if (xmax > 0) s->xmax = xmax;
+  if (ymax > 0) s->ymax = ymax;
+
+  return;
+}
+
+
+/*
+ * Decode the new len PSDC bytes to which data points and add them to
+ * the current stripe. Return the number of bytes which have actually
+ * been read (this will be less than len if a marker segment was 
+ * part of the data or if the final byte was 0xff were this code
+ * can not determine, whether we have a marker segment.
+ */
+static size_t decode_pscd(struct jbg_dec_state *s, unsigned char *data,
+			  size_t len)
+{
+  unsigned long stripe;
+  unsigned int layer, plane;
+  unsigned long hl, ll, y, hx, hy, lx, ly, hbpl, lbpl;
+  unsigned char *hp, *lp1, *lp2, *p1, *q1;
+  register unsigned long line_h1, line_h2, line_h3;
+  register unsigned long line_l1, line_l2, line_l3;
+  struct jbg_ardec_state *se;
+  unsigned long x;
+  int n;
+  int pix, cx = 0, slntp, shift, tx;
+
+  /* SDE loop variables */
+  stripe = s->ii[index[s->order & 7][STRIPE]];
+  layer = s->ii[index[s->order & 7][LAYER]];
+  plane = s->ii[index[s->order & 7][PLANE]];
+
+  /* forward data to arithmetic decoder */
+  se = s->s[plane] + layer - s->dl;
+  se->pscd_ptr = data;
+  se->pscd_end = data + len;
+  
+  /* number of lines per stripe in highres image */
+  hl = s->l0 << layer;
+  /* number of lines per stripe in lowres image */
+  ll = hl >> 1;
+  /* current line number in highres image */
+  y = stripe * hl + s->i;
+  /* number of pixels in highres image */
+  hx = jbg_ceil_half(s->xd, s->d - layer);
+  hy = jbg_ceil_half(s->yd, s->d - layer);
+  /* number of pixels in lowres image */
+  lx = jbg_ceil_half(hx, 1);
+  ly = jbg_ceil_half(hy, 1);
+  /* bytes per line in highres and lowres image */
+  hbpl = (hx + 7) / 8;
+  lbpl = (lx + 7) / 8;
+  /* pointer to highres and lowres image bytes */
+  hp  = s->lhp[ layer    & 1][plane] + (stripe * hl + s->i) * hbpl +
+    (s->x >> 3);
+  lp2 = s->lhp[(layer-1) & 1][plane] + (stripe * ll + (s->i >> 1)) * lbpl +
+    (s->x >> 4);
+  lp1 = lp2 + lbpl;
+
+  /* restore a few local variables */
+  line_h1 = s->line_h1;
+  line_h2 = s->line_h2;
+  line_h3 = s->line_h3;
+  line_l1 = s->line_l1;
+  line_l2 = s->line_l2;
+  line_l3 = s->line_l3;
+  x = s->x;
+
+  if (s->x == 0 && s->i == 0 &&
+      (stripe == 0 || s->reset[plane][layer - s->dl])) {
+    s->tx[plane][layer - s->dl] = s->ty[plane][layer - s->dl] = 0;
+    if (s->pseudo)
+      s->lntp[plane][layer - s->dl] = 1;
+  }
+
+#ifdef DEBUG
+  if (s->x == 0 && s->i == 0 && s->pseudo)
+    fprintf(stderr, "decode_pscd(%p, %p, %ld): s/d/p = %2lu/%2u/%2u\n",
+	    s, data, (long) len, stripe, layer, plane);
+#endif
+
+  if (layer == 0) {
+
+    /*
+     *  Decode lowest resolution layer
+     */
+
+    for (; s->i < hl && y < hy; s->i++, y++) {
+
+      /* adaptive template changes */
+      if (x == 0)
+	for (n = 0; n < s->at_moves; n++)
+	  if (s->at_line[n] == s->i) {
+	    s->tx[plane][layer - s->dl] = s->at_tx[n];
+	    s->ty[plane][layer - s->dl] = s->at_ty[n];
+#ifdef DEBUG
+	    fprintf(stderr, "ATMOVE: line=%lu, tx=%d, ty=%d.\n", s->i,
+		    s->tx[plane][layer - s->dl], s->ty[plane][layer - s->dl]);
+#endif
+	  }
+      tx = s->tx[plane][layer - s->dl];
+      shift =  tx - ((s->options & JBG_LRLTWO) ? 5 : 3);
+
+      /* typical prediction */
+      if (s->options & JBG_TPBON && s->pseudo) {
+	slntp = arith_decode(se, (s->options & JBG_LRLTWO) ? TPB2CX : TPB3CX);
+	if (se->result == JBG_MORE || se->result == JBG_MARKER)
+	  goto leave;
+	s->lntp[plane][layer - s->dl] =
+	  !(slntp ^ s->lntp[plane][layer - s->dl]);
+	if (s->lntp[plane][layer - s->dl]) {
+	  /* this line is 'not typical' and has to be coded completely */
+	  s->pseudo = 0;
+	} else {
+	  /* this line is 'typical' (i.e. identical to the previous one) */
+	  p1 = hp;
+	  if (s->i == 0 && (stripe == 0 || s->reset[plane][layer - s->dl]))
+	    while (p1 < hp + hbpl) *p1++ = 0;
+	  else {
+	    q1 = hp - hbpl;
+	    while (q1 < hp) *p1++ = *q1++;
+	  }
+	  hp += hbpl;
+	  continue;
+	}
+      }
+      
+      /*
+       * Layout of the variables line_h1, line_h2, line_h3, which contain
+       * as bits the neighbour pixels of the currently decoded pixel X:
+       *
+       *                     76543210 76543210 76543210 76543210     line_h3
+       *                     76543210 76543210 76543210 76543210     line_h2
+       *   76543210 76543210 76543210 76543210 X                     line_h1
+       */
+      
+      if (x == 0) {
+	line_h1 = line_h2 = line_h3 = 0;
+	if (s->i > 0 || (y > 0 && !s->reset[plane][layer - s->dl]))
+	  line_h2 = (long)*(hp - hbpl) << 8;
+	if (s->i > 1 || (y > 1 && !s->reset[plane][layer - s->dl]))
+	  line_h3 = (long)*(hp - hbpl - hbpl) << 8;
+      }
+      
+      /*
+       * Another tiny JBIG standard bug:
+       *
+       * While implementing the line_h3 handling here, I discovered
+       * another problem with the ITU-T T.82(1993 E) specification.
+       * This might be a somewhat pathological case, however. The
+       * standard is unclear about how a decoder should behave in the
+       * following situation:
+       *
+       * Assume we are in layer 0 and all stripes are single lines
+       * (L0=1 allowed by table 9). We are now decoding the first (and
+       * only) line of the third stripe. Assume, the first stripe was
+       * terminated by SDRST and the second stripe was terminated by
+       * SDNORM. While decoding the only line of the third stripe with
+       * the three-line template, we need access to pixels from the
+       * previous two stripes. We know that the previous stripe
+       * terminated with SDNROM, so we access the pixel from the
+       * second stripe. But do we have to replace the pixels from the
+       * first stripe by background pixels, because this stripe ended
+       * with SDRST? The standard, especially clause 6.2.5 does never
+       * mention this case, so the behaviour is undefined here. My
+       * current implementation remembers only the marker used to
+       * terminate the previous stripe. In the above example, the
+       * pixels of the first stripe are accessed despite the fact that
+       * this stripe ended with SDRST. An alternative (only slightly
+       * more complicated) implementation would be to remember the end
+       * marker (SDNORM or SDRST) of the previous two stripes in a
+       * plane/layer and to act accordingly when accessing the two
+       * previous lines. What am I supposed to do here?
+       *
+       * As the standard is unclear about the correct behaviour in the
+       * situation of the above example, I strongly suggest to avoid
+       * the following situation while encoding data with JBIG:
+       *
+       *   LRLTWO = 0, L0=1 and both SDNORM and SDRST appear in layer 0.
+       *
+       * I guess that only a very few if any encoders will switch
+       * between SDNORM and SDRST, so let us hope that this ambiguity
+       * in the standard will never cause any interoperability
+       * problems.
+       *
+       * Markus Kuhn -- 1995-04-30
+       */
+
+      /* decode line */
+      while (x < hx) {
+	if ((x & 7) == 0) {
+	  if (x < hbpl * 8 - 8 &&
+	      (s->i > 0 || (y > 0 && !s->reset[plane][layer - s->dl]))) {
+	    line_h2 |= *(hp - hbpl + 1);
+	    if (s->i > 1 || (y > 1 && !s->reset[plane][layer - s->dl]))
+	      line_h3 |= *(hp - hbpl - hbpl + 1);
+	  }
+	}
+	if (s->options & JBG_LRLTWO) {
+	  /* two line template */
+	  do {
+	    if (tx)
+	      pix = arith_decode(se, (((line_h2 >> 9) & 0x3e0) |
+				      ((line_h1 >> shift) & 0x010) |
+				      (line_h1 & 0x00f)));
+	    else
+	      pix = arith_decode(se, (((line_h2 >> 9) & 0x3f0) |
+				      (line_h1 & 0x00f)));
+	    if (se->result == JBG_MORE || se->result == JBG_MARKER)
+	      goto leave;
+	    line_h1 = (line_h1 << 1) | pix;
+	    line_h2 <<= 1;
+	  } while ((++x & 7) && x < hx);
+	} else {
+	  /* three line template */
+	  do {
+	    if (tx) 
+	      pix = arith_decode(se, (((line_h3 >>  7) & 0x380) |
+				      ((line_h2 >> 11) & 0x078) |
+				      ((line_h1 >> shift) & 0x004) |
+				      (line_h1 & 0x003)));
+	    else
+	      pix = arith_decode(se, (((line_h3 >>  7) & 0x380) |
+				      ((line_h2 >> 11) & 0x07c) |
+				      (line_h1 & 0x003)));
+	    if (se->result == JBG_MORE || se->result == JBG_MARKER)
+	      goto leave;
+	    
+	    line_h1 = (line_h1 << 1) | pix;
+	    line_h2 <<= 1;
+	    line_h3 <<= 1;
+	  } while ((++x & 7) && x < hx);
+	} /* if (s->options & JBG_LRLTWO) */
+	*hp++ = line_h1;
+      } /* while */
+      *(hp - 1) <<= hbpl * 8 - hx;
+      x = 0;
+      s->pseudo = 1;
+    } /* for (i = ...) */
+    
+  } else {
+
+    /*
+     *  Decode differential layer
+     */
+
+    for (; s->i < hl && y < hy; s->i++, y++) {
+
+      /* adaptive template changes */
+      if (x == 0)
+	for (n = 0; n < s->at_moves; n++)
+	  if (s->at_line[n] == s->i) {
+	    s->tx[plane][layer - s->dl] = s->at_tx[n];
+	    s->ty[plane][layer - s->dl] = s->at_ty[n];
+#ifdef DEBUG
+	    fprintf(stderr, "ATMOVE: line=%lu, tx=%d, ty=%d.\n", s->i,
+		    s->tx[plane][layer - s->dl], s->ty[plane][layer - s->dl]);
+#endif
+	  }
+      tx = s->tx[plane][layer - s->dl];
+      shift = tx - 3;
+
+      /* handle lower border of low-resolution image */
+      if ((s->i >> 1) >= ll - 1 || (y >> 1) >= ly - 1)
+	lp1 = lp2;
+
+      /* typical prediction */
+      if (s->options & JBG_TPDON && s->pseudo) {
+	s->lntp[plane][layer - s->dl] = arith_decode(se, TPDCX);
+	if (se->result == JBG_MORE || se->result == JBG_MARKER)
+	  goto leave;
+	s->pseudo = 0;
+      }
+
+
+      /*
+       * Layout of the variables line_h1, line_h2, line_h3, which contain
+       * as bits the high resolution neighbour pixels of the currently
+       * decoded highres pixel X:
+       *
+       *                     76543210 76543210 76543210 76543210     line_h3
+       *                     76543210 76543210 76543210 76543210     line_h2
+       *   76543210 76543210 76543210 76543210 X                     line_h1
+       *
+       * Layout of the variables line_l1, line_l2, line_l3, which contain
+       * the low resolution pixels near the currently decoded pixel as bits.
+       * The lowres pixel in which the currently coded highres pixel is
+       * located is marked as Y:
+       *
+       *                     76543210 76543210 76543210 76543210     line_l3
+       *                     76543210 76543210 Y6543210 76543210     line_l2
+       *                     76543210 76543210 76543210 76543210     line_l1
+       */
+      
+
+      if (x == 0) {
+	line_h1 = line_h2 = line_h3 = line_l1 = line_l2 = line_l3 = 0;
+	if (s->i > 0 || (y > 0 && !s->reset[plane][layer - s->dl])) {
+	  line_h2 = (long)*(hp - hbpl) << 8;
+	  if (s->i > 1 || (y > 1 && !s->reset[plane][layer - s->dl]))
+	    line_h3 = (long)*(hp - hbpl - hbpl) << 8;
+	}
+	if (s->i > 1 || (y > 1 && !s->reset[plane][layer-s->dl]))
+	  line_l3 = (long)*(lp2 - lbpl) << 8;
+	line_l2 = (long)*lp2 << 8;
+	line_l1 = (long)*lp1 << 8;
+      }
+      
+      /* decode line */
+      while (x < hx) {
+	if ((x & 15) == 0)
+	  if ((x >> 1) < lbpl * 8 - 8) {
+	    line_l1 |= *(lp1 + 1);
+	    line_l2 |= *(lp2 + 1);
+	    if (s->i > 1 || 
+		(y > 1 && !s->reset[plane][layer - s->dl]))
+	      line_l3 |= *(lp2 - lbpl + 1);
+	  }
+	do {
+
+	  assert(hp  - (s->lhp[ layer     &1][plane] + (stripe * hl + s->i)
+			* hbpl) == (ptrdiff_t) x >> 3);
+	  assert(lp2 - (s->lhp[(layer-1) &1][plane] + (stripe * ll + (s->i>>1))
+			* lbpl) == (ptrdiff_t) x >> 4);
+
+	  if ((x & 7) == 0)
+	    if (x < hbpl * 8 - 8) {
+	      if (s->i > 0 || (y > 0 && !s->reset[plane][layer - s->dl])) {
+		line_h2 |= *(hp + 1 - hbpl);
+		if (s->i > 1 || (y > 1 && !s->reset[plane][layer - s->dl]))
+		  line_h3 |= *(hp + 1 - hbpl - hbpl);
+	      }
+	    }
+	  do {
+	    if (!s->lntp[plane][layer - s->dl])
+              cx = (((line_l3 >> 14) & 0x007) |
+                    ((line_l2 >> 11) & 0x038) |
+                    ((line_l1 >> 8)  & 0x1c0));
+	    if (!s->lntp[plane][layer - s->dl] &&
+		(cx == 0x000 || cx == 0x1ff)) {
+	      /* pixels are typical and have not to be decoded */
+	      do {
+		line_h1 = (line_h1 << 1) | (cx & 1);
+	      } while ((++x & 1) && x < hx);
+	      line_h2 <<= 2;  line_h3 <<= 2;
+	    } else 
+	      do {
+		
+		/* deterministic prediction */
+		if (s->options & JBG_DPON)
+		  if ((y & 1) == 0)
+		    if ((x & 1) == 0) 
+		      /* phase 0 */
+		      pix = s->dppriv[((line_l3 >> 15) & 0x003) |
+				      ((line_l2 >> 13) & 0x00c) |
+				      ((line_h1 <<  4) & 0x010) |
+				      ((line_h2 >>  9) & 0x0e0)];
+		    else
+		      /* phase 1 */
+		      pix = s->dppriv[(((line_l3 >> 15) & 0x003) |
+				       ((line_l2 >> 13) & 0x00c) |
+				       ((line_h1 <<  4) & 0x030) |
+				       ((line_h2 >>  9) & 0x1c0)) + 256];
+		  else
+		    if ((x & 1) == 0)
+		      /* phase 2 */
+		      pix = s->dppriv[(((line_l3 >> 15) & 0x003) |
+				       ((line_l2 >> 13) & 0x00c) |
+				       ((line_h1 <<  4) & 0x010) |
+				       ((line_h2 >>  9) & 0x0e0) |
+				       ((line_h3 >>  6) & 0x700)) + 768];
+		    else
+		      /* phase 3 */
+		      pix = s->dppriv[(((line_l3 >> 15) & 0x003) |
+				       ((line_l2 >> 13) & 0x00c) |
+				       ((line_h1 <<  4) & 0x030) |
+				       ((line_h2 >>  9) & 0x1c0) |
+				       ((line_h3 >>  6) & 0xe00)) + 2816];
+		else
+		  pix = 2;
+
+		if (pix & 2) {
+		  if (tx)
+		    cx = ((line_h1         & 0x003) |
+			  (((line_h1 << 2) >> shift) & 0x010) |
+			  ((line_h2 >> 12) & 0x00c) |
+			  ((line_h3 >> 10) & 0x020));
+		  else
+		    cx = ((line_h1         & 0x003) |
+			  ((line_h2 >> 12) & 0x01c) |
+			  ((line_h3 >> 10) & 0x020));
+		  if (x & 1)
+		    cx |= (((line_l2 >> 8) & 0x0c0) |
+			   ((line_l1 >> 6) & 0x300)) | (1UL << 10);
+		  else
+		    cx |= (((line_l2 >> 9) & 0x0c0) |
+			   ((line_l1 >> 7) & 0x300));
+		  cx |= (y & 1) << 11;
+
+		  pix = arith_decode(se, cx);
+		  if (se->result == JBG_MORE || se->result == JBG_MARKER)
+		    goto leave;
+		}
+
+		line_h1 = (line_h1 << 1) | pix;
+		line_h2 <<= 1;
+		line_h3 <<= 1;
+		
+	      } while ((++x & 1) && x < hx);
+	    line_l1 <<= 1; line_l2 <<= 1;  line_l3 <<= 1;
+	  } while ((x & 7) && x < hx);
+	  *hp++ = line_h1;
+	} while ((x & 15) && x < hx);
+	++lp1;
+	++lp2;
+      } /* while */
+      x = 0;
+      
+      *(hp - 1) <<= hbpl * 8 - hx;
+      if ((s->i & 1) == 0) {
+	/* low resolution pixels are used twice */
+	lp1 -= lbpl;
+	lp2 -= lbpl;
+      } else
+	s->pseudo = 1;
+      
+    } /* for (i = ...) */
+    
+  }
+
+ leave:
+
+  /* save a few local variables */
+  s->line_h1 = line_h1;
+  s->line_h2 = line_h2;
+  s->line_h3 = line_h3;
+  s->line_l1 = line_l1;
+  s->line_l2 = line_l2;
+  s->line_l3 = line_l3;
+  s->x = x;
+
+  return se->pscd_ptr - data;
+}
+
+
+/*
+ * Provide a new BIE fragment to the decoder.
+ *
+ * If cnt is not NULL, then *cnt will contain after the call the
+ * number of actually read bytes. If the data was not complete, then
+ * the return value will be JBG_EAGAIN and *cnt == len. In case this
+ * function has returned with JBG_EOK, then it has reached the end of
+ * a BIE but it can be called again with data from the next BIE if
+ * there exists one in order to get to a higher resolution layer. In
+ * case the return value was JBG_EOK_INTR then this function can be
+ * called again with the rest of the BIE, because parsing the BIE has
+ * been interrupted by a jbg_dec_maxsize() specification. In both
+ * cases the remaining len - *cnt bytes of the previous block will
+ * have to passed to this function again (if len > *cnt). In case of
+ * any other return value than JBG_EOK, JBG_EOK_INTR or JBG_EAGAIN, a
+ * serious problem has occurred and the only function you should call
+ * is jbg_dec_free() in order to remove the mess (and probably
+ * jbg_strerror() in order to find out what to tell the user).
+ */
+int jbg_dec_in(struct jbg_dec_state *s, unsigned char *data, size_t len,
+	       size_t *cnt)
+{
+  int i, j, required_length;
+  unsigned long x, y;
+  unsigned long is[3], ie[3];
+  long hsize, lsize;
+  extern char jbg_dptable[];
+  size_t dummy_cnt;
+
+  if (!cnt) cnt = &dummy_cnt;
+  *cnt = 0;
+  if (len < 1) return JBG_EAGAIN;
+
+  /* read in 20-byte BIH */
+  if (s->bie_len < 20) {
+    while (s->bie_len < 20 && *cnt < len)
+      s->buffer[s->bie_len++] = data[(*cnt)++];
+    if (s->bie_len < 20) 
+      return JBG_EAGAIN;
+    if (s->buffer[1] < s->buffer[0])
+      return JBG_EINVAL;
+    /* test whether this looks like a valid JBIG header at all */
+    if (s->buffer[3] != 0 || (s->buffer[18] & 0xf0) != 0 ||
+	(s->buffer[19] & 0x80) != 0)
+      return JBG_EINVAL;
+    if (s->buffer[0] != s->d + 1)
+      return JBG_ENOCONT;
+    s->dl = s->buffer[0];
+    s->d = s->buffer[1];
+    if (s->dl == 0)
+      s->planes = s->buffer[2];
+    else
+      if (s->planes != s->buffer[2])
+	return JBG_ENOCONT;
+    x = (((long) s->buffer[ 4] << 24) | ((long) s->buffer[ 5] << 16) |
+	 ((long) s->buffer[ 6] <<  8) | (long) s->buffer[ 7]);
+    y = (((long) s->buffer[ 8] << 24) | ((long) s->buffer[ 9] << 16) |
+	 ((long) s->buffer[10] <<  8) | (long) s->buffer[11]);
+    if (s->dl != 0 && ((s->xd << (s->d - s->dl + 1)) != x &&
+		       (s->yd << (s->d - s->dl + 1)) != y))
+      return JBG_ENOCONT;
+    s->xd = x;
+    s->yd = y;
+    s->l0 = (((long) s->buffer[12] << 24) | ((long) s->buffer[13] << 16) |
+	     ((long) s->buffer[14] <<  8) | (long) s->buffer[15]);
+    if (!s->planes || !s->xd || !s->yd || !s->l0)
+      return JBG_EINVAL;
+    s->mx = s->buffer[16];
+    if (s->mx > 127)
+      return JBG_EINVAL;
+    s->my = s->buffer[17];
+    if (s->mx > 32 || s->my > 0) 
+      return JBG_EIMPL;
+    s->order = s->buffer[18];
+    if (index[s->order & 7][0] < 0)
+      return JBG_EINVAL;
+    /* HITOLO and SEQ currently not yet implemented */
+    if (s->dl != s->d && (s->order & JBG_HITOLO || s->order & JBG_SEQ))
+      return JBG_EIMPL;
+    s->options = s->buffer[19];
+
+    /* calculate number of stripes that will be required */
+    s->stripes = ((s->yd >> s->d) +
+		  ((((1UL << s->d) - 1) & s->xd) != 0) + s->l0 - 1) / s->l0;
+
+    /* some initialization */
+    s->ii[index[s->order & 7][STRIPE]] = 0;
+    s->ii[index[s->order & 7][LAYER]] = s->dl;
+    s->ii[index[s->order & 7][PLANE]] = 0;
+    /* bytes required for resolution layer D and D-1 */
+    hsize = ((s->xd + 7) / 8) * s->yd;
+    lsize = ((jbg_ceil_half(s->xd, 1) + 7) / 8) *
+      jbg_ceil_half(s->yd, 1);
+    if (s->dl == 0) {
+      s->s = checked_malloc(s->planes * sizeof(struct jbg_ardec_state *));
+      s->tx = checked_malloc(s->planes * sizeof(int *));
+      s->ty = checked_malloc(s->planes * sizeof(int *));
+      s->reset = checked_malloc(s->planes * sizeof(int *));
+      s->lntp = checked_malloc(s->planes * sizeof(int *));
+      s->lhp[0] = checked_malloc(s->planes * sizeof(unsigned char *));
+      s->lhp[1] = checked_malloc(s->planes * sizeof(unsigned char *));
+      for (i = 0; i < s->planes; i++) {
+	s->s[i] = checked_malloc((s->d - s->dl + 1) *
+				 sizeof(struct jbg_ardec_state));
+	s->tx[i] = checked_malloc((s->d - s->dl + 1) * sizeof(int));
+	s->ty[i] = checked_malloc((s->d - s->dl + 1) * sizeof(int));
+	s->reset[i] = checked_malloc((s->d - s->dl + 1) * sizeof(int));
+	s->lntp[i] = checked_malloc((s->d - s->dl + 1) * sizeof(int));
+	s->lhp[s->d    &1][i] = checked_malloc(sizeof(unsigned char) * hsize);
+	s->lhp[(s->d-1)&1][i] = checked_malloc(sizeof(unsigned char) * lsize);
+      }
+    } else {
+      for (i = 0; i < s->planes; i++) {
+	s->s[i] = checked_realloc(s->s[i], (s->d - s->dl + 1) *
+				  sizeof(struct jbg_ardec_state));
+	s->tx[i] = checked_realloc(s->tx[i], (s->d - s->dl + 1) * sizeof(int));
+	s->ty[i] = checked_realloc(s->ty[i], (s->d - s->dl + 1) * sizeof(int));
+	s->reset[i] = checked_realloc(s->reset[i],
+				      (s->d - s->dl +1) * sizeof(int));
+	s->lntp[i] = checked_realloc(s->lntp[i],
+				     (s->d - s->dl +1) * sizeof(int));
+	s->lhp[s->d    &1][i] = checked_realloc(s->lhp[s->d    & 1][i],
+						sizeof(unsigned char) * hsize);
+	s->lhp[(s->d-1)&1][i] = checked_realloc(s->lhp[(s->d-1)&1][i],
+						sizeof(unsigned char) * lsize);
+      }
+    }
+    for (i = 0; i < s->planes; i++)
+      for (j = 0; j <= s->d - s->dl; j++)
+	arith_decode_init(s->s[i] + j, 0);
+    if (s->dl == 0 || (s->options & JBG_DPON && !(s->options & JBG_DPPRIV)))
+      s->dppriv = jbg_dptable;
+    s->comment_skip = 0;
+    s->buf_len = 0;
+    s->x = 0;
+    s->i = 0;
+    s->pseudo = 1;
+    s->at_moves = 0;
+  }
+
+  /* read in DPTABLE */
+  if (s->bie_len < 20 + 1728 && 
+      (s->options & (JBG_DPON | JBG_DPPRIV | JBG_DPLAST)) ==
+      (JBG_DPON | JBG_DPPRIV)) {
+    assert(s->bie_len >= 20);
+    while (s->bie_len < 20 + 1728 && *cnt < len)
+      s->buffer[s->bie_len++ - 20] = data[(*cnt)++];
+    if (s->bie_len < 20 + 1728) 
+      return JBG_EAGAIN;
+    if (!s->dppriv || s->dppriv == jbg_dptable)
+      s->dppriv = checked_malloc(sizeof(char) * 1728);
+    jbg_dppriv2int(s->dppriv, s->buffer);
+  }
+
+  /*
+   * BID processing loop
+   */
+  
+  while (*cnt < len) {
+
+    /* process floating marker segments */
+
+    /* skip COMMENT contents */
+    if (s->comment_skip) {
+      if (s->comment_skip <= len - *cnt) {
+	*cnt += s->comment_skip;
+	s->comment_skip = 0;
+      } else {
+	s->comment_skip -= len - *cnt;
+	*cnt = len;
+      }
+      continue;
+    }
+
+    /* load complete marker segments into s->buffer for processing */
+    if (s->buf_len > 0) {
+      assert(s->buffer[0] == MARKER_ESC);
+      while (s->buf_len < 2 && *cnt < len)
+	s->buffer[s->buf_len++] = data[(*cnt)++];
+      if (s->buf_len < 2) continue;
+      switch (s->buffer[1]) {
+      case MARKER_COMMENT: required_length = 6; break;
+      case MARKER_ATMOVE:  required_length = 8; break;
+      case MARKER_NEWLEN:  required_length = 6; break;
+      case MARKER_ABORT:
+      case MARKER_SDNORM:
+      case MARKER_SDRST:   required_length = 2; break;
+      case MARKER_STUFF:
+	/* forward stuffed 0xff to arithmetic decoder */
+	s->buf_len = 0;
+	decode_pscd(s, s->buffer, 2);
+	continue;
+      default:
+	return JBG_EMARKER;
+      }
+      while (s->buf_len < required_length && *cnt < len)
+	s->buffer[s->buf_len++] = data[(*cnt)++];
+      if (s->buf_len < required_length) continue;
+      /* now the buffer is filled with exactly one marker segment */
+      switch (s->buffer[1]) {
+      case MARKER_COMMENT:
+	s->comment_skip = 
+	  (((long) s->buffer[2] << 24) | ((long) s->buffer[3] << 16) |
+	   ((long) s->buffer[4] <<  8) | (long) s->buffer[5]);
+	break;
+      case MARKER_ATMOVE:
+	if (s->at_moves < JBG_ATMOVES_MAX) {
+	  s->at_line[s->at_moves] =
+	    (((long) s->buffer[2] << 24) | ((long) s->buffer[3] << 16) |
+	     ((long) s->buffer[4] <<  8) | (long) s->buffer[5]);
+	  s->at_tx[s->at_moves] = (signed char) s->buffer[6];
+	  s->at_ty[s->at_moves] = s->buffer[7];
+	  if (s->at_tx[s->at_moves] < - (int) s->mx ||
+	      s->at_tx[s->at_moves] >   (int) s->mx ||
+	      s->at_ty[s->at_moves] >   (int) s->my ||
+	      (s->at_ty[s->at_moves] == 0 && s->at_tx[s->at_moves] < 0))
+	    return JBG_EINVAL;
+	  s->at_moves++;
+	} else
+	  return JBG_EINVAL;
+	break;
+      case MARKER_NEWLEN:
+	y = (((long) s->buffer[2] << 24) | ((long) s->buffer[3] << 16) |
+	     ((long) s->buffer[4] <<  8) | (long) s->buffer[5]);
+	if (y > s->yd || !(s->options & JBG_VLENGTH))
+	  return JBG_EINVAL;
+	s->yd = y;
+	/* calculate again number of stripes that will be required */
+	s->stripes = 
+	  ((s->yd >> s->d) +
+	   ((((1UL << s->d) - 1) & s->xd) != 0) + s->l0 - 1) / s->l0;
+	break;
+      case MARKER_ABORT:
+	return JBG_EABORT;
+	
+      case MARKER_SDNORM:
+      case MARKER_SDRST:
+	/* decode final pixels based on trailing zero bytes */
+	decode_pscd(s, s->buffer, 2);
+
+	arith_decode_init(s->s[s->ii[index[s->order & 7][PLANE]]] + 
+			  s->ii[index[s->order & 7][LAYER]] - s->dl,
+			  s->ii[index[s->order & 7][STRIPE]] != s->stripes - 1
+			  && s->buffer[1] != MARKER_SDRST);
+	
+	s->reset[s->ii[index[s->order & 7][PLANE]]]
+	  [s->ii[index[s->order & 7][LAYER]] - s->dl] =
+	    (s->buffer[1] == MARKER_SDRST);
+	
+	/* prepare for next SDE */
+	s->x = 0;
+	s->i = 0;
+	s->pseudo = 1;
+	s->at_moves = 0;
+	
+	/* increment layer/stripe/plane loop variables */
+	/* start and end value for each loop: */
+	is[index[s->order & 7][STRIPE]] = 0;
+	ie[index[s->order & 7][STRIPE]] = s->stripes - 1;
+	is[index[s->order & 7][LAYER]] = s->dl;
+	ie[index[s->order & 7][LAYER]] = s->d;
+	is[index[s->order & 7][PLANE]] = 0;
+	ie[index[s->order & 7][PLANE]] = s->planes - 1;
+	i = 2;  /* index to innermost loop */
+	do {
+	  j = 0;  /* carry flag */
+	  if (++s->ii[i] > ie[i]) {
+	    /* handling overflow of loop variable */
+	    j = 1;
+	    if (i > 0)
+	      s->ii[i] = is[i];
+	  }
+	} while (--i >= 0 && j);
+
+	s->buf_len = 0;
+	
+	/* check whether this have been all SDEs */
+	if (j) {
+	  s->bie_len = 0;
+	  return JBG_EOK;
+	}
+
+	/* check whether we have to abort because of xmax/ymax */
+	if (index[s->order & 7][LAYER] == 0 && i < 0) {
+	  /* LAYER is the outermost loop and we have just gone to next layer */
+	  if (jbg_ceil_half(s->xd, s->d - s->ii[0]) > s->xmax ||
+	      jbg_ceil_half(s->yd, s->d - s->ii[0]) > s->ymax) {
+	    s->xmax = 4294967295UL;
+	    s->ymax = 4294967295UL;
+	    return JBG_EOK_INTR;
+	  }
+	  if (s->ii[0] > (unsigned long) s->dmax) {
+	    s->dmax = 256;
+	    return JBG_EOK_INTR;
+	  }
+	}
+
+	break;
+      }
+      s->buf_len = 0;
+
+    } else if (data[*cnt] == MARKER_ESC)
+      s->buffer[s->buf_len++] = data[(*cnt)++];
+
+    else {
+
+      /* we have found PSCD bytes */
+      *cnt += decode_pscd(s, data + *cnt, len - *cnt);
+      if (*cnt < len && data[*cnt] != 0xff) {
+#ifdef DEBUG
+	fprintf(stderr, "PSCD was longer than expected, unread bytes "
+		"%02x %02x %02x %02x ...\n", data[*cnt], data[*cnt+1],
+		data[*cnt+2], data[*cnt+3]);
+#endif
+	return JBG_EINVAL;
+      }
+      
+    }
+  }  /* of BID processing loop 'while (*cnt < len) ...' */
+
+  return JBG_EAGAIN;
+}
+
+
+/*
+ * After jbg_dec_in() returned JBG_EOK or JBG_EOK_INTR, you can call this
+ * function in order to find out the width of the image.
+ */
+long jbg_dec_getwidth(const struct jbg_dec_state *s)
+{
+  if (s->d < 0)
+    return -1;
+  if (index[s->order & 7][LAYER] == 0) {
+    if (s->ii[0] < 1)
+      return -1;
+    else
+      return jbg_ceil_half(s->xd, s->d - (s->ii[0] - 1));
+  }
+
+  return s->xd;
+}
+
+
+/*
+ * After jbg_dec_in() returned JBG_EOK or JBG_EOK_INTR, you can call this
+ * function in order to find out the height of the image.
+ */
+long jbg_dec_getheight(const struct jbg_dec_state *s)
+{
+  if (s->d < 0)
+    return -1;
+  if (index[s->order & 7][LAYER] == 0) {
+    if (s->ii[0] < 1)
+      return -1;
+    else
+      return jbg_ceil_half(s->yd, s->d - (s->ii[0] - 1));
+  }
+  
+  return s->yd;
+}
+
+
+/*
+ * After jbg_dec_in() returned JBG_EOK or JBG_EOK_INTR, you can call this
+ * function in order to get a pointer to the image.
+ */
+unsigned char *jbg_dec_getimage(const struct jbg_dec_state *s, int plane)
+{
+  if (s->d < 0)
+    return NULL;
+  if (index[s->order & 7][LAYER] == 0) {
+    if (s->ii[0] < 1)
+      return NULL;
+    else
+      return s->lhp[(s->ii[0] - 1) & 1][plane];
+  }
+  
+  return s->lhp[s->d & 1][plane];
+}
+
+
+/*
+ * After jbg_dec_in() returned JBG_EOK or JBG_EOK_INTR, you can call
+ * this function in order to find out the size in bytes of one
+ * bitplane of the image.
+ */
+long jbg_dec_getsize(const struct jbg_dec_state *s)
+{
+  if (s->d < 0)
+    return -1;
+  if (index[s->order & 7][LAYER] == 0) {
+    if (s->ii[0] < 1)
+      return -1;
+    else
+      return 
+	((jbg_ceil_half(s->xd, s->d - (s->ii[0] - 1)) + 7) / 8) *
+	jbg_ceil_half(s->yd, s->d - (s->ii[0] - 1));
+  }
+  
+  return ((s->xd + 7) / 8) * s->yd;
+}
+
+
+/*
+ * After jbg_dec_in() returned JBG_EOK or JBG_EOK_INTR, you can call
+ * this function in order to find out the size of the image that you
+ * can retrieve with jbg_merge_planes().
+ */
+long jbg_dec_getsize_merged(const struct jbg_dec_state *s)
+{
+  if (s->d < 0)
+    return -1;
+  if (index[s->order & 7][LAYER] == 0) {
+    if (s->ii[0] < 1)
+      return -1;
+    else
+      return 
+	jbg_ceil_half(s->xd, s->d - (s->ii[0] - 1)) *
+	jbg_ceil_half(s->yd, s->d - (s->ii[0] - 1)) *
+	((s->planes + 7) / 8);
+  }
+  
+  return s->xd * s->yd * ((s->planes + 7) / 8);
+}
+
+
+/* 
+ * The destructor function which releases any resources obtained by the
+ * other decoder functions.
+ */
+void jbg_dec_free(struct jbg_dec_state *s)
+{
+  int i;
+
+  if (s->d < 0 || s->s == NULL)
+    return;
+  s->d = -2;
+
+  for (i = 0; i < s->planes; i++) {
+    checked_free(s->s[i]);
+    checked_free(s->tx[i]);
+    checked_free(s->ty[i]);
+    checked_free(s->reset[i]);
+    checked_free(s->lntp[i]);
+    checked_free(s->lhp[0][i]);
+    checked_free(s->lhp[1][i]);
+  }
+  
+  checked_free(s->s);
+  checked_free(s->tx);
+  checked_free(s->ty);
+  checked_free(s->reset);
+  checked_free(s->lntp);
+  checked_free(s->lhp[0]);
+  checked_free(s->lhp[1]);
+
+  s->s = NULL;
+
+  return;
+}
+
+
+/*
+ * Split bigendian integer pixel field into separate bit planes. In the
+ * src array, every pixel is represented by a ((has_planes + 7) / 8) byte
+ * long word, most significant byte first. While has_planes describes
+ * the number of used bits per pixel in the source image, encode_plane
+ * is the number of most significant bits among those that we
+ * actually transfer to dest.
+ */
+void jbg_split_planes(unsigned long x, unsigned long y, int has_planes,
+		      int encode_planes,
+		      const unsigned char *src, unsigned char **dest,
+		      int use_graycode)
+{
+  unsigned bpl = (x + 7) / 8;           /* bytes per line in dest plane */
+  unsigned i, k = 8;
+  int p;
+  unsigned long line;
+  extern void *memset(void *s, int c, size_t n);
+  unsigned prev;     /* previous *src byte shifted by 8 bit to the left */
+  register int bits, msb = has_planes - 1;
+  int bitno;
+
+  /* sanity checks */
+  if (encode_planes > has_planes)
+    encode_planes = has_planes;
+  use_graycode = use_graycode != 0 && encode_planes > 1;
+  
+  for (p = 0; p < encode_planes; p++)
+    memset(dest[p], 0, bpl * y);
+  
+  for (line = 0; line < y; line++) {                 /* lines loop */
+    for (i = 0; i * 8 < x; i++) {                    /* dest bytes loop */
+      for (k = 0; k < 8 && i * 8 + k < x; k++) {     /* pixel loop */
+	prev = 0;
+	for (p = 0; p < encode_planes; p++) {        /* bit planes loop */
+	  /* calculate which bit in *src do we want */
+	  bitno = (msb - p) & 7;
+	  /* put this bit with its left neighbor right adjusted into bits */
+	  bits = (prev | *src) >> bitno;
+	  /* go to next *src byte, but keep old */
+	  if (bitno == 0)
+	    prev = *src++;
+	  /* make space for inserting new bit */
+	  dest[p][bpl * line + i] <<= 1;
+	  /* insert bit, if requested apply Gray encoding */
+	  dest[p][bpl * line + i] |= (bits ^ (use_graycode & (bits>>1))) & 1;
+	  /*
+	   * Theorem: Let b(n),...,b(1),b(0) be the digits of a
+	   * binary word and let g(n),...,g(1),g(0) be the digits of the
+	   * corresponding Gray code word, then g(i) = b(i) xor b(i+1).
+	   */
+	}
+	/* skip unused *src bytes */
+	for (;p < has_planes; p++)
+	  if (((has_planes - 1 - p) & 7) == 0)
+	    src++;
+      }
+    }
+    for (p = 0; p < encode_planes; p++)              /* right padding loop */
+      dest[p][bpl * (line + 1) - 1] <<= 8 - k;
+  }
+  
+  return;
+}
+
+/* 
+ * Merge the separate bit planes decoded by the JBIG decoder into an
+ * integer pixel field. This is essentially the counterpart to
+ * jbg_split_planes(). */
+void jbg_dec_merge_planes(const struct jbg_dec_state *s, int use_graycode,
+			  void (*data_out)(unsigned char *start, size_t len,
+					   void *file), void *file)
+{
+#define BUFLEN 4096
+  int bpp, bpl;
+  unsigned long line;
+  unsigned i, k = 8;
+  int p, q;
+  unsigned char buf[BUFLEN];
+  unsigned char *bp = buf;
+  unsigned char **src;
+  unsigned long x, y;
+  unsigned v;
+
+  /* sanity check */
+  use_graycode = use_graycode != 0;
+  
+  x = jbg_dec_getwidth(s);
+  y = jbg_dec_getheight(s);
+  if (x <= 0 || y <= 0)
+    return;
+  bpp = (s->planes + 7) / 8;   /* bytes per pixel in dest image */
+  bpl = (x + 7) / 8;           /* bytes per line in src plane */
+
+  if (index[s->order & 7][LAYER] == 0)
+    if (s->ii[0] < 1)
+      return;
+    else
+      src = s->lhp[(s->ii[0] - 1) & 1];
+  else
+    src = s->lhp[s->d & 1];
+  
+  for (line = 0; line < y; line++) {                    /* lines loop */
+    for (i = 0; i * 8 < x; i++) {                       /* src bytes loop */
+      for (k = 0; k < 8 && i * 8 + k < x; k++) {        /* pixel loop */
+	for (p = (s->planes-1) & ~7; p >= 0; p -= 8) {  /* dest bytes loop */
+	  v = 0;
+	  for (q = 0; q < 8 && p+q < s->planes; q++)    /* pixel bit loop */
+	    v = (v << 1) |
+	      (((src[p+q][bpl * line + i] >> (7 - k)) & 1) ^
+	       (use_graycode & v));
+	  *bp++ = v;
+	  if (bp - buf == BUFLEN) {
+	    data_out(buf, BUFLEN, file);
+	    bp = buf;
+	  }
+	}
+      }
+    }
+  }
+  
+  if (bp - buf > 0)
+    data_out(buf, bp - buf, file);
+  
+  return;
+}