split pmfileio.c out of libpm.c

git-svn-id: http://svn.code.sf.net/p/netpbm/code/trunk@478 9d0c8265-081b-0410-96cb-a4ca84ce46f8

1 files changed, 948 insertions, 0 deletions

diff --git a/lib/pmfileio.c b/lib/pmfileio.c
new file mode 100644
index 00000000..e2cd3d06
--- /dev/null
+++ b/lib/pmfileio.c
@@ -0,0 +1,948 @@
+/**************************************************************************
+                                 pmfileio.c
+***************************************************************************
+  This file contains fundamental file I/O stuff for libnetpbm.
+  These are external functions, unlike 'fileio.c', but are not
+  particular to any Netpbm format.
+**************************************************************************/
+#define _SVID_SOURCE
+    /* Make sure P_tmpdir is defined in GNU libc 2.0.7 (_XOPEN_SOURCE 500
+       does it in other libc's).  pm_config.h defines TMPDIR as P_tmpdir
+       in some environments.
+    */
+#define _XOPEN_SOURCE 500    /* Make sure ftello, fseeko are defined */
+#define _LARGEFILE_SOURCE 1  /* Make sure ftello, fseeko are defined */
+#define _LARGEFILE64_SOURCE 1 
+#define _FILE_OFFSET_BITS 64
+    /* This means ftello() is really ftello64() and returns a 64 bit file
+       position.  Unless the C library doesn't have ftello64(), in which 
+       case ftello() is still just ftello().
+
+       Likewise for all the other C library file functions.
+
+       And off_t and fpos_t are 64 bit types instead of 32.  Consequently,
+       pm_filepos_t might be 64 bits instead of 32.
+    */
+#define _LARGE_FILES  
+    /* This does for AIX what _FILE_OFFSET_BITS=64 does for GNU */
+#define _LARGE_FILE_API
+    /* This makes the the x64() functions available on AIX */
+
+#include <unistd.h>
+#include <stdio.h>
+#include <fcntl.h>
+#include <stdarg.h>
+#include <string.h>
+#include <errno.h>
+#ifdef __DJGPP__
+  #include <io.h>
+#endif
+
+#include "pm_c_util.h"
+#include "mallocvar.h"
+#include "nstring.h"
+
+#include "pm.h"
+
+
+
+/* File open/close that handles "-" as stdin/stdout and checks errors. */
+
+FILE*
+pm_openr(const char * const name) {
+    FILE* f;
+
+    if (strcmp(name, "-") == 0)
+        f = stdin;
+    else {
+#ifndef VMS
+        f = fopen(name, "rb");
+#else
+        f = fopen(name, "r", "ctx=stm");
+#endif
+        if (f == NULL) 
+            pm_error("Unable to open file '%s' for reading.  "
+                     "fopen() returns errno %d (%s)", 
+                     name, errno, strerror(errno));
+    }
+    return f;
+}
+
+
+
+FILE*
+pm_openw(const char * const name) {
+    FILE* f;
+
+    if (strcmp(name, "-") == 0)
+        f = stdout;
+    else {
+#ifndef VMS
+        f = fopen(name, "wb");
+#else
+        f = fopen(name, "w", "mbc=32", "mbf=2");  /* set buffer factors */
+#endif
+        if (f == NULL) 
+            pm_error("Unable to open file '%s' for writing.  "
+                     "fopen() returns errno %d (%s)", 
+                     name, errno, strerror(errno));
+    }
+    return f;
+}
+
+
+
+static const char *
+tmpDir(void) {
+/*----------------------------------------------------------------------------
+   Return the name of the directory in which we should create temporary
+   files.
+
+   The name is a constant in static storage.
+-----------------------------------------------------------------------------*/
+    const char * tmpdir;
+        /* running approximation of the result */
+
+    tmpdir = getenv("TMPDIR");   /* Unix convention */
+
+    if (!tmpdir || strlen(tmpdir) == 0)
+        tmpdir = getenv("TMP");  /* Windows convention */
+
+    if (!tmpdir || strlen(tmpdir) == 0)
+        tmpdir = getenv("TEMP"); /* Windows convention */
+
+    if (!tmpdir || strlen(tmpdir) == 0)
+        tmpdir = TMPDIR;
+
+    return tmpdir;
+}
+
+
+
+static int
+mkstempx(char * const filenameBuffer) {
+/*----------------------------------------------------------------------------
+  This is meant to be equivalent to POSIX mkstemp().
+
+  On some old systems, mktemp() is a security hazard that allows a hacker
+  to read or write our temporary file or cause us to read or write some
+  unintended file.  On other systems, mkstemp() does not exist.
+
+  A Windows/mingw environment is one which doesn't have mkstemp()
+  (2006.06.15).
+
+  We assume that if a system doesn't have mkstemp() that its mktemp()
+  is safe, or that the total situation is such that the problems of
+  mktemp() are not a problem for the user.
+-----------------------------------------------------------------------------*/
+    int retval;
+    int fd;
+    unsigned int attempts;
+    bool gotFile;
+    bool error;
+
+    for (attempts = 0, gotFile = FALSE, error = FALSE;
+         !gotFile && !error && attempts < 100;
+         ++attempts) {
+
+        char * rc;
+        rc = mktemp(filenameBuffer);
+
+        if (rc == NULL)
+            error = TRUE;
+        else {
+            int rc;
+
+            rc = open(filenameBuffer, O_CREAT | O_EXCL, S_IRUSR | S_IWUSR);
+
+            if (rc == 0) {
+                fd = rc;
+                gotFile = TRUE;
+            } else {
+                if (errno == EEXIST) {
+                    /* We'll just have to keep trying */
+                } else 
+                    error = TRUE;
+            }
+        }
+    }    
+    if (gotFile)
+        retval = fd;
+    else
+        retval = -1;
+
+    return retval;
+}
+
+
+
+static int
+mkstemp2(char * const filenameBuffer) {
+
+#if HAVE_MKSTEMP
+    if (0)
+        mkstempx(NULL);  /* defeat compiler unused function warning */
+    return mkstemp(filenameBuffer);
+#else
+    return mkstempx(filenameBuffer);
+#endif
+}
+
+
+
+static void
+makeTmpfileWithTemplate(const char *  const filenameTemplate,
+                        FILE **       const filePP,
+                        const char ** const filenameP,
+                        const char ** const errorP) {
+    
+    char * filenameBuffer;  /* malloc'ed */
+
+    filenameBuffer = strdup(filenameTemplate);
+
+    if (filenameBuffer == NULL)
+        asprintfN(errorP, "Unable to allocate storage for temporary "
+                  "file name");
+    else {
+        int rc;
+        
+        rc = mkstemp2(filenameBuffer);
+        
+        if (rc < 0)
+            asprintfN(errorP,
+                      "Unable to create temporary file according to name "
+                      "pattern '%s'.  mkstemp() failed with errno %d (%s)",
+                      filenameTemplate, errno, strerror(errno));
+        else {
+            int const fd = rc;
+            
+            FILE * fileP;
+            fileP = fdopen(fd, "w+b");
+            
+            if (fileP == NULL)
+                asprintfN(errorP, "Unable to create temporary file.  "
+                          "fdopen() failed with errno %d (%s)",
+                          errno, strerror(errno));
+            else {
+                *errorP = NULL;
+                *filePP = fileP;
+                *filenameP = filenameBuffer;
+            }
+            if (*errorP) {
+                unlink(filenameBuffer);
+                close(fd);
+            }
+        }
+        if (*errorP)
+            strfree(filenameBuffer);
+    }
+}
+
+
+
+void
+pm_make_tmpfile(FILE **       const filePP,
+                const char ** const filenameP) {
+
+    const char * filenameTemplate;
+    unsigned int fnamelen;
+    const char * tmpdir;
+    const char * dirseparator;
+    const char * error;
+
+    fnamelen = strlen(pm_progname) + 10; /* "/" + "_XXXXXX\0" */
+
+    tmpdir = tmpDir();
+
+    if (tmpdir[strlen(tmpdir) - 1] == '/')
+        dirseparator = "";
+    else
+        dirseparator = "/";
+    
+    asprintfN(&filenameTemplate, "%s%s%s%s", 
+              tmpdir, dirseparator, pm_progname, "_XXXXXX");
+
+    if (filenameTemplate == NULL)
+        asprintfN(&error,
+                  "Unable to allocate storage for temporary file name");
+    else {
+        makeTmpfileWithTemplate(filenameTemplate, filePP, filenameP, &error);
+
+        strfree(filenameTemplate);
+    }
+    if (error) {
+        pm_errormsg("%s", error);
+        strfree(error);
+        pm_longjmp();
+    }
+}
+
+
+
+FILE * 
+pm_tmpfile(void) {
+
+    FILE * fileP;
+    const char * tmpfile;
+
+    pm_make_tmpfile(&fileP, &tmpfile);
+
+    unlink(tmpfile);
+
+    strfree(tmpfile);
+
+    return fileP;
+}
+
+
+
+FILE *
+pm_openr_seekable(const char name[]) {
+/*----------------------------------------------------------------------------
+  Open the file named by name[] such that it is seekable (i.e. it can be
+  rewound and read in multiple passes with fseek()).
+
+  If the file is actually seekable, this reduces to the same as
+  pm_openr().  If not, we copy the named file to a temporary file
+  and return that file's stream descriptor.
+
+  We use a file that the operating system recognizes as temporary, so
+  it picks the filename and deletes the file when Caller closes it.
+-----------------------------------------------------------------------------*/
+    int stat_rc;
+    int seekable;  /* logical: file is seekable */
+    struct stat statbuf;
+    FILE * original_file;
+    FILE * seekable_file;
+
+    original_file = pm_openr((char *) name);
+
+    /* I would use fseek() to determine if the file is seekable and 
+       be a little more general than checking the type of file, but I
+       don't have reliable information on how to do that.  I have seen
+       streams be partially seekable -- you can, for example seek to
+       0 if the file is positioned at 0 but you can't actually back up
+       to 0.  I have seen documentation that says the errno for an
+       unseekable stream is EBADF and in practice seen ESPIPE.
+
+       On the other hand, regular files are always seekable and even if
+       some other file is, it doesn't hurt much to assume it isn't.
+    */
+
+    stat_rc = fstat(fileno(original_file), &statbuf);
+    if (stat_rc == 0 && S_ISREG(statbuf.st_mode))
+        seekable = TRUE;
+    else 
+        seekable = FALSE;
+
+    if (seekable) {
+        seekable_file = original_file;
+    } else {
+        seekable_file = pm_tmpfile();
+        
+        /* Copy the input into the temporary seekable file */
+        while (!feof(original_file) && !ferror(original_file) 
+               && !ferror(seekable_file)) {
+            char buffer[4096];
+            int bytes_read;
+            bytes_read = fread(buffer, 1, sizeof(buffer), original_file);
+            fwrite(buffer, 1, bytes_read, seekable_file);
+        }
+        if (ferror(original_file))
+            pm_error("Error reading input file into temporary file.  "
+                     "Errno = %s (%d)", strerror(errno), errno);
+        if (ferror(seekable_file))
+            pm_error("Error writing input into temporary file.  "
+                     "Errno = %s (%d)", strerror(errno), errno);
+        pm_close(original_file);
+        {
+            int seek_rc;
+            seek_rc = fseek(seekable_file, 0, SEEK_SET);
+            if (seek_rc != 0)
+                pm_error("fseek() failed to rewind temporary file.  "
+                         "Errno = %s (%d)", strerror(errno), errno);
+        }
+    }
+    return seekable_file;
+}
+
+
+
+void
+pm_close(FILE * const f) {
+    fflush(f);
+    if (ferror(f))
+        pm_message("A file read or write error occurred at some point");
+    if (f != stdin)
+        if (fclose(f) != 0)
+            pm_error("close of file failed with errno %d (%s)",
+                     errno, strerror(errno));
+}
+
+
+
+/* The pnmtopng package uses pm_closer() and pm_closew() instead of 
+   pm_close(), apparently because the 1999 Pbmplus package has them.
+   I don't know what the difference is supposed to be.
+*/
+
+void
+pm_closer(FILE * const f) {
+    pm_close(f);
+}
+
+
+
+void
+pm_closew(FILE * const f) {
+    pm_close(f);
+}
+
+
+
+/* Endian I/O.
+
+   Before Netpbm 10.27 (March 2005), these would return failure on EOF
+   or I/O failure.  For backward compatibility, they still have the return
+   code, but it is always zero and the routines abort the program in case
+   of EOF or I/O failure.  A program that wants to handle failure differently
+   must use lower level (C library) interfaces.  But that level of detail
+   is uncharacteristic of a Netpbm program; the ease of programming that
+   comes with not checking a return code is more Netpbm.
+
+   It is also for historical reasons that these return signed values,
+   when clearly unsigned would make more sense.
+*/
+
+
+
+static void
+abortWithReadError(FILE * const ifP) {
+
+    if (feof(ifP))
+        pm_error("Unexpected end of input file");
+    else
+        pm_error("Error (not EOF) reading file.");
+}
+
+
+
+void
+pm_readchar(FILE * const ifP,
+            char * const cP) {
+    
+    int c;
+
+    c = getc(ifP);
+    if (c == EOF)
+        abortWithReadError(ifP);
+
+    *cP = c;
+}
+
+
+
+void
+pm_writechar(FILE * const ofP,
+             char   const c) {
+
+    putc(c, ofP);
+}
+
+
+
+int
+pm_readbigshort(FILE *  const ifP, 
+                short * const sP) {
+    int c;
+
+    unsigned short s;
+
+    c = getc(ifP);
+    if (c == EOF)
+        abortWithReadError(ifP);
+    s = (c & 0xff) << 8;
+    c = getc(ifP);
+    if (c == EOF)
+        abortWithReadError(ifP);
+    s |= c & 0xff;
+
+    *sP = s;
+
+    return 0;
+}
+
+
+
+int
+pm_writebigshort(FILE * const ofP, 
+                 short  const s) {
+
+    putc((s >> 8) & 0xff, ofP);
+    putc(s & 0xff, ofP);
+
+    return 0;
+}
+
+
+
+int
+pm_readbiglong(FILE * const ifP, 
+               long * const lP) {
+
+    int c;
+    unsigned long l;
+
+    c = getc(ifP);
+    if (c == EOF)
+        abortWithReadError(ifP);
+    l = c << 24;
+    c = getc(ifP);
+    if (c == EOF)
+        abortWithReadError(ifP);
+    l |= c << 16;
+    c = getc(ifP);
+    if (c == EOF)
+        abortWithReadError(ifP);
+    l |= c << 8;
+    c = getc(ifP);
+    if (c == EOF)
+        abortWithReadError(ifP);
+    l |= c;
+
+    *lP = l;
+
+    return 0;
+}
+
+
+
+int
+pm_writebiglong(FILE * const ofP, 
+                long   const l) {
+
+    putc((l >> 24) & 0xff, ofP);
+    putc((l >> 16) & 0xff, ofP);
+    putc((l >>  8) & 0xff, ofP);
+    putc((l >>  0) & 0xff, ofP);
+
+    return 0;
+}
+
+
+
+int
+pm_readlittleshort(FILE *  const ifP, 
+                   short * const sP) {
+    int c;
+    unsigned short s;
+
+    c = getc(ifP);
+    if (c == EOF)
+        abortWithReadError(ifP);
+    s = c & 0xff;
+
+    c = getc(ifP);
+    if (c == EOF)
+        abortWithReadError(ifP);
+    s |= (c & 0xff) << 8;
+
+    *sP = s;
+
+    return 0;
+}
+
+
+
+int
+pm_writelittleshort(FILE * const ofP, 
+                    short  const s) {
+
+    putc((s >> 0) & 0xff, ofP);
+    putc((s >> 8) & 0xff, ofP);
+
+    return 0;
+}
+
+
+
+int
+pm_readlittlelong(FILE * const ifP, 
+                  long * const lP) {
+    int c;
+    unsigned long l;
+
+    c = getc(ifP);
+    if (c == EOF)
+        abortWithReadError(ifP);
+    l = c;
+    c = getc(ifP);
+    if (c == EOF)
+        abortWithReadError(ifP);
+    l |= c << 8;
+    c = getc(ifP);
+    if (c == EOF)
+        abortWithReadError(ifP);
+    l |= c << 16;
+    c = getc(ifP);
+    if (c == EOF)
+        abortWithReadError(ifP);
+    l |= c << 24;
+
+    *lP = l;
+
+    return 0;
+}
+
+
+
+int
+pm_writelittlelong(FILE * const ofP, 
+                   long   const l) {
+
+    putc((l >>  0) & 0xff, ofP);
+    putc((l >>  8) & 0xff, ofP);
+    putc((l >> 16) & 0xff, ofP);
+    putc((l >> 24) & 0xff, ofP);
+
+    return 0;
+}
+
+
+
+int 
+pm_readmagicnumber(FILE * const ifP) {
+
+    int ich1, ich2;
+
+    ich1 = getc(ifP);
+    ich2 = getc(ifP);
+    if (ich1 == EOF || ich2 == EOF)
+        pm_error( "Error reading magic number from Netpbm image stream.  "
+                  "Most often, this "
+                  "means your input file is empty." );
+
+    return ich1 * 256 + ich2;
+}
+
+
+
+/* Read a file of unknown size to a buffer. Return the number of bytes
+   read. Allocate more memory as we need it. The calling routine has
+   to free() the buffer.
+
+   Oliver Trepte, oliver@fysik4.kth.se, 930613
+*/
+
+#define PM_BUF_SIZE 16384      /* First try this size of the buffer, then
+                                  double this until we reach PM_MAX_BUF_INC */
+#define PM_MAX_BUF_INC 65536   /* Don't allocate more memory in larger blocks
+                                  than this. */
+
+char *
+pm_read_unknown_size(FILE * const file, 
+                     long * const nread) {
+    long nalloc;
+    char * buf;
+    bool eof;
+
+    *nread = 0;
+    nalloc = PM_BUF_SIZE;
+    MALLOCARRAY(buf, nalloc);
+
+    eof = FALSE;  /* initial value */
+
+    while(!eof) {
+        int val;
+
+        if (*nread >= nalloc) { /* We need a larger buffer */
+            if (nalloc > PM_MAX_BUF_INC)
+                nalloc += PM_MAX_BUF_INC;
+            else
+                nalloc += nalloc;
+            REALLOCARRAY_NOFAIL(buf, nalloc);
+        }
+
+        val = getc(file);
+        if (val == EOF)
+            eof = TRUE;
+        else 
+            buf[(*nread)++] = val;
+    }
+    return buf;
+}
+
+
+
+union cheat {
+    uint32n l;
+    short s;
+    unsigned char c[4];
+};
+
+
+
+short
+pm_bs_short(short const s) {
+    union cheat u;
+    unsigned char t;
+
+    u.s = s;
+    t = u.c[0];
+    u.c[0] = u.c[1];
+    u.c[1] = t;
+    return u.s;
+}
+
+
+
+long
+pm_bs_long(long const l) {
+    union cheat u;
+    unsigned char t;
+
+    u.l = l;
+    t = u.c[0];
+    u.c[0] = u.c[3];
+    u.c[3] = t;
+    t = u.c[1];
+    u.c[1] = u.c[2];
+    u.c[2] = t;
+    return u.l;
+}
+
+
+
+void
+pm_tell2(FILE *       const fileP, 
+         void *       const fileposP,
+         unsigned int const fileposSize) {
+/*----------------------------------------------------------------------------
+   Return the current file position as *filePosP, which is a buffer
+   'fileposSize' bytes long.  Abort the program if error, including if
+   *fileP isn't a file that has a position.
+-----------------------------------------------------------------------------*/
+    /* Note: FTELLO() is either ftello() or ftell(), depending on the
+       capabilities of the underlying C library.  It is defined in
+       pm_config.h.  ftello(), in turn, may be either ftell() or
+       ftello64(), as implemented by the C library.
+    */
+    pm_filepos const filepos = FTELLO(fileP);
+    if (filepos < 0)
+        pm_error("ftello() to get current file position failed.  "
+                 "Errno = %s (%d)\n", strerror(errno), errno);
+
+    if (fileposSize == sizeof(pm_filepos)) {
+        pm_filepos * const fileposP_filepos = fileposP;
+        *fileposP_filepos = filepos;
+    } else if (fileposSize == sizeof(long)) {
+        if (sizeof(pm_filepos) > sizeof(long) &&
+            filepos >= (pm_filepos) 1 << (sizeof(long)*8))
+            pm_error("File size is too large to represent in the %u bytes "
+                     "that were provided to pm_tell2()", fileposSize);
+        else {
+            long * const fileposP_long = fileposP;
+            *fileposP_long = (long)filepos;
+        }
+    } else
+        pm_error("File position size passed to pm_tell() is invalid: %u.  "
+                 "Valid sizes are %u and %u", 
+                 fileposSize, (unsigned int)sizeof(pm_filepos),
+                 (unsigned int) sizeof(long));
+}
+
+
+
+unsigned int
+pm_tell(FILE * const fileP) {
+    
+    long filepos;
+
+    pm_tell2(fileP, &filepos, sizeof(filepos));
+
+    return filepos;
+}
+
+
+
+void
+pm_seek2(FILE *             const fileP, 
+         const pm_filepos * const fileposP,
+         unsigned int       const fileposSize) {
+/*----------------------------------------------------------------------------
+   Position file *fileP to position *fileposP.  Abort if error, including
+   if *fileP isn't a seekable file.
+-----------------------------------------------------------------------------*/
+    if (fileposSize == sizeof(pm_filepos)) 
+        /* Note: FSEEKO() is either fseeko() or fseek(), depending on the
+           capabilities of the underlying C library.  It is defined in
+           pm_config.h.  fseeko(), in turn, may be either fseek() or
+           fseeko64(), as implemented by the C library.
+        */
+        FSEEKO(fileP, *fileposP, SEEK_SET);
+    else if (fileposSize == sizeof(long)) {
+        long const fileposLong = *(long *)fileposP;
+        fseek(fileP, fileposLong, SEEK_SET);
+    } else
+        pm_error("File position size passed to pm_seek() is invalid: %u.  "
+                 "Valid sizes are %u and %u", 
+                 fileposSize, (unsigned int)sizeof(pm_filepos),
+                 (unsigned int) sizeof(long));
+}
+
+
+
+void
+pm_seek(FILE * const fileP, unsigned long filepos) {
+/*----------------------------------------------------------------------------
+-----------------------------------------------------------------------------*/
+
+    pm_filepos fileposBuff;
+
+    fileposBuff = filepos;
+
+    pm_seek2(fileP, &fileposBuff, sizeof(fileposBuff));
+}
+
+
+
+void
+pm_nextimage(FILE * const file, int * const eofP) {
+/*----------------------------------------------------------------------------
+   Position the file 'file' to the next image in the stream, assuming it is
+   now positioned just after the current image.  I.e. read off any white
+   space at the end of the current image's raster.  Note that the raw formats
+   don't permit such white space, but this routine tolerates it anyway, 
+   because the plain formats do permit white space after the raster.
+
+   Iff there is no next image, return *eofP == TRUE.
+
+   Note that in practice, we will not normally see white space here in
+   a plain PPM or plain PGM stream because the routine to read a
+   sample from the image reads one character of white space after the
+   sample in order to know where the sample ends.  There is not
+   normally more than one character of white space (a newline) after
+   the last sample in the raster.  But plain PBM is another story.  No white
+   space is required between samples of a plain PBM image.  But the raster
+   normally ends with a newline nonetheless.  Since the sample reading code
+   will not have read that newline, it is there for us to read now.
+-----------------------------------------------------------------------------*/
+    bool eof;
+    bool nonWhitespaceFound;
+
+    eof = FALSE;
+    nonWhitespaceFound = FALSE;
+
+    while (!eof && !nonWhitespaceFound) {
+        int c;
+        c = getc(file);
+        if (c == EOF) {
+            if (feof(file)) 
+                eof = TRUE;
+            else
+                pm_error("File error on getc() to position to image");
+        } else {
+            if (!isspace(c)) {
+                int rc;
+
+                nonWhitespaceFound = TRUE;
+
+                /* Have to put the non-whitespace character back in
+                   the stream -- it's part of the next image.  
+                */
+                rc = ungetc(c, file);
+                if (rc == EOF) 
+                    pm_error("File error doing ungetc() "
+                             "to position to image.");
+            }
+        }
+    }
+    *eofP = eof;
+}
+
+
+
+void
+pm_check(FILE *               const file, 
+         enum pm_check_type   const check_type, 
+         pm_filepos           const need_raster_size,
+         enum pm_check_code * const retval_p) {
+/*----------------------------------------------------------------------------
+   This is not defined for use outside of libnetpbm.
+-----------------------------------------------------------------------------*/
+    struct stat statbuf;
+    pm_filepos curpos;  /* Current position of file; -1 if none */
+    int rc;
+
+#ifdef LARGEFILEDEBUG
+    pm_message("pm_filepos received by pm_check() is %u bytes.",
+               sizeof(pm_filepos));
+#endif
+    /* Note: FTELLO() is either ftello() or ftell(), depending on the
+       capabilities of the underlying C library.  It is defined in
+       pm_config.h.  ftello(), in turn, may be either ftell() or
+       ftello64(), as implemented by the C library.
+    */
+    curpos = FTELLO(file);
+    if (curpos >= 0) {
+        /* This type of file has a current position */
+            
+        rc = fstat(fileno(file), &statbuf);
+        if (rc != 0) 
+            pm_error("fstat() failed to get size of file, though ftello() "
+                     "successfully identified\n"
+                     "the current position.  Errno=%s (%d)",
+                     strerror(errno), errno);
+        else if (!S_ISREG(statbuf.st_mode)) {
+            /* Not a regular file; we can't know its size */
+            if (retval_p) *retval_p = PM_CHECK_UNCHECKABLE;
+        } else {
+            pm_filepos const have_raster_size = statbuf.st_size - curpos;
+            
+            if (have_raster_size < need_raster_size)
+                pm_error("File has invalid format.  The raster should "
+                         "contain %u bytes, but\n"
+                         "the file ends after only %u bytes.",
+                         (unsigned int) need_raster_size, 
+                         (unsigned int) have_raster_size);
+            else if (have_raster_size > need_raster_size) {
+                if (retval_p) *retval_p = PM_CHECK_TOO_LONG;
+            } else {
+                if (retval_p) *retval_p = PM_CHECK_OK;
+            }
+        }
+    } else
+        if (retval_p) *retval_p = PM_CHECK_UNCHECKABLE;
+}
+
+
+
+void
+pm_drain(FILE *         const fileP,
+         unsigned int   const limit,
+         unsigned int * const bytesReadP) {
+/*----------------------------------------------------------------------------
+  Read bytes from *fileP until EOF and return as *bytesReadP how many there
+  were.
+
+  But don't read any more than 'limit'.
+
+  This is a good thing to call after reading an input file to be sure you
+  didn't leave some input behind, which could mean you didn't properly
+  interpret the file.
+-----------------------------------------------------------------------------*/
+    unsigned int bytesRead;
+    bool eof;
+
+    for (bytesRead = 0, eof = false; !eof && bytesRead < limit;) {
+
+        int rc;
+
+        rc = fgetc(fileP);
+
+        eof = (rc == EOF);
+        if (!eof)
+            ++bytesRead;
+    }
+    *bytesReadP = bytesRead;
+}