Adjust wide data buffer pointers during fseek and ftell

[BZ #14543]
Set the internal buffer state correctly whenever the external buffer
state is modified by fseek by either computing the current
_IO_read_ptr/end for the internal buffer based on the new _IO_read_ptr
in the external buffer or converting the content read into the
external buffer, up to the extent of the requested fseek offset.

3 files changed, 234 insertions, 1 deletions

diff --git a/libio/Makefile b/libio/Makefile
index e2a7efdc1c..0d28cea59c 100644
--- a/libio/Makefile
+++ b/libio/Makefile
@@ -59,7 +59,7 @@ tests = tst_swprintf tst_wprintf tst_swscanf tst_wscanf tst_getwc tst_putwc   \
 	tst-memstream1 tst-memstream2 \
 	tst-wmemstream1 tst-wmemstream2 \
 	bug-memstream1 bug-wmemstream1 \
-	tst-setvbuf1 tst-popen1 tst-fgetwc bug-wsetpos bug-fclose1
+	tst-setvbuf1 tst-popen1 tst-fgetwc bug-wsetpos bug-fclose1 tst-fseek
 ifeq (yes,$(build-shared))
 # Add test-fopenloc only if shared library is enabled since it depends on
 # shared localedata objects.
@@ -158,6 +158,7 @@ bug-ungetwc2-ENV = LOCPATH=$(common-objpfx)localedata
 tst-swscanf-ENV = LOCPATH=$(common-objpfx)localedata
 bug-ftell-ENV = LOCPATH=$(common-objpfx)localedata
 tst-fgetwc-ENV = LOCPATH=$(common-objpfx)localedata
+tst-fseek-ENV = LOCPATH=$(common-objpfx)localedata
 
 generated = tst-fopenloc.mtrace tst-fopenloc.check
 
diff --git a/libio/tst-fseek.c b/libio/tst-fseek.c
new file mode 100644
index 0000000000..457a087785
--- /dev/null
+++ b/libio/tst-fseek.c
@@ -0,0 +1,173 @@
+/* Verify that fseek/ftell combination works for wide chars.
+   Copyright (C) 2012 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library 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
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <locale.h>
+#include <errno.h>
+#include <wchar.h>
+#include <unistd.h>
+#include <string.h>
+
+/* Defined in test-skeleton.c.  */
+static int create_temp_file (const char *base, char **filename);
+
+
+static int
+do_seek_end (FILE *fp)
+{
+  long save;
+
+  if (fputws (L"abc\n", fp) == -1)
+    {
+      printf ("do_seek_end: fputws: %s\n", strerror (errno));
+      return 1;
+    }
+
+  save = ftell (fp);
+  rewind (fp);
+
+  if (fseek (fp, 0, SEEK_END) == -1)
+    {
+      printf ("do_seek_end: fseek: %s\n", strerror (errno));
+      return 1;
+    }
+
+  if (save != ftell (fp))
+    {
+      printf ("save = %ld, ftell = %ld\n", save, ftell (fp));
+      return 1;
+    }
+
+  return 0;
+}
+
+int
+do_seek_set (FILE *fp)
+{
+  long save1, save2;
+
+  if (fputws (L"ゅう\n", fp) == -1)
+    {
+      printf ("seek_set: fputws(1): %s\n", strerror (errno));
+      return 1;
+    }
+
+  save1 = ftell (fp);
+
+  if (fputws (L"ゅう\n", fp) == -1)
+    {
+      printf ("seek_set: fputws(2): %s\n", strerror (errno));
+      return 1;
+    }
+
+  save2 = ftell (fp);
+
+  if (fputws (L"ゅう\n", fp) == -1)
+    {
+      printf ("seek_set: fputws(3): %s\n", strerror (errno));
+      return 1;
+    }
+
+  if (fseek (fp, save1, SEEK_SET) == -1)
+    {
+      printf ("seek_set: fseek(1): %s\n", strerror (errno));
+      return 1;
+    }
+
+  if (save1 != ftell (fp))
+    {
+      printf ("save1 = %ld, ftell = %ld\n", save1, ftell (fp));
+      return 1;
+    }
+
+  if (fseek (fp, save2, SEEK_SET) == -1)
+    {
+      printf ("seek_set: fseek(2): %s\n", strerror (errno));
+      return 1;
+    }
+
+  if (save2 != ftell (fp))
+    {
+      printf ("save2 = %ld, ftell = %ld\n", save2, ftell (fp));
+      return 1;
+    }
+
+  return 0;
+}
+
+static int
+do_test (void)
+{
+  if (setlocale (LC_ALL, "ja_JP.UTF-8") == NULL)
+    {
+      printf ("Cannot set ja_JP.UTF-8 locale.\n");
+      exit (1);
+    }
+
+  /* Retain messages in English.  */
+  if (setlocale (LC_MESSAGES, "en_US.ISO-8859-1") == NULL)
+    {
+      printf ("Cannot set LC_MESSAGES to en_US.ISO-8859-1 locale.\n");
+      exit (1);
+    }
+
+  int ret = 0;
+  char *filename;
+  int fd = create_temp_file ("tst-fseek.out", &filename);
+
+  if (fd == -1)
+    return 1;
+
+  FILE *fp = fdopen (fd, "w+");
+  if (fp == NULL)
+    {
+      printf ("seek_set: fopen: %s\n", strerror (errno));
+      close (fd);
+      return 1;
+    }
+
+  if (do_seek_set (fp))
+    {
+      printf ("SEEK_SET test failed\n");
+      ret = 1;
+    }
+
+  /* Reopen the file.  */
+  fclose (fp);
+  fp = fopen (filename, "w+");
+  if (fp == NULL)
+    {
+      printf ("seek_end: fopen: %s\n", strerror (errno));
+      return 1;
+    }
+
+  if (do_seek_end (fp))
+    {
+      printf ("SEEK_END test failed\n");
+      ret = 1;
+    }
+
+  fclose (fp);
+
+  return ret;
+}
+
+
+#define TEST_FUNCTION do_test ()
+#include "../test-skeleton.c"
diff --git a/libio/wfileops.c b/libio/wfileops.c
index b790029ffc..d3f46b2ed1 100644
--- a/libio/wfileops.c
+++ b/libio/wfileops.c
@@ -545,6 +545,57 @@ _IO_wfile_sync (fp)
 }
 libc_hidden_def (_IO_wfile_sync)
 
+/* Adjust the internal buffer pointers to reflect the state in the external
+   buffer.  The content between fp->_IO_read_base and fp->_IO_read_ptr is
+   assumed to be converted and available in the range
+   fp->_wide_data->_IO_read_base and fp->_wide_data->_IO_read_end.
+
+   Returns 0 on success and -1 on error with the _IO_ERR_SEEN flag set.  */
+static inline int
+adjust_wide_data (_IO_FILE *fp, bool do_convert)
+{
+  struct _IO_codecvt *cv = fp->_codecvt;
+
+  int clen = (*cv->__codecvt_do_encoding) (cv);
+
+  /* Take the easy way out for constant length encodings if we don't need to
+     convert.  */
+  if (!do_convert && clen > 0)
+    {
+      fp->_wide_data->_IO_read_end += ((fp->_IO_read_ptr - fp->_IO_read_base)
+				       / clen);
+      goto done;
+    }
+
+  enum __codecvt_result status;
+  const char *read_stop = (const char *) fp->_IO_read_base;
+  do
+    {
+
+      fp->_wide_data->_IO_last_state = fp->_wide_data->_IO_state;
+      status = (*cv->__codecvt_do_in) (cv, &fp->_wide_data->_IO_state,
+				       fp->_IO_read_base, fp->_IO_read_ptr,
+				       &read_stop,
+				       fp->_wide_data->_IO_read_base,
+				       fp->_wide_data->_IO_buf_end,
+				       &fp->_wide_data->_IO_read_end);
+
+      /* Should we return EILSEQ?  */
+      if (__builtin_expect (status == __codecvt_error, 0))
+	{
+	  fp->_flags |= _IO_ERR_SEEN;
+	  return -1;
+	}
+    }
+  while (__builtin_expect (status == __codecvt_partial, 0));
+
+done:
+  /* Now seek to _IO_read_end to behave as if we have read it all in.  */
+  fp->_wide_data->_IO_read_ptr = fp->_wide_data->_IO_read_end;
+
+  return 0;
+}
+
 _IO_off64_t
 _IO_wfile_seekoff (fp, offset, dir, mode)
      _IO_FILE *fp;
@@ -693,6 +744,10 @@ _IO_wfile_seekoff (fp, offset, dir, mode)
 		     fp->_wide_data->_IO_buf_base);
 	  _IO_wsetp (fp, fp->_wide_data->_IO_buf_base,
 		     fp->_wide_data->_IO_buf_base);
+
+	  if (adjust_wide_data (fp, false))
+	    goto dumb;
+
 	  _IO_mask_flags (fp, 0, _IO_EOF_SEEN);
 	  goto resync;
 	}
@@ -733,6 +788,10 @@ _IO_wfile_seekoff (fp, offset, dir, mode)
   _IO_wsetg (fp, fp->_wide_data->_IO_buf_base,
 	     fp->_wide_data->_IO_buf_base, fp->_wide_data->_IO_buf_base);
   _IO_wsetp (fp, fp->_wide_data->_IO_buf_base, fp->_wide_data->_IO_buf_base);
+
+  if (adjust_wide_data (fp, true))
+    goto dumb;
+
   fp->_offset = result + count;
   _IO_mask_flags (fp, 0, _IO_EOF_SEEN);
   return offset;