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Fix _pdfioFileSeek with whence==SEEK_CUR

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Fix seek offset after trailer.

Look at the last 1k of the file to find the startxref marker.
This commit is contained in:
Michael R Sweet 2023-12-12 12:24:49 -05:00
parent 038fd8686b
commit f4aa951165
No known key found for this signature in database
GPG Key ID: BE67C75EC81F3244
2 changed files with 36 additions and 15 deletions
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8
pdfio-common.c
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@ -141,7 +141,7 @@ _pdfioFileGets(pdfio_file_t *pdf, // I - PDF file
*bufend = buffer + bufsize - 1; // Pointer to end of buffer
PDFIO_DEBUG("_pdfioFileGets(pdf=%p, buffer=%p, bufsize=%lu) bufpos=%ld, buffer=%p, bufptr=%p, bufend=%p\n", pdf, buffer, (unsigned long)bufsize, (long)pdf->bufpos, pdf->buffer, pdf->bufptr, pdf->bufend);
PDFIO_DEBUG("_pdfioFileGets(pdf=%p, buffer=%p, bufsize=%lu) bufpos=%ld, buffer=%p, bufptr=%p, bufend=%p, offset=%lu\n", pdf, buffer, (unsigned long)bufsize, (long)pdf->bufpos, pdf->buffer, pdf->bufptr, pdf->bufend, (unsigned long)(pdf->bufpos + (pdf->bufptr - pdf->buffer)));
while (!eol)
{
@ -356,12 +356,12 @@ _pdfioFileSeek(pdfio_file_t *pdf, // I - PDF file
off_t offset, // I - Offset
int whence) // I - Offset base
{
PDFIO_DEBUG("_pdfioFileSeek(pdf=%p, offset=%ld, whence=%d)\n", pdf, (long)offset, whence);
PDFIO_DEBUG("_pdfioFileSeek(pdf=%p, offset=%ld, whence=%d) pdf->bufpos=%lu\n", pdf, (long)offset, whence, (unsigned long)(pdf ? pdf->bufpos : 0));
// Adjust offset for relative seeks...
if (whence == SEEK_CUR)
{
offset += pdf->bufpos;
offset += pdf->bufpos + (pdf->bufptr - pdf->buffer);
whence = SEEK_SET;
}
@ -404,7 +404,7 @@ _pdfioFileSeek(pdfio_file_t *pdf, // I - PDF file
return (-1);
}
PDFIO_DEBUG("_pdfioFileSeek: Reset bufpos=%ld.\n", (long)pdf->bufpos);
PDFIO_DEBUG("_pdfioFileSeek: Reset bufpos=%ld, offset=%lu.\n", (long)pdf->bufpos, (unsigned long)offset);
PDFIO_DEBUG("_pdfioFileSeek: buffer=%p, bufptr=%p, bufend=%p\n", pdf->buffer, pdf->bufptr, pdf->bufend);
pdf->bufpos = offset;

43
pdfio-file.c
View File

@ -1154,8 +1154,10 @@ pdfioFileOpen(
void *error_data) // I - Error callback data, if any
{
pdfio_file_t *pdf; // PDF file
char line[1024], // Line from file
*ptr; // Pointer into line
char line[1025], // Line from file
*ptr, // Pointer into line
*end; // End of line
ssize_t bytes; // Bytes read
off_t xref_offset; // Offset to xref table
@ -1210,21 +1212,29 @@ pdfioFileOpen(
// Copy the version number...
pdf->version = strdup(line + 5);
// Grab the last 32 characters of the file to find the start of the xref table...
if (_pdfioFileSeek(pdf, -32, SEEK_END) < 0)
// Grab the last 1k of the file to find the start of the xref table...
if (_pdfioFileSeek(pdf, -1024, SEEK_END) < 0)
{
_pdfioFileError(pdf, "Unable to read startxref data.");
goto error;
}
if (_pdfioFileRead(pdf, line, 32) < 32)
if ((bytes = _pdfioFileRead(pdf, line, sizeof(line) - 1)) < 1)
{
_pdfioFileError(pdf, "Unable to read startxref data.");
goto error;
}
line[32] = '\0';
if ((ptr = strstr(line, "startxref")) == NULL)
line[bytes] = '\0';
end = line + bytes - 9;
for (ptr = line; ptr < end; ptr ++)
{
if (!memcmp(ptr, "startxref", 9))
break;
}
if (ptr >= end)
{
_pdfioFileError(pdf, "Unable to find start of xref table.");
goto error;
@ -1407,7 +1417,7 @@ add_obj(pdfio_file_t *pdf, // I - PDF file
obj->generation = generation;
obj->offset = offset;
PDFIO_DEBUG("add_obj: obj=%p, ->pdf=%p, ->number=%lu\n", obj, pdf, (unsigned long)obj->number);
PDFIO_DEBUG("add_obj: obj=%p, ->pdf=%p, ->number=%lu, ->offset=%lu\n", obj, pdf, (unsigned long)obj->number, (unsigned long)offset);
// Re-sort object array as needed...
if (pdf->num_objs > 1 && pdf->objs[pdf->num_objs - 2]->number > number)
@ -1976,22 +1986,31 @@ load_xref(
else if (!strncmp(line, "xref", 4) && (!line[4] || isspace(line[4] & 255)))
{
// Read the xref tables
off_t trailer_offset = _pdfioFileTell(pdf);
// Offset of current line
PDFIO_DEBUG("load_xref: Reading xref table starting at offset %lu\n", (unsigned long)trailer_offset);
while (_pdfioFileGets(pdf, line, sizeof(line)))
{
PDFIO_DEBUG("load_xref: '%s' at offset %lu\n", line, (unsigned long)trailer_offset);
if (!strncmp(line, "trailer", 7) && (!line[7] || isspace(line[7] & 255)))
{
if (line[7])
{
// Probably the start of the trailer dictionary, rewind the file so
// we can read it...
_pdfioFileSeek(pdf, 7 - strlen(line), SEEK_CUR);
_pdfioFileSeek(pdf, trailer_offset + 7, SEEK_SET);
}
break;
}
else if (!line[0])
else
{
continue;
trailer_offset = _pdfioFileTell(pdf);
if (!line[0])
continue;
}
if (sscanf(line, "%jd%jd", &number, &num_objects) != 2)
@ -2052,6 +2071,8 @@ load_xref(
if (!add_obj(pdf, (size_t)number, (unsigned short)generation, offset))
return (false);
}
trailer_offset = _pdfioFileTell(pdf);
}
if (strncmp(line, "trailer", 7))