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Fix implementation of LZWDecode filter to account for the EarlyChange parameter

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(somewhat buried, very frustrating...)

Add some debugging and update the test suite to find page metadata in any parent
page object.
This commit is contained in:
Michael R Sweet
2026-01-16 15:57:43 -05:00
parent e6e0b84dfc
commit 65098b5509
5 changed files with 74 additions and 26 deletions
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27
pdfio-lzw.c
View File

@@ -28,7 +28,8 @@ static int lzw_get_code(_pdfio_lzw_t *lzw);
//
_pdfio_lzw_t * // O - LZW state
_pdfioLZWCreate(int code_size) // I - Data code size in bits (typically 8 for PDF, 2-8 for GIF)
_pdfioLZWCreate(int code_size, // I - Data code size in bits (typically 8 for PDF, 2-8 for GIF)
int early) // I - Number of early codes
{
_pdfio_lzw_t *lzw; // LZW state
@@ -38,6 +39,7 @@ _pdfioLZWCreate(int code_size) // I - Data code size in bits (typically 8 for P
lzw->def_code_size = code_size + 1;
lzw->clear_code = (short)(1 << code_size);
lzw->eod_code = lzw->clear_code + 1;
lzw->early = early;
lzw_clear(lzw);
}
@@ -81,6 +83,7 @@ _pdfioLZWInflate(_pdfio_lzw_t *lzw) // I - LZW state
{
*(lzw->next_out++) = *(--lzw->stptr);
lzw->avail_out --;
PDFIO_DEBUG("_pdfioLZWInflate: Unrolled value %d, stptr=%p(%ld), avail_out=%u\n", *(lzw->stptr), (void *)lzw->stptr, lzw->stptr - lzw->stack, (unsigned)lzw->avail_out);
}
// Loop as long as we have room in the output buffer and data in the input
@@ -121,19 +124,20 @@ _pdfioLZWInflate(_pdfio_lzw_t *lzw) // I - LZW state
continue;
}
PDFIO_DEBUG("_pdfioLZWInflate: in_code=%d.\n", in_code);
PDFIO_DEBUG("_pdfioLZWInflate: in_code=%d, old_code=%d.\n", in_code, lzw->old_code);
cur_code = in_code;
if (cur_code >= lzw->next_code)
{
PDFIO_DEBUG("_pdfioLZWInflate: New cur_code=%d, next_code=%d\n", cur_code, lzw->next_code);
*(lzw->stptr++) = lzw->first_code;
cur_code = lzw->old_code;
}
while (cur_code >= lzw->clear_code)
{
PDFIO_DEBUG("_pdfioLZWInflate: cur_code=%d\n", cur_code);
PDFIO_DEBUG("_pdfioLZWInflate: cur_code=%d (%d,%d)\n", cur_code, lzw->table[cur_code].prefix_code, lzw->table[cur_code].suffix);
// Protect against overflow/loops...
if (lzw->stptr >= (lzw->stack + sizeof(lzw->stack) / sizeof(lzw->stack[0])))
@@ -168,16 +172,17 @@ _pdfioLZWInflate(_pdfio_lzw_t *lzw) // I - LZW state
if ((cur_code = lzw->next_code) < 4096)
{
PDFIO_DEBUG("_pdfioLZWInflate: Adding code %d (%d,%d)\n", cur_code, lzw->old_code, lzw->first_code);
PDFIO_DEBUG("_pdfioLZWInflate: Adding code %d (%d,%d), next_size_code=%d\n", cur_code, lzw->old_code, lzw->first_code, lzw->next_size_code);
lzw->table[cur_code].prefix_code = lzw->old_code;
lzw->table[cur_code].suffix = lzw->first_code;
lzw->next_code ++;
if (lzw->next_code >= lzw->next_size_code && lzw->next_size_code < 4096)
if (lzw->next_code >= lzw->next_size_code && lzw->cur_code_size < 12)
{
lzw->next_size_code *= 2;
lzw->cur_code_size ++;
lzw->next_size_code = (1 << lzw->cur_code_size) - lzw->early;
PDFIO_DEBUG("_pdfioLZWInflate: Increased code size to %u, next_size_code=%u\n", lzw->cur_code_size, lzw->next_size_code);
}
}
@@ -187,6 +192,7 @@ _pdfioLZWInflate(_pdfio_lzw_t *lzw) // I - LZW state
{
*(lzw->next_out++) = *(--lzw->stptr);
lzw->avail_out --;
PDFIO_DEBUG("_pdfioLZWInflate: Unrolled value %d, stptr=%p(%ld), avail_out=%u\n", *(lzw->stptr), (void *)lzw->stptr, lzw->stptr - lzw->stack, (unsigned)lzw->avail_out);
}
}
@@ -208,7 +214,7 @@ lzw_clear(_pdfio_lzw_t *lzw) // I - LZW state
lzw->cur_code_size = lzw->def_code_size;
lzw->next_code = lzw->clear_code + 2;
lzw->next_size_code = 2 * lzw->clear_code;
lzw->next_size_code = (1 << lzw->cur_code_size) - lzw->early;
lzw->first_code = 0xffff;
lzw->old_code = 0xffff;
@@ -281,7 +287,7 @@ lzw_get_code(_pdfio_lzw_t *lzw) // I - LZW state
}
}
PDFIO_DEBUG("lzw_get_code: in_bit=%u, in_bits=%u, in_bytes=<...%02X%02X...>, cur_code_size=%u\n", lzw->in_bit, lzw->in_bits, lzw->in_bytes[lzw->in_bit / 8], lzw->in_bytes[lzw->in_bit / 8 + 1], lzw->cur_code_size);
PDFIO_DEBUG("lzw_get_code: in_bit=%u, in_bits=%u, in_bytes=<...%02X%02X%02X...>, cur_code_size=%u\n", lzw->in_bit, lzw->in_bits, lzw->in_bytes[lzw->in_bit / 8], lzw->in_bytes[lzw->in_bit / 8 + 1], lzw->in_bytes[lzw->in_bit / 8 + 2], lzw->cur_code_size);
// Now extract the code from the buffer...
for (code = 0, in_bit = lzw->in_bit, remaining = lzw->cur_code_size; remaining > 0; in_bit += bits, remaining -= bits)
@@ -303,7 +309,12 @@ lzw_get_code(_pdfio_lzw_t *lzw) // I - LZW state
// Save the updated position in the input buffer and return the code...
lzw->in_bit = in_bit;
#ifdef DEBUG
if (code >= 0x20 && code < 0x7f)
PDFIO_DEBUG("lzw_get_code: Returning %u('%c').\n", code, code);
else
PDFIO_DEBUG("lzw_get_code: Returning %u.\n", code);
#endif // DEBUG
return ((int)code);
}

16
pdfio-page.c
View File

@@ -1,7 +1,7 @@
//
// PDF page functions for PDFio.
//
// Copyright © 2021-2022 by Michael R Sweet.
// Copyright © 2021-2026 by Michael R Sweet.
//
// Licensed under Apache License v2.0. See the file "LICENSE" for more
// information.
@@ -87,14 +87,28 @@ pdfioPageOpenStream(
// Contents value
PDFIO_DEBUG("pdfioPageOpenStream(page=%p(%lu), n=%lu, decode=%s)\n", (void *)page, page ? (unsigned long)page->number : 0, (unsigned long)n, decode ? "true" : "false");
if (!contents)
{
PDFIO_DEBUG("pdfioPageOpenStream: No contents.\n");
return (NULL);
}
else if (contents->type == PDFIO_VALTYPE_ARRAY && n < pdfioArrayGetSize(contents->value.array))
{
PDFIO_DEBUG("pdfioPageOpenStream: Contents is array, opening numbered content stream.\n");
return (pdfioObjOpenStream(pdfioArrayGetObj(contents->value.array, n), decode));
}
else if (n)
{
PDFIO_DEBUG("pdfioPageOpenStream: Numbered stream does not exist.\n");
return (NULL);
}
else
{
PDFIO_DEBUG("pdfioPageOpenStream: Opening single content stream.\n");
return (pdfioObjOpenStream(pdfioFileFindObj(page->pdf, contents->value.indirect.number), decode));
}
}

5
pdfio-private.h
View File

@@ -227,7 +227,8 @@ typedef struct _pdfio_lzw_s // LZW state
uint8_t *next_out; // Next output byte
size_t avail_out; // Available output bytes
uint8_t cur_code_size, // Current code size
def_code_size; // Initial/default code size
def_code_size, // Initial/default code size
early; // Early code change offset
uint16_t clear_code, // Clear code
eod_code, // End code
next_code, // Next code to be used
@@ -451,7 +452,7 @@ extern off_t _pdfioFileSeek(pdfio_file_t *pdf, off_t offset, int whence) _PDFIO
extern off_t _pdfioFileTell(pdfio_file_t *pdf) _PDFIO_INTERNAL;
extern bool _pdfioFileWrite(pdfio_file_t *pdf, const void *buffer, size_t bytes) _PDFIO_INTERNAL;
extern _pdfio_lzw_t *_pdfioLZWCreate(int def_code_size) _PDFIO_INTERNAL;
extern _pdfio_lzw_t *_pdfioLZWCreate(int def_code_size, int early) _PDFIO_INTERNAL;
extern void _pdfioLZWDelete(_pdfio_lzw_t *lzw) _PDFIO_INTERNAL;
extern bool _pdfioLZWInflate(_pdfio_lzw_t *lzw) _PDFIO_INTERNAL;

20
pdfio-stream.c
View File

@@ -610,7 +610,7 @@ _pdfioStreamOpen(pdfio_obj_t *obj, // I - Object
st->cbsize = 4096;
if ((st->cbuffer = malloc(st->cbsize)) == NULL)
{
_pdfioFileError(st->pdf, "Unable to allocate %lu bytes for Flate compression buffer.", (unsigned long)st->cbsize);
_pdfioFileError(st->pdf, "Unable to allocate %lu bytes for FlateDecode decompression buffer.", (unsigned long)st->cbsize);
goto error;
}
@@ -633,16 +633,28 @@ _pdfioStreamOpen(pdfio_obj_t *obj, // I - Object
if ((status = inflateInit(&(st->flate))) != Z_OK)
{
_pdfioFileError(st->pdf, "Unable to start Flate filter: %s", zstrerror(status));
_pdfioFileError(st->pdf, "Unable to start FlateDecode filter: %s", zstrerror(status));
goto error;
}
}
else
{
// LZW decompression...
if ((st->lzw = _pdfioLZWCreate(/*code_size*/8)) == NULL)
int early = 1;
if (pdfioDictGetType(params, "EarlyChange") == PDFIO_VALTYPE_NUMBER)
{
_pdfioFileError(st->pdf, "Unable to initialize LZW filter: %s", strerror(errno));
early = (int)pdfioDictGetNumber(params, "EarlyChange");
if (early < 0 || early > 100)
{
_pdfioFileError(st->pdf, "Bad EarlyChange value %d for LZWDecode filter.", early);
goto error;
}
}
if ((st->lzw = _pdfioLZWCreate(/*code_size*/8, early)) == NULL)
{
_pdfioFileError(st->pdf, "Unable to initialize LZWDecode filter: %s", strerror(errno));
goto error;
}

30
testpdfio.c
View File

@@ -12,6 +12,7 @@
//
// Options:
//
// --decode Decode object stream
// --help Show help
// --password PASSWORD Set access password
// --verbose Be verbose
@@ -34,7 +35,7 @@
static int do_crypto_tests(void);
static int do_lzw_tests(void);
static int do_pdfa_tests(void);
static int do_test_file(const char *filename, const char *outfile, int objnum, const char *password, bool verbose);
static int do_test_file(const char *filename, const char *outfile, int objnum, const char *password, bool decode, bool verbose);
static int do_unit_tests(void);
static int draw_image(pdfio_stream_t *st, const char *name, double x, double y, double w, double h, const char *label);
static bool error_cb(pdfio_file_t *pdf, const char *message, bool *error);
@@ -75,11 +76,16 @@ main(int argc, // I - Number of command-line arguments
{
int i; // Looping var
const char *password = NULL; // Password
bool verbose = false; // Be verbose?
bool decode = false, // Decode object stream?
verbose = false; // Be verbose?
for (i = 1; i < argc; i ++)
{
if (!strcmp(argv[i], "--help"))
if (!strcmp(argv[i], "--decode"))
{
decode = true;
}
else if (!strcmp(argv[i], "--help"))
{
return (usage(stdout));
}
@@ -108,14 +114,14 @@ main(int argc, // I - Number of command-line arguments
else if ((i + 1) < argc && isdigit(argv[i + 1][0] & 255))
{
// filename.pdf object-number
if (do_test_file(argv[i], /*outfile*/NULL, atoi(argv[i + 1]), password, verbose))
if (do_test_file(argv[i], /*outfile*/NULL, atoi(argv[i + 1]), password, decode, verbose))
ret = 1;
i ++;
}
else
{
if (do_test_file(argv[i], argv[i + 1], /*objnum*/0, password, verbose))
if (do_test_file(argv[i], argv[i + 1], /*objnum*/0, password, decode, verbose))
ret = 1;
if (argv[i + 1])
@@ -405,7 +411,7 @@ do_lzw_tests(void)
testBegin("_pdfioLZWCreate(8)");
testEnd((lzw = _pdfioLZWCreate(/*code_size*/8)) != NULL);
testEnd((lzw = _pdfioLZWCreate(/*code_size*/8, /*early*/1)) != NULL);
if (!lzw)
return (1);
@@ -538,6 +544,7 @@ do_test_file(const char *filename, // I - PDF filename
const char *outfile, // I - Output filename, if any
int objnum, // I - Object number to dump, if any
const char *password, // I - Password for file
bool decode, // I - Decode object?
bool verbose) // I - Be verbose?
{
int status = 0; // Exit status
@@ -586,7 +593,7 @@ do_test_file(const char *filename, // I - PDF filename
filter = pdfioDictGetName(dict, "Filter");
if ((st = pdfioObjOpenStream(obj, filter && !strcmp(filter, "FlateDecode"))) == NULL)
if ((st = pdfioObjOpenStream(obj, decode || (filter && !strcmp(filter, "FlateDecode")))) == NULL)
{
_pdfioValueDebug(&obj->value, stdout);
putchar('\n');
@@ -655,10 +662,13 @@ do_test_file(const char *filename, // I - PDF filename
if (!pdfioDictGetRect(dict, "MediaBox", &media_box))
{
if ((obj = pdfioDictGetObj(dict, "Parent")) != NULL)
pdfio_obj_t *parent; // Parent object
while ((parent = pdfioDictGetObj(dict, "Parent")) != NULL)
{
dict = pdfioObjGetDict(obj);
pdfioDictGetRect(dict, "MediaBox", &media_box);
dict = pdfioObjGetDict(parent);
if (pdfioDictGetRect(dict, "MediaBox", &media_box))
break;
}
}