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[libpng16] Unknown handling fixes and clean up. This adds more correct option

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control of the unknown handling, corrects the pre-existing bug where
the per-chunk 'keep' setting is ignored and makes it possible to skip
IDAT chunks in the sequential reader (broken in earlier 1.6 versions).
There is a new test program, test-unknown.c, which is a work in progress
(not currently part of the test suite).  Comments in the header files now
explain how the unknown handling works.
This commit is contained in:
John Bowler
2012-08-15 22:53:00 -05:00
committed by Glenn Randers-Pehrson
parent b593b3f035
commit e9567514dd
15 changed files with 1498 additions and 443 deletions
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131
pngwrite.c
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@@ -18,6 +18,54 @@
#ifdef PNG_WRITE_SUPPORTED
#ifdef PNG_WRITE_UNKNOWN_CHUNKS_SUPPORTED
/* Write out all the unknown chunks for the current given location */
static void
write_unknown_chunks(png_structrp png_ptr, png_const_inforp info_ptr,
unsigned int where)
{
if (info_ptr->unknown_chunks_num)
{
png_const_unknown_chunkp up;
png_debug(5, "writing extra chunks");
for (up = info_ptr->unknown_chunks;
up < info_ptr->unknown_chunks + info_ptr->unknown_chunks_num;
++up)
if (up->location & where)
{
int keep = png_handle_as_unknown(png_ptr, up->name);
/* NOTE: this code is radically different from the read side in the
* matter of handling an ancilliary unknown chunk. In the read side
* the default behavior is to discard it, in the code below the default
* behavior is to write it. Critical chunks are, however, only
* written if explicitly listed or if the default is set to write all
* unknown chunks.
*
* The default handling is also slightly weird - it is not possible to
* stop the writing of all unsafe-to-copy chunks!
*
* TODO: REVIEW: this would seem to be a bug.
*/
if (keep != PNG_HANDLE_CHUNK_NEVER &&
((up->name[3] & 0x20) /* safe-to-copy overrides everything */ ||
keep == PNG_HANDLE_CHUNK_ALWAYS ||
(keep == PNG_HANDLE_CHUNK_AS_DEFAULT &&
png_ptr->unknown_default == PNG_HANDLE_CHUNK_ALWAYS)))
{
/* TODO: review, what is wrong with a zero length unknown chunk? */
if (up->size == 0)
png_warning(png_ptr, "Writing zero-length unknown chunk");
png_write_chunk(png_ptr, up->name, up->data, up->size);
}
}
}
}
#endif /* PNG_WRITE_UNKNOWN_CHUNKS_SUPPORTED */
/* Writes all the PNG information. This is the suggested way to use the
* library. If you have a new chunk to add, make a function to write it,
* and put it in the correct location here. If you want the chunk written
@@ -54,10 +102,12 @@ png_write_info_before_PLTE(png_structrp png_ptr, png_const_inforp info_ptr)
info_ptr->bit_depth, info_ptr->color_type, info_ptr->compression_type,
info_ptr->filter_type,
#ifdef PNG_WRITE_INTERLACING_SUPPORTED
info_ptr->interlace_type);
info_ptr->interlace_type
#else
0);
0
#endif
);
/* The rest of these check to see if the valid field has the appropriate
* flag set, and if it does, writes the chunk.
*
@@ -125,34 +175,9 @@ png_write_info_before_PLTE(png_structrp png_ptr, png_const_inforp info_ptr)
#endif
#ifdef PNG_WRITE_UNKNOWN_CHUNKS_SUPPORTED
if (info_ptr->unknown_chunks_num)
{
png_unknown_chunk *up;
png_debug(5, "writing extra chunks");
for (up = info_ptr->unknown_chunks;
up < info_ptr->unknown_chunks + info_ptr->unknown_chunks_num;
up++)
{
int keep = png_handle_as_unknown(png_ptr, up->name);
if (keep != PNG_HANDLE_CHUNK_NEVER &&
up->location &&
!(up->location & PNG_HAVE_PLTE) &&
!(up->location & PNG_HAVE_IDAT) &&
!(up->location & PNG_AFTER_IDAT) &&
((up->name[3] & 0x20) || keep == PNG_HANDLE_CHUNK_ALWAYS ||
(png_ptr->flags & PNG_FLAG_KEEP_UNSAFE_CHUNKS)))
{
if (up->size == 0)
png_warning(png_ptr, "Writing zero-length unknown chunk");
png_write_chunk(png_ptr, up->name, up->data, up->size);
}
}
}
write_unknown_chunks(png_ptr, info_ptr, PNG_HAVE_IHDR);
#endif
png_ptr->mode |= PNG_WROTE_INFO_BEFORE_PLTE;
}
}
@@ -302,29 +327,7 @@ png_write_info(png_structrp png_ptr, png_const_inforp info_ptr)
#endif /* tEXt */
#ifdef PNG_WRITE_UNKNOWN_CHUNKS_SUPPORTED
if (info_ptr->unknown_chunks_num)
{
png_unknown_chunk *up;
png_debug(5, "writing extra chunks");
for (up = info_ptr->unknown_chunks;
up < info_ptr->unknown_chunks + info_ptr->unknown_chunks_num;
up++)
{
int keep = png_handle_as_unknown(png_ptr, up->name);
if (keep != PNG_HANDLE_CHUNK_NEVER &&
up->location &&
(up->location & PNG_HAVE_PLTE) &&
!(up->location & PNG_HAVE_IDAT) &&
!(up->location & PNG_AFTER_IDAT) &&
((up->name[3] & 0x20) || keep == PNG_HANDLE_CHUNK_ALWAYS ||
(png_ptr->flags & PNG_FLAG_KEEP_UNSAFE_CHUNKS)))
{
png_write_chunk(png_ptr, up->name, up->data, up->size);
}
}
}
write_unknown_chunks(png_ptr, info_ptr, PNG_HAVE_PLTE);
#endif
}
@@ -416,27 +419,7 @@ png_write_end(png_structrp png_ptr, png_inforp info_ptr)
}
#endif
#ifdef PNG_WRITE_UNKNOWN_CHUNKS_SUPPORTED
if (info_ptr->unknown_chunks_num)
{
png_unknown_chunk *up;
png_debug(5, "writing extra chunks");
for (up = info_ptr->unknown_chunks;
up < info_ptr->unknown_chunks + info_ptr->unknown_chunks_num;
up++)
{
int keep = png_handle_as_unknown(png_ptr, up->name);
if (keep != PNG_HANDLE_CHUNK_NEVER &&
up->location &&
(up->location & PNG_AFTER_IDAT) &&
((up->name[3] & 0x20) || keep == PNG_HANDLE_CHUNK_ALWAYS ||
(png_ptr->flags & PNG_FLAG_KEEP_UNSAFE_CHUNKS)))
{
png_write_chunk(png_ptr, up->name, up->data, up->size);
}
}
}
write_unknown_chunks(png_ptr, info_ptr, PNG_AFTER_IDAT);
#endif
}
@@ -889,7 +872,7 @@ png_write_destroy(png_structrp png_ptr)
png_free(png_ptr, png_ptr->inv_filter_costs);
#endif
#ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
#ifdef PNG_UNKNOWN_CHUNKS_SUPPORTED
png_free(png_ptr, png_ptr->chunk_list);
#endif