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[libpng16] Allow fine grain control of unknown chunk APIs. This change allows

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png_set_keep_unknown_chunks() to be turned off if not required and causes
both read and write to behave appropriately (on read this is only possible
if the user callback is used to handle unknown chunks).  The change
also removes the support for storing unknown chunks in the info_struct
if the only unknown handling enabled is via the callback, allowing libpng
to be configured with callback reading and none of the unnecessary code.
This commit is contained in:
John Bowler
2012-08-16 16:12:13 -05:00
committed by Glenn Randers-Pehrson
parent 025d415838
commit 4a6c6df6c7
7 changed files with 74 additions and 20 deletions
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29
scripts/pnglibconf.dfa
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@@ -647,13 +647,13 @@ option UNKNOWN_CHUNKS
# set by png_set_unknown_chunks will be written otherwise it is an error to call
# that API on a write struct.
option WRITE_UNKNOWN_CHUNKS requires WRITE requires UNKNOWN_CHUNKS
option WRITE_UNKNOWN_CHUNKS enables STORE_UNKNOWN_CHUNKS SET_UNKNOWN_CHUNKS
option WRITE_UNKNOWN_CHUNKS enables STORE_UNKNOWN_CHUNKS
# The first way to read user chunks is to have libpng save them for a later call
# to png_get_unknown_chunks, the application must call
# png_set_keep_unknown_chunks to cause this to actually happen (see png.h)
option SAVE_UNKNOWN_CHUNKS requires READ requires UNKNOWN_CHUNKS
option SAVE_UNKNOWN_CHUNKS enables READ_UNKNOWN_CHUNKS
option SAVE_UNKNOWN_CHUNKS requires READ requires SET_UNKNOWN_CHUNKS
option SAVE_UNKNOWN_CHUNKS enables READ_UNKNOWN_CHUNKS STORE_UNKNOWN_CHUNKS
# The second approach is to use an application provided callback to process the
# chunks, the callback can either handle the chunk entirely itself or request
@@ -664,23 +664,26 @@ option SAVE_UNKNOWN_CHUNKS enables READ_UNKNOWN_CHUNKS
option READ_USER_CHUNKS requires READ requires UNKNOWN_CHUNKS
option READ_USER_CHUNKS enables READ_UNKNOWN_CHUNKS USER_CHUNKS
# A further option allows known chunks to be handled using the unknown code by
# providing the relevant chunks to png_set_keep_unknown_chunks. This is turned
# on by the following option. In 1.6.0 turning this option *off* no longer
# disables png_set_keep_unknown_chunks, a behavior which effectively prevented
# unknown chunk saving by the first mechanism on read.
# Two further options are provided to allow detailed control of the handling.
# The first enables png_set_keep_unknown_chunks; this allows the default to be
# changed from discarding unknown chunks and allows per-chunk control. This is
# required to use the SAVE_UNKNOWN_CHUNKS option. If enabled this option also
# applies to write (see png.h), otherwise the write API simply writes all the
# chunks it is given.
#
# Notice that this option no longer affects the write code either. It can be
# safely disabled and will prevent applications stopping libpng reading known
# chunks.
# The second option extends the unknown handling to allow known chunks to be
# handled as though they were unknown. This option doesn't change any APIs, it
# merely turns on the code to check known as well as unknown chunks.
#
# This option no longer affects the write code. It can be safely disabled and
# will prevent applications stopping libpng reading known chunks.
option SET_UNKNOWN_CHUNKS requires UNKNOWN_CHUNKS
option HANDLE_AS_UNKNOWN requires SET_UNKNOWN_CHUNKS
# The following options are derived from the above and should not be turned on
# explicitly.
option READ_UNKNOWN_CHUNKS requires UNKNOWN_CHUNKS disabled
option READ_UNKNOWN_CHUNKS enables STORE_UNKNOWN_CHUNKS SET_UNKNOWN_CHUNKS
option STORE_UNKNOWN_CHUNKS requires UNKNOWN_CHUNKS disabled
option SET_UNKNOWN_CHUNKS requires UNKNOWN_CHUNKS disabled
option CONVERT_tIME requires WRITE_ANCILLARY_CHUNKS
# The "tm" structure is not supported on WindowsCE