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authorTimothy Pearson <kb9vqf@pearsoncomputing.net>2011-11-08 12:31:36 -0600
committerTimothy Pearson <kb9vqf@pearsoncomputing.net>2011-11-08 12:31:36 -0600
commitd796c9dd933ab96ec83b9a634feedd5d32e1ba3f (patch)
tree6e3dcca4f77e20ec8966c666aac7c35bd4704053 /src/3rdparty/libpng/Y2KINFO
downloadtqt3-d796c9dd933ab96ec83b9a634feedd5d32e1ba3f.tar.gz
tqt3-d796c9dd933ab96ec83b9a634feedd5d32e1ba3f.zip
Test conversion to TQt3 from Qt3 8c6fc1f8e35fd264dd01c582ca5e7549b32ab731
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+ Y2K compliance in libpng:
+ =========================
+
+ October 3, 2002
+
+ Since the PNG Development group is an ad-hoc body, we can't make
+ an official declaration.
+
+ This is your unofficial assurance that libpng from version 0.71 and
+ upward through 1.2.5 are Y2K compliant. It is my belief that earlier
+ versions were also Y2K compliant.
+
+ Libpng only has three year fields. One is a 2-byte unsigned integer
+ that will hold years up to 65535. The other two hold the date in text
+ format, and will hold years up to 9999.
+
+ The integer is
+ "png_uint_16 year" in png_time_struct.
+
+ The strings are
+ "png_charp time_buffer" in png_struct and
+ "near_time_buffer", which is a local character string in png.c.
+
+ There are seven time-related functions:
+
+ png_convert_to_rfc_1123() in png.c
+ (formerly png_convert_to_rfc_1152() in error)
+ png_convert_from_struct_tm() in pngwrite.c, called in pngwrite.c
+ png_convert_from_time_t() in pngwrite.c
+ png_get_tIME() in pngget.c
+ png_handle_tIME() in pngrutil.c, called in pngread.c
+ png_set_tIME() in pngset.c
+ png_write_tIME() in pngwutil.c, called in pngwrite.c
+
+ All appear to handle dates properly in a Y2K environment. The
+ png_convert_from_time_t() function calls gmtime() to convert from system
+ clock time, which returns (year - 1900), which we properly convert to
+ the full 4-digit year. There is a possibility that applications using
+ libpng are not passing 4-digit years into the png_convert_to_rfc_1123()
+ function, or that they are incorrectly passing only a 2-digit year
+ instead of "year - 1900" into the png_convert_from_struct_tm() function,
+ but this is not under our control. The libpng documentation has always
+ stated that it works with 4-digit years, and the APIs have been
+ documented as such.
+
+ The tIME chunk itself is also Y2K compliant. It uses a 2-byte unsigned
+ integer to hold the year, and can hold years as large as 65535.
+
+ zlib, upon which libpng depends, is also Y2K compliant. It contains
+ no date-related code.
+
+
+ Glenn Randers-Pehrson
+ libpng maintainer
+ PNG Development Group