Y2K compliance in libpng:+
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   =========================+
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+
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      September 10, 2009+
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+
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      Since the PNG Development group is an ad-hoc body, we can't make+
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      an official declaration.+
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+
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      This is your unofficial assurance that libpng from version 0.71 and+
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      upward through 1.2.40 are Y2K compliant.  It is my belief that earlier+
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      versions were also Y2K compliant.+
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+
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      Libpng only has three year fields.  One is a 2-byte unsigned integer+
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      that will hold years up to 65535.  The other two hold the date in text+
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      format, and will hold years up to 9999.+
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+
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      The integer is+
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          "png_uint_16 year" in png_time_struct.+
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+
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      The strings are+
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          "png_charp time_buffer" in png_struct and+
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          "near_time_buffer", which is a local character string in png.c.+
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+
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      There are seven time-related functions:+
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+
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          png_convert_to_rfc_1123() in png.c+
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            (formerly png_convert_to_rfc_1152() in error)+
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          png_convert_from_struct_tm() in pngwrite.c, called in pngwrite.c+
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          png_convert_from_time_t() in pngwrite.c+
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          png_get_tIME() in pngget.c+
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          png_handle_tIME() in pngrutil.c, called in pngread.c+
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          png_set_tIME() in pngset.c+
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          png_write_tIME() in pngwutil.c, called in pngwrite.c+
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+
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      All appear to handle dates properly in a Y2K environment.  The+
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      png_convert_from_time_t() function calls gmtime() to convert from system+
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      clock time, which returns (year - 1900), which we properly convert to+
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      the full 4-digit year.  There is a possibility that applications using+
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      libpng are not passing 4-digit years into the png_convert_to_rfc_1123()+
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      function, or that they are incorrectly passing only a 2-digit year+
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      instead of "year - 1900" into the png_convert_from_struct_tm() function,+
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      but this is not under our control.  The libpng documentation has always+
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      stated that it works with 4-digit years, and the APIs have been+
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      documented as such.+
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+
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      The tIME chunk itself is also Y2K compliant.  It uses a 2-byte unsigned+
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      integer to hold the year, and can hold years as large as 65535.+
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+
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      zlib, upon which libpng depends, is also Y2K compliant.  It contains+
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      no date-related code.+
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+
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+
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         Glenn Randers-Pehrson+
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         libpng maintainer+
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         PNG Development Group+
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