Update libjpeg from 6b to 8b.
[reactos.git] / rosapps / lib / libpng / docs / Y2KINFO
1 Y2K compliance in libpng:
2 =========================
3
4 December 14, 2007
5
6 Since the PNG Development group is an ad-hoc body, we can't make
7 an official declaration.
8
9 This is your unofficial assurance that libpng from version 0.71 and
10 upward through 1.2.24 are Y2K compliant. It is my belief that earlier
11 versions were also Y2K compliant.
12
13 Libpng only has three year fields. One is a 2-byte unsigned integer
14 that will hold years up to 65535. The other two hold the date in text
15 format, and will hold years up to 9999.
16
17 The integer is
18 "png_uint_16 year" in png_time_struct.
19
20 The strings are
21 "png_charp time_buffer" in png_struct and
22 "near_time_buffer", which is a local character string in png.c.
23
24 There are seven time-related functions:
25
26 png_convert_to_rfc_1123() in png.c
27 (formerly png_convert_to_rfc_1152() in error)
28 png_convert_from_struct_tm() in pngwrite.c, called in pngwrite.c
29 png_convert_from_time_t() in pngwrite.c
30 png_get_tIME() in pngget.c
31 png_handle_tIME() in pngrutil.c, called in pngread.c
32 png_set_tIME() in pngset.c
33 png_write_tIME() in pngwutil.c, called in pngwrite.c
34
35 All appear to handle dates properly in a Y2K environment. The
36 png_convert_from_time_t() function calls gmtime() to convert from system
37 clock time, which returns (year - 1900), which we properly convert to
38 the full 4-digit year. There is a possibility that applications using
39 libpng are not passing 4-digit years into the png_convert_to_rfc_1123()
40 function, or that they are incorrectly passing only a 2-digit year
41 instead of "year - 1900" into the png_convert_from_struct_tm() function,
42 but this is not under our control. The libpng documentation has always
43 stated that it works with 4-digit years, and the APIs have been
44 documented as such.
45
46 The tIME chunk itself is also Y2K compliant. It uses a 2-byte unsigned
47 integer to hold the year, and can hold years as large as 65535.
48
49 zlib, upon which libpng depends, is also Y2K compliant. It contains
50 no date-related code.
51
52
53 Glenn Randers-Pehrson
54 libpng maintainer
55 PNG Development Group