Mercurial > fife-parpg

annotate ext/libpng-1.2.29/Y2KINFO @ 357:2cdce58c1109

Find changesets by keywords (author, files, the commit message), revision number or hash, or revset expression.
Fixes the scroll areas in the pychan demo. fixes[t:363]
author prock@33b003aa-7bff-0310-803a-e67f0ece8222
date Fri, 25 Sep 2009 19:48:07 +0000
parents 4a0efb7baf70
children
rev   line source
0
4a0efb7baf70 * Datasets becomes the new trunk and retires after that :-)
mvbarracuda@33b003aa-7bff-0310-803a-e67f0ece8222
parents:
diff changeset
1 Y2K compliance in libpng:
4a0efb7baf70 * Datasets becomes the new trunk and retires after that :-)
mvbarracuda@33b003aa-7bff-0310-803a-e67f0ece8222
parents:
diff changeset
2 =========================
4a0efb7baf70 * Datasets becomes the new trunk and retires after that :-)
mvbarracuda@33b003aa-7bff-0310-803a-e67f0ece8222
parents:
diff changeset
3
4a0efb7baf70 * Datasets becomes the new trunk and retires after that :-)
mvbarracuda@33b003aa-7bff-0310-803a-e67f0ece8222
parents:
diff changeset
4 May 8, 2008
4a0efb7baf70 * Datasets becomes the new trunk and retires after that :-)
mvbarracuda@33b003aa-7bff-0310-803a-e67f0ece8222
parents:
diff changeset
5
4a0efb7baf70 * Datasets becomes the new trunk and retires after that :-)
mvbarracuda@33b003aa-7bff-0310-803a-e67f0ece8222
parents:
diff changeset
6 Since the PNG Development group is an ad-hoc body, we can't make
4a0efb7baf70 * Datasets becomes the new trunk and retires after that :-)
mvbarracuda@33b003aa-7bff-0310-803a-e67f0ece8222
parents:
diff changeset
7 an official declaration.
4a0efb7baf70 * Datasets becomes the new trunk and retires after that :-)
mvbarracuda@33b003aa-7bff-0310-803a-e67f0ece8222
parents:
diff changeset
8
4a0efb7baf70 * Datasets becomes the new trunk and retires after that :-)
mvbarracuda@33b003aa-7bff-0310-803a-e67f0ece8222
parents:
diff changeset
9 This is your unofficial assurance that libpng from version 0.71 and
4a0efb7baf70 * Datasets becomes the new trunk and retires after that :-)
mvbarracuda@33b003aa-7bff-0310-803a-e67f0ece8222
parents:
diff changeset
10 upward through 1.2.29 are Y2K compliant. It is my belief that earlier
4a0efb7baf70 * Datasets becomes the new trunk and retires after that :-)
mvbarracuda@33b003aa-7bff-0310-803a-e67f0ece8222
parents:
diff changeset
11 versions were also Y2K compliant.
4a0efb7baf70 * Datasets becomes the new trunk and retires after that :-)
mvbarracuda@33b003aa-7bff-0310-803a-e67f0ece8222
parents:
diff changeset
12
4a0efb7baf70 * Datasets becomes the new trunk and retires after that :-)
mvbarracuda@33b003aa-7bff-0310-803a-e67f0ece8222
parents:
diff changeset
13 Libpng only has three year fields. One is a 2-byte unsigned integer
4a0efb7baf70 * Datasets becomes the new trunk and retires after that :-)
mvbarracuda@33b003aa-7bff-0310-803a-e67f0ece8222
parents:
diff changeset
14 that will hold years up to 65535. The other two hold the date in text
4a0efb7baf70 * Datasets becomes the new trunk and retires after that :-)
mvbarracuda@33b003aa-7bff-0310-803a-e67f0ece8222
parents:
diff changeset
15 format, and will hold years up to 9999.
4a0efb7baf70 * Datasets becomes the new trunk and retires after that :-)
mvbarracuda@33b003aa-7bff-0310-803a-e67f0ece8222
parents:
diff changeset
16
4a0efb7baf70 * Datasets becomes the new trunk and retires after that :-)
mvbarracuda@33b003aa-7bff-0310-803a-e67f0ece8222
parents:
diff changeset
17 The integer is
4a0efb7baf70 * Datasets becomes the new trunk and retires after that :-)
mvbarracuda@33b003aa-7bff-0310-803a-e67f0ece8222
parents:
diff changeset
18 "png_uint_16 year" in png_time_struct.
4a0efb7baf70 * Datasets becomes the new trunk and retires after that :-)
mvbarracuda@33b003aa-7bff-0310-803a-e67f0ece8222
parents:
diff changeset
19
4a0efb7baf70 * Datasets becomes the new trunk and retires after that :-)
mvbarracuda@33b003aa-7bff-0310-803a-e67f0ece8222
parents:
diff changeset
20 The strings are
4a0efb7baf70 * Datasets becomes the new trunk and retires after that :-)
mvbarracuda@33b003aa-7bff-0310-803a-e67f0ece8222
parents:
diff changeset
21 "png_charp time_buffer" in png_struct and
4a0efb7baf70 * Datasets becomes the new trunk and retires after that :-)
mvbarracuda@33b003aa-7bff-0310-803a-e67f0ece8222
parents:
diff changeset
22 "near_time_buffer", which is a local character string in png.c.
4a0efb7baf70 * Datasets becomes the new trunk and retires after that :-)
mvbarracuda@33b003aa-7bff-0310-803a-e67f0ece8222
parents:
diff changeset
23
4a0efb7baf70 * Datasets becomes the new trunk and retires after that :-)
mvbarracuda@33b003aa-7bff-0310-803a-e67f0ece8222
parents:
diff changeset
24 There are seven time-related functions:
4a0efb7baf70 * Datasets becomes the new trunk and retires after that :-)
mvbarracuda@33b003aa-7bff-0310-803a-e67f0ece8222
parents:
diff changeset
25
4a0efb7baf70 * Datasets becomes the new trunk and retires after that :-)
mvbarracuda@33b003aa-7bff-0310-803a-e67f0ece8222
parents:
diff changeset
26 png_convert_to_rfc_1123() in png.c
4a0efb7baf70 * Datasets becomes the new trunk and retires after that :-)
mvbarracuda@33b003aa-7bff-0310-803a-e67f0ece8222
parents:
diff changeset
27 (formerly png_convert_to_rfc_1152() in error)
4a0efb7baf70 * Datasets becomes the new trunk and retires after that :-)
mvbarracuda@33b003aa-7bff-0310-803a-e67f0ece8222
parents:
diff changeset
28 png_convert_from_struct_tm() in pngwrite.c, called in pngwrite.c
4a0efb7baf70 * Datasets becomes the new trunk and retires after that :-)
mvbarracuda@33b003aa-7bff-0310-803a-e67f0ece8222
parents:
diff changeset
29 png_convert_from_time_t() in pngwrite.c
4a0efb7baf70 * Datasets becomes the new trunk and retires after that :-)
mvbarracuda@33b003aa-7bff-0310-803a-e67f0ece8222
parents:
diff changeset
30 png_get_tIME() in pngget.c
4a0efb7baf70 * Datasets becomes the new trunk and retires after that :-)
mvbarracuda@33b003aa-7bff-0310-803a-e67f0ece8222
parents:
diff changeset
31 png_handle_tIME() in pngrutil.c, called in pngread.c
4a0efb7baf70 * Datasets becomes the new trunk and retires after that :-)
mvbarracuda@33b003aa-7bff-0310-803a-e67f0ece8222
parents:
diff changeset
32 png_set_tIME() in pngset.c
4a0efb7baf70 * Datasets becomes the new trunk and retires after that :-)
mvbarracuda@33b003aa-7bff-0310-803a-e67f0ece8222
parents:
diff changeset
33 png_write_tIME() in pngwutil.c, called in pngwrite.c
4a0efb7baf70 * Datasets becomes the new trunk and retires after that :-)
mvbarracuda@33b003aa-7bff-0310-803a-e67f0ece8222
parents:
diff changeset
34
4a0efb7baf70 * Datasets becomes the new trunk and retires after that :-)
mvbarracuda@33b003aa-7bff-0310-803a-e67f0ece8222
parents:
diff changeset
35 All appear to handle dates properly in a Y2K environment. The
4a0efb7baf70 * Datasets becomes the new trunk and retires after that :-)
mvbarracuda@33b003aa-7bff-0310-803a-e67f0ece8222
parents:
diff changeset
36 png_convert_from_time_t() function calls gmtime() to convert from system
4a0efb7baf70 * Datasets becomes the new trunk and retires after that :-)
mvbarracuda@33b003aa-7bff-0310-803a-e67f0ece8222
parents:
diff changeset
37 clock time, which returns (year - 1900), which we properly convert to
4a0efb7baf70 * Datasets becomes the new trunk and retires after that :-)
mvbarracuda@33b003aa-7bff-0310-803a-e67f0ece8222
parents:
diff changeset
38 the full 4-digit year. There is a possibility that applications using
4a0efb7baf70 * Datasets becomes the new trunk and retires after that :-)
mvbarracuda@33b003aa-7bff-0310-803a-e67f0ece8222
parents:
diff changeset
39 libpng are not passing 4-digit years into the png_convert_to_rfc_1123()
4a0efb7baf70 * Datasets becomes the new trunk and retires after that :-)
mvbarracuda@33b003aa-7bff-0310-803a-e67f0ece8222
parents:
diff changeset
40 function, or that they are incorrectly passing only a 2-digit year
4a0efb7baf70 * Datasets becomes the new trunk and retires after that :-)
mvbarracuda@33b003aa-7bff-0310-803a-e67f0ece8222
parents:
diff changeset
41 instead of "year - 1900" into the png_convert_from_struct_tm() function,
4a0efb7baf70 * Datasets becomes the new trunk and retires after that :-)
mvbarracuda@33b003aa-7bff-0310-803a-e67f0ece8222
parents:
diff changeset
42 but this is not under our control. The libpng documentation has always
4a0efb7baf70 * Datasets becomes the new trunk and retires after that :-)
mvbarracuda@33b003aa-7bff-0310-803a-e67f0ece8222
parents:
diff changeset
43 stated that it works with 4-digit years, and the APIs have been
4a0efb7baf70 * Datasets becomes the new trunk and retires after that :-)
mvbarracuda@33b003aa-7bff-0310-803a-e67f0ece8222
parents:
diff changeset
44 documented as such.
4a0efb7baf70 * Datasets becomes the new trunk and retires after that :-)
mvbarracuda@33b003aa-7bff-0310-803a-e67f0ece8222
parents:
diff changeset
45
4a0efb7baf70 * Datasets becomes the new trunk and retires after that :-)
mvbarracuda@33b003aa-7bff-0310-803a-e67f0ece8222
parents:
diff changeset
46 The tIME chunk itself is also Y2K compliant. It uses a 2-byte unsigned
4a0efb7baf70 * Datasets becomes the new trunk and retires after that :-)
mvbarracuda@33b003aa-7bff-0310-803a-e67f0ece8222
parents:
diff changeset
47 integer to hold the year, and can hold years as large as 65535.
4a0efb7baf70 * Datasets becomes the new trunk and retires after that :-)
mvbarracuda@33b003aa-7bff-0310-803a-e67f0ece8222
parents:
diff changeset
48
4a0efb7baf70 * Datasets becomes the new trunk and retires after that :-)
mvbarracuda@33b003aa-7bff-0310-803a-e67f0ece8222
parents:
diff changeset
49 zlib, upon which libpng depends, is also Y2K compliant. It contains
4a0efb7baf70 * Datasets becomes the new trunk and retires after that :-)
mvbarracuda@33b003aa-7bff-0310-803a-e67f0ece8222
parents:
diff changeset
50 no date-related code.
4a0efb7baf70 * Datasets becomes the new trunk and retires after that :-)
mvbarracuda@33b003aa-7bff-0310-803a-e67f0ece8222
parents:
diff changeset
51
4a0efb7baf70 * Datasets becomes the new trunk and retires after that :-)
mvbarracuda@33b003aa-7bff-0310-803a-e67f0ece8222
parents:
diff changeset
52
4a0efb7baf70 * Datasets becomes the new trunk and retires after that :-)
mvbarracuda@33b003aa-7bff-0310-803a-e67f0ece8222
parents:
diff changeset
53 Glenn Randers-Pehrson
4a0efb7baf70 * Datasets becomes the new trunk and retires after that :-)
mvbarracuda@33b003aa-7bff-0310-803a-e67f0ece8222
parents:
diff changeset
54 libpng maintainer
4a0efb7baf70 * Datasets becomes the new trunk and retires after that :-)
mvbarracuda@33b003aa-7bff-0310-803a-e67f0ece8222
parents:
diff changeset
55 PNG Development Group