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[libpng16] Fixed png_save_int_32 when int is not 2's complement (John Bowler).

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John Bowler
2015-08-21 14:42:00 -05:00
committed by Glenn Randers-Pehrson
parent 39be3b81da
commit 33a97c5c8a
3 changed files with 24 additions and 19 deletions
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23
png.c
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@@ -671,19 +671,20 @@ png_init_io(png_structrp png_ptr, png_FILE_p fp)
# endif
# ifdef PNG_SAVE_INT_32_SUPPORTED
/* The png_save_int_32 function assumes integers are stored in two's
* complement format. If this isn't the case, then this routine needs to
* be modified to write data in two's complement format. Note that,
* the following works correctly even if png_int_32 has more than 32 bits
* (compare the more complex code required on read for sign extension.)
/* PNG signed integers are saved in 32-bit 2's complement format. ANSI C-90
* defines a cast of a signed integer to an unsigned integer either to preserve
* the value, if it is positive, or to calculate:
*
* (UNSIGNED_MAX+1) + integer
*
* Where UNSIGNED_MAX is the appropriate maximum unsigned value, so when the
* negative integral value is added the result will be an unsigned value
* correspnding to the 2's complement representation.
*/
void PNGAPI
png_save_int_32(png_bytep buf, png_int_32 i)
{
buf[0] = (png_byte)((i >> 24) & 0xff);
buf[1] = (png_byte)((i >> 16) & 0xff);
buf[2] = (png_byte)((i >> 8) & 0xff);
buf[3] = (png_byte)(i & 0xff);
png_save_uint_32(buf, i);
}
# endif
@@ -774,13 +775,13 @@ png_get_copyright(png_const_structrp png_ptr)
#else
# ifdef __STDC__
return PNG_STRING_NEWLINE \
"libpng version 1.6.19beta03 - August 19, 2015" PNG_STRING_NEWLINE \
"libpng version 1.6.19beta03 - August 21, 2015" PNG_STRING_NEWLINE \
"Copyright (c) 1998-2015 Glenn Randers-Pehrson" PNG_STRING_NEWLINE \
"Copyright (c) 1996-1997 Andreas Dilger" PNG_STRING_NEWLINE \
"Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc." \
PNG_STRING_NEWLINE;
# else
return "libpng version 1.6.19beta03 - August 19, 2015\
return "libpng version 1.6.19beta03 - August 21, 2015\
Copyright (c) 1998-2015 Glenn Randers-Pehrson\
Copyright (c) 1996-1997 Andreas Dilger\
Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.";