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/* png.c - location for general purpose png functions
libpng 1.0 beta 3 - version 0.89
For conditions of distribution and use, see copyright notice in png.h
Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
May 25, 1996
*/
#define PNG_INTERNAL
#define PNG_NO_EXTERN
#include "png.h"
/* version information for c files. This better match the version
string defined in png.h */
char png_libpng_ver[] = "0.89";
/* place to hold the signiture string for a png file. */
png_byte FARDATA png_sig[8] = {137, 80, 78, 71, 13, 10, 26, 10};
/* constant strings for known chunk types. If you need to add a chunk,
add a string holding the name here. If you want to make the code
portable to EBCDIC machines, use ASCII numbers, not characters. */
png_byte FARDATA png_IHDR[4] = { 73, 72, 68, 82};
png_byte FARDATA png_IDAT[4] = { 73, 68, 65, 84};
png_byte FARDATA png_IEND[4] = { 73, 69, 78, 68};
png_byte FARDATA png_PLTE[4] = { 80, 76, 84, 69};
png_byte FARDATA png_gAMA[4] = {103, 65, 77, 65};
png_byte FARDATA png_sBIT[4] = {115, 66, 73, 84};
png_byte FARDATA png_cHRM[4] = { 99, 72, 82, 77};
png_byte FARDATA png_tRNS[4] = {116, 82, 78, 83};
png_byte FARDATA png_bKGD[4] = { 98, 75, 71, 68};
png_byte FARDATA png_hIST[4] = {104, 73, 83, 84};
png_byte FARDATA png_tEXt[4] = {116, 69, 88, 116};
png_byte FARDATA png_zTXt[4] = {122, 84, 88, 116};
png_byte FARDATA png_pHYs[4] = {112, 72, 89, 115};
png_byte FARDATA png_oFFs[4] = {111, 70, 70, 115};
png_byte FARDATA png_tIME[4] = {116, 73, 77, 69};
/* arrays to facilitate easy interlacing - use pass (0 - 6) as index */
/* start of interlace block */
int FARDATA png_pass_start[] = {0, 4, 0, 2, 0, 1, 0};
/* offset to next interlace block */
int FARDATA png_pass_inc[] = {8, 8, 4, 4, 2, 2, 1};
/* start of interlace block in the y direction */
int FARDATA png_pass_ystart[] = {0, 0, 4, 0, 2, 0, 1};
/* offset to next interlace block in the y direction */
int FARDATA png_pass_yinc[] = {8, 8, 8, 4, 4, 2, 2};
/* width of interlace block */
/* this is not currently used - if you need it, uncomment it here and
in png.h
int FARDATA png_pass_width[] = {8, 4, 4, 2, 2, 1, 1};
*/
/* height of interlace block */
/* this is not currently used - if you need it, uncomment it here and
in png.h
int FARDATA png_pass_height[] = {8, 8, 4, 4, 2, 2, 1};
*/
/* mask to determine which pixels are valid in a pass */
int FARDATA png_pass_mask[] = {0x80, 0x08, 0x88, 0x22, 0xaa, 0x55, 0xff};
/* mask to determine which pixels to overwrite while displaying */
int FARDATA png_pass_dsp_mask[] = {0xff, 0x0f, 0xff, 0x33, 0xff, 0x55, 0xff};
int
png_check_sig(png_bytep sig, int num)
{
if (num > 8)
num = 8;
if (num < 1)
return 0;
return (!png_memcmp(sig, png_sig, num));
}
/* Function to allocate memory for zlib. */
voidpf
png_zalloc(voidpf png_ptr, uInt items, uInt size)
{
png_voidp ptr;
png_uint_32 num_bytes;
ptr = png_large_malloc((png_structp)png_ptr,
(png_uint_32)items * (png_uint_32)size);
num_bytes = (png_uint_32)items * (png_uint_32)size;
if (num_bytes > (png_uint_32)0x7fff)
{
png_memset(ptr, 0, (png_size_t)0x8000L);
png_memset((png_bytep)ptr + (png_size_t)0x8000L, 0,
(png_size_t)(num_bytes - (png_uint_32)0x8000L));
}
else
{
png_memset(ptr, 0, (png_size_t)num_bytes);
}
return (voidpf)(ptr);
}
/* function to free memory for zlib */
void
png_zfree(voidpf png_ptr, voidpf ptr)
{
png_large_free((png_structp)png_ptr, (png_voidp)ptr);
}
/* reset the crc variable to 32 bits of 1's. Care must be taken
in case crc is > 32 bits to leave the top bits 0 */
void
png_reset_crc(png_structp png_ptr)
{
/* set crc to all 1's */
png_ptr->crc = 0xffffffffL;
}
/* Note: the crc code below was copied from the sample code in the
PNG spec, with appropriate modifications made to ensure the
variables are large enough */
/* table of crc's of all 8-bit messages. If you wish to png_malloc this
table, turn this into a pointer, and png_malloc it in make_crc_table().
You may then want to hook it into png_struct and free it with the
destroy functions. */
static png_uint_32 crc_table[256];
/* Flag: has the table been computed? Initially false. */
static int crc_table_computed = 0;
/* make the table for a fast crc */
static void
make_crc_table(void)
{
png_uint_32 c;
int n, k;
for (n = 0; n < 256; n++)
{
c = (png_uint_32)n;
for (k = 0; k < 8; k++)
c = c & 1 ? 0xedb88320L ^ (c >> 1) : c >> 1;
crc_table[n] = c;
}
crc_table_computed = 1;
}
/* update a running crc with the bytes buf[0..len-1]--the crc should be
initialized to all 1's, and the transmitted value is the 1's complement
of the final running crc. */
static png_uint_32
update_crc(png_uint_32 crc, png_bytep buf, png_uint_32 len)
{
png_uint_32 c;
png_bytep p;
png_uint_32 n;
c = crc;
p = buf;
n = len;
if (!crc_table_computed)
{
make_crc_table();
}
if (n > 0) do
{
c = crc_table[(png_byte)((c ^ (*p++)) & 0xff)] ^ (c >> 8);
} while (--n);
return c;
}
/* calculate the crc over a section of data. Note that while we
are passing in a 32 bit value for length, on 16 bit machines, you
would need to use huge pointers to access all that data. If you
need this, put huge here and above. */
void
png_calculate_crc(png_structp png_ptr, png_bytep ptr,
png_uint_32 length)
{
png_ptr->crc = update_crc(png_ptr->crc, ptr, length);
}
png_infop
png_create_info_struct(png_structp png_ptr)
{
png_infop info_ptr;
if ((info_ptr = (png_infop)png_create_struct(PNG_STRUCT_INFO)) != NULL)
{
png_memset(info_ptr, 0, sizeof(png_info));
png_ptr->do_free |= PNG_FREE_INFO;
}
return info_ptr;
}
void
png_info_init(png_infop info)
{
/* set everything to 0 */
png_memset(info, 0, sizeof (png_info));
}
/* This function returns a pointer to the io_ptr associated with the user
functions. The application should free any memory associated with this
pointer before png_write_destroy and png_read_destroy are called. */
png_voidp
png_get_io_ptr(png_structp png_ptr)
{
return png_ptr->io_ptr;
}
/* Initialize the default input/output functions for the png file. If you
change the read, or write routines, you can call either png_set_read_fn()
or png_set_write_fn() instead of png_init_io(). */
void
png_init_io(png_structp png_ptr, FILE *fp)
{
png_ptr->io_ptr = (png_voidp)fp;
}
These are the contents of the former NiCE NeXT User Group NeXTSTEP/OpenStep software archive, currently hosted by Netfuture.ch.