public static int stbi__zexpand(stbi__zbuf *z, sbyte *zout, int n)
{
sbyte *q;
var cur = 0;
var limit = 0;
var old_limit = 0;
z->zout = zout;
if (z->z_expandable == 0)
{
return(stbi__err("output buffer limit"));
}
cur = (int)(z->zout - z->zout_start);
limit = old_limit = (int)(z->zout_end - z->zout_start);
while (cur + n > limit)
{
limit *= 2;
}
q = (sbyte *)CRuntime.realloc(z->zout_start, (ulong)limit);
if (q == null)
{
return(stbi__err("outofmem"));
}
z->zout_start = q;
z->zout = q + cur;
z->zout_end = q + limit;
return(1);
}
public static int stbi__zhuffman_decode_slowpath(stbi__zbuf *a, stbi__zhuffman *z)
{
var b = 0;
var s = 0;
var k = 0;
k = stbi__bit_reverse((int)a->code_buffer, 16);
for (s = 9 + 1; ; ++s)
{
if (k < z->maxcode[s])
{
break;
}
}
if (s >= 16)
{
return(-1);
}
b = (k >> (16 - s)) - z->firstcode[s] + z->firstsymbol[s];
if (b >= 288)
{
return(-1);
}
if (z->size[b] != s)
{
return(-1);
}
a->code_buffer >>= s;
a->num_bits -= s;
return(z->value[b]);
}
public static int stbi__zhuffman_decode(stbi__zbuf *a, stbi__zhuffman *z)
{
var b = 0;
var s = 0;
if (a->num_bits < 16)
{
if (stbi__zeof(a) != 0)
{
return(-1);
}
stbi__fill_bits(a);
}
b = z->fast[a->code_buffer & ((1 << 9) - 1)];
if (b != 0)
{
s = b >> 9;
a->code_buffer >>= s;
a->num_bits -= s;
return(b & 511);
}
return(stbi__zhuffman_decode_slowpath(a, z));
}
public static int stbi__do_zlib(stbi__zbuf *a, sbyte *obuf, int olen, int exp, int parse_header)
{
a->zout_start = obuf;
a->zout = obuf;
a->zout_end = obuf + olen;
a->z_expandable = exp;
return(stbi__parse_zlib(a, parse_header));
}
public static void stbi__fill_bits(stbi__zbuf *z)
{
do
{
z->code_buffer |= (uint)stbi__zget8(z) << z->num_bits;
z->num_bits += 8;
} while (z->num_bits <= 24);
}
public static byte stbi__zget8(stbi__zbuf *z)
{
if (z->zbuffer >= z->zbuffer_end)
{
return(0);
}
return(*z->zbuffer++);
}
public static uint stbi__zreceive(stbi__zbuf *z, int n)
{
uint k = 0;
if (z->num_bits < n)
{
stbi__fill_bits(z);
}
k = (uint)(z->code_buffer & ((1 << n) - 1));
z->code_buffer >>= n;
z->num_bits -= n;
return(k);
}
public static int stbi__parse_uncompressed_block(stbi__zbuf *a)
{
var header = stackalloc byte[4];
var len = 0;
var nlen = 0;
var k = 0;
if ((a->num_bits & 7) != 0)
{
stbi__zreceive(a, a->num_bits & 7);
}
k = 0;
while (a->num_bits > 0)
{
header[k++] = (byte)(a->code_buffer & 255);
a->code_buffer >>= 8;
a->num_bits -= 8;
}
if (a->num_bits < 0)
{
return(stbi__err("zlib corrupt"));
}
while (k < 4)
{
header[k++] = stbi__zget8(a);
}
len = header[1] * 256 + header[0];
nlen = header[3] * 256 + header[2];
if (nlen != (len ^ 0xffff))
{
return(stbi__err("zlib corrupt"));
}
if (a->zbuffer + len > a->zbuffer_end)
{
return(stbi__err("read past buffer"));
}
if (a->zout + len > a->zout_end)
{
if (stbi__zexpand(a, a->zout, len) == 0)
{
return(0);
}
}
CRuntime.memcpy(a->zout, a->zbuffer, (ulong)len);
a->zbuffer += len;
a->zout += len;
return(1);
}
public static void stbi__fill_bits(stbi__zbuf *z)
{
do
{
if (z->code_buffer >= 1U << z->num_bits)
{
z->zbuffer = z->zbuffer_end;
return;
}
z->code_buffer |= (uint)stbi__zget8(z) << z->num_bits;
z->num_bits += 8;
} while (z->num_bits <= 24);
}
public static int stbi__parse_zlib_header(stbi__zbuf *a)
{
var cmf = (int)stbi__zget8(a);
var cm = cmf & 15;
var flg = (int)stbi__zget8(a);
if ((cmf * 256 + flg) % 31 != 0)
{
return(stbi__err("bad zlib header"));
}
if ((flg & 32) != 0)
{
return(stbi__err("no preset dict"));
}
if (cm != 8)
{
return(stbi__err("bad compression"));
}
return(1);
}
public static int stbi__parse_zlib(stbi__zbuf *a, int parse_header)
{
var final = 0;
var type = 0;
if (parse_header != 0)
{
if (stbi__parse_zlib_header(a) == 0)
{
return(0);
}
}
a->num_bits = 0;
a->code_buffer = 0;
do
{
final = (int)stbi__zreceive(a, 1);
type = (int)stbi__zreceive(a, 2);
if (type == 0)
{
if (stbi__parse_uncompressed_block(a) == 0)
{
return(0);
}
}
else if (type == 3)
{
return(0);
}
else
{
if (type == 1)
{
fixed(byte *b = stbi__zdefault_length)
{
if (stbi__zbuild_huffman(&a->z_length, b, 288) == 0)
{
return(0);
}
}
fixed(byte *b = stbi__zdefault_distance)
{
if (stbi__zbuild_huffman(&a->z_distance, b, 32) == 0)
{
return(0);
}
}
}
else
{
if (stbi__compute_huffman_codes(a) == 0)
{
return(0);
}
}
if (stbi__parse_huffman_block(a) == 0)
{
return(0);
}
}
} while (final == 0);
return(1);
}
public static int stbi__compute_huffman_codes(stbi__zbuf *a)
{
var z_codelength = new stbi__zhuffman();
var lencodes = stackalloc byte[286 + 32 + 137];
var codelength_sizes = stackalloc byte[19];
var i = 0;
var n = 0;
var hlit = (int)(stbi__zreceive(a, 5) + 257);
var hdist = (int)(stbi__zreceive(a, 5) + 1);
var hclen = (int)(stbi__zreceive(a, 4) + 4);
var ntot = hlit + hdist;
CRuntime.memset(codelength_sizes, 0, (ulong)(19 * sizeof(byte)));
for (i = 0; i < hclen; ++i)
{
var s = (int)stbi__zreceive(a, 3);
codelength_sizes[length_dezigzag[i]] = (byte)s;
}
if (stbi__zbuild_huffman(&z_codelength, codelength_sizes, 19) == 0)
{
return(0);
}
n = 0;
while (n < ntot)
{
var c = stbi__zhuffman_decode(a, &z_codelength);
if (c < 0 || c >= 19)
{
return(stbi__err("bad codelengths"));
}
if (c < 16)
{
lencodes[n++] = (byte)c;
}
else
{
var fill = (byte)0;
if (c == 16)
{
c = (int)(stbi__zreceive(a, 2) + 3);
if (n == 0)
{
return(stbi__err("bad codelengths"));
}
fill = lencodes[n - 1];
}
else if (c == 17)
{
c = (int)(stbi__zreceive(a, 3) + 3);
}
else
{
c = (int)(stbi__zreceive(a, 7) + 11);
}
if (ntot - n < c)
{
return(stbi__err("bad codelengths"));
}
CRuntime.memset(lencodes + n, fill, (ulong)c);
n += c;
}
}
if (n != ntot)
{
return(stbi__err("bad codelengths"));
}
if (stbi__zbuild_huffman(&a->z_length, lencodes, hlit) == 0)
{
return(0);
}
if (stbi__zbuild_huffman(&a->z_distance, lencodes + hlit, hdist) == 0)
{
return(0);
}
return(1);
}
public static int stbi__parse_huffman_block(stbi__zbuf *a)
{
var zout = a->zout;
for (; ;)
{
var z = stbi__zhuffman_decode(a, &a->z_length);
if (z < 256)
{
if (z < 0)
{
return(stbi__err("bad huffman code"));
}
if (zout >= a->zout_end)
{
if (stbi__zexpand(a, zout, 1) == 0)
{
return(0);
}
zout = a->zout;
}
*zout++ = (sbyte)z;
}
else
{
byte *p;
var len = 0;
var dist = 0;
if (z == 256)
{
a->zout = zout;
return(1);
}
z -= 257;
len = stbi__zlength_base[z];
if (stbi__zlength_extra[z] != 0)
{
len += (int)stbi__zreceive(a, stbi__zlength_extra[z]);
}
z = stbi__zhuffman_decode(a, &a->z_distance);
if (z < 0)
{
return(stbi__err("bad huffman code"));
}
dist = stbi__zdist_base[z];
if (stbi__zdist_extra[z] != 0)
{
dist += (int)stbi__zreceive(a, stbi__zdist_extra[z]);
}
if (zout - a->zout_start < dist)
{
return(stbi__err("bad dist"));
}
if (zout + len > a->zout_end)
{
if (stbi__zexpand(a, zout, len) == 0)
{
return(0);
}
zout = a->zout;
}
p = (byte *)(zout - dist);
if (dist == 1)
{
var v = *p;
if (len != 0)
{
do
{
*zout++ = (sbyte)v;
} while (--len != 0);
}
}
else
{
if (len != 0)
{
do
{
*zout++ = (sbyte)*p++;
} while (--len != 0);
}
}
}
}
}
public static byte stbi__zget8(stbi__zbuf *z)
{
return((byte)(stbi__zeof(z) != 0 ? 0 : *z->zbuffer++));
}
public static int stbi__zeof(stbi__zbuf *z)
{
return(z->zbuffer >= z->zbuffer_end ? 1 : 0);
}