public static int stbi__zbuild_huffman(stbi__zhuffman *z, byte *sizelist, int num)
{
var i = 0;
var k = 0;
var code = 0;
var next_code = stackalloc int[16];
var sizes = stackalloc int[17];
CRuntime.memset(sizes, 0, (ulong)sizeof(int));
CRuntime.memset(z->fast, 0, (ulong)((1 << 9) * sizeof(ushort)));
for (i = 0; i < num; ++i)
{
++sizes[sizelist[i]];
}
sizes[0] = 0;
for (i = 1; i < 16; ++i)
{
if (sizes[i] > 1 << i)
{
return(stbi__err("bad sizes"));
}
}
code = 0;
for (i = 1; i < 16; ++i)
{
next_code[i] = code;
z->firstcode[i] = (ushort)code;
z->firstsymbol[i] = (ushort)k;
code = code + sizes[i];
if (sizes[i] != 0)
{
if (code - 1 >= 1 << i)
{
return(stbi__err("bad codelengths"));
}
}
z->maxcode[i] = code << (16 - i);
code <<= 1;
k += sizes[i];
}
z->maxcode[16] = 0x10000;
for (i = 0; i < num; ++i)
{
var s = (int)sizelist[i];
if (s != 0)
{
var c = next_code[s] - z->firstcode[s] + z->firstsymbol[s];
var fastv = (ushort)((s << 9) | i);
z->size[c] = (byte)s;
z->value[c] = (ushort)i;
if (s <= 9)
{
var j = stbi__bit_reverse(next_code[s], s);
while (j < 1 << 9)
{
z->fast[j] = fastv;
j += 1 << s;
}
}
++next_code[s];
}
}
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);
}
