public static int stbi__zhuffman_decode(StbiZbuf *a, StbiZhuffman *z)
{
var b = 0;
var s = 0;
if (a->num_bits < 16)
{
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__zhuffman_decode_slowpath(StbiZbuf *a, StbiZhuffman *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];
a->code_buffer >>= s;
a->num_bits -= s;
return(z->value[b]);
}
public static int stbi__zbuild_huffman(StbiZhuffman *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);
}
