static int zhuffman_decode_slowpath(zbuf a, zhuffman z)
{
int b, s, k;
// not resolved by fast table, so compute it the slow way
// use jpeg approach, which requires MSbits at top
k = bit_reverse((int)a.code_buffer, 16);
for (s = ZFAST_BITS + 1; ; ++s)
{
if (k < z.maxcode[s])
{
break;
}
}
if (s == 16)
{
return(-1); // invalid code!
}
// code size is s, so:
b = (k >> (16 - s)) - z.firstcode[s] + z.firstsymbol[s];
Debug.Assert(z.size[b] == s);
a.code_buffer >>= s;
a.num_bits -= s;
return(z.value[b]);
}
static int zexpand(zbuf z, int zout, int n) // need to make room for n bytes
{
byte[] q;
int cur, limit;
z.pzout = zout;
if (z.z_expandable == 0)
{
throw new Exception("output buffer limit,Corrupt PNG");
}
cur = z.pzout - z.pzout_start;
limit = z.pzout_end - z.pzout_start;
while (cur + n > limit)
{
limit *= 2;
}
q = realloc(ref z.zout_start, limit);
if (q == null)
{
throw new Exception("Out of memory");
}
z.pzout_start = 0;
z.pzout = cur;
z.pzout_end = limit;
return(1);
}
static byte zget8(zbuf z)
{
if (z.pzbuffer >= z.pzbuffer_end)
{
return(0);
}
return(z.zbuffer[z.pzbuffer++]);
}
static int do_zlib(zbuf a, byte[] obuf, int olen, int exp, int parse_header)
{
a.zout_start = obuf;
a.pzout_start = 0;
a.pzout = 0;
a.pzout_end = olen;
a.z_expandable = exp;
return(parse_zlib(a, parse_header));
}
static void fill_bits(zbuf z)
{
do
{
Debug.Assert(z.code_buffer < (1U << z.num_bits));
z.code_buffer |= (uint)(zget8(z) << z.num_bits);
z.num_bits += 8;
} while (z.num_bits <= 24);
}
public static int zlib_decode_buffer(byte[] obuffer, int olen, byte[] ibuffer, int ilen)
{
zbuf a = new zbuf();
a.zbuffer = ibuffer;
a.pzbuffer_end = ilen;
if (do_zlib(a, obuffer, olen, 0, 1) != 0)
return (int)(a.pzout - a.pzout_start);
else
return -1;
}
static int compute_huffman_codes(zbuf a)
{
zhuffman z_codelength = new zhuffman();
byte[] lencodes = new byte[286 + 32 + 137];//padding for maximum single op
byte[] codelength_sizes = new byte[19];
int i, n;
int hlit = (int)zreceive(a, 5) + 257;
int hdist = (int)zreceive(a, 5) + 1;
int hclen = (int)zreceive(a, 4) + 4;
for (i = 0; i < hclen; ++i)
{
int s = (int)zreceive(a, 3);
codelength_sizes[length_dezigzag[i]] = (byte)s;
}
if (zbuild_huffman(z_codelength, codelength_sizes, 19) == 0) return 0;
n = 0;
while (n < hlit + hdist)
{
int c = zhuffman_decode(a, z_codelength);
Debug.Assert(c >= 0 && c < 19);
if (c < 16)
lencodes[n++] = (byte)c;
else if (c == 16)
{
c = (int)zreceive(a, 2) + 3;
{
byte value = lencodes[n - 1];
int last = n + c;
for (int idx = n; idx < last; idx++)
lencodes[idx] = value;
}
n += c;
}
else if (c == 17)
{
c = (int)zreceive(a, 3) + 3;
Array.Clear(lencodes, n, c);
n += c;
}
else
{
Debug.Assert(c == 18);
c = (int)zreceive(a, 7) + 11;
Array.Clear(lencodes, n, c);
n += c;
}
}
if (n != hlit + hdist) throw new Exception("bad codelengths,Corrupt PNG");
if (zbuild_huffman(a.z_length, lencodes, hlit) == 0) return 0;
if (zbuild_huffman(a.z_distance, lencodes, hdist, hlit) == 0) return 0;
return 1;
}
static uint zreceive(zbuf z, int n)
{
uint k;
if (z.num_bits < n)
{
fill_bits(z);
}
k = z.code_buffer & (uint)((1 << n) - 1);
z.code_buffer >>= n;
z.num_bits -= n;
return(k);
}
public static int zlib_decode_buffer(byte[] obuffer, int olen, byte[] ibuffer, int ilen)
{
zbuf a = new zbuf();
a.zbuffer = ibuffer;
a.pzbuffer_end = ilen;
if (do_zlib(a, obuffer, olen, 0, 1) != 0)
{
return((int)(a.pzout - a.pzout_start));
}
else
{
return(-1);
}
}
static int parse_uncomperssed_block(zbuf a)
{
byte[] header = new byte[4];
int len, nlen, k;
if ((a.num_bits & 7) != 0)
{
zreceive(a, a.num_bits & 7); // discard
}
// drain the bit-packed data into header
k = 0;
while (a.num_bits > 0)
{
header[k++] = (byte)a.code_buffer; // suppress MSVC run-time check
a.code_buffer >>= 8;
a.num_bits -= 8;
}
Debug.Assert(a.num_bits == 0);
// now fill header the normal way
while (k < 4)
{
header[k++] = zget8(a);
}
len = header[1] * 256 + header[0];
nlen = header[3] * 256 + header[2];
if (nlen != (len ^ 0xffff))
{
throw new Exception("zlib corrupt,Corrupt PNG");
}
if (a.pzbuffer + len > a.pzbuffer_end)
{
throw new Exception("read past buffer,Corrupt PNG");
}
if (a.pzout + len > a.pzout_end)
{
if (zexpand(a, a.pzout, len) == 0)
{
return(0);
}
}
Array.Copy(a.zbuffer, a.pzbuffer, a.zout_start, a.pzout, len);
a.pzbuffer += len;
a.pzout += len;
return(1);
}
public static byte[] zlib_decode(byte[] buffer, int len, int initial_size, ref int outlen, int parse_header = 1)
{
zbuf a = new zbuf();
byte[] p = new byte[initial_size];
if (p == null) return null;
a.zbuffer = buffer;
a.pzbuffer = 0;
a.pzbuffer_end = len;
if (do_zlib(a, p, initial_size, 1, parse_header) != 0)
{
outlen = (int)(a.pzout - a.pzout_start);
return a.zout_start;
}
else
{
return null;
}
}
static int zhuffman_decode(zbuf a, zhuffman z)
{
int b, s;
if (a.num_bits < 16)
{
fill_bits(a);
}
b = z.fast[a.code_buffer & ZFAST_MASK];
if (b != 0)
{
s = b >> 9;
a.code_buffer >>= s;
a.num_bits -= s;
return(b & 511);
}
return(zhuffman_decode_slowpath(a, z));
}
public static byte[] zlib_decode(byte[] buffer, int len, int initial_size, ref int outlen, int parse_header = 1)
{
zbuf a = new zbuf();
byte[] p = new byte[initial_size];
if (p == null)
{
return(null);
}
a.zbuffer = buffer;
a.pzbuffer = 0;
a.pzbuffer_end = len;
if (do_zlib(a, p, initial_size, 1, parse_header) != 0)
{
outlen = (int)(a.pzout - a.pzout_start);
return(a.zout_start);
}
else
{
return(null);
}
}
static int parse_zlib_header(zbuf a)
{
int cmf = zget8(a);
int cm = cmf & 15;
/* int cinfo = cmf >> 4; */
int flg = zget8(a);
if ((cmf * 256 + flg) % 31 != 0)
{
throw new Exception("bad zlib header,Corrupt PNG"); // zlib spec
}
if ((flg & 32) != 0)
{
throw new Exception("no preset dict,Corrupt PNG"); // preset dictionary not allowed in png
}
if (cm != 8)
{
throw new Exception("bad compression,Corrupt PNG"); // DEFLATE required for png
}
// window = 1 << (8 + cinfo)... but who cares, we fully buffer output
return(1);
}
// need to make room for n bytes
static int zexpand(zbuf z, int zout, int n)
{
byte[] q;
int cur, limit;
z.pzout = zout;
if (z.z_expandable == 0) throw new Exception("output buffer limit,Corrupt PNG");
cur = z.pzout - z.pzout_start;
limit = z.pzout_end - z.pzout_start;
while (cur + n > limit)
limit *= 2;
q = realloc(ref z.zout_start, limit);
if (q == null) throw new Exception("Out of memory");
z.pzout_start = 0;
z.pzout = cur;
z.pzout_end = limit;
return 1;
}
static int parse_zlib_header(zbuf a)
{
int cmf = zget8(a);
int cm = cmf & 15;
/* int cinfo = cmf >> 4; */
int flg = zget8(a);
if ((cmf * 256 + flg) % 31 != 0) throw new Exception("bad zlib header,Corrupt PNG");// zlib spec
if ((flg & 32) != 0) throw new Exception("no preset dict,Corrupt PNG"); // preset dictionary not allowed in png
if (cm != 8) throw new Exception("bad compression,Corrupt PNG"); // DEFLATE required for png
// window = 1 << (8 + cinfo)... but who cares, we fully buffer output
return 1;
}
static int parse_zlib(zbuf a, int parse_header)
{
int final, type;
if (parse_header != 0)
if (parse_zlib_header(a) == 0) return 0;
a.num_bits = 0;
a.code_buffer = 0;
do
{
final = (int)zreceive(a, 1);
type = (int)zreceive(a, 2);
if (type == 0)
{
if (parse_uncomperssed_block(a) == 0) return 0;
}
else if (type == 3)
{
return 0;
}
else
{
if (type == 1)
{
// use fixed code lengths
if (zdefault_distance[31] == 0) init_zdefaults();
if (zbuild_huffman(a.z_length, zdefault_length, 288) == 0) return 0;
if (zbuild_huffman(a.z_distance, zdefault_distance, 32) == 0) return 0;
}
else
{
if (compute_huffman_codes(a) == 0) return 0;
}
if (parse_huffman_block(a) == 0) return 0;
}
} while (final == 0);
return 1;
}
static int parse_huffman_block(zbuf a)
{
int zout = a.pzout;
for (; ;)
{
int z = (int)zhuffman_decode(a, a.z_length);
if (z < 256)
{
if (z < 0)
{
throw new Exception("bad huffman code,Corrupt PNG"); // error in huffman codes
}
if (zout >= a.pzout_end)
{
if (zexpand(a, zout, 1) == 0)
{
return(0);
}
zout = a.pzout;
}
a.zout_start[zout++] = (byte)z;
}
else
{
int p;
int len, dist;
if (z == 256)
{
a.pzout = zout;
return(1);
}
z -= 257;
len = zlength_base[z];
if (zlength_extra[z] != 0)
{
len += (int)zreceive(a, zlength_extra[z]);
}
z = zhuffman_decode(a, a.z_distance);
if (z < 0)
{
throw new Exception("bad huffman code,Corrupt PNG");
}
dist = zdist_base[z];
if (zdist_extra[z] != 0)
{
dist += (int)zreceive(a, zdist_extra[z]);
}
if (zout - a.pzout_start < dist)
{
throw new Exception("bad dist,Corrupt PNG");
}
if (zout + len > a.pzout_end)
{
if (zexpand(a, zout, len) == 0)
{
return(0);
}
zout = a.pzout;
}
p = zout - dist;
if (dist == 1)
{ // run of one byte; common in images.
do
{
a.zout_start[zout++] = a.zout_start[p];
} while ((--len) != 0); //todo fix
}
else
{
do
{
a.zout_start[zout++] = a.zout_start[p++];
} while ((--len) != 0); //todo fix
}
}
}
}
static int zhuffman_decode_slowpath(zbuf a, zhuffman z)
{
int b, s, k;
// not resolved by fast table, so compute it the slow way
// use jpeg approach, which requires MSbits at top
k = bit_reverse((int)a.code_buffer, 16);
for (s = ZFAST_BITS + 1; ; ++s)
if (k < z.maxcode[s])
break;
if (s == 16) return -1; // invalid code!
// code size is s, so:
b = (k >> (16 - s)) - z.firstcode[s] + z.firstsymbol[s];
Debug.Assert(z.size[b] == s);
a.code_buffer >>= s;
a.num_bits -= s;
return z.value[b];
}
static int compute_huffman_codes(zbuf a)
{
zhuffman z_codelength = new zhuffman();
byte[] lencodes = new byte[286 + 32 + 137];//padding for maximum single op
byte[] codelength_sizes = new byte[19];
int i, n;
int hlit = (int)zreceive(a, 5) + 257;
int hdist = (int)zreceive(a, 5) + 1;
int hclen = (int)zreceive(a, 4) + 4;
for (i = 0; i < hclen; ++i)
{
int s = (int)zreceive(a, 3);
codelength_sizes[length_dezigzag[i]] = (byte)s;
}
if (zbuild_huffman(z_codelength, codelength_sizes, 19) == 0)
{
return(0);
}
n = 0;
while (n < hlit + hdist)
{
int c = zhuffman_decode(a, z_codelength);
Debug.Assert(c >= 0 && c < 19);
if (c < 16)
{
lencodes[n++] = (byte)c;
}
else if (c == 16)
{
c = (int)zreceive(a, 2) + 3;
{
byte value = lencodes[n - 1];
int last = n + c;
for (int idx = n; idx < last; idx++)
{
lencodes[idx] = value;
}
}
n += c;
}
else if (c == 17)
{
c = (int)zreceive(a, 3) + 3;
Array.Clear(lencodes, n, c);
n += c;
}
else
{
Debug.Assert(c == 18);
c = (int)zreceive(a, 7) + 11;
Array.Clear(lencodes, n, c);
n += c;
}
}
if (n != hlit + hdist)
{
throw new Exception("bad codelengths,Corrupt PNG");
}
if (zbuild_huffman(a.z_length, lencodes, hlit) == 0)
{
return(0);
}
if (zbuild_huffman(a.z_distance, lencodes, hdist, hlit) == 0)
{
return(0);
}
return(1);
}
static byte zget8(zbuf z)
{
if (z.pzbuffer >= z.pzbuffer_end) return 0;
return z.zbuffer[z.pzbuffer++];
}
static void fill_bits(zbuf z)
{
do
{
Debug.Assert(z.code_buffer < (1U << z.num_bits));
z.code_buffer |= (uint)(zget8(z) << z.num_bits);
z.num_bits += 8;
} while (z.num_bits <= 24);
}
static int zhuffman_decode(zbuf a, zhuffman z)
{
int b, s;
if (a.num_bits < 16) fill_bits(a);
b = z.fast[a.code_buffer & ZFAST_MASK];
if (b != 0)
{
s = b >> 9;
a.code_buffer >>= s;
a.num_bits -= s;
return b & 511;
}
return zhuffman_decode_slowpath(a, z);
}
static int parse_huffman_block(zbuf a)
{
int zout = a.pzout;
for (; ; )
{
int z = (int)zhuffman_decode(a, a.z_length);
if (z < 256)
{
if (z < 0) throw new Exception("bad huffman code,Corrupt PNG"); // error in huffman codes
if (zout >= a.pzout_end)
{
if (zexpand(a, zout, 1) == 0) return 0;
zout = a.pzout;
}
a.zout_start[zout++] = (byte)z;
}
else
{
int p;
int len, dist;
if (z == 256)
{
a.pzout = zout;
return 1;
}
z -= 257;
len = zlength_base[z];
if (zlength_extra[z] != 0) len += (int)zreceive(a, zlength_extra[z]);
z = zhuffman_decode(a, a.z_distance);
if (z < 0) throw new Exception("bad huffman code,Corrupt PNG");
dist = zdist_base[z];
if (zdist_extra[z] != 0) dist += (int)zreceive(a, zdist_extra[z]);
if (zout - a.pzout_start < dist) throw new Exception("bad dist,Corrupt PNG");
if (zout + len > a.pzout_end)
{
if (zexpand(a, zout, len) == 0) return 0;
zout = a.pzout;
}
p = zout - dist;
if (dist == 1)
{ // run of one byte; common in images.
do a.zout_start[zout++] = a.zout_start[p]; while ((--len) != 0); //todo fix
}
else
{
do a.zout_start[zout++] = a.zout_start[p++]; while ((--len) != 0); //todo fix
}
}
}
}
static uint zreceive(zbuf z, int n)
{
uint k;
if (z.num_bits < n) fill_bits(z);
k = z.code_buffer & (uint)((1 << n) - 1);
z.code_buffer >>= n;
z.num_bits -= n;
return k;
}
static int parse_uncomperssed_block(zbuf a)
{
byte[] header = new byte[4];
int len, nlen, k;
if ((a.num_bits & 7) != 0)
zreceive(a, a.num_bits & 7); // discard
// drain the bit-packed data into header
k = 0;
while (a.num_bits > 0)
{
header[k++] = (byte)a.code_buffer; // suppress MSVC run-time check
a.code_buffer >>= 8;
a.num_bits -= 8;
}
Debug.Assert(a.num_bits == 0);
// now fill header the normal way
while (k < 4)
header[k++] = zget8(a);
len = header[1] * 256 + header[0];
nlen = header[3] * 256 + header[2];
if (nlen != (len ^ 0xffff)) throw new Exception("zlib corrupt,Corrupt PNG");
if (a.pzbuffer + len > a.pzbuffer_end) throw new Exception("read past buffer,Corrupt PNG");
if (a.pzout + len > a.pzout_end)
if (zexpand(a, a.pzout, len) == 0) return 0;
Array.Copy(a.zbuffer, a.pzbuffer, a.zout_start, a.pzout, len);
a.pzbuffer += len;
a.pzout += len;
return 1;
}
static int do_zlib(zbuf a, byte[] obuf, int olen, int exp, int parse_header)
{
a.zout_start = obuf;
a.pzout_start = 0;
a.pzout = 0;
a.pzout_end = olen;
a.z_expandable = exp;
return parse_zlib(a, parse_header);
}
static int parse_zlib(zbuf a, int parse_header)
{
int final, type;
if (parse_header != 0)
{
if (parse_zlib_header(a) == 0)
{
return(0);
}
}
a.num_bits = 0;
a.code_buffer = 0;
do
{
final = (int)zreceive(a, 1);
type = (int)zreceive(a, 2);
if (type == 0)
{
if (parse_uncomperssed_block(a) == 0)
{
return(0);
}
}
else if (type == 3)
{
return(0);
}
else
{
if (type == 1)
{
// use fixed code lengths
if (zdefault_distance[31] == 0)
{
init_zdefaults();
}
if (zbuild_huffman(a.z_length, zdefault_length, 288) == 0)
{
return(0);
}
if (zbuild_huffman(a.z_distance, zdefault_distance, 32) == 0)
{
return(0);
}
}
else
{
if (compute_huffman_codes(a) == 0)
{
return(0);
}
}
if (parse_huffman_block(a) == 0)
{
return(0);
}
}
} while (final == 0);
return(1);
}