public static int ReadHuffmanCode(int alphabet_size, HuffmanCode[] tables, int table, BitReader br)
{
int table_size = 0;
byte simple_code_or_skip;
byte[] code_lengths = new byte[alphabet_size];
br.ReadMoreInput();
/* simple_code_or_skip is used as follows:
* 1 for simple code;
* 0 for no skipping, 2 skips 2 code lengths, 3 skips 3 code lengths */
simple_code_or_skip = (byte)br.ReadBits(2);
if (simple_code_or_skip == 1)
{
/* Read symbols, codes & code lengths directly. */
int max_bits_counter = alphabet_size - 1;
int max_bits = 0;
int[] symbols = new int[4];
int num_symbols = (int)br.ReadBits(2) + 1;
while (max_bits_counter > 0)
{
max_bits_counter >>= 1;
max_bits++;
}
for (int i = 0; i < num_symbols; i++)
{
symbols[i] = (int)br.ReadBits(max_bits) % alphabet_size;
code_lengths[symbols[i]] = 2;
}
code_lengths[symbols[0]] = 1;
switch (num_symbols)
{
case 1:
break;
case 3:
if ((symbols[0] == symbols[1]) ||
(symbols[0] == symbols[2]) ||
(symbols[1] == symbols[2]))
{
throw new Exception("[ReadHuffmanCode] invalid symbols");
}
break;
case 2:
if (symbols[0] == symbols[1])
{
throw new Exception("[ReadHuffmanCode] invalid symbols");
}
code_lengths[symbols[1]] = 1;
break;
case 4:
if ((symbols[0] == symbols[1]) ||
(symbols[0] == symbols[2]) ||
(symbols[0] == symbols[3]) ||
(symbols[1] == symbols[2]) ||
(symbols[1] == symbols[3]) ||
(symbols[2] == symbols[3]))
{
throw new Exception("[ReadHuffmanCode] invalid symbols");
}
if (br.ReadBits(1) == 1)
{
code_lengths[symbols[2]] = 3;
code_lengths[symbols[3]] = 3;
}
else
{
code_lengths[symbols[0]] = 2;
}
break;
}
}
else /* Decode Huffman-coded code lengths. */
{
byte[] code_length_code_lengths = new byte[CODE_LENGTH_CODES];
int space = 32;
int num_codes = 0;
for (int i = simple_code_or_skip; i < CODE_LENGTH_CODES && space > 0; i++)
{
int code_len_idx = kCodeLengthCodeOrder[i];
int p = 0;
ushort v;
br.FillBitWindow();
p += (int)(br.val_ >> br.bit_pos_) & 15;
HuffmanCode huff = Huffman.CodeLengthCodeLengths[p];
br.bit_pos_ += huff.Bits;
v = huff.Value;
code_length_code_lengths[code_len_idx] = (byte)v;
if (v != 0)
{
space -= (32 >> v);
++num_codes;
}
}
if (!(num_codes == 1 || space == 0))
{
throw new Exception("[ReadHuffmanCode] invalid num_codes or space");
}
ReadHuffmanCodeLengths(code_length_code_lengths, alphabet_size, code_lengths, br);
}
table_size = Huffman.BuildHuffmanTable(tables, table, HUFFMAN_TABLE_BITS, code_lengths, alphabet_size);
if (table_size == 0)
{
throw new Exception("[ReadHuffmanCode] Huffman.BuildHuffmanTable failed: ");
}
return(table_size);
}
public static void ReadHuffmanCodeLengths(byte[] code_length_code_lengths, int num_symbols, byte[] code_lengths, BitReader br)
{
int symbol = 0;
int prev_code_len = kDefaultCodeLength;
int repeat = 0;
int repeat_code_len = 0;
int space = 32768;
HuffmanCode[] table = new HuffmanCode[32];
for (int i = 0; i < 32; i++)
{
table[i] = new HuffmanCode(0, 0);
}
Huffman.BuildHuffmanTable(table, 0, 5, code_length_code_lengths, CODE_LENGTH_CODES);
while (symbol < num_symbols && space > 0)
{
int p = 0;
byte code_len;
br.ReadMoreInput();
br.FillBitWindow();
p += (int)((br.val_ >> br.bit_pos_) & 31);
br.bit_pos_ += table[p].Bits;
code_len = (byte)table[p].Value;
if (code_len < kCodeLengthRepeatCode)
{
repeat = 0;
code_lengths[symbol++] = (byte)code_len;
if (code_len != 0)
{
prev_code_len = code_len;
space -= 32768 >> code_len;
}
}
else
{
int extra_bits = code_len - 14;
int old_repeat;
int repeat_delta;
int new_len = 0;
if (code_len == kCodeLengthRepeatCode)
{
new_len = prev_code_len;
}
if (repeat_code_len != new_len)
{
repeat = 0;
repeat_code_len = new_len;
}
old_repeat = repeat;
if (repeat > 0)
{
repeat -= 2;
repeat <<= extra_bits;
}
repeat += (int)br.ReadBits(extra_bits) + 3;
repeat_delta = repeat - old_repeat;
if (symbol + repeat_delta > num_symbols)
{
throw new Exception("[ReadHuffmanCodeLengths] symbol + repeat_delta > num_symbols");
}
for (int x = 0; x < repeat_delta; x++)
{
code_lengths[symbol + x] = (byte)repeat_code_len;
}
symbol += repeat_delta;
if (repeat_code_len != 0)
{
space -= repeat_delta << (15 - repeat_code_len);
}
}
}
if (space != 0)
{
throw new Exception("[ReadHuffmanCodeLengths] space = " + space);
}
for (; symbol < num_symbols; symbol++)
{
code_lengths[symbol] = 0;
}
}
