private static int ReadSymbol(int[] table, int offset, BitReader br)
{
BitReader.FillBitWindow(br);
offset += (int)((ulong)br.accumulator >> br.bitOffset) & HUFFMAN_TABLE_MASK;
int n = (table[offset] >> 16) - HUFFMAN_TABLE_BITS;
if (n > 0)
{
br.bitOffset += HUFFMAN_TABLE_BITS;
offset += table[offset] & 0xFFFF;
offset += (int)((ulong)br.accumulator >> br.bitOffset) & ((1 << n) - 1);
}
br.bitOffset += table[offset] >> 16;
return(table[offset] & 0xFFFF);
}
public static void ReadHuffmanCode(int alphabetSize, int[] table, int offset, BitReader br)
{
bool ok = true;
int simpleCodeOrSkip;
BitReader.ReadMoreInput(br);
// TODO: Avoid allocation.
int[] codeLengths = new int[alphabetSize];
simpleCodeOrSkip = BitReader.ReadBits(br, 2);
if (simpleCodeOrSkip == 1)
{ // Read symbols, codes & code lengths directly.
int maxBitsCounter = alphabetSize - 1;
int maxBits = 0;
int[] symbols = new int[4];
int numSymbols = BitReader.ReadBits(br, 2) + 1;
while (maxBitsCounter != 0)
{
maxBitsCounter >>= 1;
maxBits++;
}
Utils.FillWithZeroes(codeLengths, 0, alphabetSize);
for (int i = 0; i < numSymbols; i++)
{
symbols[i] = BitReader.ReadBits(br, maxBits) % alphabetSize;
codeLengths[symbols[i]] = 2;
}
codeLengths[symbols[0]] = 1;
switch (numSymbols)
{
case 1:
break;
case 2:
ok = symbols[0] != symbols[1];
codeLengths[symbols[1]] = 1;
break;
case 3:
ok = symbols[0] != symbols[1] && symbols[0] != symbols[2] && symbols[1] != symbols[2];
break;
case 4:
ok = symbols[0] != symbols[1] && symbols[0] != symbols[2] && symbols[0] != symbols[3] &&
symbols[1] != symbols[2] && symbols[1] != symbols[3] && symbols[2] != symbols[3];
if (BitReader.ReadBits(br, 1) == 1)
{
codeLengths[symbols[2]] = 3;
codeLengths[symbols[3]] = 3;
}
else
{
codeLengths[symbols[0]] = 2;
}
break;
}
}
else
{ // Decode Huffman-coded code lengths.
int[] codeLengthCodeLengths = new int[CODE_LENGTH_CODES];
int space = 32;
int numCodes = 0;
for (int i = simpleCodeOrSkip; i < CODE_LENGTH_CODES && space > 0; i++)
{
int codeLenIdx = CODE_LENGTH_CODE_ORDER[i];
BitReader.FillBitWindow(br);
int p = (int)((ulong)br.accumulator >> br.bitOffset) & 15;
// TODO: Demultiplex FIXED_TABLE.
br.bitOffset += FIXED_TABLE[p] >> 16;
int v = FIXED_TABLE[p] & 0xFFFF;
codeLengthCodeLengths[codeLenIdx] = v;
if (v != 0)
{
space -= (32 >> v);
numCodes++;
}
}
ok = (numCodes == 1 || space == 0);
ReadHuffmanCodeLengths(codeLengthCodeLengths, alphabetSize, codeLengths, br);
}
if (!ok)
{
throw new BrotliRuntimeException("Can't readHuffmanCode"); // COV_NF_LINE
}
Huffman.BuildHuffmanTable(table, offset, HUFFMAN_TABLE_BITS, codeLengths, alphabetSize);
}
private static void ReadHuffmanCodeLengths(
int[] codeLengthCodeLengths, int numSymbols, int[] codeLengths, BitReader br)
{
int symbol = 0;
int prevCodeLen = DEFAULT_CODE_LENGTH;
int repeat = 0;
int repeatCodeLen = 0;
int space = 32768;
int[] table = new int[32];
Huffman.BuildHuffmanTable(table, 0, 5, codeLengthCodeLengths, CODE_LENGTH_CODES);
while (symbol < numSymbols && space > 0)
{
BitReader.ReadMoreInput(br);
BitReader.FillBitWindow(br);
int p = (int)(((ulong)br.accumulator >> br.bitOffset)) & 31;
br.bitOffset += table[p] >> 16;
int codeLen = table[p] & 0xFFFF;
if (codeLen < CODE_LENGTH_REPEAT_CODE)
{
repeat = 0;
codeLengths[symbol++] = codeLen;
if (codeLen != 0)
{
prevCodeLen = codeLen;
space -= 32768 >> codeLen;
}
}
else
{
int extraBits = codeLen - 14;
int newLen = 0;
if (codeLen == CODE_LENGTH_REPEAT_CODE)
{
newLen = prevCodeLen;
}
if (repeatCodeLen != newLen)
{
repeat = 0;
repeatCodeLen = newLen;
}
int oldRepeat = repeat;
if (repeat > 0)
{
repeat -= 2;
repeat <<= extraBits;
}
repeat += BitReader.ReadBits(br, extraBits) + 3;
int repeatDelta = repeat - oldRepeat;
if (symbol + repeatDelta > numSymbols)
{
throw new BrotliRuntimeException("symbol + repeatDelta > numSymbols"); // COV_NF_LINE
}
for (int i = 0; i < repeatDelta; i++)
{
codeLengths[symbol++] = repeatCodeLen;
}
if (repeatCodeLen != 0)
{
space -= repeatDelta << (15 - repeatCodeLen);
}
}
}
if (space != 0)
{
throw new BrotliRuntimeException("Unused space"); // COV_NF_LINE
}
// TODO: Pass max_symbol to Huffman table builder instead?
Utils.FillWithZeroes(codeLengths, symbol, numSymbols - symbol);
}