/// <summary>
/// Decodes the huffman encoded symbols in the input stream.
/// </summary>
/// <returns>
/// false if more input is needed, true if output window is
/// full or the current block ends.
/// </returns>
/// <exception cref="SharpZipBaseException">
/// if deflated stream is invalid.
/// </exception>
private bool DecodeHuffman()
{
int free = outputWindow.GetFreeSpace();
while (free >= 258)
{
int symbol;
switch (mode)
{
case DECODE_HUFFMAN:
// This is the inner loop so it is optimized a bit
while (((symbol = litlenTree.GetSymbol(input)) & ~0xff) == 0)
{
outputWindow.Write(symbol);
if (--free < 258)
{
return true;
}
}
if (symbol < 257)
{
if (symbol < 0)
{
return false;
}
else
{
// symbol == 256: end of block
distTree = null;
litlenTree = null;
mode = DECODE_BLOCKS;
return true;
}
}
try
{
repLength = CPLENS[symbol - 257];
neededBits = CPLEXT[symbol - 257];
}
catch (Exception)
{
throw new SharpZipBaseException("Illegal rep length code");
}
goto case DECODE_HUFFMAN_LENBITS; // fall through
case DECODE_HUFFMAN_LENBITS:
if (neededBits > 0)
{
mode = DECODE_HUFFMAN_LENBITS;
int i = input.PeekBits(neededBits);
if (i < 0)
{
return false;
}
input.DropBits(neededBits);
repLength += i;
}
mode = DECODE_HUFFMAN_DIST;
goto case DECODE_HUFFMAN_DIST; // fall through
case DECODE_HUFFMAN_DIST:
symbol = distTree.GetSymbol(input);
if (symbol < 0)
{
return false;
}
try
{
repDist = CPDIST[symbol];
neededBits = CPDEXT[symbol];
}
catch (Exception)
{
throw new SharpZipBaseException("Illegal rep dist code");
}
goto case DECODE_HUFFMAN_DISTBITS; // fall through
case DECODE_HUFFMAN_DISTBITS:
if (neededBits > 0)
{
mode = DECODE_HUFFMAN_DISTBITS;
int i = input.PeekBits(neededBits);
if (i < 0)
{
return false;
}
input.DropBits(neededBits);
repDist += i;
}
outputWindow.Repeat(repLength, repDist);
free -= repLength;
mode = DECODE_HUFFMAN;
break;
default:
throw new SharpZipBaseException("Inflater unknown mode");
}
}
return true;
}
/// <summary>
/// Resets the inflater so that a new stream can be decompressed. All
/// pending input and output will be discarded.
/// </summary>
public void Reset()
{
mode = noHeader ? DECODE_BLOCKS : DECODE_HEADER;
totalIn = 0;
totalOut = 0;
input.Reset();
outputWindow.Reset();
dynHeader = null;
litlenTree = null;
distTree = null;
isLastBlock = false;
adler.Reset();
}
/// <summary>
/// Decodes the deflated stream.
/// </summary>
/// <returns>
/// false if more input is needed, or if finished.
/// </returns>
/// <exception cref="SharpZipBaseException">
/// if deflated stream is invalid.
/// </exception>
private bool Decode()
{
switch (mode) {
case DECODE_HEADER:
return DecodeHeader();
case DECODE_DICT:
return DecodeDict();
case DECODE_CHKSUM:
return DecodeChksum();
case DECODE_BLOCKS:
if (isLastBlock) {
if (noHeader) {
mode = FINISHED;
return false;
} else {
input.SkipToByteBoundary();
neededBits = 32;
mode = DECODE_CHKSUM;
return true;
}
}
int type = input.PeekBits(3);
if (type < 0) {
return false;
}
input.DropBits(3);
if ((type & 1) != 0) {
isLastBlock = true;
}
switch (type >> 1){
case DeflaterConstants.STORED_BLOCK:
input.SkipToByteBoundary();
mode = DECODE_STORED_LEN1;
break;
case DeflaterConstants.STATIC_TREES:
litlenTree = InflaterHuffmanTree.defLitLenTree;
distTree = InflaterHuffmanTree.defDistTree;
mode = DECODE_HUFFMAN;
break;
case DeflaterConstants.DYN_TREES:
dynHeader = new InflaterDynHeader();
mode = DECODE_DYN_HEADER;
break;
default:
throw new SharpZipBaseException("Unknown block type " + type);
}
return true;
case DECODE_STORED_LEN1:
{
if ((uncomprLen = input.PeekBits(16)) < 0) {
return false;
}
input.DropBits(16);
mode = DECODE_STORED_LEN2;
}
goto case DECODE_STORED_LEN2; // fall through
case DECODE_STORED_LEN2:
{
int nlen = input.PeekBits(16);
if (nlen < 0) {
return false;
}
input.DropBits(16);
if (nlen != (uncomprLen ^ 0xffff)) {
throw new SharpZipBaseException("broken uncompressed block");
}
mode = DECODE_STORED;
}
goto case DECODE_STORED; // fall through
case DECODE_STORED:
{
int more = outputWindow.CopyStored(input, uncomprLen);
uncomprLen -= more;
if (uncomprLen == 0) {
mode = DECODE_BLOCKS;
return true;
}
return !input.IsNeedingInput;
}
case DECODE_DYN_HEADER:
if (!dynHeader.Decode(input)) {
return false;
}
litlenTree = dynHeader.BuildLitLenTree();
distTree = dynHeader.BuildDistTree();
mode = DECODE_HUFFMAN;
goto case DECODE_HUFFMAN; // fall through
case DECODE_HUFFMAN:
case DECODE_HUFFMAN_LENBITS:
case DECODE_HUFFMAN_DIST:
case DECODE_HUFFMAN_DISTBITS:
return DecodeHuffman();
case FINISHED:
return false;
default:
throw new SharpZipBaseException("Inflater.Decode unknown mode");
}
}
static InflaterHuffmanTree()
{
try {
byte[] codeLengths = new byte[288];
int i = 0;
while (i < 144) {
codeLengths[i++] = 8;
}
while (i < 256) {
codeLengths[i++] = 9;
}
while (i < 280) {
codeLengths[i++] = 7;
}
while (i < 288) {
codeLengths[i++] = 8;
}
defLitLenTree = new InflaterHuffmanTree(codeLengths);
codeLengths = new byte[32];
i = 0;
while (i < 32) {
codeLengths[i++] = 5;
}
defDistTree = new InflaterHuffmanTree(codeLengths);
} catch (Exception) {
throw new SharpZipBaseException("InflaterHuffmanTree: static tree length illegal");
}
}
