public Decode ( |
||
input | ||
리턴 | bool |
public bool Decode(StreamManipulator input)
{
decode_loop:
for (;;) {
switch (mode) {
case LNUM:
lnum = input.PeekBits(5);
if (lnum < 0) {
return false;
}
lnum += 257;
input.DropBits(5);
// System.err.println("LNUM: "+lnum);
mode = DNUM;
goto case DNUM; // fall through
case DNUM:
dnum = input.PeekBits(5);
if (dnum < 0) {
return false;
}
dnum++;
input.DropBits(5);
// System.err.println("DNUM: "+dnum);
num = lnum + dnum;
litdistLens = new byte[num];
mode = BLNUM;
goto case BLNUM; // fall through
case BLNUM:
blnum = input.PeekBits(4);
if (blnum < 0) {
return false;
}
blnum += 4;
input.DropBits(4);
blLens = new byte[19];
ptr = 0;
// System.err.println("BLNUM: "+blnum);
mode = BLLENS;
goto case BLLENS; // fall through
case BLLENS:
while (ptr < blnum) {
int len = input.PeekBits(3);
if (len < 0) {
return false;
}
input.DropBits(3);
// System.err.println("blLens["+BL_ORDER[ptr]+"]: "+len);
blLens[BL_ORDER[ptr]] = (byte)len;
ptr++;
}
blTree = new InflaterHuffmanTree(blLens);
blLens = null;
ptr = 0;
mode = LENS;
goto case LENS; // fall through
case LENS: {
int symbol;
while (((symbol = blTree.GetSymbol(input)) & ~15) == 0) {
/* Normal case: symbol in [0..15] */
// System.err.println("litdistLens["+ptr+"]: "+symbol);
litdistLens[ptr++] = lastLen = (byte)symbol;
if (ptr == num) {
/* Finished */
return true;
}
}
/* need more input ? */
if (symbol < 0) {
return false;
}
/* otherwise repeat code */
if (symbol >= 17) {
/* repeat zero */
// System.err.println("repeating zero");
lastLen = 0;
} else {
if (ptr == 0) {
throw new SharpZipBaseException();
}
}
repSymbol = symbol - 16;
}
mode = REPS;
goto case REPS; // fall through
case REPS: {
int bits = repBits[repSymbol];
int count = input.PeekBits(bits);
if (count < 0) {
return false;
}
input.DropBits(bits);
count += repMin[repSymbol];
// System.err.println("litdistLens repeated: "+count);
if (ptr + count > num) {
throw new SharpZipBaseException();
}
while (count-- > 0) {
litdistLens[ptr++] = lastLen;
}
if (ptr == num) {
/* Finished */
return true;
}
}
mode = LENS;
goto decode_loop;
}
}
}
/// <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"); } }