|
public Decode ( |
||
| input | ||
| return | 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");
}
}
