// Copy up to length of bytes from input directly.
// This is used for uncompressed block.
public int CopyFrom(InputBuffer input, int length) {
length = Math.Min(Math.Min(length, WindowSize - bytesUsed), input.AvailableBytes);
int copied;
// We might need wrap around to copy all bytes.
int tailLen = WindowSize - end;
if (length > tailLen) {
// copy the first part
copied = input.CopyTo(window, end, tailLen);
if (copied == tailLen) {
// only try to copy the second part if we have enough bytes in input
copied += input.CopyTo(window, 0, length - tailLen);
}
}
else {
// only one copy is needed if there is no wrap around.
copied = input.CopyTo(window, end, length);
}
end = (end + copied) & WindowMask;
bytesUsed += copied;
return copied;
}
IFileFormatReader formatReader; // class to decode header and footer (e.g. gzip)
public Inflater() {
output = new OutputWindow();
input = new InputBuffer();
codeList = new byte[HuffmanTree.MaxLiteralTreeElements + HuffmanTree.MaxDistTreeElements];
codeLengthTreeCodeLength = new byte[HuffmanTree.NumberOfCodeLengthTreeElements];
Reset();
}
public bool ReadFooter(InputBuffer input) {
input.SkipToByteBoundary();
if (gzipFooterSubstate == GzipHeaderState.ReadingCRC) {
while (loopCounter < 4) {
int bits = input.GetBits(8);
if (bits < 0) {
return false;
}
expectedCrc32 |= ((uint)bits << (8 * loopCounter));
loopCounter++;
}
gzipFooterSubstate = GzipHeaderState.ReadingFileSize;
loopCounter = 0;
}
if (gzipFooterSubstate == GzipHeaderState.ReadingFileSize) {
if (loopCounter == 0)
expectedOutputStreamSizeModulo = 0;
while (loopCounter < 4) {
int bits = input.GetBits(8);
if (bits < 0) {
return false;
}
expectedOutputStreamSizeModulo |= ((uint) bits << (8 * loopCounter));
loopCounter++;
}
}
return true;
}
public bool ReadHeader(InputBuffer input) {
while (true) {
int bits;
switch (gzipHeaderSubstate) {
case GzipHeaderState.ReadingID1:
bits = input.GetBits(8);
if (bits < 0) {
return false;
}
if (bits != GZipConstants.ID1) {
throw new InvalidDataException(SR.GetString(SR.CorruptedGZipHeader));
}
gzipHeaderSubstate = GzipHeaderState.ReadingID2;
goto case GzipHeaderState.ReadingID2;
case GzipHeaderState.ReadingID2:
bits = input.GetBits(8);
if (bits < 0) {
return false;
}
if (bits != GZipConstants.ID2) {
throw new InvalidDataException(SR.GetString(SR.CorruptedGZipHeader));
}
gzipHeaderSubstate = GzipHeaderState.ReadingCM;
goto case GzipHeaderState.ReadingCM;
case GzipHeaderState.ReadingCM:
bits = input.GetBits(8);
if (bits < 0) {
return false;
}
if (bits != GZipConstants.Deflate) { // compression mode must be 8 (deflate)
throw new InvalidDataException(SR.GetString(SR.UnknownCompressionMode));
}
gzipHeaderSubstate = GzipHeaderState.ReadingFLG; ;
goto case GzipHeaderState.ReadingFLG;
case GzipHeaderState.ReadingFLG:
bits = input.GetBits(8);
if (bits < 0) {
return false;
}
gzip_header_flag = bits;
gzipHeaderSubstate = GzipHeaderState.ReadingMMTime;
loopCounter = 0; // 4 MMTIME bytes
goto case GzipHeaderState.ReadingMMTime;
case GzipHeaderState.ReadingMMTime:
bits = 0;
while (loopCounter < 4) {
bits = input.GetBits(8);
if (bits < 0) {
return false;
}
loopCounter++;
}
gzipHeaderSubstate = GzipHeaderState.ReadingXFL;
loopCounter = 0;
goto case GzipHeaderState.ReadingXFL;
case GzipHeaderState.ReadingXFL: // ignore XFL
bits = input.GetBits(8);
if (bits < 0) {
return false;
}
gzipHeaderSubstate = GzipHeaderState.ReadingOS;
goto case GzipHeaderState.ReadingOS;
case GzipHeaderState.ReadingOS: // ignore OS
bits = input.GetBits(8);
if (bits < 0) {
return false;
}
gzipHeaderSubstate = GzipHeaderState.ReadingXLen1;
goto case GzipHeaderState.ReadingXLen1;
case GzipHeaderState.ReadingXLen1:
if ((gzip_header_flag & (int)GZipOptionalHeaderFlags.ExtraFieldsFlag) == 0) {
goto case GzipHeaderState.ReadingFileName;
}
bits = input.GetBits(8);
if (bits < 0) {
return false;
}
gzip_header_xlen = bits;
gzipHeaderSubstate = GzipHeaderState.ReadingXLen2;
goto case GzipHeaderState.ReadingXLen2;
case GzipHeaderState.ReadingXLen2:
bits = input.GetBits(8);
if (bits < 0) {
return false;
}
gzip_header_xlen |= (bits << 8);
gzipHeaderSubstate = GzipHeaderState.ReadingXLenData;
loopCounter = 0; // 0 bytes of XLEN data read so far
goto case GzipHeaderState.ReadingXLenData;
case GzipHeaderState.ReadingXLenData:
bits = 0;
while (loopCounter < gzip_header_xlen) {
bits = input.GetBits(8);
if (bits < 0) {
return false;
}
loopCounter++;
}
gzipHeaderSubstate = GzipHeaderState.ReadingFileName;
loopCounter = 0;
goto case GzipHeaderState.ReadingFileName;
case GzipHeaderState.ReadingFileName:
if ((gzip_header_flag & (int)GZipOptionalHeaderFlags.FileNameFlag) == 0) {
gzipHeaderSubstate = GzipHeaderState.ReadingComment;
goto case GzipHeaderState.ReadingComment;
}
do {
bits = input.GetBits(8);
if (bits < 0) {
return false;
}
if (bits == 0) { // see '\0' in the file name string
break;
}
} while (true);
gzipHeaderSubstate = GzipHeaderState.ReadingComment;
goto case GzipHeaderState.ReadingComment;
case GzipHeaderState.ReadingComment:
if ((gzip_header_flag & (int)GZipOptionalHeaderFlags.CommentFlag) == 0) {
gzipHeaderSubstate = GzipHeaderState.ReadingCRC16Part1;
goto case GzipHeaderState.ReadingCRC16Part1;
}
do {
bits = input.GetBits(8);
if (bits < 0) {
return false;
}
if (bits == 0) { // see '\0' in the file name string
break;
}
} while (true);
gzipHeaderSubstate = GzipHeaderState.ReadingCRC16Part1;
goto case GzipHeaderState.ReadingCRC16Part1;
case GzipHeaderState.ReadingCRC16Part1:
if ((gzip_header_flag & (int)GZipOptionalHeaderFlags.CRCFlag) == 0) {
gzipHeaderSubstate = GzipHeaderState.Done;
goto case GzipHeaderState.Done;
}
bits = input.GetBits(8); // ignore crc
if (bits < 0) {
return false;
}
gzipHeaderSubstate = GzipHeaderState.ReadingCRC16Part2;
goto case GzipHeaderState.ReadingCRC16Part2;
case GzipHeaderState.ReadingCRC16Part2:
bits = input.GetBits(8); // ignore crc
if (bits < 0) {
return false;
}
gzipHeaderSubstate = GzipHeaderState.Done;
goto case GzipHeaderState.Done;
case GzipHeaderState.Done:
return true;
default:
Debug.Assert(false, "We should not reach unknown state!");
throw new InvalidDataException(SR.GetString(SR.UnknownState));
}
}
}
//
// This function will try to get enough bits from input and
// try to decode the bits.
// If there are no enought bits in the input, this function will return -1.
//
public int GetNextSymbol(InputBuffer input) {
// Try to load 16 bits into input buffer if possible and get the bitBuffer value.
// If there aren't 16 bits available we will return all we have in the
// input buffer.
uint bitBuffer = input.TryLoad16Bits();
if( input.AvailableBits == 0) { // running out of input.
return -1;
}
// decode an element
int symbol = table[bitBuffer & tableMask];
if( symbol < 0) { // this will be the start of the binary tree
// navigate the tree
uint mask = (uint)1 << tableBits;
do
{
symbol = -symbol;
if ((bitBuffer & mask) == 0)
symbol = left[symbol];
else
symbol = right[symbol];
mask <<= 1;
} while (symbol < 0);
}
int codeLength = codeLengthArray[symbol];
// huffman code lengths must be at least 1 bit long
if (codeLength <= 0)
{
throw new InvalidDataException(SR.GetString(SR.InvalidHuffmanData));
}
//
// If this code is longer than the # bits we had in the bit buffer (i.e.
// we read only part of the code), we can hit the entry in the table or the tree
// for another symbol. However the length of another symbol will not match the
// available bits count.
if (codeLength > input.AvailableBits)
{
// We already tried to load 16 bits and maximum length is 15,
// so this means we are running out of input.
return -1;
}
input.SkipBits(codeLength);
return symbol;
}