public bool ReadGzipHeader() {
int bits;
switch (this.gzipHeaderSubstate) {
case GZIPHeaderState.ReadingID1:
bits = this.input.GetBits(8);
if (bits >= 0) {
if (bits != 0x1f) {
throw new InvalidDataException("The magic number in GZip header is not correct. Make sure you are passing in a GZip stream.");
}
this.gzipHeaderSubstate = GZIPHeaderState.ReadingID2;
break;
}
return false;
case GZIPHeaderState.ReadingID2:
break;
case GZIPHeaderState.ReadingCM:
goto Label_00AF;
case GZIPHeaderState.ReadingFLG:
goto Label_00DD;
case GZIPHeaderState.ReadingMMTime:
goto Label_0105;
case GZIPHeaderState.ReadingXFL:
goto Label_0141;
case GZIPHeaderState.ReadingOS:
goto Label_015B;
case GZIPHeaderState.ReadingXLen1:
goto Label_0175;
case GZIPHeaderState.ReadingXLen2:
goto Label_01A3;
case GZIPHeaderState.ReadingXLenData:
goto Label_01D5;
case GZIPHeaderState.ReadingFileName:
goto Label_0217;
case GZIPHeaderState.ReadingComment:
goto Label_0249;
case GZIPHeaderState.ReadingCRC16Part1:
goto Label_027C;
case GZIPHeaderState.ReadingCRC16Part2:
goto Label_02AB;
case GZIPHeaderState.Done:
goto Label_02C6;
default:
throw new InvalidDataException("Decoder is in some unknown state. This might be caused by corrupted data.");
}
bits = this.input.GetBits(8);
if (bits < 0) {
return false;
}
if (bits != 0x8b) {
throw new InvalidDataException("The magic number in GZip header is not correct. Make sure you are passing in a GZip stream.");
}
this.gzipHeaderSubstate = GZIPHeaderState.ReadingCM;
Label_00AF:
bits = this.input.GetBits(8);
if (bits < 0) {
return false;
}
if (bits != 8) {
throw new InvalidDataException("The compression mode specified in GZip header is unknown.");
}
this.gzipHeaderSubstate = GZIPHeaderState.ReadingFLG;
Label_00DD:
bits = this.input.GetBits(8);
if (bits < 0) {
return false;
}
this.gzip_header_flag = bits;
this.gzipHeaderSubstate = GZIPHeaderState.ReadingMMTime;
this.loopCounter = 0;
Label_0105:
bits = 0;
while (this.loopCounter < 4) {
if (this.input.GetBits(8) < 0) {
return false;
}
this.loopCounter++;
}
this.gzipHeaderSubstate = GZIPHeaderState.ReadingXFL;
this.loopCounter = 0;
Label_0141:
if (this.input.GetBits(8) < 0) {
return false;
}
this.gzipHeaderSubstate = GZIPHeaderState.ReadingOS;
Label_015B:
if (this.input.GetBits(8) < 0) {
return false;
}
this.gzipHeaderSubstate = GZIPHeaderState.ReadingXLen1;
Label_0175:
if ((this.gzip_header_flag & 4) == 0) {
goto Label_0217;
}
bits = this.input.GetBits(8);
if (bits < 0) {
return false;
}
this.gzip_header_xlen = bits;
this.gzipHeaderSubstate = GZIPHeaderState.ReadingXLen2;
Label_01A3:
bits = this.input.GetBits(8);
if (bits < 0) {
return false;
}
this.gzip_header_xlen |= bits << 8;
this.gzipHeaderSubstate = GZIPHeaderState.ReadingXLenData;
this.loopCounter = 0;
Label_01D5:
bits = 0;
while (this.loopCounter < this.gzip_header_xlen) {
if (this.input.GetBits(8) < 0) {
return false;
}
this.loopCounter++;
}
this.gzipHeaderSubstate = GZIPHeaderState.ReadingFileName;
this.loopCounter = 0;
Label_0217:
if ((this.gzip_header_flag & 8) == 0) {
this.gzipHeaderSubstate = GZIPHeaderState.ReadingComment;
}
else {
do {
bits = this.input.GetBits(8);
if (bits < 0) {
return false;
}
}
while (bits != 0);
this.gzipHeaderSubstate = GZIPHeaderState.ReadingComment;
}
Label_0249:
if ((this.gzip_header_flag & 0x10) == 0) {
this.gzipHeaderSubstate = GZIPHeaderState.ReadingCRC16Part1;
}
else {
do {
bits = this.input.GetBits(8);
if (bits < 0) {
return false;
}
}
while (bits != 0);
this.gzipHeaderSubstate = GZIPHeaderState.ReadingCRC16Part1;
}
Label_027C:
if ((this.gzip_header_flag & 2) == 0) {
this.gzipHeaderSubstate = GZIPHeaderState.Done;
goto Label_02C6;
}
if (this.input.GetBits(8) < 0) {
return false;
}
this.gzipHeaderSubstate = GZIPHeaderState.ReadingCRC16Part2;
Label_02AB:
if (this.input.GetBits(8) < 0) {
return false;
}
this.gzipHeaderSubstate = GZIPHeaderState.Done;
Label_02C6:
return true;
}
//Each block of compressed data begins with 3 header bits
// containing the following data:
// first bit BFINAL
// next 2 bits BTYPE
// Note that the header bits do not necessarily begin on a byte
// boundary, since a block does not necessarily occupy an integral
// number of bytes.
// BFINAL is set if and only if this is the last block of the data
// set.
// BTYPE specifies how the data are compressed, as follows:
// 00 - no compression
// 01 - compressed with fixed Huffman codes
// 10 - compressed with dynamic Huffman codes
// 11 - reserved (error)
// The only difference between the two compressed cases is how the
// Huffman codes for the literal/length and distance alphabets are
// defined.
//
// This function returns true for success (end of block or output window is full,)
// false if we are short of input
//
private bool Decode()
{
bool eob = false;
bool result = false;
if (Finished())
{
return(true);
}
if (using_gzip)
{
if (state == InflaterState.ReadingGZIPHeader)
{
if (!gZipDecoder.ReadGzipHeader())
{
return(false);
}
state = InflaterState.ReadingBFinal;
}
else if (state == InflaterState.StartReadingGZIPFooter || state == InflaterState.ReadingGZIPFooter)
{
if (!gZipDecoder.ReadGzipFooter())
{
return(false);
}
state = InflaterState.VerifyingGZIPFooter;
return(true);
}
}
if (state == InflaterState.ReadingBFinal) // reading bfinal bit
// Need 1 bit
{
if (!input.EnsureBitsAvailable(1))
{
return(false);
}
bfinal = input.GetBits(1);
state = InflaterState.ReadingBType;
}
if (state == InflaterState.ReadingBType)
{
// Need 2 bits
if (!input.EnsureBitsAvailable(2))
{
state = InflaterState.ReadingBType;
return(false);
}
blockType = (BlockType)input.GetBits(2);
if (blockType == BlockType.Dynamic)
{
Debug.WriteLineIf(CompressionTracingSwitch.Informational, "Decoding Dynamic Block", "Compression");
state = InflaterState.ReadingNumLitCodes;
}
else if (blockType == BlockType.Static)
{
Debug.WriteLineIf(CompressionTracingSwitch.Informational, "Decoding Static Block", "Compression");
literalLengthTree = HuffmanTree.StaticLiteralLengthTree;
distanceTree = HuffmanTree.StaticDistanceTree;
state = InflaterState.DecodeTop;
}
else if (blockType == BlockType.Uncompressed)
{
Debug.WriteLineIf(CompressionTracingSwitch.Informational, "Decoding UnCompressed Block", "Compression");
state = InflaterState.UncompressedAligning;
}
else
{
throw new InvalidDataException(SR.GetString(SR.UnknownBlockType));
}
}
if (blockType == BlockType.Dynamic)
{
if (state < InflaterState.DecodeTop) // we are reading the header
{
result = DecodeDynamicBlockHeader();
}
else
{
result = DecodeBlock(out eob); // this can returns true when output is full
}
}
else if (blockType == BlockType.Static)
{
result = DecodeBlock(out eob);
}
else if (blockType == BlockType.Uncompressed)
{
result = DecodeUncompressedBlock(out eob);
}
else
{
throw new InvalidDataException(SR.GetString(SR.UnknownBlockType));
}
//
// If we reached the end of the block and the block we were decoding had
// bfinal=1 (final block)
//
if (eob && (bfinal != 0))
{
if (using_gzip)
{
state = InflaterState.StartReadingGZIPFooter;
}
else
{
state = InflaterState.Done;
}
}
return(result);
}
