// 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; }