public void ZipCrc32() { var underTestCrc32 = new ZipCrc32(); Assert.AreEqual(0x0, underTestCrc32.Value); underTestCrc32.Update(check); Assert.AreEqual(0xCBF43926, underTestCrc32.Value); underTestCrc32.Reset(); Assert.AreEqual(0x0, underTestCrc32.Value); exceptionTesting(underTestCrc32); }
/// <summary> /// Reads uncompressed data into an array of bytes. /// </summary> /// <param name="buffer"> /// The buffer to read uncompressed data into. /// </param> /// <param name="offset"> /// The offset indicating where the data should be placed. /// </param> /// <param name="count"> /// The number of uncompressed bytes to be read. /// </param> /// <returns>Returns the number of bytes actually read.</returns> public override int Read(byte[] buffer, int offset, int count) { // A GZIP file can contain multiple blocks of compressed data, although this is quite rare. // A compressed block could potentially be empty, so we need to loop until we reach EOF or // we find data. while (true) { // If we haven't read the header for this block, read it if (!readGZIPHeader) { // Try to read header. If there is no header (0 bytes available), this is EOF. If there is // an incomplete header, this will throw an exception. try { if (!ReadHeader()) { return(0); } } catch (Exception ex) when(completedLastBlock && (ex is InvalidDataException || ex is EndOfStreamException)) { // if we completed the last block (i.e. we're in a stream that has multiple blocks concatenated // we want to return gracefully from any header parsing exceptions since sometimes there may // be trailing garbage on a stream return(0); } } // Try to read compressed data var bytesRead = base.Read(buffer, offset, count); if (bytesRead > 0) { crc.Update(buffer, offset, bytesRead); } // If this is the end of stream, read the footer if (Inflater.IsDone) { ReadFooter(); } if (bytesRead > 0) { return(bytesRead); } } }
bool ReadHeader() { // Initialize CRC for this block crc = new ZipCrc32(); // Make sure there is data in file. We can't rely on ReadLeByte() to fill the buffer, as this could be EOF, // which is fine, but ReadLeByte() throws an exception if it doesn't find data, so we do this part ourselves. if (InputBuffer.Available <= 0) { InputBuffer.Fill(); if (InputBuffer.Available <= 0) { // No header, EOF. return(false); } } // 1. Check the two magic bytes var headCRC = new ZipCrc32(); var magic = InputBuffer.ReadLeByte(); if (magic < 0) { throw new EndOfStreamException("EOS reading GZIP header"); } headCRC.Update(magic); if (magic != (GZipConstants.MAGIC >> 8)) { throw new InvalidDataException("Error GZIP header, first magic byte doesn't match"); } // magic = baseInputStream.ReadByte(); magic = InputBuffer.ReadLeByte(); if (magic < 0) { throw new EndOfStreamException("EOS reading GZIP header"); } if (magic != (GZipConstants.MAGIC & 0xFF)) { throw new InvalidDataException("Error GZIP header, second magic byte doesn't match"); } headCRC.Update(magic); // 2. Check the compression type (must be 8) var compressionType = InputBuffer.ReadLeByte(); if (compressionType < 0) { throw new EndOfStreamException("EOS reading GZIP header"); } if (compressionType != 8) { throw new InvalidDataException("Error GZIP header, data not in deflate format"); } headCRC.Update(compressionType); // 3. Check the flags var flags = InputBuffer.ReadLeByte(); if (flags < 0) { throw new EndOfStreamException("EOS reading GZIP header"); } headCRC.Update(flags); /* This flag byte is divided into individual bits as follows: * * bit 0 FTEXT * bit 1 FHCRC * bit 2 FEXTRA * bit 3 FNAME * bit 4 FCOMMENT * bit 5 reserved * bit 6 reserved * bit 7 reserved */ // 3.1 Check the reserved bits are zero if ((flags & 0xE0) != 0) { throw new InvalidDataException("Reserved flag bits in GZIP header != 0"); } // 4.-6. Skip the modification time, extra flags, and OS type for (var i = 0; i < 6; i++) { var readByte = InputBuffer.ReadLeByte(); if (readByte < 0) { throw new EndOfStreamException("EOS reading GZIP header"); } headCRC.Update(readByte); } // 7. Read extra field if ((flags & (int)GZipFlags.Extra) != 0) { // XLEN is total length of extra subfields, we will skip them all int len1, len2; len1 = InputBuffer.ReadLeByte(); len2 = InputBuffer.ReadLeByte(); if ((len1 < 0) || (len2 < 0)) { throw new EndOfStreamException("EOS reading GZIP header"); } headCRC.Update(len1); headCRC.Update(len2); var extraLen = (len2 << 8) | len1; // gzip is LSB first for (var i = 0; i < extraLen; i++) { var readByte = InputBuffer.ReadLeByte(); if (readByte < 0) { throw new EndOfStreamException("EOS reading GZIP header"); } headCRC.Update(readByte); } } // 8. Read file name if ((flags & (int)GZipFlags.Name) != 0) { int readByte; while ((readByte = InputBuffer.ReadLeByte()) > 0) { headCRC.Update(readByte); } if (readByte < 0) { throw new EndOfStreamException("EOS reading GZIP header"); } headCRC.Update(readByte); } // 9. Read comment if ((flags & (int)GZipFlags.Comment) != 0) { int readByte; while ((readByte = InputBuffer.ReadLeByte()) > 0) { headCRC.Update(readByte); } if (readByte < 0) { throw new EndOfStreamException("EOS reading GZIP header"); } headCRC.Update(readByte); } // 10. Read header CRC if ((flags & (int)GZipFlags.CRC) != 0) { int tempByte; var crcval = InputBuffer.ReadLeByte(); if (crcval < 0) { throw new EndOfStreamException("EOS reading GZIP header"); } tempByte = InputBuffer.ReadLeByte(); if (tempByte < 0) { throw new EndOfStreamException("EOS reading GZIP header"); } crcval = (crcval << 8) | tempByte; if (crcval != ((int)headCRC.Value & 0xffff)) { throw new InvalidDataException("Header CRC value mismatch"); } } readGZIPHeader = true; return(true); }