// switching to Inflater now
/// <summary>Parse the gzip trailer (assuming we're in the appropriate state).</summary>
/// <remarks>
/// Parse the gzip trailer (assuming we're in the appropriate state).
/// In order to deal with degenerate cases (e.g., user buffer is one byte
/// long), we copy trailer bytes (all 8 of 'em) to a local buffer.</p>
/// See http://www.ietf.org/rfc/rfc1952.txt for the gzip spec.
/// </remarks>
/// <exception cref="System.IO.IOException"/>
private void ExecuteTrailerState()
{
if (userBufLen <= 0)
{
return;
}
// verify that the CRC-32 of the decompressed stream matches the value
// stored in the gzip trailer
if (state == BuiltInGzipDecompressor.GzipStateLabel.TrailerCrc)
{
// localBuf was empty before we handed off to Inflater, so we handle this
// exactly like header fields
System.Diagnostics.Debug.Assert((localBufOff < 4));
// initially 0, but may need multiple calls
int n = Math.Min(userBufLen, 4 - localBufOff);
CopyBytesToLocal(n);
if (localBufOff >= 4)
{
long streamCRC = ReadUIntLE(localBuf, 0);
if (streamCRC != crc.GetValue())
{
throw new IOException("gzip stream CRC failure");
}
localBufOff = 0;
crc.Reset();
state = BuiltInGzipDecompressor.GzipStateLabel.TrailerSize;
}
}
if (userBufLen <= 0)
{
return;
}
// verify that the mod-2^32 decompressed stream size matches the value
// stored in the gzip trailer
if (state == BuiltInGzipDecompressor.GzipStateLabel.TrailerSize)
{
System.Diagnostics.Debug.Assert((localBufOff < 4));
// initially 0, but may need multiple calls
int n = Math.Min(userBufLen, 4 - localBufOff);
CopyBytesToLocal(n);
// modifies userBufLen, etc.
if (localBufOff >= 4)
{
// should be strictly ==
long inputSize = ReadUIntLE(localBuf, 0);
if (inputSize != (inflater.GetBytesWritten() & unchecked ((long)(0xffffffffL))))
{
throw new IOException("stored gzip size doesn't match decompressed size");
}
localBufOff = 0;
state = BuiltInGzipDecompressor.GzipStateLabel.Finished;
}
}
if (state == BuiltInGzipDecompressor.GzipStateLabel.Finished)
{
return;
}
}