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// Copyright 2008, Google Inc.
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
// * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
// * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
// The GZipHeader class allows you to parse a gzip header, such as you
// might find at the beginning of a file compressed by gzip (ie, a .gz
// file), or at the beginning of an HTTP response that uses a gzip
// Content-Encoding. See RFC 1952 for the specification for the gzip
// header.
//
// The model is that you call ReadMore() for each chunk of bytes
// you've read from a file or socket.
//
#ifndef NET_BASE_GZIPHEADER_H__
#define NET_BASE_GZIPHEADER_H__
#include "base/basictypes.h"
class GZipHeader {
public:
GZipHeader() {
Reset();
}
~GZipHeader() {
}
// Wipe the slate clean and start from scratch.
void Reset() {
state_ = IN_HEADER_ID1;
flags_ = 0;
extra_length_ = 0;
}
enum Status {
INCOMPLETE_HEADER, // don't have all the bits yet...
COMPLETE_HEADER, // complete, valid header
INVALID_HEADER, // found something invalid in the header
};
// Attempt to parse the given buffer as the next installment of
// bytes from a gzip header. If the bytes we've seen so far do not
// yet constitute a complete gzip header, return
// INCOMPLETE_HEADER. If these bytes do not constitute a *valid*
// gzip header, return INVALID_HEADER. When we've seen a complete
// gzip header, return COMPLETE_HEADER and set the pointer pointed
// to by header_end to the first byte beyond the gzip header.
Status ReadMore(const char* inbuf, int inbuf_len,
const char** header_end);
private:
static const uint8 magic[]; // gzip magic header
enum { // flags (see RFC)
FLAG_FTEXT = 0x01, // bit 0 set: file probably ascii text
FLAG_FHCRC = 0x02, // bit 1 set: header CRC present
FLAG_FEXTRA = 0x04, // bit 2 set: extra field present
FLAG_FNAME = 0x08, // bit 3 set: original file name present
FLAG_FCOMMENT = 0x10, // bit 4 set: file comment present
FLAG_RESERVED = 0xE0, // bits 5..7: reserved
};
enum State {
// The first 10 bytes are the fixed-size header:
IN_HEADER_ID1,
IN_HEADER_ID2,
IN_HEADER_CM,
IN_HEADER_FLG,
IN_HEADER_MTIME_BYTE_0,
IN_HEADER_MTIME_BYTE_1,
IN_HEADER_MTIME_BYTE_2,
IN_HEADER_MTIME_BYTE_3,
IN_HEADER_XFL,
IN_HEADER_OS,
IN_XLEN_BYTE_0,
IN_XLEN_BYTE_1,
IN_FEXTRA,
IN_FNAME,
IN_FCOMMENT,
IN_FHCRC_BYTE_0,
IN_FHCRC_BYTE_1,
IN_DONE,
};
int state_; // our current State in the parsing FSM: an int so we can ++
uint8 flags_; // the flags byte of the header ("FLG" in the RFC)
uint16 extra_length_; // how much of the "extra field" we have yet to read
};
#endif // NET_BASE_GZIPHEADER_H__
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