1 // Copyright (c) 2011 The Chromium Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style license that can be 3 // found in the LICENSE file. 4 5 // The GZipHeader class allows you to parse a gzip header, such as you 6 // might find at the beginning of a file compressed by gzip (ie, a .gz 7 // file), or at the beginning of an HTTP response that uses a gzip 8 // Content-Encoding. See RFC 1952 for the specification for the gzip 9 // header. 10 // 11 // The model is that you call ReadMore() for each chunk of bytes 12 // you've read from a file or socket. 13 // 14 15 #ifndef NET_BASE_GZIP_HEADER_H_ 16 #define NET_BASE_GZIP_HEADER_H_ 17 #pragma once 18 19 #include "base/basictypes.h" 20 21 namespace net { 22 23 class GZipHeader { 24 public: 25 enum Status { 26 INCOMPLETE_HEADER, // don't have all the bits yet... 27 COMPLETE_HEADER, // complete, valid header 28 INVALID_HEADER, // found something invalid in the header 29 }; 30 31 GZipHeader(); 32 ~GZipHeader(); 33 34 // Wipe the slate clean and start from scratch. 35 void Reset(); 36 37 // Attempt to parse the given buffer as the next installment of 38 // bytes from a gzip header. If the bytes we've seen so far do not 39 // yet constitute a complete gzip header, return 40 // INCOMPLETE_HEADER. If these bytes do not constitute a *valid* 41 // gzip header, return INVALID_HEADER. When we've seen a complete 42 // gzip header, return COMPLETE_HEADER and set the pointer pointed 43 // to by header_end to the first byte beyond the gzip header. 44 Status ReadMore(const char* inbuf, 45 int inbuf_len, 46 const char** header_end); 47 private: 48 enum { // flags (see RFC) 49 FLAG_FTEXT = 0x01, // bit 0 set: file probably ascii text 50 FLAG_FHCRC = 0x02, // bit 1 set: header CRC present 51 FLAG_FEXTRA = 0x04, // bit 2 set: extra field present 52 FLAG_FNAME = 0x08, // bit 3 set: original file name present 53 FLAG_FCOMMENT = 0x10, // bit 4 set: file comment present 54 FLAG_RESERVED = 0xE0, // bits 5..7: reserved 55 }; 56 57 enum State { 58 // The first 10 bytes are the fixed-size header: 59 IN_HEADER_ID1, 60 IN_HEADER_ID2, 61 IN_HEADER_CM, 62 IN_HEADER_FLG, 63 IN_HEADER_MTIME_BYTE_0, 64 IN_HEADER_MTIME_BYTE_1, 65 IN_HEADER_MTIME_BYTE_2, 66 IN_HEADER_MTIME_BYTE_3, 67 IN_HEADER_XFL, 68 IN_HEADER_OS, 69 70 IN_XLEN_BYTE_0, 71 IN_XLEN_BYTE_1, 72 IN_FEXTRA, 73 74 IN_FNAME, 75 76 IN_FCOMMENT, 77 78 IN_FHCRC_BYTE_0, 79 IN_FHCRC_BYTE_1, 80 81 IN_DONE, 82 }; 83 84 static const uint8 magic[]; // gzip magic header 85 86 int state_; // our current State in the parsing FSM: an int so we can ++ 87 uint8 flags_; // the flags byte of the header ("FLG" in the RFC) 88 uint16 extra_length_; // how much of the "extra field" we have yet to read 89 90 DISALLOW_COPY_AND_ASSIGN(GZipHeader); 91 }; 92 93 } // namespace net 94 95 #endif // NET_BASE_GZIP_HEADER_H_ 96