1 // Copyright 2014 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_FILTER_GZIP_HEADER_H_ 16 #define NET_FILTER_GZIP_HEADER_H_ 17 18 #include "base/basictypes.h" 19 20 namespace net { 21 22 class GZipHeader { 23 public: 24 enum Status { 25 INCOMPLETE_HEADER, // don't have all the bits yet... 26 COMPLETE_HEADER, // complete, valid header 27 INVALID_HEADER, // found something invalid in the header 28 }; 29 30 GZipHeader(); 31 ~GZipHeader(); 32 33 // Wipe the slate clean and start from scratch. 34 void Reset(); 35 36 // Attempt to parse the given buffer as the next installment of 37 // bytes from a gzip header. If the bytes we've seen so far do not 38 // yet constitute a complete gzip header, return 39 // INCOMPLETE_HEADER. If these bytes do not constitute a *valid* 40 // gzip header, return INVALID_HEADER. When we've seen a complete 41 // gzip header, return COMPLETE_HEADER and set the pointer pointed 42 // to by header_end to the first byte beyond the gzip header. 43 Status ReadMore(const char* inbuf, 44 int inbuf_len, 45 const char** header_end); 46 private: 47 enum { // flags (see RFC) 48 FLAG_FTEXT = 0x01, // bit 0 set: file probably ascii text 49 FLAG_FHCRC = 0x02, // bit 1 set: header CRC present 50 FLAG_FEXTRA = 0x04, // bit 2 set: extra field present 51 FLAG_FNAME = 0x08, // bit 3 set: original file name present 52 FLAG_FCOMMENT = 0x10, // bit 4 set: file comment present 53 FLAG_RESERVED = 0xE0, // bits 5..7: reserved 54 }; 55 56 enum State { 57 // The first 10 bytes are the fixed-size header: 58 IN_HEADER_ID1, 59 IN_HEADER_ID2, 60 IN_HEADER_CM, 61 IN_HEADER_FLG, 62 IN_HEADER_MTIME_BYTE_0, 63 IN_HEADER_MTIME_BYTE_1, 64 IN_HEADER_MTIME_BYTE_2, 65 IN_HEADER_MTIME_BYTE_3, 66 IN_HEADER_XFL, 67 IN_HEADER_OS, 68 69 IN_XLEN_BYTE_0, 70 IN_XLEN_BYTE_1, 71 IN_FEXTRA, 72 73 IN_FNAME, 74 75 IN_FCOMMENT, 76 77 IN_FHCRC_BYTE_0, 78 IN_FHCRC_BYTE_1, 79 80 IN_DONE, 81 }; 82 83 static const uint8 magic[]; // gzip magic header 84 85 int state_; // our current State in the parsing FSM: an int so we can ++ 86 uint8 flags_; // the flags byte of the header ("FLG" in the RFC) 87 uint16 extra_length_; // how much of the "extra field" we have yet to read 88 89 DISALLOW_COPY_AND_ASSIGN(GZipHeader); 90 }; 91 92 } // namespace net 93 94 #endif // NET_FILTER_GZIP_HEADER_H_ 95