openvcdiff | 311c714 | 2008-08-26 19:29:25 +0000 | [diff] [blame] | 1 | // Copyright 2008 Google Inc. |
| 2 | // Author: Lincoln Smith |
| 3 | // |
| 4 | // Licensed under the Apache License, Version 2.0 (the "License"); |
| 5 | // you may not use this file except in compliance with the License. |
| 6 | // You may obtain a copy of the License at |
| 7 | // |
| 8 | // http://www.apache.org/licenses/LICENSE-2.0 |
| 9 | // |
| 10 | // Unless required by applicable law or agreed to in writing, software |
| 11 | // distributed under the License is distributed on an "AS IS" BASIS, |
| 12 | // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 13 | // See the License for the specific language governing permissions and |
| 14 | // limitations under the License. |
| 15 | // |
| 16 | // Types and value definitions to support the implementation of RFC 3284 - |
| 17 | // The VCDIFF Generic Differencing and Compression Data Format. |
| 18 | // The RFC text can be found at http://www.faqs.org/rfcs/rfc3284.html |
| 19 | // Many of the definitions below reference sections in that text. |
| 20 | |
| 21 | #ifndef OPEN_VCDIFF_VCDIFF_DEFS_H_ |
| 22 | #define OPEN_VCDIFF_VCDIFF_DEFS_H_ |
| 23 | |
| 24 | #include <config.h> |
openvcdiff | 28db807 | 2008-10-10 23:29:11 +0000 | [diff] [blame] | 25 | #include <limits.h> // UCHAR_MAX |
openvcdiff | 311c714 | 2008-08-26 19:29:25 +0000 | [diff] [blame] | 26 | #include <stdint.h> // int32_t |
openvcdiff | 311c714 | 2008-08-26 19:29:25 +0000 | [diff] [blame] | 27 | |
| 28 | namespace open_vcdiff { |
| 29 | |
| 30 | enum VCDiffResult { |
| 31 | RESULT_SUCCESS = 0, |
| 32 | // Many functions within open-vcdiff return signed integer types, |
| 33 | // and can also return either of these special negative values: |
| 34 | // |
| 35 | // An error occurred while performing the requested operation. |
| 36 | RESULT_ERROR = -1, |
| 37 | // The end of available data was reached |
| 38 | // before the requested operation could be completed. |
| 39 | RESULT_END_OF_DATA = -2 |
| 40 | }; |
| 41 | |
| 42 | // The delta file header section as described in section 4.1 of the RFC: |
| 43 | // |
| 44 | // "Each delta file starts with a header section organized as below. |
| 45 | // Note the convention that square-brackets enclose optional items. |
| 46 | // |
| 47 | // Header1 - byte = 0xD6 |
| 48 | // Header2 - byte = 0xC3 |
| 49 | // Header3 - byte = 0xC4 |
| 50 | // Header4 - byte |
| 51 | // Hdr_Indicator - byte |
| 52 | // [Secondary compressor ID] - byte |
| 53 | // [Length of code table data] - integer |
| 54 | // [Code table data] |
| 55 | // |
| 56 | // The first three Header bytes are the ASCII characters 'V', 'C' and |
| 57 | // 'D' with their most significant bits turned on (in hexadecimal, the |
| 58 | // values are 0xD6, 0xC3, and 0xC4). The fourth Header byte is |
| 59 | // currently set to zero. In the future, it might be used to indicate |
| 60 | // the version of Vcdiff." |
| 61 | // |
| 62 | typedef struct DeltaFileHeader { |
| 63 | unsigned char header1; // Always 0xD6 ('V' | 0x80) |
| 64 | unsigned char header2; // Always 0xC3 ('C' | 0x80) |
| 65 | unsigned char header3; // Always 0xC4 ('D' | 0x80) |
| 66 | unsigned char header4; // 0x00 for standard format, 'S' if extensions used |
| 67 | unsigned char hdr_indicator; |
| 68 | } DeltaFileHeader; |
| 69 | |
| 70 | // The possible values for the Hdr_Indicator field, as described |
| 71 | // in section 4.1 of the RFC: |
| 72 | // |
| 73 | // "The Hdr_Indicator byte shows if there is any initialization data |
| 74 | // required to aid in the reconstruction of data in the Window sections. |
| 75 | // This byte MAY have non-zero values for either, both, or neither of |
| 76 | // the two bits VCD_DECOMPRESS and VCD_CODETABLE below: |
| 77 | // |
| 78 | // 7 6 5 4 3 2 1 0 |
| 79 | // +-+-+-+-+-+-+-+-+ |
| 80 | // | | | | | | | | | |
| 81 | // +-+-+-+-+-+-+-+-+ |
| 82 | // ^ ^ |
| 83 | // | | |
| 84 | // | +-- VCD_DECOMPRESS |
| 85 | // +---- VCD_CODETABLE |
| 86 | // |
| 87 | // If bit 0 (VCD_DECOMPRESS) is non-zero, this indicates that a |
| 88 | // secondary compressor may have been used to further compress certain |
| 89 | // parts of the delta encoding data [...]" |
| 90 | // [Secondary compressors are not supported by open-vcdiff.] |
| 91 | // |
| 92 | // "If bit 1 (VCD_CODETABLE) is non-zero, this indicates that an |
| 93 | // application-defined code table is to be used for decoding the delta |
| 94 | // instructions. [...]" |
| 95 | // |
| 96 | const unsigned char VCD_DECOMPRESS = 0x01; |
| 97 | const unsigned char VCD_CODETABLE = 0x02; |
| 98 | |
| 99 | // The possible values for the Win_Indicator field, as described |
| 100 | // in section 4.2 of the RFC: |
| 101 | // |
| 102 | // "Win_Indicator: |
| 103 | // |
| 104 | // This byte is a set of bits, as shown: |
| 105 | // |
| 106 | // 7 6 5 4 3 2 1 0 |
| 107 | // +-+-+-+-+-+-+-+-+ |
| 108 | // | | | | | | | | | |
| 109 | // +-+-+-+-+-+-+-+-+ |
| 110 | // ^ ^ |
| 111 | // | | |
| 112 | // | +-- VCD_SOURCE |
| 113 | // +---- VCD_TARGET |
| 114 | // |
| 115 | // If bit 0 (VCD_SOURCE) is non-zero, this indicates that a |
| 116 | // segment of data from the "source" file was used as the |
| 117 | // corresponding source window of data to encode the target |
| 118 | // window. The decoder will use this same source data segment to |
| 119 | // decode the target window. |
| 120 | // |
| 121 | // If bit 1 (VCD_TARGET) is non-zero, this indicates that a |
| 122 | // segment of data from the "target" file was used as the |
| 123 | // corresponding source window of data to encode the target |
| 124 | // window. As above, this same source data segment is used to |
| 125 | // decode the target window. |
| 126 | // |
| 127 | // The Win_Indicator byte MUST NOT have more than one of the bits |
| 128 | // set (non-zero). It MAY have none of these bits set." |
| 129 | // |
| 130 | const unsigned char VCD_SOURCE = 0x01; |
| 131 | const unsigned char VCD_TARGET = 0x02; |
| 132 | // If this flag is set, the delta window includes an Adler32 checksum |
| 133 | // of the target window data. Not part of the RFC draft standard. |
| 134 | const unsigned char VCD_CHECKSUM = 0x04; |
| 135 | |
| 136 | // The possible values for the Delta_Indicator field, as described |
| 137 | // in section 4.3 of the RFC: |
| 138 | // |
| 139 | // "Delta_Indicator: |
| 140 | // This byte is a set of bits, as shown: |
| 141 | // |
| 142 | // 7 6 5 4 3 2 1 0 |
| 143 | // +-+-+-+-+-+-+-+-+ |
| 144 | // | | | | | | | | | |
| 145 | // +-+-+-+-+-+-+-+-+ |
| 146 | // ^ ^ ^ |
| 147 | // | | | |
| 148 | // | | +-- VCD_DATACOMP |
| 149 | // | +---- VCD_INSTCOMP |
| 150 | // +------ VCD_ADDRCOMP |
| 151 | // |
| 152 | // VCD_DATACOMP: bit value 1. |
| 153 | // VCD_INSTCOMP: bit value 2. |
| 154 | // VCD_ADDRCOMP: bit value 4. |
| 155 | // |
| 156 | // [...] If the bit VCD_DECOMPRESS (Section 4.1) was on, each of these |
| 157 | // sections may have been compressed using the specified secondary |
| 158 | // compressor. The bit positions 0 (VCD_DATACOMP), 1 |
| 159 | // (VCD_INSTCOMP), and 2 (VCD_ADDRCOMP) respectively indicate, if |
| 160 | // non-zero, that the corresponding parts are compressed." |
| 161 | // [Secondary compressors are not supported, so open-vcdiff decoding will fail |
| 162 | // if these bits are not all zero.] |
| 163 | // |
| 164 | const unsigned char VCD_DATACOMP = 0x01; |
| 165 | const unsigned char VCD_INSTCOMP = 0x02; |
| 166 | const unsigned char VCD_ADDRCOMP = 0x04; |
| 167 | |
| 168 | // A COPY address has 32 bits, which places a limit |
| 169 | // of 2GB on the maximum combined size of the dictionary plus |
| 170 | // the target window (= the chunk of data to be encoded.) |
| 171 | typedef int32_t VCDAddress; |
| 172 | |
| 173 | // The address modes used for COPY instructions, as defined in |
| 174 | // section 5.3 of the RFC. |
| 175 | // |
| 176 | // The first two modes (0 and 1) are defined as SELF (addressing forward |
| 177 | // from the beginning of the source window) and HERE (addressing backward |
| 178 | // from the current position in the source window + previously decoded |
| 179 | // target data.) |
| 180 | // |
| 181 | // After those first two modes, there are a variable number of NEAR modes |
| 182 | // (which take a recently-used address and add a positive offset to it) |
| 183 | // and SAME modes (which match a previously-used address using a "hash" of |
| 184 | // the lowest bits of the address.) The number of NEAR and SAME modes |
| 185 | // depends on the defined size of the address cache; since this number is |
| 186 | // variable, these modes cannot be specified as enum values. |
| 187 | enum VCDiffModes { |
| 188 | VCD_SELF_MODE = 0, |
| 189 | VCD_HERE_MODE = 1, |
| 190 | VCD_FIRST_NEAR_MODE = 2, |
| 191 | VCD_MAX_MODES = UCHAR_MAX + 1 // 256 |
| 192 | }; |
| 193 | |
| 194 | } // namespace open_vcdiff |
| 195 | |
| 196 | #endif // OPEN_VCDIFF_VCDIFF_DEFS_H_ |