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Diffstat (limited to 'src/vcdiff_defs.h')
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diff --git a/src/vcdiff_defs.h b/src/vcdiff_defs.h new file mode 100644 index 0000000..b59af53 --- /dev/null +++ b/src/vcdiff_defs.h @@ -0,0 +1,196 @@ +// Copyright 2008 Google Inc. +// Author: Lincoln Smith +// +// Licensed under the Apache License, Version 2.0 (the "License"); +// you may not use this file except in compliance with the License. +// You may obtain a copy of the License at +// +// http://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, software +// distributed under the License is distributed on an "AS IS" BASIS, +// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +// See the License for the specific language governing permissions and +// limitations under the License. +// +// Types and value definitions to support the implementation of RFC 3284 - +// The VCDIFF Generic Differencing and Compression Data Format. +// The RFC text can be found at http://www.faqs.org/rfcs/rfc3284.html +// Many of the definitions below reference sections in that text. + +#ifndef OPEN_VCDIFF_VCDIFF_DEFS_H_ +#define OPEN_VCDIFF_VCDIFF_DEFS_H_ + +#include <config.h> +#include <limits.h> // UCHAR_MAX +#include <stdint.h> // int32_t + +namespace open_vcdiff { + +enum VCDiffResult { + RESULT_SUCCESS = 0, + // Many functions within open-vcdiff return signed integer types, + // and can also return either of these special negative values: + // + // An error occurred while performing the requested operation. + RESULT_ERROR = -1, + // The end of available data was reached + // before the requested operation could be completed. + RESULT_END_OF_DATA = -2 +}; + +// The delta file header section as described in section 4.1 of the RFC: +// +// "Each delta file starts with a header section organized as below. +// Note the convention that square-brackets enclose optional items. +// +// Header1 - byte = 0xD6 +// Header2 - byte = 0xC3 +// Header3 - byte = 0xC4 +// Header4 - byte +// Hdr_Indicator - byte +// [Secondary compressor ID] - byte +// [Length of code table data] - integer +// [Code table data] +// +// The first three Header bytes are the ASCII characters 'V', 'C' and +// 'D' with their most significant bits turned on (in hexadecimal, the +// values are 0xD6, 0xC3, and 0xC4). The fourth Header byte is +// currently set to zero. In the future, it might be used to indicate +// the version of Vcdiff." +// +typedef struct DeltaFileHeader { + unsigned char header1; // Always 0xD6 ('V' | 0x80) + unsigned char header2; // Always 0xC3 ('C' | 0x80) + unsigned char header3; // Always 0xC4 ('D' | 0x80) + unsigned char header4; // 0x00 for standard format, 'S' if extensions used + unsigned char hdr_indicator; +} DeltaFileHeader; + +// The possible values for the Hdr_Indicator field, as described +// in section 4.1 of the RFC: +// +// "The Hdr_Indicator byte shows if there is any initialization data +// required to aid in the reconstruction of data in the Window sections. +// This byte MAY have non-zero values for either, both, or neither of +// the two bits VCD_DECOMPRESS and VCD_CODETABLE below: +// +// 7 6 5 4 3 2 1 0 +// +-+-+-+-+-+-+-+-+ +// | | | | | | | | | +// +-+-+-+-+-+-+-+-+ +// ^ ^ +// | | +// | +-- VCD_DECOMPRESS +// +---- VCD_CODETABLE +// +// If bit 0 (VCD_DECOMPRESS) is non-zero, this indicates that a +// secondary compressor may have been used to further compress certain +// parts of the delta encoding data [...]" +// [Secondary compressors are not supported by open-vcdiff.] +// +// "If bit 1 (VCD_CODETABLE) is non-zero, this indicates that an +// application-defined code table is to be used for decoding the delta +// instructions. [...]" +// +const unsigned char VCD_DECOMPRESS = 0x01; +const unsigned char VCD_CODETABLE = 0x02; + +// The possible values for the Win_Indicator field, as described +// in section 4.2 of the RFC: +// +// "Win_Indicator: +// +// This byte is a set of bits, as shown: +// +// 7 6 5 4 3 2 1 0 +// +-+-+-+-+-+-+-+-+ +// | | | | | | | | | +// +-+-+-+-+-+-+-+-+ +// ^ ^ +// | | +// | +-- VCD_SOURCE +// +---- VCD_TARGET +// +// If bit 0 (VCD_SOURCE) is non-zero, this indicates that a +// segment of data from the "source" file was used as the +// corresponding source window of data to encode the target +// window. The decoder will use this same source data segment to +// decode the target window. +// +// If bit 1 (VCD_TARGET) is non-zero, this indicates that a +// segment of data from the "target" file was used as the +// corresponding source window of data to encode the target +// window. As above, this same source data segment is used to +// decode the target window. +// +// The Win_Indicator byte MUST NOT have more than one of the bits +// set (non-zero). It MAY have none of these bits set." +// +const unsigned char VCD_SOURCE = 0x01; +const unsigned char VCD_TARGET = 0x02; +// If this flag is set, the delta window includes an Adler32 checksum +// of the target window data. Not part of the RFC draft standard. +const unsigned char VCD_CHECKSUM = 0x04; + +// The possible values for the Delta_Indicator field, as described +// in section 4.3 of the RFC: +// +// "Delta_Indicator: +// This byte is a set of bits, as shown: +// +// 7 6 5 4 3 2 1 0 +// +-+-+-+-+-+-+-+-+ +// | | | | | | | | | +// +-+-+-+-+-+-+-+-+ +// ^ ^ ^ +// | | | +// | | +-- VCD_DATACOMP +// | +---- VCD_INSTCOMP +// +------ VCD_ADDRCOMP +// +// VCD_DATACOMP: bit value 1. +// VCD_INSTCOMP: bit value 2. +// VCD_ADDRCOMP: bit value 4. +// +// [...] If the bit VCD_DECOMPRESS (Section 4.1) was on, each of these +// sections may have been compressed using the specified secondary +// compressor. The bit positions 0 (VCD_DATACOMP), 1 +// (VCD_INSTCOMP), and 2 (VCD_ADDRCOMP) respectively indicate, if +// non-zero, that the corresponding parts are compressed." +// [Secondary compressors are not supported, so open-vcdiff decoding will fail +// if these bits are not all zero.] +// +const unsigned char VCD_DATACOMP = 0x01; +const unsigned char VCD_INSTCOMP = 0x02; +const unsigned char VCD_ADDRCOMP = 0x04; + +// A COPY address has 32 bits, which places a limit +// of 2GB on the maximum combined size of the dictionary plus +// the target window (= the chunk of data to be encoded.) +typedef int32_t VCDAddress; + +// The address modes used for COPY instructions, as defined in +// section 5.3 of the RFC. +// +// The first two modes (0 and 1) are defined as SELF (addressing forward +// from the beginning of the source window) and HERE (addressing backward +// from the current position in the source window + previously decoded +// target data.) +// +// After those first two modes, there are a variable number of NEAR modes +// (which take a recently-used address and add a positive offset to it) +// and SAME modes (which match a previously-used address using a "hash" of +// the lowest bits of the address.) The number of NEAR and SAME modes +// depends on the defined size of the address cache; since this number is +// variable, these modes cannot be specified as enum values. +enum VCDiffModes { + VCD_SELF_MODE = 0, + VCD_HERE_MODE = 1, + VCD_FIRST_NEAR_MODE = 2, + VCD_MAX_MODES = UCHAR_MAX + 1 // 256 +}; + +} // namespace open_vcdiff + +#endif // OPEN_VCDIFF_VCDIFF_DEFS_H_ |