| // 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. |
| |
| #ifndef OPEN_VCDIFF_HEADERPARSER_H_ |
| #define OPEN_VCDIFF_HEADERPARSER_H_ |
| |
| #include <config.h> |
| #include <stddef.h> // NULL |
| #include <stdint.h> // int32_t, uint32_t |
| #include "checksum.h" // VCDChecksum |
| #include "vcdiff_defs.h" // VCDiffResult |
| |
| namespace open_vcdiff { |
| |
| // This class contains a contiguous memory buffer with start and end pointers, |
| // as well as a position pointer which shows how much of the buffer has been |
| // parsed and how much remains. |
| // |
| // Because no virtual destructor is defined for ParseableChunk, a pointer to |
| // a child class of ParseableChunk must be destroyed using its specific type, |
| // rather than as a ParseableChunk*. |
| class ParseableChunk { |
| public: |
| ParseableChunk(const char* data_start, size_t data_size) { |
| SetDataBuffer(data_start, data_size); |
| } |
| |
| const char* End() const { return end_; } |
| |
| // The number of bytes remaining to be parsed. This is not necessarily the |
| // same as the initial size of the buffer; it changes with each call to |
| // Advance(). |
| size_t UnparsedSize() const { |
| return end_ - position_; |
| } |
| |
| // The number of bytes that have already been parsed. |
| size_t ParsedSize() const { |
| return position_ - start_; |
| } |
| |
| bool Empty() const { return 0 == UnparsedSize(); } |
| |
| // The start of the data remaining to be parsed. |
| const char* UnparsedData() const { return position_; } |
| |
| // Returns a pointer to the start of the data remaining to be parsed. |
| const char** UnparsedDataAddr() { return &position_; } |
| |
| // Moves the parsing position forward by number_of_bytes. |
| void Advance(size_t number_of_bytes); |
| |
| // Jumps the parsing position to a new location. |
| void SetPosition(const char* position); |
| |
| // Jumps the parsing position to the end of the data chunk. |
| void Finish() { |
| position_ = end_; |
| } |
| |
| // Jumps the parsing position so that there are now number_of_bytes |
| // bytes left to parse. This number should be smaller than the size of data |
| // to be parsed before the function was called. |
| void FinishExcept(size_t number_of_bytes); |
| |
| void SetDataBuffer(const char* data_start, size_t data_size) { |
| start_ = data_start; |
| end_ = data_start + data_size; |
| position_ = start_; |
| } |
| |
| private: |
| const char* start_; |
| const char* end_; |
| |
| // The current parsing position within the data chunk. |
| // Must always respect start_ <= position_ <= end_. |
| const char* position_; |
| |
| // Making these private avoids implicit copy constructor & assignment operator |
| ParseableChunk(const ParseableChunk&); |
| void operator=(const ParseableChunk&); |
| }; |
| |
| // Represents one of the three sections in the delta window, as described in |
| // RFC section 4.3: |
| // * Data section for ADDs and RUNs |
| // * Instructions and sizes section |
| // * Addresses section for COPYs |
| // When using the interleaved format, data and addresses are pulled from the |
| // instructions and sizes section rather than being stored in separate sections. |
| // For that reason, this class allows one DeltaWindowSection to be based on |
| // another, such that the same position pointer is shared by both sections; |
| // i.e., UnparsedDataAddr() returns the same value for both objects. |
| // To achieve this end, one extra level of indirection (a pointer to a |
| // ParseableChunk object) is added. |
| class DeltaWindowSection { |
| public: |
| DeltaWindowSection() : parseable_chunk_(NULL), owned_(true) { } |
| |
| ~DeltaWindowSection() { |
| FreeChunk(); |
| } |
| |
| void Init(const char* data_start, size_t data_size) { |
| if (owned_ && parseable_chunk_) { |
| // Reuse the already-allocated ParseableChunk object. |
| parseable_chunk_->SetDataBuffer(data_start, data_size); |
| } else { |
| parseable_chunk_ = new ParseableChunk(data_start, data_size); |
| owned_ = true; |
| } |
| } |
| |
| void Init(DeltaWindowSection* original) { |
| FreeChunk(); |
| parseable_chunk_ = original->parseable_chunk_; |
| owned_ = false; |
| } |
| |
| void Invalidate() { FreeChunk(); } |
| |
| bool IsOwned() const { return owned_; } |
| |
| // The following functions just pass their arguments to the underlying |
| // ParseableChunk object. |
| |
| const char* End() const { |
| return parseable_chunk_->End(); |
| } |
| |
| size_t UnparsedSize() const { |
| return parseable_chunk_->UnparsedSize(); |
| } |
| |
| size_t ParsedSize() const { |
| return parseable_chunk_->ParsedSize(); |
| } |
| |
| bool Empty() const { |
| return parseable_chunk_->Empty(); |
| } |
| |
| const char* UnparsedData() const { |
| return parseable_chunk_->UnparsedData(); |
| } |
| |
| const char** UnparsedDataAddr() { |
| return parseable_chunk_->UnparsedDataAddr(); |
| } |
| |
| void Advance(size_t number_of_bytes) { |
| return parseable_chunk_->Advance(number_of_bytes); |
| } |
| private: |
| void FreeChunk() { |
| if (owned_) { |
| delete parseable_chunk_; |
| } |
| parseable_chunk_ = NULL; |
| } |
| |
| // Will be NULL until Init() has been called. If owned_ is true, this will |
| // point to a ParseableChunk object that has been allocated with "new" and |
| // must be deleted by this DeltaWindowSection object. If owned_ is false, |
| // this points at the parseable_chunk_ owned by a different DeltaWindowSection |
| // object. In this case, it is important to free the DeltaWindowSection which |
| // does not own the ParseableChunk before (or simultaneously to) freeing the |
| // DeltaWindowSection that owns it, or else deleted memory may be accessed. |
| ParseableChunk* parseable_chunk_; |
| bool owned_; |
| |
| // Making these private avoids implicit copy constructor & assignment operator |
| DeltaWindowSection(const DeltaWindowSection&); |
| void operator=(const DeltaWindowSection&); |
| }; |
| |
| // Used to parse the bytes and Varints that make up the delta file header |
| // or delta window header. |
| class VCDiffHeaderParser { |
| public: |
| // header_start should be the start of the header to be parsed; |
| // data_end is the position just after the last byte of available data |
| // (which may extend far past the end of the header.) |
| VCDiffHeaderParser(const char* header_start, const char* data_end); |
| |
| // One of these functions should be called for each element of the header. |
| // variable_description is a description of the value that we are attempting |
| // to parse, and will only be used to create descriptive error messages. |
| // If the function returns true, then the element was parsed successfully |
| // and its value has been placed in *value. If the function returns false, |
| // then *value is unchanged, and GetResult() can be called to return the |
| // reason that the element could not be parsed, which will be either |
| // RESULT_ERROR (an error occurred), or RESULT_END_OF_DATA (the limit data_end |
| // was reached before the end of the element to be parsed.) Once one of these |
| // functions has returned false, further calls to any of the Parse... |
| // functions will also return false without performing any additional actions. |
| // Typical usage is as follows: |
| // int32_t segment_length = 0; |
| // if (!header_parser.ParseInt32("segment length", &segment_length)) { |
| // return header_parser.GetResult(); |
| // } |
| // |
| // The following example takes advantage of the fact that calling a Parse... |
| // function after an error or end-of-data condition is legal and does nothing. |
| // It can thus parse more than one element in a row and check the status |
| // afterwards. If the first call to ParseInt32() fails, the second will have |
| // no effect: |
| // |
| // int32_t segment_length = 0, segment_position = 0; |
| // header_parser.ParseInt32("segment length", &segment_length)); |
| // header_parser.ParseInt32("segment position", &segment_position)); |
| // if (RESULT_SUCCESS != header_parser.GetResult()) { |
| // return header_parser.GetResult(); |
| // } |
| // |
| bool ParseByte(unsigned char* value); |
| bool ParseInt32(const char* variable_description, int32_t* value); |
| bool ParseUInt32(const char* variable_description, uint32_t* value); |
| bool ParseChecksum(const char* variable_description, VCDChecksum* value); |
| bool ParseSize(const char* variable_description, size_t* value); |
| |
| // Parses the first three elements of the delta window header: |
| // |
| // Win_Indicator - byte |
| // [Source segment size] - integer (VarintBE format) |
| // [Source segment position] - integer (VarintBE format) |
| // |
| // Returns true if the values were parsed successfully and the values were |
| // found to be acceptable. Returns false otherwise, in which case |
| // GetResult() can be called to return the reason that the two values |
| // could not be validated. This will be either RESULT_ERROR (an error |
| // occurred and was logged), or RESULT_END_OF_DATA (the limit data_end was |
| // reached before the end of the values to be parsed.) If return value is |
| // true, then *win_indicator, *source_segment_length, and |
| // *source_segment_position are populated with the parsed values. Otherwise, |
| // the values of these output arguments are undefined. |
| // |
| // dictionary_size: The size of the dictionary (source) file. Used to |
| // validate the limits of source_segment_length and |
| // source_segment_position if the source segment is taken from the |
| // dictionary (i.e., if the parsed *win_indicator equals VCD_SOURCE.) |
| // decoded_target_size: The size of the target data that has been decoded |
| // so far, including all target windows. Used to validate the limits of |
| // source_segment_length and source_segment_position if the source segment |
| // is taken from the target (i.e., if the parsed *win_indicator equals |
| // VCD_TARGET.) |
| // allow_vcd_target: If this argument is false, and the parsed *win_indicator |
| // is VCD_TARGET, then an error is produced; if true, VCD_TARGET is |
| // allowed. |
| // win_indicator (output): Points to a single unsigned char (not an array) |
| // that will receive the parsed value of Win_Indicator. |
| // source_segment_length (output): The parsed length of the source segment. |
| // source_segment_position (output): The parsed zero-based index in the |
| // source/target file from which the source segment is to be taken. |
| bool ParseWinIndicatorAndSourceSegment(size_t dictionary_size, |
| size_t decoded_target_size, |
| bool allow_vcd_target, |
| unsigned char* win_indicator, |
| size_t* source_segment_length, |
| size_t* source_segment_position); |
| |
| // Parses the following two elements of the delta window header: |
| // |
| // Length of the delta encoding - integer (VarintBE format) |
| // Size of the target window - integer (VarintBE format) |
| // |
| // Return conditions and values are the same as for |
| // ParseWinIndicatorAndSourceSegment(), above. |
| // |
| bool ParseWindowLengths(size_t* target_window_length); |
| |
| // May only be called after ParseWindowLengths() has returned RESULT_SUCCESS. |
| // Returns a pointer to the end of the delta window (which might not point to |
| // a valid memory location if there is insufficient input data.) |
| // |
| const char* EndOfDeltaWindow() const; |
| |
| // Parses the following element of the delta window header: |
| // |
| // Delta_Indicator - byte |
| // |
| // Because none of the bits in Delta_Indicator are used by this implementation |
| // of VCDIFF, this function does not have an output argument to return the |
| // value of that field. It may return RESULT_SUCCESS, RESULT_ERROR, or |
| // RESULT_END_OF_DATA as with the other Parse...() functions. |
| // |
| bool ParseDeltaIndicator(); |
| |
| // Parses the following 3 elements of the delta window header: |
| // |
| // Length of data for ADDs and RUNs - integer (VarintBE format) |
| // Length of instructions and sizes - integer (VarintBE format) |
| // Length of addresses for COPYs - integer (VarintBE format) |
| // |
| // If has_checksum is true, it also looks for the following element: |
| // |
| // Adler32 checksum - unsigned 32-bit integer (VarintBE format) |
| // |
| // Return conditions and values are the same as for |
| // ParseWinIndicatorAndSourceSegment(), above. |
| // |
| bool ParseSectionLengths(bool has_checksum, |
| size_t* add_and_run_data_length, |
| size_t* instructions_and_sizes_length, |
| size_t* addresses_length, |
| VCDChecksum* checksum); |
| |
| // If one of the Parse... functions returned false, this function |
| // can be used to find the result code (RESULT_ERROR or RESULT_END_OF_DATA) |
| // describing the reason for the most recent parse failure. If none of the |
| // Parse... functions has returned false, returns RESULT_SUCCESS. |
| VCDiffResult GetResult() const { |
| return return_code_; |
| } |
| |
| // The following functions just pass their arguments to the underlying |
| // ParseableChunk object. |
| |
| const char* End() const { |
| return parseable_chunk_.End(); |
| } |
| |
| size_t UnparsedSize() const { |
| return parseable_chunk_.UnparsedSize(); |
| } |
| |
| size_t ParsedSize() const { |
| return parseable_chunk_.ParsedSize(); |
| } |
| |
| const char* UnparsedData() const { |
| return parseable_chunk_.UnparsedData(); |
| } |
| |
| private: |
| // Parses two variable-length integers representing the source segment length |
| // and source segment position (== offset.) Checks whether the source segment |
| // length and position would cause it to exceed the size of the source file or |
| // target file. Returns true if the values were parsed successfully and the |
| // values were found to be acceptable. Returns false otherwise, in which case |
| // GetResult() can be called to return the reason that the two values could |
| // not be validated, which will be either RESULT_ERROR (an error occurred and |
| // was logged), or RESULT_END_OF_DATA (the limit data_end was reached before |
| // the end of the integers to be parsed.) |
| // from_size: The requested size of the source segment. |
| // from_boundary_name: A NULL-terminated string naming the end of the |
| // source or target file, used in error messages. |
| // from_name: A NULL-terminated string naming the source or target file, |
| // also used in error messages. |
| // source_segment_length (output): The parsed length of the source segment. |
| // source_segment_position (output): The parsed zero-based index in the |
| // source/target file from which the source segment is to be taken. |
| // |
| bool ParseSourceSegmentLengthAndPosition(size_t from_size, |
| const char* from_boundary_name, |
| const char* from_name, |
| size_t* source_segment_length, |
| size_t* source_segment_position); |
| |
| ParseableChunk parseable_chunk_; |
| |
| // Contains the result code of the last Parse...() operation that failed |
| // (RESULT_ERROR or RESULT_END_OF_DATA). If no Parse...() method has been |
| // called, or if all calls to Parse...() were successful, then this contains |
| // RESULT_SUCCESS. |
| VCDiffResult return_code_; |
| |
| // Will be zero until ParseWindowLengths() has been called. After |
| // ParseWindowLengths() has been called successfully, this contains the |
| // parsed length of the delta encoding. |
| size_t delta_encoding_length_; |
| |
| // Will be NULL until ParseWindowLengths() has been called. After |
| // ParseWindowLengths() has been called successfully, this points to the |
| // beginning of the section of the current window titled "The delta encoding" |
| // in the RFC, i.e., to the position just after the length of the delta |
| // encoding. |
| const char* delta_encoding_start_; |
| |
| // Making these private avoids implicit copy constructor & assignment operator |
| VCDiffHeaderParser(const VCDiffHeaderParser&); |
| void operator=(const VCDiffHeaderParser&); |
| }; |
| |
| } // namespace open_vcdiff |
| |
| #endif // OPEN_VCDIFF_HEADERPARSER_H_ |