src/instruction_map.h - external/github.com/google/open-vcdiff - Git at Google

 // 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.
 //
 // There are two different representations of a Code Table's contents:
 // VCDiffCodeTableData is the same as the format given in section 7
 // of the RFC, and is used for transmission and decoding.  However,
 // on the encoding side, it is useful to have a representation that
 // can map efficiently from delta instructions to opcodes:
 // VCDiffInstructionMap.  A VCDiffInstructionMap is constructed
 // using a VCDiffCodeTableData.  For a custom code table, it is recommended
 // that the VCDiffCodeTableData be defined as a static struct and that the
 // VCDiffInstructionMap be a static pointer that gets initialized only once.

 #ifndef OPEN_VCDIFF_INSTRUCTION_MAP_H_
 #define OPEN_VCDIFF_INSTRUCTION_MAP_H_

 #include <config.h>
 #include "codetable.h"
 #include "vcdiff_defs.h"

 namespace open_vcdiff {

 // An alternate representation of the data in a VCDiffCodeTableData that
 // optimizes for fast encoding, that is, for taking a delta instruction
 // inst (also known as instruction type), size, and mode and arriving at
 // the corresponding opcode.
 //
 class VCDiffInstructionMap {
  public:
   // Create a VCDiffInstructionMap from the information in code_table_data.
   // Does not save a pointer to code_table_data after using its contents
   // to create the instruction->opcode mappings.  The caller *must* have
   // verified that code_table_data->Validate() returned true before
   // attempting to use this constructor.
   // max_mode is the maximum value for the mode of a COPY instruction.
   //
   VCDiffInstructionMap(const VCDiffCodeTableData& code_table_data,
                        unsigned char max_mode);

   static VCDiffInstructionMap* GetDefaultInstructionMap();

   // Finds an opcode that has the given inst, size, and mode for its first
   // instruction  and NOOP for its second instruction (or vice versa.)
   // Returns kNoOpcode if the code table does not have any matching
   // opcode. Otherwise, returns an opcode value between 0 and 255.
   //
   // If this function returns kNoOpcode for size > 0, the caller will
   // usually want to try again with size == 0 to find an opcode that
   // doesn't have a fixed size value.
   //
   // If this function returns kNoOpcode for size == 0, it is an error condition,
   // because any code table that passed the Validate() check should have a way
   // of expressing all combinations of inst and mode with size=0.
   //
   OpcodeOrNone LookupFirstOpcode(unsigned char inst,
                                  unsigned char size,
                                  unsigned char mode) const {
     return first_instruction_map_.Lookup(inst, size, mode);
   }

   // Given a first opcode (presumed to have been returned by a previous call to
   // lookupFirstOpcode), finds an opcode that has the same first instruction as
   // the first opcode, and has the given inst, size, and mode for its second
   // instruction.
   //
   // If this function returns kNoOpcode for size > 0, the caller will
   // usually want to try again with size == 0 to find an opcode that
   // doesn't have a fixed size value.
   //
   OpcodeOrNone LookupSecondOpcode(unsigned char first_opcode,
                                   unsigned char inst,
                                   unsigned char size,
                                   unsigned char mode) const {
     return second_instruction_map_.Lookup(first_opcode, inst, size, mode);
   }

  private:
   // Data structure used to implement LookupFirstOpcode efficiently.
   //
   class FirstInstructionMap {
    public:
     FirstInstructionMap(int num_insts_and_modes, int max_size_1);
     ~FirstInstructionMap();

     void Add(unsigned char inst,
              unsigned char size,
              unsigned char mode,
              unsigned char opcode) {
       OpcodeOrNone* opcode_slot = &first_opcodes_[inst + mode][size];
       if (*opcode_slot == kNoOpcode) {
         *opcode_slot = opcode;
       }
     }

     // See comments for LookupFirstOpcode, above.
     //
     OpcodeOrNone Lookup(unsigned char inst,
                         unsigned char size,
                         unsigned char mode) const {
       int inst_mode = (inst == VCD_COPY) ? (inst + mode) : inst;
       if (size > max_size_1_) {
         return kNoOpcode;
       }
       // Lookup specific-sized opcode
       return first_opcodes_[inst_mode][size];
     }

    private:
     // The number of possible combinations of inst (a VCDiffInstructionType) and
     // mode.  Since the mode is only used for COPY instructions, this number
     // is not (number of VCDiffInstructionType values) * (number of modes), but
     // rather (number of VCDiffInstructionType values other than VCD_COPY)
     // + (number of COPY modes).
     //
     // Compressing inst and mode into a single integer relies on
     // VCD_COPY being the last instruction type.  The inst+mode values are:
     // 0 (NOOP), 1 (ADD), 2 (RUN), 3 (COPY mode 0), 4 (COPY mode 1), ...
     //
     const int num_instruction_type_modes_;

     // The maximum value of a size1 element in code_table_data
     //
     const int max_size_1_;

     // There are two levels to first_opcodes_:
     // 1) A dynamically-allocated pointer array of size
     //    num_instruction_type_modes_ (one element for each combination of inst
     //    and mode.)  Every element of this array is non-NULL and contains
     //    a pointer to:
     // 2) A dynamically-allocated array of OpcodeOrNone values, with one element
     //    for each possible first instruction size (size1) in the code table.
     //    (In the default code table, for example, the maximum size used is 18,
     //    so these arrays would have 19 elements representing values 0
     //    through 18.)
     //
     OpcodeOrNone** first_opcodes_;

     // Making these private avoids implicit copy constructor
     // and assignment operator
     FirstInstructionMap(const FirstInstructionMap&);  // NOLINT
     void operator=(const FirstInstructionMap&);
   } first_instruction_map_;

   // Data structure used to implement LookupSecondOpcode efficiently.
   //
   class SecondInstructionMap {
    public:
     SecondInstructionMap(int num_insts_and_modes, int max_size_2);
     ~SecondInstructionMap();
     void Add(unsigned char first_opcode,
              unsigned char inst,
              unsigned char size,
              unsigned char mode,
              unsigned char second_opcode);

     // See comments for LookupSecondOpcode, above.
     OpcodeOrNone Lookup(unsigned char first_opcode,
                         unsigned char inst,
                         unsigned char size,
                         unsigned char mode) const;
    private:
     // See the member of the same name in FirstInstructionMap.
     const int num_instruction_type_modes_;

     // The maximum value of a size2 element in code_table_data
     const int max_size_2_;

     // There are three levels to second_opcodes_:
     // 1) A statically-allocated pointer array with one element
     //    for each possible opcode.  Each element can be NULL, or can point to:
     // 2) A dynamically-allocated pointer array of size
     //    num_instruction_type_modes_ (one element for each combination of inst
     //    and mode.)  Each element can be NULL, or can point to:
     // 3) A dynamically-allocated array with one element for each possible
     //    second instruction size in the code table.  (In the default code
     //    table, for example, the maximum size used is 6, so these arrays would
     //    have 7 elements representing values 0 through 6.)
     //
     OpcodeOrNone** second_opcodes_[VCDiffCodeTableData::kCodeTableSize];

     // Making these private avoids implicit copy constructor
     // and assignment operator
     SecondInstructionMap(const SecondInstructionMap&);  // NOLINT
     void operator=(const SecondInstructionMap&);
   } second_instruction_map_;

   static VCDiffInstructionMap* default_instruction_map;

   // Making these private avoids implicit copy constructor & assignment operator
   VCDiffInstructionMap(const VCDiffInstructionMap&);  // NOLINT
   void operator=(const VCDiffInstructionMap&);
 };

 };  // namespace open_vcdiff

 #endif  // OPEN_VCDIFF_INSTRUCTION_MAP_H_
	// 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.
	//
	// There are two different representations of a Code Table's contents:
	// VCDiffCodeTableData is the same as the format given in section 7
	// of the RFC, and is used for transmission and decoding. However,
	// on the encoding side, it is useful to have a representation that
	// can map efficiently from delta instructions to opcodes:
	// VCDiffInstructionMap. A VCDiffInstructionMap is constructed
	// using a VCDiffCodeTableData. For a custom code table, it is recommended
	// that the VCDiffCodeTableData be defined as a static struct and that the
	// VCDiffInstructionMap be a static pointer that gets initialized only once.

	#ifndef OPEN_VCDIFF_INSTRUCTION_MAP_H_
	#define OPEN_VCDIFF_INSTRUCTION_MAP_H_

	#include <config.h>
	#include "codetable.h"
	#include "vcdiff_defs.h"

	namespace open_vcdiff {

	// An alternate representation of the data in a VCDiffCodeTableData that
	// optimizes for fast encoding, that is, for taking a delta instruction
	// inst (also known as instruction type), size, and mode and arriving at
	// the corresponding opcode.
	//
	class VCDiffInstructionMap {
	public:
	// Create a VCDiffInstructionMap from the information in code_table_data.
	// Does not save a pointer to code_table_data after using its contents
	// to create the instruction->opcode mappings. The caller must have
	// verified that code_table_data->Validate() returned true before
	// attempting to use this constructor.
	// max_mode is the maximum value for the mode of a COPY instruction.
	//
	VCDiffInstructionMap(const VCDiffCodeTableData& code_table_data,
	unsigned char max_mode);

	static VCDiffInstructionMap* GetDefaultInstructionMap();

	// Finds an opcode that has the given inst, size, and mode for its first
	// instruction and NOOP for its second instruction (or vice versa.)
	// Returns kNoOpcode if the code table does not have any matching
	// opcode. Otherwise, returns an opcode value between 0 and 255.
	//
	// If this function returns kNoOpcode for size > 0, the caller will
	// usually want to try again with size == 0 to find an opcode that
	// doesn't have a fixed size value.
	//
	// If this function returns kNoOpcode for size == 0, it is an error condition,
	// because any code table that passed the Validate() check should have a way
	// of expressing all combinations of inst and mode with size=0.
	//
	OpcodeOrNone LookupFirstOpcode(unsigned char inst,
	unsigned char size,
	unsigned char mode) const {
	return first_instruction_map_.Lookup(inst, size, mode);
	}

	// Given a first opcode (presumed to have been returned by a previous call to
	// lookupFirstOpcode), finds an opcode that has the same first instruction as
	// the first opcode, and has the given inst, size, and mode for its second
	// instruction.
	//
	// If this function returns kNoOpcode for size > 0, the caller will
	// usually want to try again with size == 0 to find an opcode that
	// doesn't have a fixed size value.
	//
	OpcodeOrNone LookupSecondOpcode(unsigned char first_opcode,
	unsigned char inst,
	unsigned char size,
	unsigned char mode) const {
	return second_instruction_map_.Lookup(first_opcode, inst, size, mode);
	}

	private:
	// Data structure used to implement LookupFirstOpcode efficiently.
	//
	class FirstInstructionMap {
	public:
	FirstInstructionMap(int num_insts_and_modes, int max_size_1);
	~FirstInstructionMap();

	void Add(unsigned char inst,
	unsigned char size,
	unsigned char mode,
	unsigned char opcode) {
	OpcodeOrNone* opcode_slot = &first_opcodes_[inst + mode][size];
	if (*opcode_slot == kNoOpcode) {
	*opcode_slot = opcode;
	}
	}

	// See comments for LookupFirstOpcode, above.
	//
	OpcodeOrNone Lookup(unsigned char inst,
	unsigned char size,
	unsigned char mode) const {
	int inst_mode = (inst == VCD_COPY) ? (inst + mode) : inst;
	if (size > max_size_1_) {
	return kNoOpcode;
	}
	// Lookup specific-sized opcode
	return first_opcodes_[inst_mode][size];
	}

	private:
	// The number of possible combinations of inst (a VCDiffInstructionType) and
	// mode. Since the mode is only used for COPY instructions, this number
	// is not (number of VCDiffInstructionType values) * (number of modes), but
	// rather (number of VCDiffInstructionType values other than VCD_COPY)
	// + (number of COPY modes).
	//
	// Compressing inst and mode into a single integer relies on
	// VCD_COPY being the last instruction type. The inst+mode values are:
	// 0 (NOOP), 1 (ADD), 2 (RUN), 3 (COPY mode 0), 4 (COPY mode 1), ...
	//
	const int num_instruction_type_modes_;

	// The maximum value of a size1 element in code_table_data
	//
	const int max_size_1_;

	// There are two levels to first_opcodes_:
	// 1) A dynamically-allocated pointer array of size
	// num_instruction_type_modes_ (one element for each combination of inst
	// and mode.) Every element of this array is non-NULL and contains
	// a pointer to:
	// 2) A dynamically-allocated array of OpcodeOrNone values, with one element
	// for each possible first instruction size (size1) in the code table.
	// (In the default code table, for example, the maximum size used is 18,
	// so these arrays would have 19 elements representing values 0
	// through 18.)
	//
	OpcodeOrNone** first_opcodes_;

	// Making these private avoids implicit copy constructor
	// and assignment operator
	FirstInstructionMap(const FirstInstructionMap&); // NOLINT
	void operator=(const FirstInstructionMap&);
	} first_instruction_map_;

	// Data structure used to implement LookupSecondOpcode efficiently.
	//
	class SecondInstructionMap {
	public:
	SecondInstructionMap(int num_insts_and_modes, int max_size_2);
	~SecondInstructionMap();
	void Add(unsigned char first_opcode,
	unsigned char inst,
	unsigned char size,
	unsigned char mode,
	unsigned char second_opcode);

	// See comments for LookupSecondOpcode, above.
	OpcodeOrNone Lookup(unsigned char first_opcode,
	unsigned char inst,
	unsigned char size,
	unsigned char mode) const;
	private:
	// See the member of the same name in FirstInstructionMap.
	const int num_instruction_type_modes_;

	// The maximum value of a size2 element in code_table_data
	const int max_size_2_;

	// There are three levels to second_opcodes_:
	// 1) A statically-allocated pointer array with one element
	// for each possible opcode. Each element can be NULL, or can point to:
	// 2) A dynamically-allocated pointer array of size
	// num_instruction_type_modes_ (one element for each combination of inst
	// and mode.) Each element can be NULL, or can point to:
	// 3) A dynamically-allocated array with one element for each possible
	// second instruction size in the code table. (In the default code
	// table, for example, the maximum size used is 6, so these arrays would
	// have 7 elements representing values 0 through 6.)
	//
	OpcodeOrNone** second_opcodes_[VCDiffCodeTableData::kCodeTableSize];

	// Making these private avoids implicit copy constructor
	// and assignment operator
	SecondInstructionMap(const SecondInstructionMap&); // NOLINT
	void operator=(const SecondInstructionMap&);
	} second_instruction_map_;

	static VCDiffInstructionMap* default_instruction_map;

	// Making these private avoids implicit copy constructor & assignment operator
	VCDiffInstructionMap(const VCDiffInstructionMap&); // NOLINT
	void operator=(const VCDiffInstructionMap&);
	};

	}; // namespace open_vcdiff

	#endif // OPEN_VCDIFF_INSTRUCTION_MAP_H_