lzw.h

采用C++编写的已经封装好的lzw压缩算法

// LZW.h: interface for the CLZW class.
//
//////////////////////////////////////////////////////////////////////

#if !defined(AFX_LZW_H__0BC8178C_3AB9_4B75_97D8_8B36939F1A28__INCLUDED_)
#define AFX_LZW_H__0BC8178C_3AB9_4B75_97D8_8B36939F1A28__INCLUDED_

#if _MSC_VER > 1000
#pragma once
#endif // _MSC_VER > 1000

#define VALUE
#define FUNCTION
#define INIT_BITS 9
#define MAX_BITS  14           /* Do not exceed 14 with this program */
#define HASHING_SHIFT MAX_BITS - 8

#if MAX_BITS == 14            /* Set the table size. Must be a prime    */
#define TABLE_SIZE 18041      /* number somewhat larger than 2^MAX_BITS.*/
#elif MAX_BITS == 13
#define TABLE_SIZE 9029
#else
#define TABLE_SIZE 5021
#endif

#define CLEAR_TABLE 256    /* Code to flush the string table */
#define TERMINATOR  257    /* To mark EOF Condition, instead of MAX_VALUE */
#define FIRST_CODE  258    /* First available code for code_value table */
#define CHECK_TIME  100    /* Check comp ratio every CHECK_TIME chars input */

#define MAXVAL(n) (( 1 <<( n )) -1)   /* max_value formula macro */

class CLZW  
{
public:
	CLZW();
	virtual ~CLZW();

public FUNCTION:
	bool compress(const char *input, const char *output);
	bool expand(const char *input, const char *output);

private VALUE:
	int *code_value;						/* This is the code value array */
	unsigned int *prefix_code;				/* This array holds the prefix codes */
	unsigned char *append_character;		/* This array holds the appended chars */
	unsigned char decode_stack[4000];		/* This array holds the decoded string */
	int num_bits;							/* Starting with 9 bit codes */
	unsigned long bytes_in,bytes_out;		/* Used to monitor compression ratio */
	unsigned int max_code;							/* old MAX_CODE */
	unsigned long checkpoint;				/* For compression ratio monitoring */

	int output_bit_count;
	unsigned long output_bit_buffer;
	int input_bit_count;
	unsigned long input_bit_buffer;

private FUNCTION:
	unsigned int find_match(unsigned int hash_prefix, unsigned int hash_character);
	unsigned char *decode_string(unsigned char *buffer, unsigned int code);
	unsigned int input_code(FILE *input);
	void output_code(FILE *output, unsigned int code);
	void compress(FILE *input, FILE *output);
	void expand(FILE *input, FILE *output);
	void InitGlobalVar();
};

#endif // !defined(AFX_LZW_H__0BC8178C_3AB9_4B75_97D8_8B36939F1A28__INCLUDED_)