RLE.rar_visual c

/*********************************************************************************************************** RLE.c 本演示程序提供了游程长度编码法的压缩和解压缩函数，并实现了对图象 文件的压缩和解压缩 **********************************************************************************************************/ #include <stdio.h> #include <string.h> #include <stdlib.h> #define MAX_LEN (0x7f) /* maximum length for runs or sequences */ #define MAX_RUN_HEADER (0xff) /* bit 7 == 1 : run follows */ /* bit 6 - 0 : length of run */ #define MAX_SEQ_HEADER (0x7f) /* bit 7 == 0 : unencode sequence follows */ /* bit 6 - 0 : length of sequence */ #define RUN (0x80) /* bit 7 == 1 : run follows */ #define SEQ (0x00) /* bit 7 == 0 : unencoded sequence follows */ /* 函数原型 */ int RLE_Compression(char * infile_name, char * outfile_name); int RLE_Decompression(char * infile_name, char * outfile_name); /* 主程序 */ void main(int argc, char *argv[]) { printf("RLE compression and decompression utility\n"); if (4 != argc) { printf("\nUsage : rle -c|d sourcefilename targetfilename\n"); exit(0); } if (! strcmp(argv[1], "-c")) { printf("\nCompress..."); RLE_Compression(argv[2], argv[3]); } else if (! strcmp(argv[1], "-d")) { printf("\nDecompress..."); RLE_Decompression(argv[2], argv[3]); } else printf("\nUnknow command.\n"); } /************************************************************************** RLE_Compression () 本函数用RLE算法对文件进行压缩 **************************************************************************/ int RLE_Compression(char * infile_name, char * outfile_name) { register int cur_char; /* a character */ register unsigned int i; /* generic index variable */ register unsigned short run_len = 0; /* length of character run so far */ int run_char; /* which char run is of */ unsigned int j; /* another index variable */ unsigned short seq_len=0; /* length of non-run sequence */ char scratch_space[256]; /* string scratch space */ char seq[MAX_LEN]; /* buffer for uncompressible data */ FILE *infile; /* file ptr to input file (uncompressed) */ FILE *outfile; /* file ptr to output file (compressed) */ if ((infile=fopen(infile_name, "rb")) == NULL) { strcpy(scratch_space, "Uable to open "); strcat(scratch_space, infile_name); puts(scratch_space); return 1; } if ((outfile=fopen(outfile_name, "wb")) == NULL) { strcpy(scratch_space, "Uable to open "); strcat(scratch_space, outfile_name); puts(scratch_space); return 1; } while (!feof(infile)) { cur_char = fgetc(infile); if (feof(infile)) continue; if (seq_len ==0) /* haven't got a sequence yet */ { if (run_len == 0) /* start a new run */ { run_char = cur_char; ++run_len; continue; } if (run_char == cur_char) /* got another char in the run */ if (++run_len == MAX_LEN) { fputc((int)MAX_RUN_HEADER, outfile); fputc((int) run_char, outfile); run_len = 0; continue; } /* got a different character */ /* than the run we were building */ if (run_len > 2) /* so write out the run and */ /* start a new one of the new */ /* character. */ { fputc((int)(RUN | run_len), outfile); fputc((int)run_char, outfile); run_len = 1; run_char = cur_char; continue; } /* run was only one or two chars, make a seq out of it instead */ for (j = 0; j < run_len; j++); /* copy 1 or 2 char run to seq[] */ { seq[seq_len] = run_char; ++seq_len; if (seq_len == MAX_LEN) /* if seq[] is full, write to disk */ { fputc((int)MAX_SEQ_HEADER, outfile); for (i = 0; i < seq_len; i++) fputc((int)seq[i], outfile); seq_len = 0; } } run_len = 0; seq[seq_len++] = cur_char; if (seq_len == MAX_LEN) /* if seq[] is full, write to disk */ { fputc((int)MAX_SEQ_HEADER, outfile); for (i = 0; i < seq_len; i++) fputc((int)seq[i], outfile); seq_len = 0; } } else /* a sequence exists */ { if (run_len != 0) /* if a run exists */ { if (cur_char == run_char ) /* add to run! Yay. */ { ++run_len; if (run_len == MAX_LEN) /* if run is full */ { /* write sequence that precedes run */ fputc((int)(SEQ | seq_len), outfile); for (i = 0; i < seq_len; i++) fputc((int)seq[i], outfile); /* write run */ fputc((int)(RUN | run_len), outfile); fputc((int)run_char, outfile); /* and start out fresh */ seq_len = run_len = 0; } /* end write full run with existing sequence */ continue; } /* end add to run for sequence exists */ /* we couldn't add to the run, and a preceding sequence */ /* exists, so write the sequence and the run, and */ /* try starting a new run with the current character. */ /* write sequence that precedes run */ fputc((int)(SEQ | seq_len), outfile); for (i = 0; i < seq_len; i++) fputc((int)seq[i], outfile); /* write run */ fputc((int)(RUN | run_len), outfile); fputc((int)run_char, outfile); /* and start a new run w/ cur_char */ seq_len = 0; run_len = 1; run_char = cur_char; continue; } /* end can't add to existing run, and preceding seq exists */ /* no run exists, but a sequences does. Try to create a run */ /* by looking at cur_char and the last char of the sequence. */ /* if that fails, add the char to the sequence. */ /* if the sequence is full, write it to disk. (Slightly non */ /* optimal; we could wait one more char. A small thing to fix */ /* if someone gets the urge... */ if (seq[seq_len - 1] == cur_char) /* if we can make a run */ { run_char = cur_char; run_len = 2;