/* File: codrle2.c   Author: David Bourgin   Creation date: 1/2/94   Last update: 24/7/95   Purpose: Example of RLE type 2 encoding with a file source to compress.*/#include <stdio.h>/* For routines printf,fgetc,fputc and rewind */#include <memory.h>/* For routine memset */#include <stdlib.h>/* For routine exit *//* Error codes sent to the caller */#define NO_ERROR      0#define BAD_FILE_NAME 1#define BAD_ARGUMENT  2/* Useful constants */#define FALSE 0#define TRUE  1/* Global variables */FILE *source_file,*dest_file;                             /* Being that fgetc=EOF only after an access                                then 'byte_stored_status' is 'TRUE' if a byte has been stored by 'fgetc'                                or 'FALSE' if there's no valid byte not already read and not handled in 'val_byte_stored' */int byte_stored_status=FALSE;int val_byte_stored;/* Pseudo procedures */#define beginning_of_data()  (byte_stored_status=FALSE,(void)rewind(source_file))#define end_of_data()  (byte_stored_status?FALSE:!(byte_stored_status=((val_byte_stored=fgetc(source_file))!=EOF)))#define read_byte()  (byte_stored_status?byte_stored_status=FALSE,(unsigned char)val_byte_stored:(unsigned char)fgetc(source_file))#define write_byte(byte)  ((void)fputc((byte),dest_file))void rle2write_rep(header_byte,repeated_byte,repetition_number)/* Returned parameters: None   Action: Writes in the output compression stream the encoding of 'repetition_number' times 'repeated_byte'.   'header_byte' is used as marker as defined in RLE 2 method   Errors: An input/output error could disturb the running of the program*/unsigned char header_byte,repeated_byte;unsigned int repetition_number;{ if (repetition_number<4)     if (repeated_byte==header_byte)        { write_byte(header_byte);          write_byte(repetition_number-1);        }     else { register unsigned int i;            for (i=1;i<=repetition_number;i++)                write_byte(repeated_byte);          }  else { write_byte(header_byte);         write_byte(repetition_number-1);         write_byte(repeated_byte);       }}void rle2write_non_rep(header_byte,non_repeated_byte)/* Returned parameters: None   Action: Writes in the output compression stream the encoding of 'non_repeated_byte'   'header_byte' is used as marker as defined in RLE 2 method   Errors: An input/output error could disturb the running of the program*/unsigned char header_byte,non_repeated_byte;{ if (non_repeated_byte==header_byte)     { write_byte(header_byte);       write_byte(0);     }  else write_byte(non_repeated_byte);}void rle2encoding()/* Returned parameters: None   Action: Compresses with RLE type 2 method all bytes read by the function read_byte   Errors: An input/output error could disturb the running of the program*/{ unsigned char byte1,byte2,header_byte;  unsigned int frame_size;  register unsigned int i;  unsigned long int lookup_table[256];  if (!end_of_data())        /* Is there at least a byte to analyze? */     {                       /* Sets up the occurrence numbers of all bytes to 0 */       (void)memset((char *)lookup_table,0,sizeof(lookup_table));                             /* This is the same to fill 'lookup_table' to 0.                                It's fastest than to loop 256 times */       while (!end_of_data())/* Valids the occurrences in 'lookup_table' in regard to the data to compress */             { byte1=read_byte();               lookup_table[byte1]++;             }       header_byte=0;       for (i=1;i<=255;i++)           if (lookup_table[i]<lookup_table[header_byte])              header_byte=i;       write_byte(header_byte);       beginning_of_data();  /* New data analysis */       byte1=read_byte();       frame_size=1;       if (!end_of_data())                             /* Are there at least two bytes? */          { byte2=read_byte();            frame_size=2;            do {             /* Real beginning of the compression */                 if (byte1==byte2)                             /* Do we meet only a sequence of identical bytes? */                    { while ((!end_of_data())&&(byte1==byte2)&&(frame_size<256))                            { byte2=read_byte();                              frame_size++;                            }                      if (byte1==byte2)                         { rle2write_rep(header_byte,byte1,frame_size);                           if (!end_of_data())                              { byte1=read_byte();                                frame_size=1;                              }                           else frame_size=0;                         }                      else { rle2write_rep(header_byte,byte1,frame_size-1);                             byte1=byte2;                             frame_size=1;                           }                    }                 else {      /* No, then don't handle the last byte */                        rle2write_non_rep(header_byte,byte1);                        byte1=byte2;                        frame_size=1;                      }                 if (!end_of_data())                    { byte2=read_byte();                      frame_size=2;                    }               }            while ((!end_of_data())||(frame_size>=2));          }       if (frame_size==1)  /* Was there a last byte to analyze? */          rle2write_non_rep(header_byte,byte1);     }}void help()/* Returned parameters: None   Action: Displays the help of the program and then stops its running   Errors: None*/{ printf("This utility enables you to compress a file by using RLE type 2 method\n");  printf("as given in 'La Video et Les Imprimantes sur PC'\n");  printf("\nUse: codrle2 source target\n");  printf("source: Name of the file to compress\n");  printf("target: Name of the compressed file\n");}int main(argc,argv)/* Returned parameters: Returns an error code (0=None)   Action: Main procedure   Errors: Detected, handled and an error code is returned, if any*/int argc;char *argv[];{ if (argc!=3)     { help();       exit(BAD_ARGUMENT);     }  else if ((source_file=fopen(argv[1],"rb"))==NULL)          { help();            exit(BAD_FILE_NAME);          }       else if ((dest_file=fopen(argv[2],"wb"))==NULL)               { help();                 exit(BAD_FILE_NAME);               }            else { rle2encoding();                   fclose(source_file);                   fclose(dest_file);                 }  printf("Execution of codrle2 completed.\n");  return (NO_ERROR);}