main-c.c

huffman coding and decoding adaptive huffman coding and decoding it is a assignment from my cours

/************************* Start of MAIN-C.C *************************/
/*
 * This is the driver program used when testing compression algorithms.
 * In order to cut back on repetitive code, this version of main is
 * used with all of the compression routines.  It in order to turn into
 * a real program, it needs to have another module that supplies one
 * routine and two strings, namely:
 *
 *     void CompressFile( FILE *input, BIT_FILE *output,
 *                        int argc, char *argv );
 *     char *Usage;
 *     char *CompressionName;
 *
 * The main() routine supplied here has the job of checking for valid
 * input and output files, opening them, and then calling the
 * compression routine.  If the files are not present, or no arguments
 * are supplied, it prints out an error message, which includes the
 * Usage string supplied by the compression module.  All of the
 * routines and strings needed by this routine are defined in the
 * main.h header file.
 *
 * After this is built into a compression program of any sort, the
 * program can be called like this:
 *
 *   main-c infile outfile [ options ]
 *
 */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "bitio.h"
#include "errhand.h"
#include "main.h"

#ifdef __STDC__

void usage_exit( char *prog_name );
void print_ratios( char *input, char *output );
long file_size( char *name );

#else

void usage_exit();
void print_ratios();
long file_size();

#endif

int main( argc, argv )
int argc;
char *argv[];
{
    BIT_FILE *output;
    FILE *input;

    setbuf( stdout, NULL );
    if ( argc < 3 )
        usage_exit( argv[ 0 ] );
    input = fopen( argv[ 1 ], "rb" );
    if ( input == NULL )
        fatal_error( "Error opening %s for input\n", argv[ 1 ] );
    output = OpenOutputBitFile( argv[ 2 ] );
    if ( output == NULL )
        fatal_error( "Error opening %s for output\n", argv[ 2 ] );
    printf( "\nCompressing %s to %s\n", argv[ 1 ], argv[ 2 ] );
    printf( "Using %s\n", CompressionName );
    CompressFile( input, output, argc - 3, argv + 3 );
    CloseOutputBitFile( output );
    fclose( input );
    print_ratios( argv[ 1 ], argv[ 2 ] );
    return( 0 );
}

/*
 * This routine just wants to print out the usage message that is
 * called for when the program is run with no parameters.  The first
 * part of the Usage statement is supposed to be just the program
 * name.  argv[ 0 ] generally holds the fully qualified path name
 * of the program being run.  I make a half-hearted attempt to strip
 * out that path info and file extension before printing it.  It should
 * get the general idea across.
 */
void usage_exit( prog_name )
char *prog_name;
{
    char *short_name;
    char *extension;

    short_name = strrchr( prog_name, '\\' );
    if ( short_name == NULL )
        short_name = strrchr( prog_name, '/' );
    if ( short_name == NULL )
        short_name = strrchr( prog_name, ':' );
    if ( short_name != NULL )
        short_name++;
    else
        short_name = prog_name;
    extension = strrchr( short_name, '.' );
    if ( extension != NULL )
        *extension = '\0';
    printf( "\nUsage:  %s %s\n", short_name, Usage );
    exit( 0 );
}

/*
 * This routine is used by main to print out get the size of a file after
 * it has been closed.  It does all the work, and returns a long.  The
 * main program gets the file size for the plain text, and the size of
 * the compressed file, and prints the ratio.
 */
#ifndef SEEK_END
#define SEEK_END 2
#endif

long file_size( name )
char *name;
{
    long eof_ftell;
    FILE *file;

    file = fopen( name, "r" );
    if ( file == NULL )
        return( 0L );
    fseek( file, 0L, SEEK_END );
    eof_ftell = ftell( file );
    fclose( file );
    return( eof_ftell );
}

/*
 * This routine prints out the compression ratios after the input
 * and output files have been closed.
 */
void print_ratios( input, output )
char *input;
char *output;
{
    long input_size;
    long output_size;
    int ratio;

    input_size = file_size( input );
    if ( input_size == 0 )
        input_size = 1;
    output_size = file_size( output );
    ratio = 100 - (int) ( output_size * 100L / input_size );
    printf( "\nInput bytes:        %ld\n", input_size );
    printf( "Output bytes:       %ld\n", output_size );
    if ( output_size == 0 )
        output_size = 1;
    printf( "Compression ratio:  %d%%\n", ratio );
}

/************************** End of MAIN-C.C **************************/