Cheap-o file carving utility :)

carver.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int read_file_into_mem( char *filename, char **memory )
{
    int size;
    FILE *fp;

    fp = fopen( filename, "rb" );
    if( fp == NULL )
    {
        *memory = NULL;
        size = -1;
    }
    else
    {
        fseek( fp, 0, SEEK_END );
        size = ftell( fp );
        fseek( fp, 0, SEEK_SET );
        *memory = (char *)malloc( sizeof(char) * (size + 1) );
        if( size != fread( *memory, sizeof(char), size, fp ) )
        {
            free(*memory);
            size = -2;
            *memory = NULL;
        }
        else {
            (*memory)[size] = '\0';
        }
        fclose( fp );
    }
    return size;
}

typedef struct {
    int offset;
    int period;
    int line_length;
} carver_opts_t;

int main( int argv, char *argc[] )
{

    char *filename = NULL;
    if( argv > 1 )
    {
        filename = argc[1];
    }
    else
    {
        fprintf( stderr, "must specify filename as first argument\n" );
        return -1;
    }
    
    carver_opts_t opts;
    opts.offset = 0x0;
    opts.period = 56;
    opts.line_length = 56;

    if( argv > 2 )
    {
        opts.offset = atoi( argc[2] );
    }
    if( argv > 3 )
    {
        opts.period = atoi( argc[3] );
    }
    if( argv > 4 )
    {
        opts.line_length = atoi( argc[4] );
    }
        
    fprintf( stderr, "offset = 0x%x period = 0x%x line_length = 0x%x\n", opts.offset, opts.period, opts.line_length );

    char *raw = NULL;
    int sz;
    if( (sz = read_file_into_mem( filename, &raw ) ) < 0 )
    {
        fprintf( stderr, "error reading file\n" );
        return -1;
    }

    char *p = raw;

    p += opts.offset;

    while( p < raw + sz )
    {
        int i;
        for( i = 0; i < opts.line_length; i++ ) 
        {
            if( (*p >= ' ' && *p <= '~') )
            {
                printf( "%c", *p );
            }
            else 
            {
                printf( " " );
            }
            p++;
        }
        printf( "\n" );
        p += opts.period - opts.line_length;
    }

    free(raw);

    return 0;
}

Usage:

./carver FILENAME OFFSET PERIOD LINE_LENGTH

./carver ../u/LADSAR/CUSMAS.RI1 1647 615 615

./carver ../u/LADSAR/CUSMST.DAT 0 207 207