Big File Reader

bigfile.c

/* 
 * Copyright (c) 2012, Muhammad Sumyandityo Noor
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without 
 * modification, are permitted provided that the following conditions are met:
 *
 * - Redistributions of source code must retain the above copyright notice, 
 *   this list of conditions and the following disclaimer.
 * - Redistributions in binary form must reproduce the above copyright notice, 
 *   this list of conditions and the following disclaimer in the documentation 
 *   and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" 
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, 
 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 
 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR 
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, 
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, 
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; 
 * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, 
 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR 
 * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF 
 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 */

// For reading Electronic Arts' .big files archives


#include <stdio.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/mman.h>
#include <string.h>
#include <stdint.h>

// Per File Entry Headers
struct big_entry_file_header {
    uint32_t offset; // big-endian
    uint32_t size;   // big-endian
};

// Archive header
struct big_header {
    char ident[4];
    uint32_t archive_size; // little-endian
    uint32_t number_of_files; // big-endian
    uint32_t first_file_offset; // big-endian
};

// Endian Check
enum
{
    O32_LITTLE_ENDIAN = 0x03020100ul,
    O32_BIG_ENDIAN = 0x00010203ul,
    O32_PDP_ENDIAN = 0x01000302ul
};

static const union { unsigned char bytes[4]; uint32_t value; } o32_host_order =
    { { 0, 1, 2, 3 } };

#define O32_HOST_ORDER (o32_host_order.value)


// byte swap 32-bit
static unsigned int inline
swapped( unsigned int num ) {
    return    ((num>>24)&0xff) | // move byte 3 to byte 0
              ((num<<8)&0xff0000) | // move byte 1 to byte 2
              ((num>>8)&0xff00) | // move byte 2 to byte 1
              ((num<<24)&0xff000000); // byte 0 to byte 3
}

// convert big endian to native endian
static unsigned int inline
big2native( unsigned int num ) {
    if (O32_HOST_ORDER == O32_LITTLE_ENDIAN) {
        return swapped(num);
    }
    else {
        return num;
    }
}

// convert little endian to native endian
static unsigned int inline
little2native(unsigned int num) {
    if (O32_HOST_ORDER == O32_BIG_ENDIAN) {
        return swapped(num);
    }
    else {
        return num;
    }
}

int main( int argc, char **argv ) {
    // file stat
    struct stat sb;
    // file length
    off_t len;
    // mapped memory address
    char *p;

    // file handle
    int fd;
    
    // archive header address
    struct big_header *ph;
    
    // hard coded [sorry, just for test !^_^]

    fd = open("/Applications/Command & Conquer Generals/Generals Data"
    "/Terrain.big", O_RDONLY);

    if (fstat(fd, &sb) == -1) {
        perror("fstat");
        return 1;
    }

    if (!S_ISREG(sb.st_mode)) {
        fprintf (stderr, "%s is not a file\n", "Invalid Big File");
        return 1;         
    }

    p = mmap(0, sb.st_size, PROT_READ, MAP_SHARED, fd, 0);

    ph = (struct big_header*) p;

    printf("Size of File      : ");
    
    if (little2native(ph->archive_size) >= 1024*1024) {
        float s = little2native(ph->archive_size) / (1024.0f * 1024.0f);
        printf("%.2f MB", s);
    }
    else if (little2native(ph->archive_size) >= 1024) {
        float s = little2native(ph->archive_size) / 1024.0f;
        printf("%.2f KB", s);
    }
    else {
        printf("%ul bytes", little2native(ph->archive_size));
    }
    printf("\n"); 
    printf("Number of Files   : %u\n", big2native(ph->number_of_files));
    printf("First File Offset : 0x%x\n", big2native(ph->first_file_offset));    
    
    char *f = p + sizeof(struct big_header);
    char *d = f;
    int i;

    for (i = 0; i < big2native(ph->number_of_files); ++i) {
        struct big_entry_file_header *eh = (struct big_entry_file_header*)d;
        d += sizeof(struct big_entry_file_header);
        printf("%s - ", d);
        while (*d != '\0') {
            ++d;
        }
        ++d;

        printf("Size %u, Offset 0x%x\n", big2native(eh->size), 
               big2native(eh->offset));
    }

    close(fd);
    munmap(p, sb.st_size);

    return 0;
}