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

int main(int argc, char* argv[])
{
    FILE *infile, *outfile;
    long fsize, i, GBIX_start;
    size_t result;
    char *buffer;
    char filename[20];

    //open file
    infile = fopen(argv[1], "rb");
    if (infile==NULL) {fputs ("File open error",stderr); return -1;}

    // get file size
    fseek(infile, 0, SEEK_END);
    fsize = ftell(infile);
    fseek(infile, 0, SEEK_SET);

    //allocate memory
    buffer = (char *)malloc(fsize);
    if (buffer==NULL) {fputs ("Memory allocation error", stderr); return -1;}

    //read file into memory
    result = fread(buffer, 1, fsize, infile);
    if (result != fsize) {fputs ("File read error", stderr); return -1;}

    //close file
    fclose(infile);

    //scan memory for breaks
    GBIX_start = 0;
    for(i = 0; i < fsize - 4; i++)
    {
        //save location of tag
        if(buffer[i] == 'G' && buffer[i + 1] == 'B' && buffer[i + 2] == 'I' && buffer[i + 3] == 'X')
        {
            //if length of file is > tag length
            if(i - GBIX_start > 4)
            {
                //notify
                printf("Found at offset: 0x%06x\n", GBIX_start);
                //create offset filename
                sprintf(filename, "%06x.pvr", GBIX_start);
                //open file
                outfile = fopen(filename, "wb");
                //check error
                if (outfile == NULL) {
                    fputs ("PVR file open error", stderr);
                    free(buffer);
                    return -1;
                }
                //write data
                result = fwrite(&buffer[GBIX_start], 1, i - GBIX_start, outfile);
                //check error
                if (result != i - GBIX_start) {
                    fputs ("File write error", stderr);
                    fclose(outfile);
                    free(buffer);
                    return -1;
                }
                //close outfile
                fclose(outfile);

                //save new tag location
                GBIX_start = i;
            }
        }
    }

    //finish last chunk
    //notify
    printf("Found at offset: 0x%06x\n", GBIX_start);
    //create offset filename
    sprintf(filename, "%06x.pvr", GBIX_start);
    //open file
    outfile = fopen(filename, "wb");
    //check error
    if (outfile == NULL) {
        fputs ("PVR file open error", stderr);
        free(buffer);
        return -1;
    }
    //write data
    result = fwrite(&buffer[GBIX_start], 1, fsize - GBIX_start, outfile);
    //check error
    if (result != fsize - GBIX_start) {
        fputs ("File write error", stderr);
        fclose(outfile);
        free(buffer);
        return -1;
    }
    //close outfile
    fclose(outfile);

    //free mem
    free(buffer);
    //success
    return 0;
}