/*
 * swap Version 0.0
 * Bart Trzynadlowski, October 27, 2000
 * Public domain
 *
 * June 11, 2001:
 *      - Updated contact information
 */

/*
 * This program swaps the bytes, words, doublewords, or quadwords in files.
 *
 * Usage:   swap <-b files, -w files, -d files, -q files>
 * Options: -?,-h   Show help
 *          -b      Byte swap (8-bit) [default]
 *          -w      Word swap (16-bit)
 *          -d      Doubleword swap (32-bit)
 *          -q      Quadword swap (64-bit)
 *
 * Contact Bart Trzynadlowski:
 *  Email: trzy@mailandnews.com
 *  WWW: http://trzy.overclocked.org
 */

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

int         swap_type = 0;  /* 0=byte, 1=word, 2=dword, 3=qword */
unsigned    mask[] = { 0, 1, 3, 7 };
unsigned    data_sz[] = { 1, 2, 4, 8 };
char        *type_l[] = { "byte", "word", "doubleword", "quadword" };
char        *type_u[] = { "Byte", "Word", "Doubleword", "Quadword" };


void Swap(unsigned char *buffer, unsigned size, char *file)
{
    unsigned        i, j;
    unsigned char   d[8];

    if (size & mask[swap_type])
    {
        fprintf(stderr, "swap: File cannot be %s-swapped: %s (%d bytes)\n",
                type_l[swap_type], file, size);
        return;
    }

    printf("swap: %s-swapping file: %s (%d bytes)... ", type_u[swap_type],
           file, size);
    for (i = 0; i < size; i += (data_sz[swap_type] * 2))
    {
        for (j = 0; j < data_sz[swap_type]; j++)
            d[j] = buffer[i + j];
        for (j = 0; j < data_sz[swap_type]; j++)
            buffer[i + j] = buffer[i + j + data_sz[swap_type]];
        for (j = 0; j < data_sz[swap_type]; j++)
            buffer[i + j + data_sz[swap_type]] = d[j];
    }
    printf("OK\n");
}

void ShowHelp()
{
    printf("swap Version 0.0 by Bart Trzynadlowski: Data-Swapping Utility\n");
    printf("Usage:      swap <-b files, -w files, -d files, -q files>\n");
    printf("Options:    -?,-h   Show this help text\n");
    printf("            -b      Swap bytes [default]\n");
    printf("            -w      Swap words\n");
    printf("            -d      Swap doublewords\n");
    printf("            -q      Swap quadwords\n");
    exit(0);
}

int main(int argc, char **argv)
{
    FILE            *fp;
    unsigned char   *buffer;
    unsigned        i, j;

    if (argc <= 1)
        ShowHelp();

    setvbuf(stdout, NULL, _IONBF, NULL); 

    for (i = 1; i < argc; i++)
    {
        if (!strcmp(argv[i], "-?") || !strcmp(argv[i], "-h"))   ShowHelp();
        else if (!strcmp(argv[i], "-b"))    swap_type = 0;
        else if (!strcmp(argv[i], "-w"))    swap_type = 1;
        else if (!strcmp(argv[i], "-d"))    swap_type = 2;
        else if (!strcmp(argv[i], "-q"))    swap_type = 3;
        else
        {
            if ((fp = fopen(argv[i], "rb+")) == NULL)
                fprintf(stderr, "swap: Failed to open file: %s\n", argv[i]);
            else
            {
                fseek(fp, 0, SEEK_END);
                fgetpos(fp, (void *) &j);
                rewind(fp);
                if ((buffer = calloc(j, sizeof(unsigned char))) == NULL)
                    fprintf(stderr, "swap: Failed to allocate %d bytes of "
                                    "memory for file: %s\n", j, argv[i]);
                else
                {
                    fread(buffer, sizeof(unsigned char), j, fp);
                    rewind(fp);
                    Swap(buffer, j, argv[i]);
                    fwrite(buffer, sizeof(unsigned char), j, fp);
                    free(buffer);
                }
                fclose(fp);
            }
        }
    }

    setvbuf(stdout, NULL, _IOLBF, NULL);

    return 0;
}