/prog/ - Little endian C array

Name: Anonymous 2008-12-23 7:18



/*

 * Copyright 2008 Anonymous

 *

 * This snippet is free software: you can redistribute it and/or modify

 * it under the terms of the GNU General Public License as published by

 * the Free Software Foundation, either version 3 of the License, or

 * (at your option) any later version.

 *

 */



#include <stdint.h>

#include <stdbool.h>

#include <stdio.h>

#include <stdlib.h>



/* The parse function allows the extraciton of various length word data from

 * a little endian buffer

 *

 * @note This function doesn't care about the buffer length, as it should be

 *       correctly specified into the fmt field.

 *

 * @param buffer The buffer containing the data;

 * @param fmt The extraction format to use

 * @param offset A internal use offset that must be initialized to zero

 * @param ret A pointer to the memory area that will contain the extracted

 *            data

 * @return true if there's still something to extract, false otherwise

 */

bool parse(const uint8_t *buffer, const char *fmt,

           uint32_t *offset, uint32_t *ret)

{

    /* Two separated words: 0 for the format; 1 for the buffer */

    uint16_t *offs;

    uint32_t shifts;

    const char *f;



    offs = (uint16_t *)offset;

    if (*(f = fmt + offs[0]) == 0)

        return false;

    buffer += offs[1];

    switch (*f) {

    case 'b':   /* Byte (8) */

        *ret = *buffer;

        offs[1] ++;

        break;

    case 'h':   /* Half word (16) */

        *ret = *(uint16_t *)buffer;

        offs[1] += 2;

        break;

    case 'w':   /* Word (32) */

        *ret = *(uint32_t *)buffer;

        offs[1] += 4;

        break;

    }

    offs[0]++;

    return true;

}





const char *format = "bhwb";

const uint8_t buf[] = {0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08};



int main(int argc, char **argv)

{

    uint32_t offset;

    uint32_t val;

    uint8_t *p;



    offset = 0;

    p = (uint8_t *) &val;

    while (parse(buf, format, &offset, &val)) {

        printf("0x%08x (", val);

        printf("0x%02x ", p[0]);

        printf("0x%02x ", p[1]);

        printf("0x%02x ", p[2]);

        printf("0x%02x)\n", p[3]);

    }

    exit(0);

}
Little endian C array

1 Name: Anonymous 2008-12-23 7:18

11 Name: Anonymous 2008-12-23 18:41

Name: Anonymous 2008-12-23 7:18

Name: Anonymous 2008-12-23 18:41
