endianness.c

/*
 $Id: $
 
 Copyright (C) 2014           Hraban Luyat
 
 This program 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 2 of the License, or
 (at your option) any later version.
 
 This program is distributed in the hope that it will be useful,
 but WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 GNU General Public License for more details.
 
 You should have received a copy of the GNU General Public License
 along with this program; if not, write to the Free Software
 Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
*/

#include "config.h"

#include <assert.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>

#include "endianness.h"
#include "scanmem.h"
#include "value.h"

static uint16_t swap_bytes16(uint16_t i)
{
    uint16_t res = i & 0xff;
    res <<= 8;
    res |= i >> 8;
    return res;
}

static uint32_t swap_bytes32(uint32_t i)
{
    uint32_t res = swap_bytes16(i);
    res <<= 16;
    res |= swap_bytes16(i >> 16);
    return res;
}

static uint64_t swap_bytes64(uint64_t i)
{
    uint64_t res = swap_bytes32(i);
    res <<= 32;
    res |= swap_bytes32(i >> 32);
    return res;
}

// swap endianness of 2, 4 or 8 byte word in-place.
void swap_bytes_var(void *p, size_t num)
{
    switch (num) {
    case sizeof(uint16_t): ; // empty statement to cheat the compiler
        uint16_t i16 = swap_bytes16(*((uint16_t *)p));
        memcpy(p, &i16, sizeof(uint16_t));
        return;
    case sizeof(uint32_t): ;
        uint32_t i32 = swap_bytes32(*((uint32_t *)p));
        memcpy(p, &i32, sizeof(uint32_t));
        return;
    case sizeof(uint64_t): ;
        uint64_t i64 = swap_bytes64(*((uint64_t *)p));
        memcpy(p, &i64, sizeof(uint64_t));
        return;
    }
    assert(false);
    return;
}

void fix_endianness(globals_t *vars, value_t *data_value)
{
    if (!vars->options.reverse_endianness) {
        return;
    }
    if (data_value->flags.u64b) {
        data_value->uint64_value = swap_bytes64(data_value->uint64_value);
    } else if (data_value->flags.u32b) {
        data_value->uint32_value = swap_bytes32(data_value->uint32_value);
    } else if (data_value->flags.u16b) {
        data_value->uint16_value = swap_bytes16(data_value->uint16_value);
    }
    return;
}