EndianCvt.c

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

#ifndef _MSC_VER
#include <byteswap.h>
#define BSWAP32 bswap_32
#define BSWAP16 bswap_16
#else // Windows
#define BSWAP32 _byteswap_ulong
#define BSWAP16 _byteswap_ushort
#endif

#ifdef __cplusplus
extern "C" {
#endif
void RomToBigEndian(void* rom, size_t romSize) {
    uint8_t firstbyte = ((uint8_t*)rom)[0];

    switch (firstbyte) {
        case 0x80:  // BE
            return; // Already BE, no need to swap
        case 0x37:
            for (size_t pos = 0; pos < (romSize / 2); pos++) {
                ((uint16_t*)rom)[pos] = BSWAP16(((uint16_t*)rom)[pos]);
            }
            return;
        case 0x40:
            for (size_t pos = 0; pos < (romSize / 4); pos++) {
                ((uint32_t*)rom)[pos] = BSWAP32(((uint32_t*)rom)[pos]);
            }
    }
}

#ifdef __cplusplus
}
#endif