upscheme/c/utils.h

#if defined(__amd64__) || defined(_M_AMD64)
#define ARCH_X86_64
#define __CPU__ 686
#elif defined(_M_IX86)  // msvs, intel, digital mars, watcom
#if !defined(__386__)
#error "unsupported target: 16-bit x86"
#endif
#define ARCH_X86
#define __CPU__ (_M_IX86 + 86)
#elif defined(__i686__)  // gnu c
#define ARCH_X86
#define __CPU__ 686
#elif defined(__i586__)  // gnu c
#define ARCH_X86
#define __CPU__ 586
#elif defined(__i486__)  // gnu c
#define ARCH_X86
#define __CPU__ 486
#elif defined(__i386__)  // gnu c
#define ARCH_X86
#define __CPU__ 386
#else
#error "unknown architecture"
#endif

char *uint2str(char *dest, size_t len, uint64_t num, uint32_t base);
int str2int(char *str, size_t len, int64_t *res, uint32_t base);
int isdigit_base(char c, int base);

#ifdef ARCH_X86_64
#define LEGACY_REGS "=Q"
#else
#define LEGACY_REGS "=q"
#endif

#if !defined(__INTEL_COMPILER) && (defined(ARCH_X86) || defined(ARCH_X86_64))
static uint16_t ByteSwap16(uint16_t x)
{
    __asm("xchgb %b0,%h0" : LEGACY_REGS(x) : "0"(x));
    return x;
}
#define bswap_16(x) ByteSwap16(x)

static uint32_t ByteSwap32(uint32_t x)
{
#if __CPU__ > 386
    __asm("bswap        %0"
          : "=r"(x)
          :
#else
    __asm("xchgb        %b0,%h0\n"
          "     rorl    $16,%0\n"
          "     xchgb   %b0,%h0"
          : LEGACY_REGS(x)
          :
#endif
          "0"(x));
    return x;
}

#define bswap_32(x) ByteSwap32(x)

static uint64_t ByteSwap64(uint64_t x)
{
#ifdef ARCH_X86_64
    __asm("bswap        %0" : "=r"(x) : "0"(x));
    return x;
#else
    register union {
        __extension__ uint64_t __ll;
        uint32_t __l[2];
    } __x;
    asm("xchgl  %0,%1"
        : "=r"(__x.__l[0]), "=r"(__x.__l[1])
        : "0"(bswap_32((unsigned long)x)),
          "1"(bswap_32((unsigned long)(x >> 32))));
    return __x.__ll;
#endif
}
#define bswap_64(x) ByteSwap64(x)

#else

#define bswap_16(x) (((x)&0x00ff) << 8 | ((x)&0xff00) >> 8)

#ifdef __INTEL_COMPILER
#define bswap_32(x) _bswap(x)
#else
#define bswap_32(x)                                       \
    ((((x)&0xff000000) >> 24) | (((x)&0x00ff0000) >> 8) | \
     (((x)&0x0000ff00) << 8) | (((x)&0x000000ff) << 24))
#endif

static uint64_t ByteSwap64(uint64_t x)
{
    union {
        uint64_t ll;
        uint32_t l[2];
    } w, r;
    w.ll = x;
    r.l[0] = bswap_32(w.l[1]);
    r.l[1] = bswap_32(w.l[0]);
    return r.ll;
}
#define bswap_64(x) ByteSwap64(x)

#endif