divide.c

来自「klibc精简化的c程序库」· C语言 代码 · 共 100 行

#include <stdint.h>
#include <signal.h>

#if BITS == 64
typedef uint64_t unum;
typedef int64_t snum;
#else
typedef uint32_t unum;
typedef int32_t snum;
#endif

#ifdef SIGNED
typedef snum xnum;
#else
typedef unum xnum;
#endif

#ifdef __cris__
static inline unum __attribute__ ((const))dstep(unum rs, unum rd)
{
	asm("dstep %1,%0": "+r"(rd):"r"(rs));
	return rd;
}

static inline unum __attribute__ ((const))lz(unum rs)
{
	unum rd;
	asm("lz %1,%0": "=r"(rd):"r"(rs));
	return rd;
}

#else
/* For testing */
static inline unum __attribute__ ((const))dstep(unum rs, unum rd)
{
	rd <<= 1;
	if (rd >= rs)
		rd -= rs;

	return rd;
}

static inline unum __attribute__ ((const))lz(unum rs)
{
	unum rd = 0;
	while (rs >= 0x7fffffff) {
		rd++;
		rs <<= 1;
	}
	return rd;
}

#endif

xnum NAME(unum num, unum den)
{
	unum quot = 0, qbit = 1;
	int minus = 0;
	xnum v;

	if (den == 0) {
		raise(SIGFPE);
		return 0;	/* If signal ignored... */
	}

	if (den == 1)
		return (xnum) (REM ? 0 : num);

#if SIGNED
	if ((snum) (num ^ den) < 0)
		minus = 1;
	if ((snum) num < 0)
		num = -num;
	if ((snum) den < 0)
		den = -den;
#endif

	den--;

	/* Left-justify denominator and count shift */
	while ((snum) den >= 0) {
		den <<= 1;
		qbit <<= 1;
	}

	while (qbit) {
		if (den <= num) {
			num -= den;
			quot += qbit;
		}
		den >>= 1;
		qbit >>= 1;
	}

	v = (xnum) (REM ? num : quot);
	if (minus)
		v = -v;
	return v;
}