lbitbits.c

来自「gcc-2.95.3 Linux下最常用的C编译器」· C语言 代码 · 共 63 行

#include "f2c.h"

#ifndef LONGBITS
#define LONGBITS 32
#endif

 integer
#ifdef KR_headers
lbit_bits(a, b, len) integer a, b, len;
#else
lbit_bits(integer a, integer b, integer len)
#endif
{
	/* Assume 2's complement arithmetic */

	unsigned long x, y;

	x = (unsigned long) a;
	y = (unsigned long)-1L;
	x >>= b;
	y <<= len;
	return (integer)(x & ~y);
	}

 integer
#ifdef KR_headers
lbit_cshift(a, b, len) integer a, b, len;
#else
lbit_cshift(integer a, integer b, integer len)
#endif
{
	unsigned long x, y, z;

	x = (unsigned long)a;
	if (len <= 0) {
		if (len == 0)
			return 0;
		goto full_len;
		}
	if (len >= LONGBITS) {
 full_len:
		if (b >= 0) {
			b %= LONGBITS;
			return (integer)(x << b | x >> LONGBITS -b );
			}
		b = -b;
		b %= LONGBITS;
		return (integer)(x << LONGBITS - b | x >> b);
		}
	y = z = (unsigned long)-1;
	y <<= len;
	z &= ~y;
	y &= x;
	x &= z;
	if (b >= 0) {
		b %= len;
		return (integer)(y | z & (x << b | x >> len - b));
		}
	b = -b;
	b %= len;
	return (integer)(y | z & (x >> b | x << len - b));
	}