qbitbits.c

来自「在Linxu程序设计当中」· C语言 代码 · 共 73 行

#include "f2c.h"
#ifdef __cplusplus
extern "C" {
#endif

#ifndef LONGBITS
#define LONGBITS 32
#endif

#ifndef LONG8BITS
#define LONG8BITS (2*LONGBITS)
#endif

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

	ulongint x, y;

	x = (ulongint) a;
	y = (ulongint)-1L;
	x >>= b;
	y <<= len;
	return (longint)(x & ~y);
	}

 longint
#ifdef KR_headers
qbit_cshift(a, b, len) longint a; integer b, len;
#else
qbit_cshift(longint a, integer b, integer len)
#endif
{
	ulongint x, y, z;

	x = (ulongint)a;
	if (len <= 0) {
		if (len == 0)
			return 0;
		goto full_len;
		}
	if (len >= LONG8BITS) {
 full_len:
		if (b >= 0) {
			b %= LONG8BITS;
			return (longint)(x << b | x >> LONG8BITS - b );
			}
		b = -b;
		b %= LONG8BITS;
		return (longint)(x << LONG8BITS - b | x >> b);
		}
	y = z = (unsigned long)-1;
	y <<= len;
	z &= ~y;
	y &= x;
	x &= z;
	if (b >= 0) {
		b %= len;
		return (longint)(y | z & (x << b | x >> len - b));
		}
	b = -b;
	b %= len;
	return (longint)(y | z & (x >> b | x << len - b));
	}
#ifdef __cplusplus
}
#endif