rand.c

来自「mips架构的bootloader,99左右的版本 但源代码现在没人更新了」· C语言 代码 · 共 47 行

/*************************************************************
 * File: lib/rand.c
 * Purpose: Part of C runtime library
 * Author: Phil Bunce ([e-mail])
 * Revision History:
 *	970304	Start of revision history
 */


unsigned long int rand_next = 1;

/*************************************************************
*  int rand()
*	Taken from the K&R C programming language book. Page 46.
*	returns a pseudo-random integer of 0..32767. Note that
*	this is compatible with the System V function rand(), not
*	with the bsd function rand() that returns 0..(2**31)-1.
*/
int rand()
{

rand_next = rand_next * 1103515245 + 12345;
return((unsigned int) (rand_next/65536) % 32768);
}

/*************************************************************
*  srand(seed)
* 	companion routine to rand(). Initializes the seed.
*/
srand(seed)
unsigned int seed;
{
rand_next = seed;
}

/*************************************************************
*  randn(limit)
*	returns a pseudo-random number in the range 0..limit.
*	Assumes that limit is less than 32000.
*/
randn(limit)
int limit;
{
return((rand()*(limit+1))/32768);
}