brk.c

这是一个同样来自贝尔实验室的和UNIX有着渊源的操作系统, 其简洁的设计和实现易于我们学习和理解

#include "lib.h"
#include <errno.h>
#include "sys9.h"

char	end[];
static	char	*bloc = { end };
extern	int	_BRK_(void*);

char *
brk(char *p)
{
	unsigned long n;

	n = (unsigned long)p;
	n += 3;
	n &= ~3;
	if(_BRK_((void*)n) < 0){
		errno = ENOMEM;
		return (char *)-1;
	}
	bloc = (char *)n;
	return 0;
}

void *
sbrk(unsigned long n)
{
	n += 3;
	n &= ~3;
	if(_BRK_((void *)(bloc+n)) < 0){
		errno = ENOMEM;
		return (void *)-1;
	}
	bloc += n;
	return (void *)(bloc-n);
}