util.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 <u.h>
#include <libc.h>
#include <draw.h>
#include <thread.h>
#include <cursor.h>
#include <mouse.h>
#include <keyboard.h>
#include <frame.h>
#include <fcall.h>
#include "dat.h"
#include "fns.h"

void
cvttorunes(char *p, int n, Rune *r, int *nb, int *nr, int *nulls)
{
	uchar *q;
	Rune *s;
	int j, w;

	/*
	 * Always guaranteed that n bytes may be interpreted
	 * without worrying about partial runes.  This may mean
	 * reading up to UTFmax-1 more bytes than n; the caller
	 * knows this.  If n is a firm limit, the caller should
	 * set p[n] = 0.
	 */
	q = (uchar*)p;
	s = r;
	for(j=0; j<n; j+=w){
		if(*q < Runeself){
			w = 1;
			*s = *q++;
		}else{
			w = chartorune(s, (char*)q);
			q += w;
		}
		if(*s)
			s++;
		else if(nulls)
				*nulls = TRUE;
	}
	*nb = (char*)q-p;
	*nr = s-r;
}

void
error(char *s)
{
	fprint(2, "rio: %s: %r\n", s);
	if(errorshouldabort)
		abort();
	threadexitsall("error");
}

void*
erealloc(void *p, uint n)
{
	p = realloc(p, n);
	if(p == nil)
		error("realloc failed");
	return p;
}

void*
emalloc(uint n)
{
	void *p;

	p = malloc(n);
	if(p == nil)
		error("malloc failed");
	memset(p, 0, n);
	return p;
}

char*
estrdup(char *s)
{
	char *p;

	p = malloc(strlen(s)+1);
	if(p == nil)
		error("strdup failed");
	strcpy(p, s);
	return p;
}

int
isalnum(Rune c)
{
	/*
	 * Hard to get absolutely right.  Use what we know about ASCII
	 * and assume anything above the Latin control characters is
	 * potentially an alphanumeric.
	 */
	if(c <= ' ')
		return FALSE;
	if(0x7F<=c && c<=0xA0)
		return FALSE;
	if(utfrune("!\"#$%&'()*+,-./:;<=>?@[\\]^`{|}~", c))
		return FALSE;
	return TRUE;
}

Rune*
strrune(Rune *s, Rune c)
{
	Rune c1;

	if(c == 0) {
		while(*s++)
			;
		return s-1;
	}

	while(c1 = *s++)
		if(c1 == c)
			return s-1;
	return nil;
}

int
min(int a, int b)
{
	if(a < b)
		return a;
	return b;
}

int
max(int a, int b)
{
	if(a > b)
		return a;
	return b;
}

char*
runetobyte(Rune *r, int n, int *ip)
{
	char *s;
	int m;

	s = emalloc(n*UTFmax+1);
	m = snprint(s, n*UTFmax+1, "%.*S", n, r);
	*ip = m;
	return s;
}