buf.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 <bio.h>
#include <ip.h>
#include <plumb.h>
#include <thread.h>
#include <fcall.h>
#include <9p.h>
#include "dat.h"
#include "fns.h"

void
initibuf(Ibuf *b, Ioproc *io, int fd)
{
	b->fd = fd;
	b->io = io;
	b->rp = b->wp = b->buf;
}

int
readibuf(Ibuf *b, char *buf, int len)
{
	int n;

	n = b->wp - b->rp;
	if(n > 0){
		if(n > len)
			n = len;
		memmove(buf, b->rp, n);
		b->rp += n;
		return n;
	}
	return ioreadn(b->io, b->fd, buf, len);
}

void
unreadline(Ibuf *b, char *line)
{
	int i, n;

	i = strlen(line);
	n = b->wp - b->rp;
	memmove(&b->buf[i+1], b->rp, n);
	memmove(b->buf, line, i);
	b->buf[i] = '\n';
	b->rp = b->buf;
	b->wp = b->rp+i+1+n;
}

int
readline(Ibuf *b, char *buf, int len)
{
	int n;
	char *p;

	len--;

	for(p = buf;;){
		if(b->rp >= b->wp){
			n = ioread(b->io, b->fd, b->wp, sizeof(b->buf)/2);
			if(n < 0)
				return -1;
			if(n == 0)
				break;
			b->wp += n;
		}
		n = *b->rp++;
		if(len > 0){
			*p++ = n;
			len--;
		}
		if(n == '\n')
			break;
	}

	/* drop trailing white */
	for(;;){
		if(p <= buf)
			break;
		n = *(p-1);
		if(n != ' ' && n != '\t' && n != '\r' && n != '\n')
			break;
		p--;
	}

	*p = 0;
	return p-buf;
}