harvey/sys/src/liblex/yyless.c

#include	<u.h>
#include	<libc.h>
#include	<stdio.h>

extern	char	yytext[];
extern	int	yyleng;
extern	int	yyprevious;

void	yyunput(int c);

void
yyless(int x)
{
	char *lastch, *ptr;

	lastch = yytext+yyleng;
	if(x>=0 && x <= yyleng)
		ptr = x + yytext;
	else
		ptr = (char*)x;
	while(lastch > ptr)
		yyunput(*--lastch);
	*lastch = 0;
	if (ptr >yytext)
		yyprevious = lastch[-1];
	yyleng = ptr-yytext;
}