date and time created 91/03/07 20:27:32 by bostic

[unix-history] / usr / src / bin / sh / input.c

/*-
 * Copyright (c) 1991 The Regents of the University of California.
 * All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Kenneth Almquist.
 *
 * %sccs.include.redist.c%
 */

#ifndef lint
static char sccsid[] = "@(#)input.c	5.1 (Berkeley) %G%";
#endif /* not lint */

/*
 * This file implements the input routines used by the parser.
 */

#include <stdio.h>	/* defines BUFSIZ */
#include "shell.h"
#include <fcntl.h>
#include <errno.h>
#include "syntax.h"
#include "input.h"
#include "output.h"
#include "memalloc.h"
#include "error.h"

#define EOF_NLEFT -99		/* value of parsenleft when EOF pushed back */


/*
 * The parsefile structure pointed to by the global variable parsefile
 * contains information about the current file being read.
 */

MKINIT
struct parsefile {
	int linno;		/* current line */
	int fd;			/* file descriptor (or -1 if string) */
	int nleft;		/* number of chars left in buffer */
	char *nextc;		/* next char in buffer */
	struct parsefile *prev;	/* preceding file on stack */
	char *buf;		/* input buffer */
};


int plinno = 1;			/* input line number */
MKINIT int parsenleft;		/* copy of parsefile->nleft */
char *parsenextc;		/* copy of parsefile->nextc */
MKINIT struct parsefile basepf;	/* top level input file */
char basebuf[BUFSIZ];		/* buffer for top level input file */
struct parsefile *parsefile = &basepf;	/* current input file */
char *pushedstring;		/* copy of parsenextc when text pushed back */
int pushednleft;		/* copy of parsenleft when text pushed back */

#ifdef __STDC__
STATIC void pushfile(void);
#else
STATIC void pushfile();
#endif



#ifdef mkinit
INCLUDE "input.h"
INCLUDE "error.h"

INIT {
	extern char basebuf[];

	basepf.nextc = basepf.buf = basebuf;
}

RESET {
	if (exception != EXSHELLPROC)
		parsenleft = 0;            /* clear input buffer */
	popallfiles();
}

SHELLPROC {
	popallfiles();
}
#endif


/*
 * Read a line from the script.
 */

char *
pfgets(line, len)
	char *line;
	{
	register char *p = line;
	int nleft = len;
	int c;

	while (--nleft > 0) {
		c = pgetc_macro();
		if (c == PEOF) {
			if (p == line)
				return NULL;
			break;
		}
		*p++ = c;
		if (c == '\n')
			break;
	}
	*p = '\0';
	return line;
}



/*
 * Read a character from the script, returning PEOF on end of file.
 * Nul characters in the input are silently discarded.
 */

int
pgetc() {
	return pgetc_macro();
}


/*
 * Refill the input buffer and return the next input character:
 *
 * 1) If a string was pushed back on the input, switch back to the regular
 *    buffer.
 * 2) If an EOF was pushed back (parsenleft == EOF_NLEFT) or we are reading
 *    from a string so we can't refill the buffer, return EOF.
 * 3) Call read to read in the characters.
 * 4) Delete all nul characters from the buffer.
 */

int
preadbuffer() {
	register char *p, *q;
	register int i;

	if (pushedstring) {
		parsenextc = pushedstring;
		pushedstring = NULL;
		parsenleft = pushednleft;
		if (--parsenleft >= 0)
			return *parsenextc++;
	}
	if (parsenleft == EOF_NLEFT || parsefile->buf == NULL)
		return PEOF;
	flushout(&output);
	flushout(&errout);
retry:
	p = parsenextc = parsefile->buf;
	i = read(parsefile->fd, p, BUFSIZ);
	if (i <= 0) {
		if (i < 0 && errno == EINTR)
			goto retry;
		parsenleft = EOF_NLEFT;
		return PEOF;
	}
	parsenleft = i - 1;

	/* delete nul characters */
	for (;;) {
		if (*p++ == '\0')
			break;
		if (--i <= 0)
			return *parsenextc++;		/* no nul characters */
	}
	q = p - 1;
	while (--i > 0) {
		if (*p != '\0')
			*q++ = *p;
		p++;
	}
	if (q == parsefile->buf)
		goto retry;			/* buffer contained nothing but nuls */
	parsenleft = q - parsefile->buf - 1;
	return *parsenextc++;
}


/*
 * Undo the last call to pgetc.  Only one character may be pushed back.
 * PEOF may be pushed back.
 */

void
pungetc() {
	parsenleft++;
	parsenextc--;
}


/*
 * Push a string back onto the input.  This code doesn't work if the user
 * tries to push back more than one string at once.
 */

void
ppushback(string, length)
	char *string;
	{
	pushedstring = parsenextc;
	pushednleft = parsenleft;
	parsenextc = string;
	parsenleft = length;
}



/*
 * Set the input to take input from a file.  If push is set, push the
 * old input onto the stack first.
 */

void
setinputfile(fname, push)
	char *fname;
	{
	int fd;
	int fd2;

	INTOFF;
	if ((fd = open(fname, O_RDONLY)) < 0)
		error("Can't open %s", fname);
	if (fd < 10) {
		fd2 = copyfd(fd, 10);
		close(fd);
		if (fd2 < 0)
			error("Out of file descriptors");
		fd = fd2;
	}
	setinputfd(fd, push);
	INTON;
}


/*
 * Like setinputfile, but takes an open file descriptor.  Call this with
 * interrupts off.
 */

void
setinputfd(fd, push) {
	if (push) {
		pushfile();
		parsefile->buf = ckmalloc(BUFSIZ);
	}
	if (parsefile->fd > 0)
		close(parsefile->fd);
	parsefile->fd = fd;
	if (parsefile->buf == NULL)
		parsefile->buf = ckmalloc(BUFSIZ);
	parsenleft = 0;
	plinno = 1;
}


/*
 * Like setinputfile, but takes input from a string.
 */

void
setinputstring(string, push)
	char *string;
	{
	INTOFF;
	if (push)
		pushfile();
	parsenextc = string;
	parsenleft = strlen(string);
	parsefile->buf = NULL;
	plinno = 1;
	INTON;
}



/*
 * To handle the "." command, a stack of input files is used.  Pushfile
 * adds a new entry to the stack and popfile restores the previous level.
 */

STATIC void
pushfile() {
	struct parsefile *pf;

	parsefile->nleft = parsenleft;
	parsefile->nextc = parsenextc;
	parsefile->linno = plinno;
	pf = (struct parsefile *)ckmalloc(sizeof (struct parsefile));
	pf->prev = parsefile;
	pf->fd = -1;
	parsefile = pf;
}


void
popfile() {
	struct parsefile *pf = parsefile;

	INTOFF;
	if (pf->fd >= 0)
		close(pf->fd);
	if (pf->buf)
		ckfree(pf->buf);
	parsefile = pf->prev;
	ckfree(pf);
	parsenleft = parsefile->nleft;
	parsenextc = parsefile->nextc;
	plinno = parsefile->linno;
	INTON;
}


/*
 * Return to top level.
 */

void
popallfiles() {
	while (parsefile != &basepf)
		popfile();
}



/*
 * Close the file(s) that the shell is reading commands from.  Called
 * after a fork is done.
 */

void
closescript() {
	popallfiles();
	if (parsefile->fd > 0) {
		close(parsefile->fd);
		parsefile->fd = 0;
	}
}