/* igets.c -- read a line of sort input
 * 
 * char	lbuf[LLEN];
 * FILE	*current;
 * FNL	*names;
 * if (NULL == igets(lbuf, LLEN, &current, &names)) error...
 * 
 * current points to a currently open file.  (If no file
 * is open, current may be NULL.)  names points to a list
 * of names of files.  The first name in the list in
 * the name of the currently open file.  Subsequent names
 * identify files from which input is to be read when
 * current is exhausted.  The name "-" is taken to mean
 * stdin.  igets reads a line, if necessary
 * closing current and opening the next file in the list.
 * current and names are updated if this is necessary.
 * igets returns NULL if there is an error or endfile on
 * current and there are no more files, or the next file
 * can't be opened.
 */
#include <stdio.h>
#include "common.h"
#include "readline.h"

char	*fgets();
int	fclose();
FILE	*fopen();

char *
igets(s, n, f, fl)
char	*s;
int	n;
FILE	**f;
FNL	**fl;
{
    FNL			*fp;

    if (NULL == *f) {
	if (NULL == *fl) return(NULL);
	if (0 == strcmp("-", (*fl)->f_n)) {
	    *f = stdin;
	}
	else {
	    if (NULL == (*f = fopen((*fl)->f_n, "r")))
		error1("unable to open %s", (*fl)->f_n);
	}
    }
    while(NULL == fgets(s, n, *f)) {
	if (EOF == fclose(*f))
	    error1("unable to close %s", (*fl)->f_n);
	fp = *fl;
	*fl = fp->f_nxt;
	free(fp->f_n);
	free(fp);
	*f = NULL;
	if (NULL == *fl) return(NULL);
	if (NULL == (*f = fopen((*fl)->f_n, "r")))
	    error1("unable to open %s", (*fl)->f_n);
    }
    return(s);
}

/* ieof -- check for endfile on input
 * 
 * FILE	*current;
 * FNL	*names;
 * int	atend;
 * atend = ieof(current, names);
 * 
 * current and names are as for igets (but note that ieof
 * expects current and names, not their addresses).  ieof
 * returns TRUE iff the end of file current has been reached
 * and there are no more files.
 * 
 * ieof uses the cumbersome method of attempting to read
 * the next char, because feof doesn't work properly on
 * the VAX.  On other machines, simpler methods should
 * work.
 */
int
ieof(f, fl)
FILE	*f;
FNL	*fl;
{
    register int	c;

    if (NULL == f) {
	return(NULL == fl);
    }
    else {
	if (
	    ((NULL == fl) || (NULL == fl->f_nxt)) &&
	    (EOF == (c = getc(f)))
	) return(TRUE);
	ungetc(c, f);
	return(FALSE);
    }
}