/* * $Id: seek.c,v 1.2 2003/10/20 18:59:57 tomcollins Exp $ * * Copyright (c) 1987 University of Maryland Computer Science Department. * All rights reserved. * Permission to copy for any purpose is hereby granted so long as this * copyright notice remains intact. * * Changed MakeSeekable to use tmpfile() - marcus@quintic.co.uk *//* * Seekable is a predicate which returns true iff a Unix fd is seekable. * * MakeSeekable forces an input stdio file to be seekable, by copying to * a temporary file if necessary. */#include <stdio.h>#include <unistd.h>#include <sys/types.h>#include <fcntl.h>#include <sys/file.h>#include <sys/stat.h>/* commented out for bsd users *//* long	lseek(); */char	*getenv();intSeekable(fd)	int fd;{	return (lseek(fd, 0L, 1) >= 0 && !isatty(fd));}intMakeSeekable(f)	register FILE *f;{	register int tf, n;	FILE *tmpf;	int blksize;#ifdef MAXBSIZE	char buf[MAXBSIZE];	struct stat st;#else	char buf[BUFSIZ];#endif	if (Seekable(fileno(f)))		return (0);	tmpf = tmpfile(); /* tmpfile() is not safe on all systems */	if (tmpf == NULL) return -1; /* Failed to create temp file */        tf = fileno(tmpf);	/* copy from input file to temp file */#ifdef MAXBSIZE	if (fstat(tf, &st))	/* how can this ever fail? */		blksize = MAXBSIZE;	else		blksize = vmin(MAXBSIZE, st.st_blksize);#else	blksize = BUFSIZ;#endif	while ((n = fread(buf, 1, blksize, f)) > 0) {		if (write(tf, buf, n) != n) {			(void) close(tf);			return (-1);		}	}	/* ferror() is broken in Ultrix 1.2; hence the && */	if (ferror(f) && !feof(f)) {		(void) close(tf);		return (-1);	}	/*	 * Now switch f to point at the temp file.  Since we hit EOF, there	 * is nothing in f's stdio buffers, so we can play a dirty trick: 	 */	clearerr(f);	if (dup2(tf, fileno(f))) {		(void) close(tf);		return (-1);	}	(void) close(tf);	return (0);}/* suggested by Ken Jones instead of MIN for better compatibility */int vmin( int x, int y){  if ( x > y ) return(x);  return(y);}