fgets.c (3363B)
1 /*- 2 * Copyright (c) 1990, 1993 3 * The Regents of the University of California. All rights reserved. 4 * 5 * This code is derived from software contributed to Berkeley by 6 * Chris Torek. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 3. All advertising materials mentioning features or use of this software 17 * must display the following acknowledgement: 18 * This product includes software developed by the University of 19 * California, Berkeley and its contributors. 20 * 4. Neither the name of the University nor the names of its contributors 21 * may be used to endorse or promote products derived from this software 22 * without specific prior written permission. 23 * 24 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 27 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 30 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 34 * SUCH DAMAGE. 35 */ 36 37 #if defined(LIBC_SCCS) && !defined(lint) 38 static char rcsid[] = "$OpenBSD: fgets.c,v 1.2 1996/08/19 08:32:33 tholo Exp $"; 39 #endif /* LIBC_SCCS and not lint */ 40 41 #include <stdio.h> 42 #include <string.h> 43 #include "local.h" 44 45 /* 46 * Read at most n-1 characters from the given file. 47 * Stop when a newline has been read, or the count runs out. 48 * Return first argument, or NULL if no characters were read. 49 */ 50 char * 51 fgets(buf, n, fp) 52 char *buf; 53 register int n; 54 register FILE *fp; 55 { 56 register size_t len; 57 register char *s; 58 register unsigned char *p, *t; 59 60 if (n <= 0) /* sanity check */ 61 return (NULL); 62 63 s = buf; 64 n--; /* leave space for NUL */ 65 while (n != 0) { 66 /* 67 * If the buffer is empty, refill it. 68 */ 69 if ((len = fp->_r) <= 0) { 70 if (__srefill(fp)) { 71 /* EOF/error: stop with partial or no line */ 72 if (s == buf) 73 return (NULL); 74 break; 75 } 76 len = fp->_r; 77 } 78 p = fp->_p; 79 80 /* 81 * Scan through at most n bytes of the current buffer, 82 * looking for '\n'. If found, copy up to and including 83 * newline, and stop. Otherwise, copy entire chunk 84 * and loop. 85 */ 86 if (len > n) 87 len = n; 88 t = memchr((void *)p, '\n', len); 89 if (t != NULL) { 90 len = ++t - p; 91 fp->_r -= len; 92 fp->_p = t; 93 (void)memcpy((void *)s, (void *)p, len); 94 s[len] = 0; 95 return (buf); 96 } 97 fp->_r -= len; 98 fp->_p += len; 99 (void)memcpy((void *)s, (void *)p, len); 100 s += len; 101 n -= len; 102 } 103 *s = 0; 104 return (buf); 105 }