1 /* $NetBSD: fgets.c,v 1.20 2003/12/14 23:56:28 lukem Exp $ */ 2 3 /*- 4 * Copyright (c) 1990, 1993 5 * The Regents of the University of California. All rights reserved. 6 * 7 * This code is derived from software contributed to Berkeley by 8 * Chris Torek. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 3. Neither the name of the University nor the names of its contributors 19 * may be used to endorse or promote products derived from this software 20 * without specific prior written permission. 21 * 22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32 * SUCH DAMAGE. 33 */ 34 35 #include <sys/cdefs.h> 36 #if defined(LIBC_SCCS) && !defined(lint) 37 #if 0 38 static char sccsid[] = "@(#)fgets.c 8.2 (Berkeley) 12/22/93"; 39 #else 40 __RCSID("$NetBSD: fgets.c,v 1.20 2003/12/14 23:56:28 lukem Exp $"); 41 #endif 42 #endif /* LIBC_SCCS and not lint */ 43 44 #include <assert.h> 45 #include <stdio.h> 46 #include <string.h> 47 #include "reentrant.h" 48 #include "local.h" 49 50 /* 51 * Read at most n-1 characters from the given file. 52 * Stop when a newline has been read, or the count runs out. 53 * Return first argument, or NULL if no characters were read. 54 */ 55 char * 56 fgets(buf, n, fp) 57 char *buf; 58 int n; 59 FILE *fp; 60 { 61 size_t len; 62 char *s; 63 unsigned char *p, *t; 64 65 _DIAGASSERT(buf != NULL); 66 _DIAGASSERT(fp != NULL); 67 if (n <= 0) /* sanity check */ 68 return (NULL); 69 70 FLOCKFILE(fp); 71 _SET_ORIENTATION(fp, -1); 72 s = buf; 73 n--; /* leave space for NUL */ 74 while (n != 0) { 75 /* 76 * If the buffer is empty, refill it. 77 */ 78 if (fp->_r <= 0) { 79 if (__srefill(fp)) { 80 /* EOF/error: stop with partial or no line */ 81 if (s == buf) { 82 FUNLOCKFILE(fp); 83 return (NULL); 84 } 85 break; 86 } 87 } 88 len = fp->_r; 89 p = fp->_p; 90 91 /* 92 * Scan through at most n bytes of the current buffer, 93 * looking for '\n'. If found, copy up to and including 94 * newline, and stop. Otherwise, copy entire chunk 95 * and loop. 96 */ 97 if (len > n) 98 len = n; 99 t = memchr((void *)p, '\n', len); 100 if (t != NULL) { 101 len = ++t - p; 102 fp->_r -= len; 103 fp->_p = t; 104 (void)memcpy((void *)s, (void *)p, len); 105 s[len] = 0; 106 FUNLOCKFILE(fp); 107 return (buf); 108 } 109 fp->_r -= len; 110 fp->_p += len; 111 (void)memcpy((void *)s, (void *)p, len); 112 s += len; 113 n -= len; 114 } 115 *s = 0; 116 FUNLOCKFILE(fp); 117 return (buf); 118 } 119