1 /* $OpenBSD: fgets.c,v 1.11 2009/06/02 22:28:18 ray Exp $ */ 2 /*- 3 * Copyright (c) 1990, 1993 4 * The Regents of the University of California. All rights reserved. 5 * 6 * This code is derived from software contributed to Berkeley by 7 * Chris Torek. 8 * 9 * Redistribution and use in source and binary forms, with or without 10 * modification, are permitted provided that the following conditions 11 * are met: 12 * 1. Redistributions of source code must retain the above copyright 13 * notice, this list of conditions and the following disclaimer. 14 * 2. Redistributions in binary form must reproduce the above copyright 15 * notice, this list of conditions and the following disclaimer in the 16 * documentation and/or other materials provided with the distribution. 17 * 3. Neither the name of the University nor the names of its contributors 18 * may be used to endorse or promote products derived from this software 19 * without specific prior written permission. 20 * 21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 24 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 31 * SUCH DAMAGE. 32 */ 33 34 #include <errno.h> 35 #include <stdio.h> 36 #include <string.h> 37 #include "local.h" 38 39 /* 40 * Read at most n-1 characters from the given file. 41 * Stop when a newline has been read, or the count runs out. 42 * Return first argument, or NULL if no characters were read. 43 * Do not return NULL if n == 1. 44 */ 45 char * 46 fgets(char *buf, int n, FILE *fp) 47 { 48 size_t len; 49 char *s; 50 unsigned char *p, *t; 51 52 if (n <= 0) { /* sanity check */ 53 errno = EINVAL; 54 return (NULL); 55 } 56 57 _SET_ORIENTATION(fp, -1); 58 s = buf; 59 n--; /* leave space for NUL */ 60 while (n != 0) { 61 /* 62 * If the buffer is empty, refill it. 63 */ 64 if (fp->_r <= 0) { 65 if (__srefill(fp)) { 66 /* EOF/error: stop with partial or no line */ 67 if (s == buf) 68 return (NULL); 69 break; 70 } 71 } 72 len = fp->_r; 73 p = fp->_p; 74 75 /* 76 * Scan through at most n bytes of the current buffer, 77 * looking for '\n'. If found, copy up to and including 78 * newline, and stop. Otherwise, copy entire chunk 79 * and loop. 80 */ 81 if (len > n) 82 len = n; 83 t = memchr((void *)p, '\n', len); 84 if (t != NULL) { 85 len = ++t - p; 86 fp->_r -= len; 87 fp->_p = t; 88 (void)memcpy((void *)s, (void *)p, len); 89 s[len] = '\0'; 90 return (buf); 91 } 92 fp->_r -= len; 93 fp->_p += len; 94 (void)memcpy((void *)s, (void *)p, len); 95 s += len; 96 n -= len; 97 } 98 *s = '\0'; 99 return (buf); 100 } 101