1 /*- 2 * Copyright (c) 1990 The Regents of the University of California. 3 * All rights reserved. 4 * 5 * This code is derived from software contributed to Berkeley by 6 * Chris Torek. 7 * 8 * %sccs.include.redist.c% 9 */ 10 11 #if defined(LIBC_SCCS) && !defined(lint) 12 static char sccsid[] = "@(#)makebuf.c 5.2 (Berkeley) 02/24/91"; 13 #endif /* LIBC_SCCS and not lint */ 14 15 #include <sys/types.h> 16 #include <sys/stat.h> 17 #include <unistd.h> 18 #include <stdio.h> 19 #include <stdlib.h> 20 #include "local.h" 21 22 /* 23 * Allocate a file buffer, or switch to unbuffered I/O. 24 * Per the ANSI C standard, ALL tty devices default to line buffered. 25 * 26 * As a side effect, we set __SOPT or __SNPT (en/dis-able fseek 27 * optimisation) right after the fstat() that finds the buffer size. 28 */ 29 void 30 __smakebuf(fp) 31 register FILE *fp; 32 { 33 register size_t size, couldbetty; 34 register void *p; 35 struct stat st; 36 37 if (fp->_flags & __SNBF) { 38 fp->_bf._base = fp->_p = fp->_nbuf; 39 fp->_bf._size = 1; 40 return; 41 } 42 if (fp->_file < 0 || fstat(fp->_file, &st) < 0) { 43 couldbetty = 0; 44 size = BUFSIZ; 45 /* do not try to optimise fseek() */ 46 fp->_flags |= __SNPT; 47 } else { 48 couldbetty = (st.st_mode & S_IFMT) == S_IFCHR; 49 size = st.st_blksize <= 0 ? BUFSIZ : st.st_blksize; 50 /* 51 * Optimise fseek() only if it is a regular file. 52 * (The test for __sseek is mainly paranoia.) 53 */ 54 if ((st.st_mode & S_IFMT) == S_IFREG && 55 fp->_seek == __sseek) { 56 fp->_flags |= __SOPT; 57 fp->_blksize = st.st_blksize; 58 } else 59 fp->_flags |= __SNPT; 60 } 61 if ((p = malloc(size)) == NULL) { 62 fp->_flags |= __SNBF; 63 fp->_bf._base = fp->_p = fp->_nbuf; 64 fp->_bf._size = 1; 65 } else { 66 __cleanup = _cleanup; 67 fp->_flags |= __SMBF; 68 fp->_bf._base = fp->_p = p; 69 fp->_bf._size = size; 70 if (couldbetty && isatty(fp->_file)) 71 fp->_flags |= __SLBF; 72 } 73 } 74