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 * %sccs.include.redist.c% 9 */ 10 11 #if defined(LIBC_SCCS) && !defined(lint) 12 static char sccsid[] = "@(#)makebuf.c 8.1 (Berkeley) 06/04/93"; 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 void *p; 34 register int flags; 35 size_t size; 36 int couldbetty; 37 38 if (fp->_flags & __SNBF) { 39 fp->_bf._base = fp->_p = fp->_nbuf; 40 fp->_bf._size = 1; 41 return; 42 } 43 flags = __swhatbuf(fp, &size, &couldbetty); 44 if ((p = malloc(size)) == NULL) { 45 fp->_flags |= __SNBF; 46 fp->_bf._base = fp->_p = fp->_nbuf; 47 fp->_bf._size = 1; 48 return; 49 } 50 __cleanup = _cleanup; 51 flags |= __SMBF; 52 fp->_bf._base = fp->_p = p; 53 fp->_bf._size = size; 54 if (couldbetty && isatty(fp->_file)) 55 flags |= __SLBF; 56 fp->_flags |= flags; 57 } 58 59 /* 60 * Internal routine to determine `proper' buffering for a file. 61 */ 62 int 63 __swhatbuf(fp, bufsize, couldbetty) 64 register FILE *fp; 65 size_t *bufsize; 66 int *couldbetty; 67 { 68 struct stat st; 69 70 if (fp->_file < 0 || fstat(fp->_file, &st) < 0) { 71 *couldbetty = 0; 72 *bufsize = BUFSIZ; 73 return (__SNPT); 74 } 75 76 /* could be a tty iff it is a character device */ 77 *couldbetty = (st.st_mode & S_IFMT) == S_IFCHR; 78 if (st.st_blksize <= 0) { 79 *bufsize = BUFSIZ; 80 return (__SNPT); 81 } 82 83 /* 84 * Optimise fseek() only if it is a regular file. (The test for 85 * __sseek is mainly paranoia.) It is safe to set _blksize 86 * unconditionally; it will only be used if __SOPT is also set. 87 */ 88 *bufsize = st.st_blksize; 89 fp->_blksize = st.st_blksize; 90 return ((st.st_mode & S_IFMT) == S_IFREG && fp->_seek == __sseek ? 91 __SOPT : __SNPT); 92 } 93