cmpbuf.c revision 256281
1/* Buffer primitives for comparison operations. 2 3 Copyright (C) 1993, 1995, 1998, 2001, 2002 Free Software Foundation, Inc. 4 5 This program is free software; you can redistribute it and/or modify 6 it under the terms of the GNU General Public License as published by 7 the Free Software Foundation; either version 2, or (at your option) 8 any later version. 9 10 This program is distributed in the hope that it will be useful, 11 but WITHOUT ANY WARRANTY; without even the implied warranty of 12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 13 GNU General Public License for more details. 14 15 You should have received a copy of the GNU General Public License 16 along with this program; see the file COPYING. 17 If not, write to the Free Software Foundation, 18 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */ 19 20#if HAVE_CONFIG_H 21# include <config.h> 22#endif 23 24#include <errno.h> 25#include <limits.h> 26 27#include <signal.h> 28#ifndef SA_RESTART 29# ifdef SA_INTERRUPT /* e.g. SunOS 4.1.x */ 30# define SA_RESTART SA_INTERRUPT 31# else 32# define SA_RESTART 0 33# endif 34#endif 35 36#if HAVE_UNISTD_H 37# include <unistd.h> 38#endif 39 40#if HAVE_INTTYPES_H 41# include <inttypes.h> 42#endif 43 44#include <sys/types.h> 45#include "cmpbuf.h" 46 47/* Determine whether an integer type is signed, and its bounds. 48 This code assumes two's (or one's!) complement with no holes. */ 49 50/* The extra casts work around common compiler bugs, 51 e.g. Cray C 5.0.3.0 when t == time_t. */ 52#ifndef TYPE_SIGNED 53# define TYPE_SIGNED(t) (! ((t) 0 < (t) -1)) 54#endif 55#ifndef TYPE_MINIMUM 56# define TYPE_MINIMUM(t) ((t) (TYPE_SIGNED (t) \ 57 ? ~ (t) 0 << (sizeof (t) * CHAR_BIT - 1) \ 58 : (t) 0)) 59#endif 60#ifndef TYPE_MAXIMUM 61# define TYPE_MAXIMUM(t) ((t) (~ (t) 0 - TYPE_MINIMUM (t))) 62#endif 63 64#ifndef PTRDIFF_MAX 65# define PTRDIFF_MAX TYPE_MAXIMUM (ptrdiff_t) 66#endif 67#ifndef SIZE_MAX 68# define SIZE_MAX TYPE_MAXIMUM (size_t) 69#endif 70#ifndef SSIZE_MAX 71# define SSIZE_MAX TYPE_MAXIMUM (ssize_t) 72#endif 73 74#undef MIN 75#define MIN(a, b) ((a) <= (b) ? (a) : (b)) 76 77/* Read NBYTES bytes from descriptor FD into BUF. 78 NBYTES must not be SIZE_MAX. 79 Return the number of characters successfully read. 80 On error, return SIZE_MAX, setting errno. 81 The number returned is always NBYTES unless end-of-file or error. */ 82 83size_t 84block_read (int fd, char *buf, size_t nbytes) 85{ 86 char *bp = buf; 87 char const *buflim = buf + nbytes; 88 size_t readlim = SSIZE_MAX; 89 90 do 91 { 92 size_t bytes_to_read = MIN (buflim - bp, readlim); 93 ssize_t nread = read (fd, bp, bytes_to_read); 94 if (nread <= 0) 95 { 96 if (nread == 0) 97 break; 98 99 /* Accommodate Tru64 5.1, which can't read more than INT_MAX 100 bytes at a time. They call that a 64-bit OS? */ 101 if (errno == EINVAL && INT_MAX < bytes_to_read) 102 { 103 readlim = INT_MAX; 104 continue; 105 } 106 107 /* This is needed for programs that have signal handlers on 108 older hosts without SA_RESTART. It also accommodates 109 ancient AIX hosts that set errno to EINTR after uncaught 110 SIGCONT. See <news:1r77ojINN85n@ftp.UU.NET> 111 (1993-04-22). */ 112 if (! SA_RESTART && errno == EINTR) 113 continue; 114 115 return SIZE_MAX; 116 } 117 bp += nread; 118 } 119 while (bp < buflim); 120 121 return bp - buf; 122} 123 124/* Least common multiple of two buffer sizes A and B. However, if 125 either A or B is zero, or if the multiple is greater than LCM_MAX, 126 return a reasonable buffer size. */ 127 128size_t 129buffer_lcm (size_t a, size_t b, size_t lcm_max) 130{ 131 size_t lcm, m, n, q, r; 132 133 /* Yield reasonable values if buffer sizes are zero. */ 134 if (!a) 135 return b ? b : 8 * 1024; 136 if (!b) 137 return a; 138 139 /* n = gcd (a, b) */ 140 for (m = a, n = b; (r = m % n) != 0; m = n, n = r) 141 continue; 142 143 /* Yield a if there is an overflow. */ 144 q = a / n; 145 lcm = q * b; 146 return lcm <= lcm_max && lcm / b == q ? lcm : a; 147} 148