1 /* Buffer primitives for comparison operations. 2 3 Copyright (C) 1993, 1995, 1998, 2001-2002, 2006, 2009-2010 Free Software 4 Foundation, Inc. 5 6 This program is free software: you can redistribute it and/or modify 7 it under the terms of the GNU General Public License as published by 8 the Free Software Foundation, either version 3 of the License, or 9 (at your option) any later version. 10 11 This program is distributed in the hope that it will be useful, 12 but WITHOUT ANY WARRANTY; without even the implied warranty of 13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 14 GNU General Public License for more details. 15 16 You should have received a copy of the GNU General Public License 17 along with this program. If not, see <http://www.gnu.org/licenses/>. */ 18 19 #include <config.h> 20 21 #include <errno.h> 22 #include <limits.h> 23 24 #include <signal.h> 25 #ifndef SA_RESTART 26 # ifdef SA_INTERRUPT /* e.g. SunOS 4.1.x */ 27 # define SA_RESTART SA_INTERRUPT 28 # else 29 # define SA_RESTART 0 30 # endif 31 #endif 32 33 #include <unistd.h> 34 #include <inttypes.h> 35 #include <sys/types.h> 36 #include "cmpbuf.h" 37 #include "intprops.h" 38 39 #ifndef PTRDIFF_MAX 40 # define PTRDIFF_MAX TYPE_MAXIMUM (ptrdiff_t) 41 #endif 42 #ifndef SIZE_MAX 43 # define SIZE_MAX TYPE_MAXIMUM (size_t) 44 #endif 45 #ifndef SSIZE_MAX 46 # define SSIZE_MAX TYPE_MAXIMUM (ssize_t) 47 #endif 48 49 #undef MIN 50 #define MIN(a, b) ((a) <= (b) ? (a) : (b)) 51 52 /* Read NBYTES bytes from descriptor FD into BUF. 53 NBYTES must not be SIZE_MAX. 54 Return the number of characters successfully read. 55 On error, return SIZE_MAX, setting errno. 56 The number returned is always NBYTES unless end-of-file or error. */ 57 58 size_t 59 block_read (int fd, char *buf, size_t nbytes) 60 { 61 char *bp = buf; 62 char const *buflim = buf + nbytes; 63 size_t readlim = MIN (SSIZE_MAX, SIZE_MAX); 64 65 do 66 { 67 size_t bytes_remaining = buflim - bp; 68 size_t bytes_to_read = MIN (bytes_remaining, readlim); 69 ssize_t nread = read (fd, bp, bytes_to_read); 70 if (nread <= 0) 71 { 72 if (nread == 0) 73 break; 74 75 /* Accommodate Tru64 5.1, which can't read more than INT_MAX 76 bytes at a time. They call that a 64-bit OS? */ 77 if (errno == EINVAL && INT_MAX < bytes_to_read) 78 { 79 readlim = INT_MAX; 80 continue; 81 } 82 83 /* This is needed for programs that have signal handlers on 84 older hosts without SA_RESTART. It also accommodates 85 ancient AIX hosts that set errno to EINTR after uncaught 86 SIGCONT. See <news:1r77ojINN85n@ftp.UU.NET> 87 (1993-04-22). */ 88 if (! SA_RESTART && errno == EINTR) 89 continue; 90 91 return SIZE_MAX; 92 } 93 bp += nread; 94 } 95 while (bp < buflim); 96 97 return bp - buf; 98 } 99 100 /* Least common multiple of two buffer sizes A and B. However, if 101 either A or B is zero, or if the multiple is greater than LCM_MAX, 102 return a reasonable buffer size. */ 103 104 size_t 105 buffer_lcm (size_t a, size_t b, size_t lcm_max) 106 { 107 size_t lcm, m, n, q, r; 108 109 /* Yield reasonable values if buffer sizes are zero. */ 110 if (!a) 111 return b ? b : 8 * 1024; 112 if (!b) 113 return a; 114 115 /* n = gcd (a, b) */ 116 for (m = a, n = b; (r = m % n) != 0; m = n, n = r) 117 continue; 118 119 /* Yield a if there is an overflow. */ 120 q = a / n; 121 lcm = q * b; 122 return lcm <= lcm_max && lcm / b == q ? lcm : a; 123 } 124