1 /* Buffer primitives for comparison operations. 2 3 Copyright (C) 1993, 1995, 1998, 2001-2002, 2006, 2009-2013, 2015-2018 Free 4 Software 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 #include <signal.h> 24 #include <unistd.h> 25 #include <stdint.h> 26 #include <inttypes.h> 27 #include <sys/types.h> 28 #include "cmpbuf.h" 29 #include "intprops.h" 30 31 #ifndef SSIZE_MAX 32 # define SSIZE_MAX TYPE_MAXIMUM (ssize_t) 33 #endif 34 35 #undef MIN 36 #define MIN(a, b) ((a) <= (b) ? (a) : (b)) 37 38 /* Read NBYTES bytes from descriptor FD into BUF. 39 NBYTES must not be SIZE_MAX. 40 Return the number of characters successfully read. 41 On error, return SIZE_MAX, setting errno. 42 The number returned is always NBYTES unless end-of-file or error. */ 43 44 size_t 45 block_read (int fd, char *buf, size_t nbytes) 46 { 47 char *bp = buf; 48 char const *buflim = buf + nbytes; 49 size_t readlim = MIN (SSIZE_MAX, SIZE_MAX); 50 51 do 52 { 53 size_t bytes_remaining = buflim - bp; 54 size_t bytes_to_read = MIN (bytes_remaining, readlim); 55 ssize_t nread = read (fd, bp, bytes_to_read); 56 if (nread <= 0) 57 { 58 if (nread == 0) 59 break; 60 61 /* Accommodate Tru64 5.1, which can't read more than INT_MAX 62 bytes at a time. They call that a 64-bit OS? */ 63 if (errno == EINVAL && INT_MAX < bytes_to_read) 64 { 65 readlim = INT_MAX; 66 continue; 67 } 68 69 /* This is needed for programs that have signal handlers on 70 older hosts without SA_RESTART. It also accommodates 71 ancient AIX hosts that set errno to EINTR after uncaught 72 SIGCONT. See <news:1r77ojINN85n@ftp.UU.NET> 73 (1993-04-22). */ 74 if (! SA_RESTART && errno == EINTR) 75 continue; 76 77 return SIZE_MAX; 78 } 79 bp += nread; 80 } 81 while (bp < buflim); 82 83 return bp - buf; 84 } 85 86 /* Least common multiple of two buffer sizes A and B. However, if 87 either A or B is zero, or if the multiple is greater than LCM_MAX, 88 return a reasonable buffer size. */ 89 90 size_t 91 buffer_lcm (size_t a, size_t b, size_t lcm_max) 92 { 93 size_t lcm, m, n, q, r; 94 95 /* Yield reasonable values if buffer sizes are zero. */ 96 if (!a) 97 return b ? b : 8 * 1024; 98 if (!b) 99 return a; 100 101 /* n = gcd (a, b) */ 102 for (m = a, n = b; (r = m % n) != 0; m = n, n = r) 103 continue; 104 105 /* Yield a if there is an overflow. */ 106 q = a / n; 107 lcm = q * b; 108 return lcm <= lcm_max && lcm / b == q ? lcm : a; 109 } 110