1/* An interface to read and write that retries after interrupts. 2 3 Copyright (C) 1993, 1994, 1998, 2002, 2003, 2004, 2005, 2006 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/* Specification. */ 22#ifdef SAFE_WRITE 23# include "safe-write.h" 24#else 25# include "safe-read.h" 26#endif 27 28/* Get ssize_t. */ 29#include <sys/types.h> 30#include <unistd.h> 31 32#include <errno.h> 33 34#ifdef EINTR 35# define IS_EINTR(x) ((x) == EINTR) 36#else 37# define IS_EINTR(x) 0 38#endif 39 40#include <limits.h> 41 42#ifdef SAFE_WRITE 43# define safe_rw safe_write 44# define rw write 45#else 46# define safe_rw safe_read 47# define rw read 48# undef const 49# define const /* empty */ 50#endif 51 52/* Read(write) up to COUNT bytes at BUF from(to) descriptor FD, retrying if 53 interrupted. Return the actual number of bytes read(written), zero for EOF, 54 or SAFE_READ_ERROR(SAFE_WRITE_ERROR) upon error. */ 55size_t 56safe_rw (int fd, void const *buf, size_t count) 57{ 58 /* Work around a bug in Tru64 5.1. Attempting to read more than 59 INT_MAX bytes fails with errno == EINVAL. See 60 <http://lists.gnu.org/archive/html/bug-gnu-utils/2002-04/msg00010.html>. 61 When decreasing COUNT, keep it block-aligned. */ 62 enum { BUGGY_READ_MAXIMUM = INT_MAX & ~8191 }; 63 64 for (;;) 65 { 66 ssize_t result = rw (fd, buf, count); 67 68 if (0 <= result) 69 return result; 70 else if (IS_EINTR (errno)) 71 continue; 72 else if (errno == EINVAL && BUGGY_READ_MAXIMUM < count) 73 count = BUGGY_READ_MAXIMUM; 74 else 75 return result; 76 } 77} 78