Stephen Hines | 758d00c | 2012-05-03 12:30:15 -0700 | [diff] [blame] | 1 | /* |
| 2 | * Copyright 2010, The Android Open Source Project |
| 3 | * |
| 4 | * Licensed under the Apache License, Version 2.0 (the "License"); |
| 5 | * you may not use this file except in compliance with the License. |
| 6 | * You may obtain a copy of the License at |
| 7 | * |
| 8 | * http://www.apache.org/licenses/LICENSE-2.0 |
| 9 | * |
| 10 | * Unless required by applicable law or agreed to in writing, software |
| 11 | * distributed under the License is distributed on an "AS IS" BASIS, |
| 12 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 13 | * See the License for the specific language governing permissions and |
| 14 | * limitations under the License. |
| 15 | */ |
| 16 | |
| 17 | #include "FileHandle.h" |
| 18 | |
| 19 | #include "DebugHelper.h" |
| 20 | |
| 21 | #include <errno.h> |
| 22 | #include <fcntl.h> |
| 23 | #include <sys/file.h> |
| 24 | #include <sys/stat.h> |
| 25 | #include <sys/types.h> |
| 26 | #include <unistd.h> |
| 27 | |
| 28 | #include <string.h> |
| 29 | |
| 30 | namespace bcc { |
| 31 | |
| 32 | int FileHandle::open(char const *filename, OpenMode::ModeType mode) { |
| 33 | static int const open_flags[2] = { |
| 34 | O_RDONLY, |
| 35 | O_RDWR | O_CREAT | O_TRUNC, |
| 36 | }; |
| 37 | |
| 38 | static int const lock_flags[2] = { LOCK_SH, LOCK_EX }; |
| 39 | |
Stephen Hines | 802d138 | 2012-05-03 12:31:09 -0700 | [diff] [blame] | 40 | #if USE_LOGGER |
Stephen Hines | 758d00c | 2012-05-03 12:30:15 -0700 | [diff] [blame] | 41 | static char const *const open_mode_str[2] = { "read", "write" }; |
Stephen Hines | 802d138 | 2012-05-03 12:31:09 -0700 | [diff] [blame] | 42 | #endif |
Stephen Hines | 758d00c | 2012-05-03 12:30:15 -0700 | [diff] [blame] | 43 | |
| 44 | static size_t const RETRY_MAX = 4; |
| 45 | |
| 46 | static useconds_t const RETRY_USEC = 200000UL; |
| 47 | |
| 48 | for (size_t i = 0; i < RETRY_MAX; ++i) { |
| 49 | // Try to open the file |
| 50 | mFD = ::open(filename, open_flags[mode], 0644); |
| 51 | |
| 52 | if (mFD < 0) { |
| 53 | if (errno == EINTR) { |
| 54 | // Interrupt occurs while opening the file. Retry. |
| 55 | continue; |
| 56 | } |
| 57 | |
| 58 | ALOGW("Unable to open %s in %s mode. (reason: %s)\n", |
| 59 | filename, open_mode_str[mode], strerror(errno)); |
| 60 | |
| 61 | return -1; |
| 62 | } |
| 63 | |
| 64 | // Try to lock the file |
| 65 | if (flock(mFD, lock_flags[mode] | LOCK_NB) < 0) { |
| 66 | ALOGW("Unable to acquire the lock immediately, block and wait now ...\n"); |
| 67 | |
| 68 | if (flock(mFD, lock_flags[mode]) < 0) { |
| 69 | ALOGE("Unable to acquire the lock. Retry ...\n"); |
| 70 | |
| 71 | ::close(mFD); |
| 72 | mFD = -1; |
| 73 | |
| 74 | usleep(RETRY_USEC); |
| 75 | continue; |
| 76 | } |
| 77 | } |
| 78 | |
| 79 | // Note: From now on, the object is correctly initialized. We have to |
| 80 | // use this->close() to close the file now. |
| 81 | |
| 82 | // Check rather we have locked the correct file or not |
| 83 | struct stat sfd, sfname; |
| 84 | |
| 85 | if (fstat(mFD, &sfd) == -1 || stat(filename, &sfname) == -1 || |
| 86 | sfd.st_dev != sfname.st_dev || sfd.st_ino != sfname.st_ino) { |
| 87 | // The file we locked is different from the given path. This may |
| 88 | // occur when someone changes the file node before we lock the file. |
| 89 | // Just close the file, and retry after sleeping. |
| 90 | |
| 91 | this->close(); |
| 92 | usleep(RETRY_USEC); |
| 93 | continue; |
| 94 | } |
| 95 | |
| 96 | // Good, we have open and lock the file correctly. |
| 97 | ALOGV("File opened. fd=%d\n", mFD); |
| 98 | return mFD; |
| 99 | } |
| 100 | |
| 101 | ALOGW("Unable to open %s in %s mode.\n", filename, open_mode_str[mode]); |
| 102 | return -1; |
| 103 | } |
| 104 | |
| 105 | |
| 106 | void FileHandle::close() { |
| 107 | if (mFD >= 0) { |
| 108 | flock(mFD, LOCK_UN); |
| 109 | ::close(mFD); |
| 110 | ALOGV("File closed. fd=%d\n", mFD); |
| 111 | mFD = -1; |
| 112 | } |
| 113 | } |
| 114 | |
| 115 | |
| 116 | ssize_t FileHandle::read(char *buf, size_t count) { |
| 117 | if (mFD < 0) { |
| 118 | return -1; |
| 119 | } |
| 120 | |
| 121 | while (true) { |
| 122 | ssize_t nread = ::read(mFD, static_cast<void *>(buf), count); |
| 123 | |
| 124 | if (nread >= 0) { |
| 125 | return nread; |
| 126 | } |
| 127 | |
| 128 | if (errno != EAGAIN && errno != EINTR) { |
| 129 | // If the errno is EAGAIN or EINTR, then we try to read again. |
| 130 | // Otherwise, consider this is a failure. And returns zero. |
| 131 | return -1; |
| 132 | } |
| 133 | } |
| 134 | |
| 135 | // Unreachable |
| 136 | return -1; |
| 137 | } |
| 138 | |
| 139 | |
| 140 | ssize_t FileHandle::write(char const *buf, size_t count) { |
| 141 | if (mFD < 0) { |
| 142 | return -1; |
| 143 | } |
| 144 | |
| 145 | ssize_t written = 0; |
| 146 | |
| 147 | while (count > 0) { |
| 148 | ssize_t nwrite = ::write(mFD, static_cast<void const *>(buf), count); |
| 149 | |
| 150 | if (nwrite < 0) { |
| 151 | if (errno != EAGAIN && errno != EINTR) { |
| 152 | return written; |
| 153 | } |
| 154 | |
| 155 | continue; |
| 156 | } |
| 157 | |
| 158 | written += nwrite; |
| 159 | count -= (size_t)nwrite; |
| 160 | buf += (size_t)nwrite; |
| 161 | } |
| 162 | |
| 163 | return written; |
| 164 | } |
| 165 | |
| 166 | |
| 167 | off_t FileHandle::seek(off_t offset, int whence) { |
| 168 | return (mFD < 0) ? -1 : lseek(mFD, offset, whence); |
| 169 | } |
| 170 | |
| 171 | |
| 172 | void FileHandle::truncate() { |
| 173 | if (mFD >= 0) { |
| 174 | if (ftruncate(mFD, 0) != 0) { |
| 175 | ALOGE("Unable to truncate the file.\n"); |
| 176 | } |
| 177 | } |
| 178 | } |
| 179 | |
| 180 | |
| 181 | } // namespace bcc |