The Android Open Source Project | 4f6e8d7 | 2008-10-21 07:00:00 -0700 | [diff] [blame] | 1 | /* |
| 2 | * Copyright (C) 2007 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 | #define LOG_TAG "selector" |
| 18 | |
| 19 | #include <assert.h> |
| 20 | #include <errno.h> |
| 21 | #include <pthread.h> |
| 22 | #include <stdlib.h> |
| 23 | #include <string.h> |
| 24 | #include <sys/types.h> |
| 25 | #include <unistd.h> |
| 26 | |
| 27 | #include <cutils/array.h> |
| 28 | #include <cutils/selector.h> |
| 29 | |
| 30 | #include "loghack.h" |
| 31 | |
| 32 | struct Selector { |
| 33 | Array* selectableFds; |
| 34 | bool looping; |
| 35 | fd_set readFds; |
| 36 | fd_set writeFds; |
| 37 | fd_set exceptFds; |
| 38 | int maxFd; |
| 39 | int wakeupPipe[2]; |
| 40 | SelectableFd* wakeupFd; |
| 41 | |
| 42 | bool inSelect; |
| 43 | pthread_mutex_t inSelectLock; |
| 44 | }; |
| 45 | |
| 46 | /** Reads and ignores wake up data. */ |
| 47 | static void eatWakeupData(SelectableFd* wakeupFd) { |
| 48 | static char garbage[64]; |
| 49 | if (read(wakeupFd->fd, garbage, sizeof(garbage)) < 0) { |
| 50 | if (errno == EINTR) { |
| 51 | LOGI("read() interrupted."); |
| 52 | } else { |
| 53 | LOG_ALWAYS_FATAL("This should never happen: %s", strerror(errno)); |
| 54 | } |
| 55 | } |
| 56 | } |
| 57 | |
| 58 | static void setInSelect(Selector* selector, bool inSelect) { |
| 59 | pthread_mutex_lock(&selector->inSelectLock); |
| 60 | selector->inSelect = inSelect; |
| 61 | pthread_mutex_unlock(&selector->inSelectLock); |
| 62 | } |
| 63 | |
| 64 | static bool isInSelect(Selector* selector) { |
| 65 | pthread_mutex_lock(&selector->inSelectLock); |
| 66 | bool inSelect = selector->inSelect; |
| 67 | pthread_mutex_unlock(&selector->inSelectLock); |
| 68 | return inSelect; |
| 69 | } |
| 70 | |
| 71 | void selectorWakeUp(Selector* selector) { |
| 72 | if (!isInSelect(selector)) { |
| 73 | // We only need to write wake-up data if we're blocked in select(). |
| 74 | return; |
| 75 | } |
| 76 | |
| 77 | static char garbage[1]; |
| 78 | if (write(selector->wakeupPipe[1], garbage, sizeof(garbage)) < 0) { |
| 79 | if (errno == EINTR) { |
| 80 | LOGI("read() interrupted."); |
| 81 | } else { |
| 82 | LOG_ALWAYS_FATAL("This should never happen: %s", strerror(errno)); |
| 83 | } |
| 84 | } |
| 85 | } |
| 86 | |
| 87 | Selector* selectorCreate(void) { |
| 88 | Selector* selector = calloc(1, sizeof(Selector)); |
| 89 | if (selector == NULL) { |
| 90 | LOG_ALWAYS_FATAL("malloc() error."); |
| 91 | } |
| 92 | selector->selectableFds = arrayCreate(); |
| 93 | |
| 94 | // Set up wake-up pipe. |
| 95 | if (pipe(selector->wakeupPipe) < 0) { |
| 96 | LOG_ALWAYS_FATAL("pipe() error: %s", strerror(errno)); |
| 97 | } |
| 98 | |
| 99 | LOGD("Wakeup fd: %d", selector->wakeupPipe[0]); |
| 100 | |
| 101 | SelectableFd* wakeupFd = selectorAdd(selector, selector->wakeupPipe[0]); |
| 102 | if (wakeupFd == NULL) { |
| 103 | LOG_ALWAYS_FATAL("malloc() error."); |
| 104 | } |
| 105 | wakeupFd->onReadable = &eatWakeupData; |
| 106 | |
| 107 | pthread_mutex_init(&selector->inSelectLock, NULL); |
| 108 | |
| 109 | return selector; |
| 110 | } |
| 111 | |
| 112 | SelectableFd* selectorAdd(Selector* selector, int fd) { |
| 113 | assert(selector != NULL); |
| 114 | |
| 115 | SelectableFd* selectableFd = calloc(1, sizeof(SelectableFd)); |
| 116 | if (selectableFd != NULL) { |
| 117 | selectableFd->selector = selector; |
| 118 | selectableFd->fd = fd; |
| 119 | |
| 120 | arrayAdd(selector->selectableFds, selectableFd); |
| 121 | } |
| 122 | |
| 123 | return selectableFd; |
| 124 | } |
| 125 | |
| 126 | /** |
| 127 | * Adds an fd to the given set if the callback is non-null. Returns true |
| 128 | * if the fd was added. |
| 129 | */ |
| 130 | static inline bool maybeAdd(SelectableFd* selectableFd, |
| 131 | void (*callback)(SelectableFd*), fd_set* fdSet) { |
| 132 | if (callback != NULL) { |
| 133 | FD_SET(selectableFd->fd, fdSet); |
| 134 | return true; |
| 135 | } |
| 136 | return false; |
| 137 | } |
| 138 | |
| 139 | /** |
| 140 | * Removes stale file descriptors and initializes file descriptor sets. |
| 141 | */ |
| 142 | static void prepareForSelect(Selector* selector) { |
| 143 | fd_set* exceptFds = &selector->exceptFds; |
| 144 | fd_set* readFds = &selector->readFds; |
| 145 | fd_set* writeFds = &selector->writeFds; |
| 146 | |
| 147 | FD_ZERO(exceptFds); |
| 148 | FD_ZERO(readFds); |
| 149 | FD_ZERO(writeFds); |
| 150 | |
| 151 | Array* selectableFds = selector->selectableFds; |
| 152 | int i = 0; |
| 153 | selector->maxFd = 0; |
| 154 | int size = arraySize(selectableFds); |
| 155 | while (i < size) { |
| 156 | SelectableFd* selectableFd = arrayGet(selectableFds, i); |
| 157 | if (selectableFd->remove) { |
| 158 | // This descriptor should be removed. |
| 159 | arrayRemove(selectableFds, i); |
| 160 | size--; |
| 161 | if (selectableFd->onRemove != NULL) { |
| 162 | selectableFd->onRemove(selectableFd); |
| 163 | } |
| 164 | free(selectableFd); |
| 165 | } else { |
| 166 | if (selectableFd->beforeSelect != NULL) { |
| 167 | selectableFd->beforeSelect(selectableFd); |
| 168 | } |
| 169 | |
| 170 | bool inSet = false; |
| 171 | if (maybeAdd(selectableFd, selectableFd->onExcept, exceptFds)) { |
| 172 | LOGD("Selecting fd %d for writing...", selectableFd->fd); |
| 173 | inSet = true; |
| 174 | } |
| 175 | if (maybeAdd(selectableFd, selectableFd->onReadable, readFds)) { |
| 176 | LOGD("Selecting fd %d for reading...", selectableFd->fd); |
| 177 | inSet = true; |
| 178 | } |
| 179 | if (maybeAdd(selectableFd, selectableFd->onWritable, writeFds)) { |
| 180 | inSet = true; |
| 181 | } |
| 182 | |
| 183 | if (inSet) { |
| 184 | // If the fd is in a set, check it against max. |
| 185 | int fd = selectableFd->fd; |
| 186 | if (fd > selector->maxFd) { |
| 187 | selector->maxFd = fd; |
| 188 | } |
| 189 | } |
| 190 | |
| 191 | // Move to next descriptor. |
| 192 | i++; |
| 193 | } |
| 194 | } |
| 195 | } |
| 196 | |
| 197 | /** |
| 198 | * Invokes a callback if the callback is non-null and the fd is in the given |
| 199 | * set. |
| 200 | */ |
| 201 | static inline void maybeInvoke(SelectableFd* selectableFd, |
| 202 | void (*callback)(SelectableFd*), fd_set* fdSet) { |
| 203 | if (callback != NULL && !selectableFd->remove && |
| 204 | FD_ISSET(selectableFd->fd, fdSet)) { |
| 205 | LOGD("Selected fd %d.", selectableFd->fd); |
| 206 | callback(selectableFd); |
| 207 | } |
| 208 | } |
| 209 | |
| 210 | /** |
| 211 | * Notifies user if file descriptors are readable or writable, or if |
| 212 | * out-of-band data is present. |
| 213 | */ |
| 214 | static void fireEvents(Selector* selector) { |
| 215 | Array* selectableFds = selector->selectableFds; |
| 216 | int size = arraySize(selectableFds); |
| 217 | int i; |
| 218 | for (i = 0; i < size; i++) { |
| 219 | SelectableFd* selectableFd = arrayGet(selectableFds, i); |
| 220 | maybeInvoke(selectableFd, selectableFd->onExcept, |
| 221 | &selector->exceptFds); |
| 222 | maybeInvoke(selectableFd, selectableFd->onReadable, |
| 223 | &selector->readFds); |
| 224 | maybeInvoke(selectableFd, selectableFd->onWritable, |
| 225 | &selector->writeFds); |
| 226 | } |
| 227 | } |
| 228 | |
| 229 | void selectorLoop(Selector* selector) { |
| 230 | // Make sure we're not already looping. |
| 231 | if (selector->looping) { |
| 232 | LOG_ALWAYS_FATAL("Already looping."); |
| 233 | } |
| 234 | selector->looping = true; |
| 235 | |
| 236 | while (true) { |
| 237 | setInSelect(selector, true); |
| 238 | |
| 239 | prepareForSelect(selector); |
| 240 | |
| 241 | LOGD("Entering select()."); |
| 242 | |
| 243 | // Select file descriptors. |
| 244 | int result = select(selector->maxFd + 1, &selector->readFds, |
| 245 | &selector->writeFds, &selector->exceptFds, NULL); |
| 246 | |
| 247 | LOGD("Exiting select()."); |
| 248 | |
| 249 | setInSelect(selector, false); |
| 250 | |
| 251 | if (result == -1) { |
| 252 | // Abort on everything except EINTR. |
| 253 | if (errno == EINTR) { |
| 254 | LOGI("select() interrupted."); |
| 255 | } else { |
| 256 | LOG_ALWAYS_FATAL("select() error: %s", |
| 257 | strerror(errno)); |
| 258 | } |
| 259 | } else if (result > 0) { |
| 260 | fireEvents(selector); |
| 261 | } |
| 262 | } |
| 263 | } |