1 files changed, 267 insertions, 0 deletions
diff --git a/libs/utils/PollLoop.cpp b/libs/utils/PollLoop.cpp
new file mode 100644
index 0000000..90a3e8b
--- /dev/null
+++ b/libs/utils/PollLoop.cpp
@@ -0,0 +1,267 @@
+//
+// Copyright 2010 The Android Open Source Project
+//
+// A select loop implementation.
+//
+#define LOG_TAG "PollLoop"
+
+//#define LOG_NDEBUG 0
+
+// Debugs poll and wake interactions.
+#define DEBUG_POLL_AND_WAKE 0
+
+// Debugs callback registration and invocation.
+#define DEBUG_CALLBACKS 1
+
+#include <cutils/log.h>
+#include <utils/PollLoop.h>
+
+#include <unistd.h>
+#include <fcntl.h>
+
+namespace android {
+
+PollLoop::PollLoop() :
+        mPolling(false) {
+    openWakePipe();
+}
+
+PollLoop::~PollLoop() {
+    closeWakePipe();
+}
+
+void PollLoop::openWakePipe() {
+    int wakeFds[2];
+    int result = pipe(wakeFds);
+    LOG_ALWAYS_FATAL_IF(result != 0, "Could not create wake pipe.  errno=%d", errno);
+
+    mWakeReadPipeFd = wakeFds[0];
+    mWakeWritePipeFd = wakeFds[1];
+
+    result = fcntl(mWakeReadPipeFd, F_SETFL, O_NONBLOCK);
+    LOG_ALWAYS_FATAL_IF(result != 0, "Could not make wake read pipe non-blocking.  errno=%d",
+            errno);
+
+    result = fcntl(mWakeWritePipeFd, F_SETFL, O_NONBLOCK);
+    LOG_ALWAYS_FATAL_IF(result != 0, "Could not make wake write pipe non-blocking.  errno=%d",
+            errno);
+
+    // Add the wake pipe to the head of the request list with a null callback.
+    struct pollfd requestedFd;
+    requestedFd.fd = mWakeReadPipeFd;
+    requestedFd.events = POLLIN;
+    mRequestedFds.insertAt(requestedFd, 0);
+
+    RequestedCallback requestedCallback;
+    requestedCallback.callback = NULL;
+    requestedCallback.data = NULL;
+    mRequestedCallbacks.insertAt(requestedCallback, 0);
+}
+
+void PollLoop::closeWakePipe() {
+    close(mWakeReadPipeFd);
+    close(mWakeWritePipeFd);
+
+    // Note: We don't need to remove the poll structure or callback entry because this
+    //       method is currently only called by the destructor.
+}
+
+bool PollLoop::pollOnce(int timeoutMillis) {
+    mLock.lock();
+    mPolling = true;
+    mLock.unlock();
+
+    bool result;
+    size_t requestedCount = mRequestedFds.size();
+
+#if DEBUG_POLL_AND_WAKE
+    LOGD("%p ~ pollOnce - waiting on %d fds", this, requestedCount);
+    for (size_t i = 0; i < requestedCount; i++) {
+        LOGD("  fd %d - events %d", mRequestedFds[i].fd, mRequestedFds[i].events);
+    }
+#endif
+
+    int respondedCount = poll(mRequestedFds.editArray(), requestedCount, timeoutMillis);
+
+    if (respondedCount == 0) {
+        // Timeout
+#if DEBUG_POLL_AND_WAKE
+        LOGD("%p ~ pollOnce - timeout", this);
+#endif
+        result = false;
+        goto Done;
+    }
+
+    if (respondedCount < 0) {
+        // Error
+#if DEBUG_POLL_AND_WAKE
+        LOGD("%p ~ pollOnce - error, errno=%d", this, errno);
+#endif
+        if (errno != EINTR) {
+            LOGW("Poll failed with an unexpected error, errno=%d", errno);
+        }
+        result = false;
+        goto Done;
+    }
+
+#if DEBUG_POLL_AND_WAKE
+    LOGD("%p ~ pollOnce - handling responses from %d fds", this, respondedCount);
+    for (size_t i = 0; i < requestedCount; i++) {
+        LOGD("  fd %d - events %d, revents %d", mRequestedFds[i].fd, mRequestedFds[i].events,
+                mRequestedFds[i].revents);
+    }
+#endif
+
+    mPendingCallbacks.clear();
+    for (size_t i = 0; i < requestedCount; i++) {
+        const struct pollfd& requestedFd = mRequestedFds.itemAt(i);
+
+        short revents = requestedFd.revents;
+        if (revents) {
+            const RequestedCallback& requestedCallback = mRequestedCallbacks.itemAt(i);
+            Callback callback = requestedCallback.callback;
+
+            if (callback) {
+                PendingCallback pendingCallback;
+                pendingCallback.fd = requestedFd.fd;
+                pendingCallback.events = requestedFd.revents;
+                pendingCallback.callback = callback;
+                pendingCallback.data = requestedCallback.data;
+                mPendingCallbacks.push(pendingCallback);
+            } else {
+                if (requestedFd.fd == mWakeReadPipeFd) {
+#if DEBUG_POLL_AND_WAKE
+                    LOGD("%p ~ pollOnce - awoken", this);
+#endif
+                    char buffer[16];
+                    ssize_t nRead;
+                    do {
+                        nRead = read(mWakeReadPipeFd, buffer, sizeof(buffer));
+                    } while (nRead == sizeof(buffer));
+                } else {
+#if DEBUG_POLL_AND_WAKE || DEBUG_CALLBACKS
+                    LOGD("%p ~ pollOnce - fd %d has no callback!", this, requestedFd.fd);
+#endif
+                }
+            }
+
+            respondedCount -= 1;
+            if (respondedCount == 0) {
+                break;
+            }
+        }
+    }
+    result = true;
+
+Done:
+    mLock.lock();
+    mPolling = false;
+    mAwake.broadcast();
+    mLock.unlock();
+
+    if (result) {
+        size_t pendingCount = mPendingCallbacks.size();
+        for (size_t i = 0; i < pendingCount; i++) {
+            const PendingCallback& pendingCallback = mPendingCallbacks.itemAt(i);
+#if DEBUG_POLL_AND_WAKE || DEBUG_CALLBACKS
+            LOGD("%p ~ pollOnce - invoking callback for fd %d", this, pendingCallback.fd);
+#endif
+
+            bool keep = pendingCallback.callback(pendingCallback.fd, pendingCallback.events,
+                    pendingCallback.data);
+            if (! keep) {
+                removeCallback(pendingCallback.fd);
+            }
+        }
+    }
+
+#if DEBUG_POLL_AND_WAKE
+    LOGD("%p ~ pollOnce - done", this);
+#endif
+    return result;
+}
+
+void PollLoop::wake() {
+#if DEBUG_POLL_AND_WAKE
+    LOGD("%p ~ wake", this);
+#endif
+
+    ssize_t nWrite = write(mWakeWritePipeFd, "W", 1);
+    if (nWrite != 1) {
+        if (errno != EAGAIN) {
+            LOGW("Could not write wake signal, errno=%d", errno);
+        }
+    }
+}
+
+void PollLoop::setCallback(int fd, int events, Callback callback, void* data) {
+#if DEBUG_CALLBACKS
+    LOGD("%p ~ setCallback - fd=%d, events=%d", this, fd, events);
+#endif
+
+    if (! events || ! callback) {
+        LOGE("Invalid attempt to set a callback with no selected poll events or no callback.");
+        removeCallback(fd);
+        return;
+    }
+
+    wakeAndLock();
+
+    struct pollfd requestedFd;
+    requestedFd.fd = fd;
+    requestedFd.events = events;
+
+    RequestedCallback requestedCallback;
+    requestedCallback.callback = callback;
+    requestedCallback.data = data;
+
+    ssize_t index = getRequestIndexLocked(fd);
+    if (index < 0) {
+        mRequestedFds.push(requestedFd);
+        mRequestedCallbacks.push(requestedCallback);
+    } else {
+        mRequestedFds.replaceAt(requestedFd, size_t(index));
+        mRequestedCallbacks.replaceAt(requestedCallback, size_t(index));
+    }
+
+    mLock.unlock();
+}
+
+bool PollLoop::removeCallback(int fd) {
+#if DEBUG_CALLBACKS
+    LOGD("%p ~ removeCallback - fd=%d", this, fd);
+#endif
+
+    wakeAndLock();
+
+    ssize_t index = getRequestIndexLocked(fd);
+    if (index >= 0) {
+        mRequestedFds.removeAt(size_t(index));
+        mRequestedCallbacks.removeAt(size_t(index));
+    }
+
+    mLock.unlock();
+    return index >= 0;
+}
+
+ssize_t PollLoop::getRequestIndexLocked(int fd) {
+    size_t requestCount = mRequestedFds.size();
+
+    for (size_t i = 0; i < requestCount; i++) {
+        if (mRequestedFds.itemAt(i).fd == fd) {
+            return i;
+        }
+    }
+
+    return -1;
+}
+
+void PollLoop::wakeAndLock() {
+    mLock.lock();
+    while (mPolling) {
+        wake();
+        mAwake.wait(mLock);
+    }
+}
+
+} // namespace android