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Update ParcelFileDescriptor to use non-blocking I/O.

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Avoids spinning up a thread just to watch a file descriptor.

Bug: 10349083
Change-Id: I814cb252f075d7a162e1286bbfd1dbec28d17796
This commit is contained in:
Jeff Brown
2015-03-10 18:38:48 -07:00
parent dc3eb4bf91
commit a34a3bdcbf
1 changed files with 31 additions and 39 deletions
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70
core/java/android/os/ParcelFileDescriptor.java
View File

@@ -19,11 +19,13 @@ package android.os;
import static android.system.OsConstants.AF_UNIX;
import static android.system.OsConstants.SEEK_SET;
import static android.system.OsConstants.SOCK_STREAM;
import static android.system.OsConstants.SOCK_SEQPACKET;
import static android.system.OsConstants.S_ISLNK;
import static android.system.OsConstants.S_ISREG;
import android.content.BroadcastReceiver;
import android.content.ContentProvider;
import android.os.MessageQueue.FileDescriptorCallback;
import android.system.ErrnoException;
import android.system.Os;
import android.system.OsConstants;
@@ -31,7 +33,6 @@ import android.system.StructStat;
import android.util.Log;
import dalvik.system.CloseGuard;
import libcore.io.IoUtils;
import libcore.io.Memory;
@@ -220,8 +221,8 @@ public class ParcelFileDescriptor implements Parcelable, Closeable {
* be opened with the requested mode.
* @see #parseMode(String)
*/
public static ParcelFileDescriptor open(
File file, int mode, Handler handler, OnCloseListener listener) throws IOException {
public static ParcelFileDescriptor open(File file, int mode, Handler handler,
final OnCloseListener listener) throws IOException {
if (handler == null) {
throw new IllegalArgumentException("Handler must not be null");
}
@@ -235,10 +236,25 @@ public class ParcelFileDescriptor implements Parcelable, Closeable {
final FileDescriptor[] comm = createCommSocketPair();
final ParcelFileDescriptor pfd = new ParcelFileDescriptor(fd, comm[0]);
// Kick off thread to watch for status updates
IoUtils.setBlocking(comm[1], true);
final ListenerBridge bridge = new ListenerBridge(comm[1], handler.getLooper(), listener);
bridge.start();
handler.getLooper().getQueue().registerFileDescriptorCallback(comm[1],
FileDescriptorCallback.EVENT_INPUT, new FileDescriptorCallback() {
@Override
public int onFileDescriptorEvents(FileDescriptor fd, int events) {
Status status = null;
if ((events & FileDescriptorCallback.EVENT_INPUT) != 0) {
final byte[] buf = new byte[MAX_STATUS];
status = readCommStatus(fd, buf);
} else if ((events & FileDescriptorCallback.EVENT_ERROR) != 0) {
status = new Status(Status.DEAD);
}
if (status != null) {
IoUtils.closeQuietly(fd);
listener.onClose(status.asIOException());
return 0; // unregister the callback
}
return EVENT_INPUT;
}
});
return pfd;
}
@@ -446,9 +462,12 @@ public class ParcelFileDescriptor implements Parcelable, Closeable {
private static FileDescriptor[] createCommSocketPair() throws IOException {
try {
// Use SOCK_SEQPACKET so that we have a guarantee that the status
// is written and read atomically as one unit and is not split
// across multiple IO operations.
final FileDescriptor comm1 = new FileDescriptor();
final FileDescriptor comm2 = new FileDescriptor();
Os.socketpair(AF_UNIX, SOCK_STREAM, 0, comm1, comm2);
Os.socketpair(AF_UNIX, SOCK_SEQPACKET, 0, comm1, comm2);
IoUtils.setBlocking(comm1, false);
IoUtils.setBlocking(comm2, false);
return new FileDescriptor[] { comm1, comm2 };
@@ -709,6 +728,7 @@ public class ParcelFileDescriptor implements Parcelable, Closeable {
writePtr += len;
}
// Must write the entire status as a single operation.
Os.write(mCommFd, buf, 0, writePtr);
} catch (ErrnoException e) {
// Reporting status is best-effort
@@ -726,6 +746,7 @@ public class ParcelFileDescriptor implements Parcelable, Closeable {
private static Status readCommStatus(FileDescriptor comm, byte[] buf) {
try {
// Must read the entire status as a single operation.
final int n = Os.read(comm, buf, 0, buf.length);
if (n == 0) {
// EOF means they're dead
@@ -1014,39 +1035,10 @@ public class ParcelFileDescriptor implements Parcelable, Closeable {
return new IOException("Unknown status: " + status);
}
}
}
/**
* Bridge to watch for remote status, and deliver to listener. Currently
* requires that communication socket is <em>blocking</em>.
*/
private static final class ListenerBridge extends Thread {
// TODO: switch to using Looper to avoid burning a thread
private FileDescriptor mCommFd;
private final Handler mHandler;
public ListenerBridge(FileDescriptor comm, Looper looper, final OnCloseListener listener) {
mCommFd = comm;
mHandler = new Handler(looper) {
@Override
public void handleMessage(Message msg) {
final Status s = (Status) msg.obj;
listener.onClose(s != null ? s.asIOException() : null);
}
};
}
@Override
public void run() {
try {
final byte[] buf = new byte[MAX_STATUS];
final Status status = readCommStatus(mCommFd, buf);
mHandler.obtainMessage(0, status).sendToTarget();
} finally {
IoUtils.closeQuietly(mCommFd);
mCommFd = null;
}
public String toString() {
return "{" + status + ": " + msg + "}";
}
}
}