Make UhidManager compatible with API 19

Author: consp1racy

server/src/main/java/com/genymobile/scrcpy/control/UhidManager.java

@@ -8,21 +8,17 @@
 import android.os.Build;
 import android.os.HandlerThread;
 import android.os.MessageQueue;
-import android.system.ErrnoException;
-import android.system.Os;
-import android.system.OsConstants;
+import android.os.Process;
 import android.util.ArrayMap;
 
-import androidx.annotation.RequiresApi;
-
 import java.io.FileDescriptor;
 import java.io.IOException;
-import java.io.InterruptedIOException;
+import java.io.RandomAccessFile;
 import java.nio.ByteBuffer;
 import java.nio.ByteOrder;
+import java.nio.channels.FileChannel;
 import java.nio.charset.StandardCharsets;
 
-@RequiresApi(AndroidVersions.API_21_ANDROID_5_0)
 public final class UhidManager {
 
     // Linux: include/uapi/linux/uhid.h
@@ -36,11 +32,11 @@ public final class UhidManager {
     private static final int SIZE_OF_UHID_EVENT = 4380; // sizeof(struct uhid_event)
 
     // Must be unique across the system
-    private static final String INPUT_PORT = "scrcpy:" + Os.getpid();
+    private static final String INPUT_PORT = "scrcpy:" + Process.myPid();
 
     private final String displayUniqueId;
 
-    private final ArrayMap<Integer, FileDescriptor> fds = new ArrayMap<>();
+    private final ArrayMap<Integer, RandomAccessFile> rafs = new ArrayMap<>();
     private final ByteBuffer buffer = ByteBuffer.allocate(SIZE_OF_UHID_EVENT).order(ByteOrder.nativeOrder());
 
     private final DeviceMessageSender sender;
@@ -59,41 +55,35 @@ public UhidManager(DeviceMessageSender sender, String displayUniqueId) {
     }
 
     public void open(int id, int vendorId, int productId, String name, byte[] reportDesc) throws IOException {
-        try {
-            FileDescriptor fd = Os.open("/dev/uhid", OsConstants.O_RDWR, 0);
-            try {
-                // First UHID device added
-                boolean firstDevice = fds.isEmpty();
-
-                FileDescriptor old = fds.put(id, fd);
-                if (old != null) {
-                    Ln.w("Duplicate UHID id: " + id);
-                    close(old);
-                }
+        try (RandomAccessFile raf = new RandomAccessFile("/dev/uhid", "rw")) {
+            // First UHID device added
+            boolean firstDevice = rafs.isEmpty();
+
+            RandomAccessFile old = rafs.put(id, raf);
+            if (old != null) {
+                Ln.w("Duplicate UHID id: " + id);
+                close(old);
+            }
 
-                String phys = mustUseInputPort() ? INPUT_PORT : null;
-                byte[] req = buildUhidCreate2Req(vendorId, productId, name, reportDesc, phys);
-                Os.write(fd, req, 0, req.length);
+            String phys = mustUseInputPort() ? INPUT_PORT : null;
+            byte[] req = buildUhidCreate2Req(vendorId, productId, name, reportDesc, phys);
+            raf.write(req, 0, req.length);
 
-                if (firstDevice) {
-                    addUniqueIdAssociation();
-                }
-                registerUhidListener(id, fd);
-            } catch (Exception e) {
-                close(fd);
-                throw e;
+            if (firstDevice) {
+                addUniqueIdAssociation();
             }
-        } catch (ErrnoException e) {
-            throw new IOException(e);
+            registerUhidListener(id, raf);
         }
     }
 
-    private void registerUhidListener(int id, FileDescriptor fd) {
+    private void registerUhidListener(int id, RandomAccessFile raf) throws IOException {
         if (Build.VERSION.SDK_INT >= AndroidVersions.API_23_ANDROID_6_0) {
+            final FileDescriptor fd = raf.getFD();
+            final FileChannel channel = raf.getChannel();
             queue.addOnFileDescriptorEventListener(fd, MessageQueue.OnFileDescriptorEventListener.EVENT_INPUT, (fd2, events) -> {
                 try {
                     buffer.clear();
-                    int r = Os.read(fd2, buffer);
+                    int r = channel.read(buffer);
                     buffer.flip();
                     if (r > 0) {
                         int type = buffer.getInt();
@@ -105,7 +95,7 @@ private void registerUhidListener(int id, FileDescriptor fd) {
                             }
                         }
                     }
-                } catch (ErrnoException | InterruptedIOException e) {
+                } catch (IOException e) {
                     Ln.e("Failed to read UHID output", e);
                     return 0;
                 }
@@ -114,8 +104,9 @@ private void registerUhidListener(int id, FileDescriptor fd) {
         }
     }
 
-    private void unregisterUhidListener(FileDescriptor fd) {
+    private void unregisterUhidListener(RandomAccessFile raf) throws IOException {
         if (Build.VERSION.SDK_INT >= AndroidVersions.API_23_ANDROID_6_0) {
+            final FileDescriptor fd = raf.getFD();
             queue.removeOnFileDescriptorEventListener(fd);
         }
     }
@@ -151,18 +142,14 @@ private static byte[] extractHidOutputData(ByteBuffer buffer) {
     }
 
     public void writeInput(int id, byte[] data) throws IOException {
-        FileDescriptor fd = fds.get(id);
-        if (fd == null) {
+        RandomAccessFile raf = rafs.get(id);
+        if (raf == null) {
             Ln.w("Unknown UHID id: " + id);
             return;
         }
 
-        try {
-            byte[] req = buildUhidInput2Req(data);
-            Os.write(fd, req, 0, req.length);
-        } catch (ErrnoException e) {
-            throw new IOException(e);
-        }
+        byte[] req = buildUhidInput2Req(data);
+        raf.write(req, 0, req.length);
     }
 
     private static byte[] buildUhidCreate2Req(int vendorId, int productId, String name, byte[] reportDesc, String phys) {
@@ -235,15 +222,15 @@ private static byte[] buildUhidInput2Req(byte[] data) {
         return buf.array();
     }
 
-    public void close(int id) {
+    public void close(int id) throws IOException {
         // Linux: Documentation/hid/uhid.rst
         // If you close() the fd, the device is automatically unregistered and destroyed internally.
-        FileDescriptor fd = fds.remove(id);
-        if (fd != null) {
-            unregisterUhidListener(fd);
-            close(fd);
+        RandomAccessFile raf = rafs.remove(id);
+        if (raf != null) {
+            unregisterUhidListener(raf);
+            close(raf);
 
-            if (fds.isEmpty()) {
+            if (rafs.isEmpty()) {
                 // Last UHID device removed
                 removeUniqueIdAssociation();
             }
@@ -253,21 +240,21 @@ public void close(int id) {
     }
 
     public void closeAll() {
-        if (fds.isEmpty()) {
+        if (rafs.isEmpty()) {
             return;
         }
 
-        for (FileDescriptor fd : fds.values()) {
-            close(fd);
+        for (RandomAccessFile raf : rafs.values()) {
+            close(raf);
         }
 
         removeUniqueIdAssociation();
     }
 
-    private static void close(FileDescriptor fd) {
+    private static void close(RandomAccessFile raf) {
         try {
-            Os.close(fd);
-        } catch (ErrnoException e) {
+            raf.close();
+        } catch (IOException e) {
             Ln.e("Failed to close uhid: " + e.getMessage());
         }
     }