Sensor: Make getId() more varied

Apps from different developers will now receive a different
ID for the same dynamic sensor.  Additionally, all apps
will now receive a different/new ID for the same dynamic
sensor after a factory reset.

Bug: 28775590, 29547335
Change-Id: I15b48b974cbb1d53cc33dfdb7b9eb5f1b562190c

diff --git a/core/java/android/hardware/Sensor.java b/core/java/android/hardware/Sensor.java
index 0f07419..c9ae69c 100644 (file)
--- a/core/java/android/hardware/Sensor.java
+++ b/core/java/android/hardware/Sensor.java
@@ -20,8 +20,6 @@ package android.hardware;
 import android.annotation.SystemApi;
 import android.os.Build;
 
-import java.util.UUID;
-
 /**
  * Class representing a sensor. Use {@link SensorManager#getSensorList} to get
  * the list of available Sensors.
@@ -806,7 +804,7 @@ public final class Sensor {
     private String  mRequiredPermission;
     private int     mMaxDelay;
     private int     mFlags;
-    private UUID    mUuid;
+    private int     mId;
 
     Sensor() {
     }
@@ -895,34 +893,28 @@ public final class Sensor {
     }
 
     /**
-     * @return The UUID of the sensor. If the sensor does not support UUID, the returned value will
-     * be an all zero UUID; if the sensor's combination of type and name is guaranteed to be unique
-     * in system, the return value will be an all "F" UUID.
+     * Do not use.
+     *
+     * This method throws an UnsupportedOperationException.
+     *
+     * Use getId() if you want a unique ID.
+     *
+     * @see getId
      *
      * @hide
      */
     @SystemApi
-    public UUID getUuid() {
-        return mUuid;
+    public java.util.UUID getUuid() {
+        throw new UnsupportedOperationException();
     }
 
     /**
-     * @return The unique id of sensor. Return value of 0 means this sensor does not support UUID;
-     * return value of -1 means this sensor can be uniquely identified in system by combination of
-     * its type and name.
+     * @return The sensor id that will be unique for the same app unless the device is factory
+     * reset. Return value of 0 means this sensor does not support this function; return value of -1
+     * means this sensor can be uniquely identified in system by combination of its type and name.
      */
     public int getId() {
-        if (mUuid.equals(ALL_0_UUID)) {
-            return 0;
-        } else if (mUuid.equals(ALL_F_UUID)) {
-            return -1;
-        } else {
-            int id = Math.abs(mUuid.hashCode()) + 1;
-            if (id <= 0) { // catch corner case when hash is Integer.MIN_VALUE and Integer.MAX_VALUE
-                id = 1;
-            }
-            return id;
-        }
+        return mId;
     }
 
     /**
@@ -1038,10 +1030,6 @@ public final class Sensor {
                 + ", power=" + mPower + ", minDelay=" + mMinDelay + "}";
     }
 
-    //special UUID hash constant
-    private final static UUID ALL_0_UUID = new UUID(0,0);
-    private final static UUID ALL_F_UUID = new UUID(~0L, ~0L);
-
     /**
      * Sets the Type associated with the sensor.
      * NOTE: to be used only by native bindings in SensorManager.
@@ -1141,24 +1129,17 @@ public final class Sensor {
     }
 
     /**
-     * Sets the UUID associated with the sensor.
+     * Sets the ID associated with the sensor.
+     *
+     * The method name is misleading; while this ID is based on the UUID,
+     * we do not pass in the actual UUID.
      *
      * NOTE: to be used only by native bindings in SensorManager.
      *
-     * @see #getUuid
-     * @see UUID
+     * @see #getId
      */
     private void setUuid(long msb, long lsb) {
-        // reuse static object if possible
-        if (msb == lsb) {
-            if (msb == 0L) {
-                mUuid = ALL_0_UUID;
-                return;
-            } else if (msb == ~0L) {
-                mUuid = ALL_F_UUID;
-                return;
-            }
-        }
-        mUuid = new UUID(msb, lsb);
+        // TODO(b/29547335): Rename this method to setId.
+        mId = (int)msb;
     }
 }

diff --git a/core/jni/android_hardware_SensorManager.cpp b/core/jni/android_hardware_SensorManager.cpp
index f4237d2..50f23bf 100644 (file)
--- a/core/jni/android_hardware_SensorManager.cpp
+++ b/core/jni/android_hardware_SensorManager.cpp
@@ -30,7 +30,6 @@
 #include <utils/Looper.h>
 #include <utils/Vector.h>
 
-#include <endian.h>   // htobe64
 #include <map>
 
 namespace {
@@ -200,19 +199,9 @@ translateNativeSensorToJavaSensor(JNIEnv *env, jobject sensor, const Sensor& nat
             env->SetObjectField(sensor, sensorOffsets.stringType, stringType);
         }
 
-        // java.util.UUID constructor UUID(long a, long b) assumes the two long inputs a and b
-        // correspond to first half and second half of the 16-byte stream in big-endian,
-        // respectively, if the byte stream is serialized according to RFC 4122 (Sec. 4.1.2).
-        //
-        // For Java UUID 12345678-90AB-CDEF-1122-334455667788, the byte stream will be
-        // (uint8_t) {0x12, 0x34, 0x56, 0x78, 0x90, 0xAB, 0xCD, 0xEF, ....} according RFC 4122.
-        //
-        // According to Java UUID constructor document, the long parameter a should be always
-        // 0x12345678980ABCDEF regardless of host machine endianess. Thus, htobe64 is used to
-        // convert int64_t read directly, which will be in host-endian, to the big-endian required
-        // by Java constructor.
-        const int64_t (&uuid)[2] = nativeSensor.getUuid().i64;
-        env->CallVoidMethod(sensor, sensorOffsets.setUuid, htobe64(uuid[0]), htobe64(uuid[1]));
+        // TODO(b/29547335): Rename "setUuid" method to "setId".
+        int64_t id = nativeSensor.getId();
+        env->CallVoidMethod(sensor, sensorOffsets.setUuid, id, 0);
     }
     return sensor;
 }