Add new SystemProperties.Handle interface

This new interface allows Java code to look up property values without
paying for the name->prop_info mapping and, in the case of looking up
scalars, without doing any allocation.

Bug: 140788621
Test: added tests
Test: atest FrameworksCoreSystemPropertiesTests
Change-Id: I46d12f62499e9e124fe9add588376d724b364d5d

1 files changed, 68 insertions, 1 deletions

diff --git a/core/java/android/os/SystemProperties.java b/core/java/android/os/SystemProperties.java
index 2b4f6f867e03..f08e1ff16999 100644
--- a/core/java/android/os/SystemProperties.java
+++ b/core/java/android/os/SystemProperties.java
@@ -26,6 +26,7 @@ import android.util.MutableInt;
 
 import com.android.internal.annotations.GuardedBy;
 
+import dalvik.annotation.optimization.CriticalNative;
 import dalvik.annotation.optimization.FastNative;
 
 import libcore.util.HexEncoding;
@@ -37,7 +38,6 @@ import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.HashMap;
 
-
 /**
  * Gives access to the system properties store.  The system properties
  * store contains a list of string key-value pairs.
@@ -118,6 +118,17 @@ public class SystemProperties {
     @UnsupportedAppUsage(maxTargetSdk = Build.VERSION_CODES.P)
     private static native boolean native_get_boolean(String key, boolean def);
 
+    @FastNative
+    private static native long native_find(String name);
+    @FastNative
+    private static native String native_get(long handle);
+    @CriticalNative
+    private static native int native_get_int(long handle, int def);
+    @CriticalNative
+    private static native long native_get_long(long handle, long def);
+    @CriticalNative
+    private static native boolean native_get_boolean(long handle, boolean def);
+
     // _NOT_ FastNative: native_set performs IPC and can block
     @UnsupportedAppUsage(maxTargetSdk = Build.VERSION_CODES.P)
     private static native void native_set(String key, String def);
@@ -303,4 +314,60 @@ public class SystemProperties {
     @UnsupportedAppUsage
     private SystemProperties() {
     }
+
+    /**
+     * Look up a property location by name.
+     * @name name of the property
+     * @return property handle or {@code null} if property isn't set
+     * @hide
+     */
+    @Nullable public static Handle find(@NonNull String name) {
+        long nativeHandle = native_find(name);
+        if (nativeHandle == 0) {
+            return null;
+        }
+        return new Handle(nativeHandle);
+    }
+
+    /**
+     * Handle to a pre-located property. Looking up a property handle in advance allows
+     * for optimal repeated lookup of a single property.
+     * @hide
+     */
+    public static final class Handle {
+
+        private final long mNativeHandle;
+
+        /**
+         * @return Value of the property
+         */
+        @NonNull public String get() {
+            return native_get(mNativeHandle);
+        }
+        /**
+         * @param def default value
+         * @return value or {@code def} on parse error
+         */
+        public int getInt(int def) {
+            return native_get_int(mNativeHandle, def);
+        }
+        /**
+         * @param def default value
+         * @return value or {@code def} on parse error
+         */
+        public long getLong(long def) {
+            return native_get_long(mNativeHandle, def);
+        }
+        /**
+         * @param def default value
+         * @return value or {@code def} on parse error
+         */
+        public boolean getBoolean(boolean def) {
+            return native_get_boolean(mNativeHandle, def);
+        }
+
+        private Handle(long nativeHandle) {
+            mNativeHandle = nativeHandle;
+        }
+    }
 }