Add range-based Parcel.hasFileDescriptors(offset, length)

To be used by lazy values in bundle. I ended up opening up as public API
for apps to use it too because I saw no reason not to, can change if
folks prefer it to be @hide though.

Test: atest -d android.os.cts.ParcelTest android.os.cts.BundleTest android.os.BundleTest android.os.ParcelTest
Bug: 195622897
Change-Id: I7bf580f94313669fe67998b32b2723544c594cde
diff --git a/core/api/current.txt b/core/api/current.txt
index 4d89cdf..49651ed 100644
--- a/core/api/current.txt
+++ b/core/api/current.txt
@@ -29976,6 +29976,7 @@
     method public int dataSize();
     method public void enforceInterface(@NonNull String);
     method public boolean hasFileDescriptors();
+    method public boolean hasFileDescriptors(int, int);
     method public byte[] marshall();
     method @NonNull public static android.os.Parcel obtain();
     method @NonNull public static android.os.Parcel obtain(@NonNull android.os.IBinder);
diff --git a/core/java/android/os/Parcel.java b/core/java/android/os/Parcel.java
index e6925cb..df1d272 100644
--- a/core/java/android/os/Parcel.java
+++ b/core/java/android/os/Parcel.java
@@ -361,6 +361,8 @@
             long thisNativePtr, long otherNativePtr, int offset, int length);
     @CriticalNative
     private static native boolean nativeHasFileDescriptors(long nativePtr);
+    private static native boolean nativeHasFileDescriptorsInRange(
+            long nativePtr, int offset, int length);
     private static native void nativeWriteInterfaceToken(long nativePtr, String interfaceName);
     private static native void nativeEnforceInterface(long nativePtr, String interfaceName);
 
@@ -687,11 +689,26 @@
     /**
      * Report whether the parcel contains any marshalled file descriptors.
      */
-    public final boolean hasFileDescriptors() {
+    public boolean hasFileDescriptors() {
         return nativeHasFileDescriptors(mNativePtr);
     }
 
     /**
+     * Report whether the parcel contains any marshalled file descriptors in the range defined by
+     * {@code offset} and {@code length}.
+     *
+     * @param offset The offset from which the range starts. Should be between 0 and
+     *     {@link #dataSize()}.
+     * @param length The length of the range. Should be between 0 and {@link #dataSize()} - {@code
+     *     offset}.
+     * @return whether there are file descriptors or not.
+     * @throws IllegalArgumentException if the parameters are out of the permitted ranges.
+     */
+    public boolean hasFileDescriptors(int offset, int length) {
+        return nativeHasFileDescriptorsInRange(mNativePtr, offset, length);
+    }
+
+    /**
      * Check if the object used in {@link #readValue(ClassLoader)} / {@link #writeValue(Object)}
      * has file descriptors.
      *
@@ -3495,15 +3512,26 @@
         int start = dataPosition();
         int type = readInt();
         if (isLengthPrefixed(type)) {
-            int length = readInt();
-            setDataPosition(MathUtils.addOrThrow(dataPosition(), length));
-            return new LazyValue(this, start, length, type, loader);
+            int objectLength = readInt();
+            int end = MathUtils.addOrThrow(dataPosition(), objectLength);
+            int valueLength = end - start;
+            setDataPosition(end);
+            return new LazyValue(this, start, valueLength, type, loader);
         } else {
             return readValue(type, loader, /* clazz */ null);
         }
     }
 
+
     private static final class LazyValue implements Supplier<Object> {
+        /**
+         *                      |   4B   |   4B   |
+         * mSource = Parcel{... |  type  | length | object | ...}
+         *                      a        b        c        d
+         * length = d - c
+         * mPosition = a
+         * mLength = d - a
+         */
         private final int mPosition;
         private final int mLength;
         private final int mType;
@@ -3551,7 +3579,7 @@
         public void writeToParcel(Parcel out) {
             Parcel source = mSource;
             if (source != null) {
-                out.appendFrom(source, mPosition, mLength + 8);
+                out.appendFrom(source, mPosition, mLength);
             } else {
                 out.writeValue(mObject);
             }
@@ -3560,7 +3588,7 @@
         public boolean hasFileDescriptors() {
             Parcel source = mSource;
             return (source != null)
-                    ? getValueParcel(source).hasFileDescriptors()
+                    ? source.hasFileDescriptors(mPosition, mLength)
                     : Parcel.hasFileDescriptors(mObject);
         }
 
@@ -3621,10 +3649,7 @@
             Parcel parcel = mValueParcel;
             if (parcel == null) {
                 parcel = Parcel.obtain();
-                // mLength is the length of object representation, excluding the type and length.
-                // mPosition is the position of the entire value container, right before the type.
-                // So, we add 4 bytes for the type + 4 bytes for the length written.
-                parcel.appendFrom(source, mPosition, mLength + 8);
+                parcel.appendFrom(source, mPosition, mLength);
                 mValueParcel = parcel;
             }
             return parcel;
diff --git a/core/jni/android_os_Parcel.cpp b/core/jni/android_os_Parcel.cpp
index ac32038..ee7f78d 100644
--- a/core/jni/android_os_Parcel.cpp
+++ b/core/jni/android_os_Parcel.cpp
@@ -655,6 +655,22 @@
     return ret;
 }
 
+static jboolean android_os_Parcel_hasFileDescriptorsInRange(JNIEnv* env, jclass clazz,
+                                                            jlong nativePtr, jint offset,
+                                                            jint length) {
+    Parcel* parcel = reinterpret_cast<Parcel*>(nativePtr);
+    if (parcel != NULL) {
+        bool result;
+        status_t err = parcel->hasFileDescriptorsInRange(offset, length, result);
+        if (err != NO_ERROR) {
+            signalExceptionForError(env, clazz, err);
+            return JNI_FALSE;
+        }
+        return result ? JNI_TRUE : JNI_FALSE;
+    }
+    return JNI_FALSE;
+}
+
 // String tries to allocate itself on the stack, within a known size, but will
 // make a heap allocation if not.
 template <size_t StackReserve>
@@ -847,6 +863,7 @@
     {"nativeAppendFrom",          "(JJII)J", (void*)android_os_Parcel_appendFrom},
     // @CriticalNative
     {"nativeHasFileDescriptors",  "(J)Z", (void*)android_os_Parcel_hasFileDescriptors},
+    {"nativeHasFileDescriptorsInRange",  "(JII)Z", (void*)android_os_Parcel_hasFileDescriptorsInRange},
     {"nativeWriteInterfaceToken", "(JLjava/lang/String;)V", (void*)android_os_Parcel_writeInterfaceToken},
     {"nativeEnforceInterface",    "(JLjava/lang/String;)V", (void*)android_os_Parcel_enforceInterface},