Merge change 4471

* changes:
  MemoryFile.isMemoryFile was internally determining the length of the ashmem region. This is actually useful information to have, so expose that more directly.

core/java/android/os/MemoryFile.java

@@ -52,7 +52,7 @@ public class MemoryFile
     private static native void native_write(FileDescriptor fd, int address, byte[] buffer,
             int srcOffset, int destOffset, int count, boolean isUnpinned) throws IOException;
     private static native void native_pin(FileDescriptor fd, boolean pin) throws IOException;
-    private static native boolean native_is_ashmem_region(FileDescriptor fd) throws IOException;
+    private static native int native_get_mapped_size(FileDescriptor fd) throws IOException;
 
     private FileDescriptor mFD;        // ashmem file descriptor
     private int mAddress;   // address of ashmem memory
@@ -300,7 +300,20 @@ public class MemoryFile
      * @hide
      */
     public static boolean isMemoryFile(FileDescriptor fd) throws IOException {
-        return native_is_ashmem_region(fd);
+        return (native_get_mapped_size(fd) >= 0);
+    }
+
+    /**
+     * Returns the size of the memory file, rounded up to a page boundary, that
+     * the file descriptor refers to, or -1 if the file descriptor does not
+     * refer to a memory file.
+     *
+     * @throws IOException If <code>fd</code> is not a valid file descriptor.
+     *
+     * @hide
+     */
+    public static int getMappedSize(FileDescriptor fd) throws IOException {
+        return native_get_mapped_size(fd);
     }
 
     /**

core/jni/android_os_MemoryFile.cpp

@@ -118,7 +118,7 @@ static void android_os_MemoryFile_pin(JNIEnv* env, jobject clazz, jobject fileDe
     }
 }
 
-static jboolean android_os_MemoryFile_is_ashmem_region(JNIEnv* env, jobject clazz,
+static jint android_os_MemoryFile_get_mapped_size(JNIEnv* env, jobject clazz,
         jobject fileDescriptor) {
     int fd = jniGetFDFromFileDescriptor(env, fileDescriptor);
     // Use ASHMEM_GET_SIZE to find out if the fd refers to an ashmem region.
@@ -129,13 +129,13 @@ static jboolean android_os_MemoryFile_is_ashmem_region(JNIEnv* env, jobject claz
         if (errno == ENOTTY) {
             // ENOTTY means that the ioctl does not apply to this object,
             // i.e., it is not an ashmem region.
-            return JNI_FALSE;
+            return (jint) -1;
         }
         // Some other error, throw exception
         jniThrowIOException(env, errno);
-        return JNI_FALSE;
+        return (jint) -1;
     }
-    return JNI_TRUE;
+    return (jint) result;
 }
 
 static const JNINativeMethod methods[] = {
@@ -146,8 +146,8 @@ static const JNINativeMethod methods[] = {
     {"native_read",  "(Ljava/io/FileDescriptor;I[BIIIZ)I", (void*)android_os_MemoryFile_read},
     {"native_write", "(Ljava/io/FileDescriptor;I[BIIIZ)V", (void*)android_os_MemoryFile_write},
     {"native_pin",   "(Ljava/io/FileDescriptor;Z)V", (void*)android_os_MemoryFile_pin},
-    {"native_is_ashmem_region", "(Ljava/io/FileDescriptor;)Z",
-            (void*)android_os_MemoryFile_is_ashmem_region}
+    {"native_get_mapped_size", "(Ljava/io/FileDescriptor;)I",
+            (void*)android_os_MemoryFile_get_mapped_size}
 };
 
 static const char* const kClassPathName = "android/os/MemoryFile";