Add getPartialObject to Java MtpDevice class.

BUG=26284424

Change-Id: Id05dc6297a1682999eee4e72972fb883fa49a5d1

api/current.txt

@@ -22452,6 +22452,7 @@ package android.mtp {
     method public int[] getObjectHandles(int, int, int);
     method public android.mtp.MtpObjectInfo getObjectInfo(int);
     method public long getParent(int);
+    method public int getPartialObject(int, int, int, byte[]) throws java.io.IOException;
     method public long getStorageId(int);
     method public int[] getStorageIds();
     method public android.mtp.MtpStorageInfo getStorageInfo(int);

api/system-current.txt

@@ -23998,6 +23998,7 @@ package android.mtp {
     method public int[] getObjectHandles(int, int, int);
     method public android.mtp.MtpObjectInfo getObjectInfo(int);
     method public long getParent(int);
+    method public int getPartialObject(int, int, int, byte[]) throws java.io.IOException;
     method public long getStorageId(int);
     method public int[] getStorageIds();
     method public android.mtp.MtpStorageInfo getStorageInfo(int);

api/test-current.txt

@@ -22460,6 +22460,7 @@ package android.mtp {
     method public int[] getObjectHandles(int, int, int);
     method public android.mtp.MtpObjectInfo getObjectInfo(int);
     method public long getParent(int);
+    method public int getPartialObject(int, int, int, byte[]) throws java.io.IOException;
     method public long getStorageId(int);
     method public int[] getStorageIds();
     method public android.mtp.MtpStorageInfo getStorageInfo(int);

media/java/android/mtp/MtpDevice.java

@@ -19,9 +19,10 @@ package android.mtp;
 import android.hardware.usb.UsbDevice;
 import android.hardware.usb.UsbDeviceConnection;
 import android.os.CancellationSignal;
-import android.os.OperationCanceledException;
 import android.os.ParcelFileDescriptor;
 
+import java.io.IOException;
+
 /**
  * This class represents an MTP or PTP device connected on the USB host bus. An application can
  * instantiate an object of this type, by referencing an attached {@link
@@ -157,6 +158,22 @@ public final class MtpDevice {
         return native_get_object(objectHandle, objectSize);
     }
 
+    /**
+     * Obtains object bytes in the specified range and writes it to an array.
+     * This call may block for an arbitrary amount of time depending on the size
+     * of the data and speed of the devices.
+     *
+     * @param objectHandle handle of the object to read
+     * @param offset Start index of reading range.
+     * @param size Size of reading range.
+     * @param buffer Array to write data.
+     * @return Size of bytes that are actually read.
+     */
+    public int getPartialObject(int objectHandle, int offset, int size, byte[] buffer)
+            throws IOException {
+        return native_get_partial_object(objectHandle, offset, size, buffer);
+    }
+
     /**
      * Returns the thumbnail data for an object as a byte array.
      * The size and format of the thumbnail data can be determined via
@@ -323,6 +340,8 @@ public final class MtpDevice {
     private native int[] native_get_object_handles(int storageId, int format, int objectHandle);
     private native MtpObjectInfo native_get_object_info(int objectHandle);
     private native byte[] native_get_object(int objectHandle, int objectSize);
+    private native int native_get_partial_object(
+            int objectHandle, int offset, int objectSize, byte[] buffer) throws IOException;
     private native byte[] native_get_thumbnail(int objectHandle);
     private native boolean native_delete_object(int objectHandle);
     private native long native_get_parent(int objectHandle);

media/jni/android_mtp_MtpDevice.cpp

@@ -29,6 +29,7 @@
 #include "JNIHelp.h"
 #include "android_runtime/AndroidRuntime.h"
 #include "android_runtime/Log.h"
+#include "nativehelper/ScopedLocalRef.h"
 #include "private/android_filesystem_config.h"
 
 #include "MtpTypes.h"
@@ -41,6 +42,8 @@ using namespace android;
 
 // ----------------------------------------------------------------------------
 
+namespace {
+
 static jfieldID field_context;
 
 jclass clazz_deviceInfo;
@@ -93,6 +96,28 @@ static jfieldID field_objectInfo_keywords;
 // MtpEvent fields
 static jfieldID field_event_eventCode;
 
+class JavaArrayWriter {
+    JNIEnv* mEnv;
+    jbyteArray mArray;
+    jsize mSize;
+
+public:
+    JavaArrayWriter(JNIEnv* env, jbyteArray array) :
+        mEnv(env), mArray(array), mSize(mEnv->GetArrayLength(mArray)) {}
+    bool write(void* data, uint32_t offset, uint32_t length) {
+        if (static_cast<uint32_t>(mSize) < offset + length) {
+            return false;
+        }
+        mEnv->SetByteArrayRegion(mArray, offset, length, static_cast<jbyte*>(data));
+        return true;
+    }
+    static bool writeTo(void* data, uint32_t offset, uint32_t length, void* clientData) {
+        return static_cast<JavaArrayWriter*>(clientData)->write(data, offset, length);
+    }
+};
+
+}
+
 MtpDevice* get_device_from_object(JNIEnv* env, jobject javaDevice)
 {
     return (MtpDevice*)env->GetLongField(javaDevice, field_context);
@@ -307,38 +332,57 @@ android_mtp_MtpDevice_get_object_info(JNIEnv *env, jobject thiz, jint objectID)
     return info;
 }
 
-struct get_object_callback_data {
-    JNIEnv *env;
-    jbyteArray array;
-};
-
-static bool get_object_callback(void* data, int offset, int length, void* clientData)
-{
-    get_object_callback_data* cbData = (get_object_callback_data *)clientData;
-    cbData->env->SetByteArrayRegion(cbData->array, offset, length, (jbyte *)data);
-    return true;
-}
-
 static jbyteArray
 android_mtp_MtpDevice_get_object(JNIEnv *env, jobject thiz, jint objectID, jint objectSize)
 {
     MtpDevice* device = get_device_from_object(env, thiz);
-    if (!device)
-        return NULL;
-
-    jbyteArray array = env->NewByteArray(objectSize);
-    if (!array) {
-        jniThrowException(env, "java/lang/OutOfMemoryError", NULL);
-        return NULL;
+    if (!device) {
+        return nullptr;
     }
 
-    get_object_callback_data data;
-    data.env = env;
-    data.array = array;
+    ScopedLocalRef<jbyteArray> array(env, env->NewByteArray(objectSize));
+    if (!array.get()) {
+        jniThrowException(env, "java/lang/OutOfMemoryError", NULL);
+        return nullptr;
+    }
 
-    if (device->readObject(objectID, get_object_callback, objectSize, &data))
-        return array;
-    return NULL;
+    JavaArrayWriter writer(env, array.get());
+
+    if (device->readObject(objectID, JavaArrayWriter::writeTo, objectSize, &writer)) {
+        return array.release();
+    }
+    return nullptr;
+}
+
+static jint
+android_mtp_MtpDevice_get_partial_object(JNIEnv *env,
+                                         jobject thiz,
+                                         jint objectID,
+                                         jint offset,
+                                         jint size,
+                                         jbyteArray array)
+{
+    if (array == nullptr) {
+        jniThrowException(env, "java/lang/IllegalArgumentException", "Array must not be null.");
+        return -1;
+    }
+
+    MtpDevice* const device = get_device_from_object(env, thiz);
+    if (!device) {
+        jniThrowException(env, "java/io/IOException", "Failed to obtain MtpDevice.");
+        return -1;
+    }
+
+    JavaArrayWriter writer(env, array);
+    const int64_t result = device->readPartialObject(
+            objectID, offset, size, JavaArrayWriter::writeTo, &writer);
+
+    if (result >= 0) {
+        return static_cast<jint>(result);
+    } else {
+        jniThrowException(env, "java/io/IOException", "Failed to read data.");
+        return -1;
+    }
 }
 
 static jbyteArray
@@ -547,6 +591,7 @@ static const JNINativeMethod gMethods[] = {
     {"native_get_object_info",  "(I)Landroid/mtp/MtpObjectInfo;",
                                         (void *)android_mtp_MtpDevice_get_object_info},
     {"native_get_object",       "(II)[B",(void *)android_mtp_MtpDevice_get_object},
+    {"native_get_partial_object", "(III[B)I", (void *) android_mtp_MtpDevice_get_partial_object},
     {"native_get_thumbnail",    "(I)[B",(void *)android_mtp_MtpDevice_get_thumbnail},
     {"native_delete_object",    "(I)Z", (void *)android_mtp_MtpDevice_delete_object},
     {"native_get_parent",       "(I)J", (void *)android_mtp_MtpDevice_get_parent},