media/jni/android_mtp_MtpDatabase.cpp

/*
 * Copyright (C) 2010 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#define LOG_TAG "MtpDatabaseJNI"
#include "utils/Log.h"

#include <assert.h>
#include <fcntl.h>
#include <inttypes.h>
#include <limits.h>
#include <stdio.h>
#include <unistd.h>

#include "jni.h"
#include "JNIHelp.h"
#include "android_runtime/AndroidRuntime.h"
#include "android_runtime/Log.h"

#include "MtpDatabase.h"
#include "MtpDataPacket.h"
#include "MtpObjectInfo.h"
#include "MtpProperty.h"
#include "MtpStringBuffer.h"
#include "MtpUtils.h"
#include "mtp.h"

extern "C" {
#include "libexif/exif-content.h"
#include "libexif/exif-data.h"
#include "libexif/exif-tag.h"
#include "libexif/exif-utils.h"
}

using namespace android;

// ----------------------------------------------------------------------------

static jmethodID method_beginSendObject;
static jmethodID method_endSendObject;
static jmethodID method_getObjectList;
static jmethodID method_getNumObjects;
static jmethodID method_getSupportedPlaybackFormats;
static jmethodID method_getSupportedCaptureFormats;
static jmethodID method_getSupportedObjectProperties;
static jmethodID method_getSupportedDeviceProperties;
static jmethodID method_setObjectProperty;
static jmethodID method_getDeviceProperty;
static jmethodID method_setDeviceProperty;
static jmethodID method_getObjectPropertyList;
static jmethodID method_getObjectInfo;
static jmethodID method_getObjectFilePath;
static jmethodID method_deleteFile;
static jmethodID method_getObjectReferences;
static jmethodID method_setObjectReferences;
static jmethodID method_sessionStarted;
static jmethodID method_sessionEnded;

static jfieldID field_context;
static jfieldID field_batteryLevel;
static jfieldID field_batteryScale;

// MtpPropertyList fields
static jfieldID field_mCount;
static jfieldID field_mResult;
static jfieldID field_mObjectHandles;
static jfieldID field_mPropertyCodes;
static jfieldID field_mDataTypes;
static jfieldID field_mLongValues;
static jfieldID field_mStringValues;


MtpDatabase* getMtpDatabase(JNIEnv *env, jobject database) {
    return (MtpDatabase *)env->GetLongField(database, field_context);
}

// ----------------------------------------------------------------------------

class MyMtpDatabase : public MtpDatabase {
private:
    jobject         mDatabase;
    jintArray       mIntBuffer;
    jlongArray      mLongBuffer;
    jcharArray      mStringBuffer;

public:
                                    MyMtpDatabase(JNIEnv *env, jobject client);
    virtual                         ~MyMtpDatabase();
    void                            cleanup(JNIEnv *env);

    virtual MtpObjectHandle         beginSendObject(const char* path,
                                            MtpObjectFormat format,
                                            MtpObjectHandle parent,
                                            MtpStorageID storage,
                                            uint64_t size,
                                            time_t modified);

    virtual void                    endSendObject(const char* path,
                                            MtpObjectHandle handle,
                                            MtpObjectFormat format,
                                            bool succeeded);

    virtual MtpObjectHandleList*    getObjectList(MtpStorageID storageID,
                                    MtpObjectFormat format,
                                    MtpObjectHandle parent);

    virtual int                     getNumObjects(MtpStorageID storageID,
                                            MtpObjectFormat format,
                                            MtpObjectHandle parent);

    // callee should delete[] the results from these
    // results can be NULL
    virtual MtpObjectFormatList*    getSupportedPlaybackFormats();
    virtual MtpObjectFormatList*    getSupportedCaptureFormats();
    virtual MtpObjectPropertyList*  getSupportedObjectProperties(MtpObjectFormat format);
    virtual MtpDevicePropertyList*  getSupportedDeviceProperties();

    virtual MtpResponseCode         getObjectPropertyValue(MtpObjectHandle handle,
                                            MtpObjectProperty property,
                                            MtpDataPacket& packet);

    virtual MtpResponseCode         setObjectPropertyValue(MtpObjectHandle handle,
                                            MtpObjectProperty property,
                                            MtpDataPacket& packet);

    virtual MtpResponseCode         getDevicePropertyValue(MtpDeviceProperty property,
                                            MtpDataPacket& packet);

    virtual MtpResponseCode         setDevicePropertyValue(MtpDeviceProperty property,
                                            MtpDataPacket& packet);

    virtual MtpResponseCode         resetDeviceProperty(MtpDeviceProperty property);

    virtual MtpResponseCode         getObjectPropertyList(MtpObjectHandle handle,
                                            uint32_t format, uint32_t property,
                                            int groupCode, int depth,
                                            MtpDataPacket& packet);

    virtual MtpResponseCode         getObjectInfo(MtpObjectHandle handle,
                                            MtpObjectInfo& info);

    virtual void*                   getThumbnail(MtpObjectHandle handle, size_t& outThumbSize);

    virtual MtpResponseCode         getObjectFilePath(MtpObjectHandle handle,
                                            MtpString& outFilePath,
                                            int64_t& outFileLength,
                                            MtpObjectFormat& outFormat);
    virtual MtpResponseCode         deleteFile(MtpObjectHandle handle);

    bool                            getObjectPropertyInfo(MtpObjectProperty property, int& type);
    bool                            getDevicePropertyInfo(MtpDeviceProperty property, int& type);

    virtual MtpObjectHandleList*    getObjectReferences(MtpObjectHandle handle);

    virtual MtpResponseCode         setObjectReferences(MtpObjectHandle handle,
                                            MtpObjectHandleList* references);

    virtual MtpProperty*            getObjectPropertyDesc(MtpObjectProperty property,
                                            MtpObjectFormat format);

    virtual MtpProperty*            getDevicePropertyDesc(MtpDeviceProperty property);

    virtual void                    sessionStarted();

    virtual void                    sessionEnded();
};

// ----------------------------------------------------------------------------

static void checkAndClearExceptionFromCallback(JNIEnv* env, const char* methodName) {
    if (env->ExceptionCheck()) {
        ALOGE("An exception was thrown by callback '%s'.", methodName);
        LOGE_EX(env);
        env->ExceptionClear();
    }
}

// ----------------------------------------------------------------------------

MyMtpDatabase::MyMtpDatabase(JNIEnv *env, jobject client)
    :   mDatabase(env->NewGlobalRef(client)),
        mIntBuffer(NULL),
        mLongBuffer(NULL),
        mStringBuffer(NULL)
{
    // create buffers for out arguments
    // we don't need to be thread-safe so this is OK
    jintArray intArray = env->NewIntArray(3);
    if (!intArray) {
        return; // Already threw.
    }
    mIntBuffer = (jintArray)env->NewGlobalRef(intArray);
    jlongArray longArray = env->NewLongArray(2);
    if (!longArray) {
        return; // Already threw.
    }
    mLongBuffer = (jlongArray)env->NewGlobalRef(longArray);
    jcharArray charArray = env->NewCharArray(256);
    if (!charArray) {
        return; // Already threw.
    }
    mStringBuffer = (jcharArray)env->NewGlobalRef(charArray);
}

void MyMtpDatabase::cleanup(JNIEnv *env) {
    env->DeleteGlobalRef(mDatabase);
    env->DeleteGlobalRef(mIntBuffer);
    env->DeleteGlobalRef(mLongBuffer);
    env->DeleteGlobalRef(mStringBuffer);
}

MyMtpDatabase::~MyMtpDatabase() {
}

MtpObjectHandle MyMtpDatabase::beginSendObject(const char* path,
                                            MtpObjectFormat format,
                                            MtpObjectHandle parent,
                                            MtpStorageID storage,
                                            uint64_t size,
                                            time_t modified) {
    JNIEnv* env = AndroidRuntime::getJNIEnv();
    jstring pathStr = env->NewStringUTF(path);
    MtpObjectHandle result = env->CallIntMethod(mDatabase, method_beginSendObject,
            pathStr, (jint)format, (jint)parent, (jint)storage,
            (jlong)size, (jlong)modified);

    if (pathStr)
        env->DeleteLocalRef(pathStr);
    checkAndClearExceptionFromCallback(env, __FUNCTION__);
    return result;
}

void MyMtpDatabase::endSendObject(const char* path, MtpObjectHandle handle,
                                MtpObjectFormat format, bool succeeded) {
    JNIEnv* env = AndroidRuntime::getJNIEnv();
    jstring pathStr = env->NewStringUTF(path);
    env->CallVoidMethod(mDatabase, method_endSendObject, pathStr,
                        (jint)handle, (jint)format, (jboolean)succeeded);

    if (pathStr)
        env->DeleteLocalRef(pathStr);
    checkAndClearExceptionFromCallback(env, __FUNCTION__);
}

MtpObjectHandleList* MyMtpDatabase::getObjectList(MtpStorageID storageID,
                                    MtpObjectFormat format,
                                    MtpObjectHandle parent) {
    JNIEnv* env = AndroidRuntime::getJNIEnv();
    jintArray array = (jintArray)env->CallObjectMethod(mDatabase, method_getObjectList,
                (jint)storageID, (jint)format, (jint)parent);
    if (!array)
        return NULL;
    MtpObjectHandleList* list = new MtpObjectHandleList();
    jint* handles = env->GetIntArrayElements(array, 0);
    jsize length = env->GetArrayLength(array);
    for (int i = 0; i < length; i++)
        list->push(handles[i]);
    env->ReleaseIntArrayElements(array, handles, 0);
    env->DeleteLocalRef(array);

    checkAndClearExceptionFromCallback(env, __FUNCTION__);
    return list;
}

int MyMtpDatabase::getNumObjects(MtpStorageID storageID,
                                MtpObjectFormat format,
                                MtpObjectHandle parent) {
    JNIEnv* env = AndroidRuntime::getJNIEnv();
    int result = env->CallIntMethod(mDatabase, method_getNumObjects,
                (jint)storageID, (jint)format, (jint)parent);

    checkAndClearExceptionFromCallback(env, __FUNCTION__);
    return result;
}

MtpObjectFormatList* MyMtpDatabase::getSupportedPlaybackFormats() {
    JNIEnv* env = AndroidRuntime::getJNIEnv();
    jintArray array = (jintArray)env->CallObjectMethod(mDatabase,
            method_getSupportedPlaybackFormats);
    if (!array)
        return NULL;
    MtpObjectFormatList* list = new MtpObjectFormatList();
    jint* formats = env->GetIntArrayElements(array, 0);
    jsize length = env->GetArrayLength(array);
    for (int i = 0; i < length; i++)
        list->push(formats[i]);
    env->ReleaseIntArrayElements(array, formats, 0);
    env->DeleteLocalRef(array);

    checkAndClearExceptionFromCallback(env, __FUNCTION__);
    return list;
}

MtpObjectFormatList* MyMtpDatabase::getSupportedCaptureFormats() {
    JNIEnv* env = AndroidRuntime::getJNIEnv();
    jintArray array = (jintArray)env->CallObjectMethod(mDatabase,
            method_getSupportedCaptureFormats);
    if (!array)
        return NULL;
    MtpObjectFormatList* list = new MtpObjectFormatList();
    jint* formats = env->GetIntArrayElements(array, 0);
    jsize length = env->GetArrayLength(array);
    for (int i = 0; i < length; i++)
        list->push(formats[i]);
    env->ReleaseIntArrayElements(array, formats, 0);
    env->DeleteLocalRef(array);

    checkAndClearExceptionFromCallback(env, __FUNCTION__);
    return list;
}

MtpObjectPropertyList* MyMtpDatabase::getSupportedObjectProperties(MtpObjectFormat format) {
    JNIEnv* env = AndroidRuntime::getJNIEnv();
    jintArray array = (jintArray)env->CallObjectMethod(mDatabase,
            method_getSupportedObjectProperties, (jint)format);
    if (!array)
        return NULL;
    MtpObjectPropertyList* list = new MtpObjectPropertyList();
    jint* properties = env->GetIntArrayElements(array, 0);
    jsize length = env->GetArrayLength(array);
    for (int i = 0; i < length; i++)
        list->push(properties[i]);
    env->ReleaseIntArrayElements(array, properties, 0);
    env->DeleteLocalRef(array);

    checkAndClearExceptionFromCallback(env, __FUNCTION__);
    return list;
}

MtpDevicePropertyList* MyMtpDatabase::getSupportedDeviceProperties() {
    JNIEnv* env = AndroidRuntime::getJNIEnv();
    jintArray array = (jintArray)env->CallObjectMethod(mDatabase,
            method_getSupportedDeviceProperties);
    if (!array)
        return NULL;
    MtpDevicePropertyList* list = new MtpDevicePropertyList();
    jint* properties = env->GetIntArrayElements(array, 0);
    jsize length = env->GetArrayLength(array);
    for (int i = 0; i < length; i++)
        list->push(properties[i]);
    env->ReleaseIntArrayElements(array, properties, 0);
    env->DeleteLocalRef(array);

    checkAndClearExceptionFromCallback(env, __FUNCTION__);
    return list;
}

MtpResponseCode MyMtpDatabase::getObjectPropertyValue(MtpObjectHandle handle,
                                            MtpObjectProperty property,
                                            MtpDataPacket& packet) {
    JNIEnv* env = AndroidRuntime::getJNIEnv();
    jobject list = env->CallObjectMethod(mDatabase, method_getObjectPropertyList,
                (jlong)handle, 0, (jlong)property, 0, 0);
    MtpResponseCode result = env->GetIntField(list, field_mResult);
    int count = env->GetIntField(list, field_mCount);
    if (result == MTP_RESPONSE_OK && count != 1)
        result = MTP_RESPONSE_GENERAL_ERROR;

    if (result == MTP_RESPONSE_OK) {
        jintArray objectHandlesArray = (jintArray)env->GetObjectField(list, field_mObjectHandles);
        jintArray propertyCodesArray = (jintArray)env->GetObjectField(list, field_mPropertyCodes);
        jintArray dataTypesArray = (jintArray)env->GetObjectField(list, field_mDataTypes);
        jlongArray longValuesArray = (jlongArray)env->GetObjectField(list, field_mLongValues);
        jobjectArray stringValuesArray = (jobjectArray)env->GetObjectField(list, field_mStringValues);

        jint* objectHandles = env->GetIntArrayElements(objectHandlesArray, 0);
        jint* propertyCodes = env->GetIntArrayElements(propertyCodesArray, 0);
        jint* dataTypes = env->GetIntArrayElements(dataTypesArray, 0);
        jlong* longValues = (longValuesArray ? env->GetLongArrayElements(longValuesArray, 0) : NULL);

        int type = dataTypes[0];
        jlong longValue = (longValues ? longValues[0] : 0);

        // special case date properties, which are strings to MTP
        // but stored internally as a uint64
        if (property == MTP_PROPERTY_DATE_MODIFIED || property == MTP_PROPERTY_DATE_ADDED) {
            char    date[20];
            formatDateTime(longValue, date, sizeof(date));
            packet.putString(date);
            goto out;
        }
        // release date is stored internally as just the year
        if (property == MTP_PROPERTY_ORIGINAL_RELEASE_DATE) {
            char    date[20];
            snprintf(date, sizeof(date), "%04" PRId64 "0101T000000", longValue);
            packet.putString(date);
            goto out;
        }

        switch (type) {
            case MTP_TYPE_INT8:
                packet.putInt8(longValue);
                break;
            case MTP_TYPE_UINT8:
                packet.putUInt8(longValue);
                break;
            case MTP_TYPE_INT16:
                packet.putInt16(longValue);
                break;
            case MTP_TYPE_UINT16:
                packet.putUInt16(longValue);
                break;
            case MTP_TYPE_INT32:
                packet.putInt32(longValue);
                break;
            case MTP_TYPE_UINT32:
                packet.putUInt32(longValue);
                break;
            case MTP_TYPE_INT64:
                packet.putInt64(longValue);
                break;
            case MTP_TYPE_UINT64:
                packet.putUInt64(longValue);
                break;
            case MTP_TYPE_INT128:
                packet.putInt128(longValue);
                break;
            case MTP_TYPE_UINT128:
                packet.putInt128(longValue);
                break;
            case MTP_TYPE_STR:
            {
                jstring stringValue = (jstring)env->GetObjectArrayElement(stringValuesArray, 0);
                const char* str = (stringValue ? env->GetStringUTFChars(stringValue, NULL) : NULL);
                if (stringValue) {
                    packet.putString(str);
                    env->ReleaseStringUTFChars(stringValue, str);
                } else {
                    packet.putEmptyString();
                }
                env->DeleteLocalRef(stringValue);
                break;
             }
            default:
                ALOGE("unsupported type in getObjectPropertyValue\n");
                result = MTP_RESPONSE_INVALID_OBJECT_PROP_FORMAT;
        }
out:
        env->ReleaseIntArrayElements(objectHandlesArray, objectHandles, 0);
        env->ReleaseIntArrayElements(propertyCodesArray, propertyCodes, 0);
        env->ReleaseIntArrayElements(dataTypesArray, dataTypes, 0);
        if (longValues)
            env->ReleaseLongArrayElements(longValuesArray, longValues, 0);

        env->DeleteLocalRef(objectHandlesArray);
        env->DeleteLocalRef(propertyCodesArray);
        env->DeleteLocalRef(dataTypesArray);
        if (longValuesArray)
            env->DeleteLocalRef(longValuesArray);
        if (stringValuesArray)
            env->DeleteLocalRef(stringValuesArray);
    }

    env->DeleteLocalRef(list);
    checkAndClearExceptionFromCallback(env, __FUNCTION__);
    return result;
}

MtpResponseCode MyMtpDatabase::setObjectPropertyValue(MtpObjectHandle handle,
                                            MtpObjectProperty property,
                                            MtpDataPacket& packet) {
    int         type;

    if (!getObjectPropertyInfo(property, type))
        return MTP_RESPONSE_OBJECT_PROP_NOT_SUPPORTED;

    JNIEnv* env = AndroidRuntime::getJNIEnv();
    jlong longValue = 0;
    jstring stringValue = NULL;

    switch (type) {
        case MTP_TYPE_INT8:
            longValue = packet.getInt8();
            break;
        case MTP_TYPE_UINT8:
            longValue = packet.getUInt8();
            break;
        case MTP_TYPE_INT16:
            longValue = packet.getInt16();
            break;
        case MTP_TYPE_UINT16:
            longValue = packet.getUInt16();
            break;
        case MTP_TYPE_INT32:
            longValue = packet.getInt32();
            break;
        case MTP_TYPE_UINT32:
            longValue = packet.getUInt32();
            break;
        case MTP_TYPE_INT64:
            longValue = packet.getInt64();
            break;
        case MTP_TYPE_UINT64:
            longValue = packet.getUInt64();
            break;
        case MTP_TYPE_STR:
        {
            MtpStringBuffer buffer;
            packet.getString(buffer);
            stringValue = env->NewStringUTF((const char *)buffer);
            break;
         }
        default:
            ALOGE("unsupported type in setObjectPropertyValue\n");
            return MTP_RESPONSE_INVALID_OBJECT_PROP_FORMAT;
    }

    jint result = env->CallIntMethod(mDatabase, method_setObjectProperty,
                (jint)handle, (jint)property, longValue, stringValue);
    if (stringValue)
        env->DeleteLocalRef(stringValue);

    checkAndClearExceptionFromCallback(env, __FUNCTION__);
    return result;
}

MtpResponseCode MyMtpDatabase::getDevicePropertyValue(MtpDeviceProperty property,
                                            MtpDataPacket& packet) {
    JNIEnv* env = AndroidRuntime::getJNIEnv();

    if (property == MTP_DEVICE_PROPERTY_BATTERY_LEVEL) {
        // special case - implemented here instead of Java
        packet.putUInt8((uint8_t)env->GetIntField(mDatabase, field_batteryLevel));
        return MTP_RESPONSE_OK;
    } else {
        int type;

        if (!getDevicePropertyInfo(property, type))
            return MTP_RESPONSE_DEVICE_PROP_NOT_SUPPORTED;

        jint result = env->CallIntMethod(mDatabase, method_getDeviceProperty,
                    (jint)property, mLongBuffer, mStringBuffer);
        if (result != MTP_RESPONSE_OK) {
            checkAndClearExceptionFromCallback(env, __FUNCTION__);
            return result;
        }

        jlong* longValues = env->GetLongArrayElements(mLongBuffer, 0);
        jlong longValue = longValues[0];
        env->ReleaseLongArrayElements(mLongBuffer, longValues, 0);

        switch (type) {
            case MTP_TYPE_INT8:
                packet.putInt8(longValue);
                break;
            case MTP_TYPE_UINT8:
                packet.putUInt8(longValue);
                break;
            case MTP_TYPE_INT16:
                packet.putInt16(longValue);
                break;
            case MTP_TYPE_UINT16:
                packet.putUInt16(longValue);
                break;
            case MTP_TYPE_INT32:
                packet.putInt32(longValue);
                break;
            case MTP_TYPE_UINT32:
                packet.putUInt32(longValue);
                break;
            case MTP_TYPE_INT64:
                packet.putInt64(longValue);
                break;
            case MTP_TYPE_UINT64:
                packet.putUInt64(longValue);
                break;
            case MTP_TYPE_INT128:
                packet.putInt128(longValue);
                break;
            case MTP_TYPE_UINT128:
                packet.putInt128(longValue);
                break;
            case MTP_TYPE_STR:
            {
                jchar* str = env->GetCharArrayElements(mStringBuffer, 0);
                packet.putString(str);
                env->ReleaseCharArrayElements(mStringBuffer, str, 0);
                break;
             }
            default:
                ALOGE("unsupported type in getDevicePropertyValue\n");
                return MTP_RESPONSE_INVALID_DEVICE_PROP_FORMAT;
        }

        checkAndClearExceptionFromCallback(env, __FUNCTION__);
        return MTP_RESPONSE_OK;
    }
}

MtpResponseCode MyMtpDatabase::setDevicePropertyValue(MtpDeviceProperty property,
                                            MtpDataPacket& packet) {
    int         type;

    if (!getDevicePropertyInfo(property, type))
        return MTP_RESPONSE_DEVICE_PROP_NOT_SUPPORTED;

    JNIEnv* env = AndroidRuntime::getJNIEnv();
    jlong longValue = 0;
    jstring stringValue = NULL;

    switch (type) {
        case MTP_TYPE_INT8:
            longValue = packet.getInt8();
            break;
        case MTP_TYPE_UINT8:
            longValue = packet.getUInt8();
            break;
        case MTP_TYPE_INT16:
            longValue = packet.getInt16();
            break;
        case MTP_TYPE_UINT16:
            longValue = packet.getUInt16();
            break;
        case MTP_TYPE_INT32:
            longValue = packet.getInt32();
            break;
        case MTP_TYPE_UINT32:
            longValue = packet.getUInt32();
            break;
        case MTP_TYPE_INT64:
            longValue = packet.getInt64();
            break;
        case MTP_TYPE_UINT64:
            longValue = packet.getUInt64();
            break;
        case MTP_TYPE_STR:
        {
            MtpStringBuffer buffer;
            packet.getString(buffer);
            stringValue = env->NewStringUTF((const char *)buffer);
            break;
         }
        default:
            ALOGE("unsupported type in setDevicePropertyValue\n");
            return MTP_RESPONSE_INVALID_OBJECT_PROP_FORMAT;
    }

    jint result = env->CallIntMethod(mDatabase, method_setDeviceProperty,
                (jint)property, longValue, stringValue);
    if (stringValue)
        env->DeleteLocalRef(stringValue);

    checkAndClearExceptionFromCallback(env, __FUNCTION__);
    return result;
}

MtpResponseCode MyMtpDatabase::resetDeviceProperty(MtpDeviceProperty /*property*/) {
    return -1;
}

MtpResponseCode MyMtpDatabase::getObjectPropertyList(MtpObjectHandle handle,
                                            uint32_t format, uint32_t property,
                                            int groupCode, int depth,
                                            MtpDataPacket& packet) {
    JNIEnv* env = AndroidRuntime::getJNIEnv();
    jobject list = env->CallObjectMethod(mDatabase, method_getObjectPropertyList,
                (jlong)handle, (jint)format, (jlong)property, (jint)groupCode, (jint)depth);
    checkAndClearExceptionFromCallback(env, __FUNCTION__);
    if (!list)
        return MTP_RESPONSE_GENERAL_ERROR;
    int count = env->GetIntField(list, field_mCount);
    MtpResponseCode result = env->GetIntField(list, field_mResult);

    packet.putUInt32(count);
    if (count > 0) {
        jintArray objectHandlesArray = (jintArray)env->GetObjectField(list, field_mObjectHandles);
        jintArray propertyCodesArray = (jintArray)env->GetObjectField(list, field_mPropertyCodes);
        jintArray dataTypesArray = (jintArray)env->GetObjectField(list, field_mDataTypes);
        jlongArray longValuesArray = (jlongArray)env->GetObjectField(list, field_mLongValues);
        jobjectArray stringValuesArray = (jobjectArray)env->GetObjectField(list, field_mStringValues);

        jint* objectHandles = env->GetIntArrayElements(objectHandlesArray, 0);
        jint* propertyCodes = env->GetIntArrayElements(propertyCodesArray, 0);
        jint* dataTypes = env->GetIntArrayElements(dataTypesArray, 0);
        jlong* longValues = (longValuesArray ? env->GetLongArrayElements(longValuesArray, 0) : NULL);

        for (int i = 0; i < count; i++) {
            packet.putUInt32(objectHandles[i]);
            packet.putUInt16(propertyCodes[i]);
            int type = dataTypes[i];
            packet.putUInt16(type);

            switch (type) {
                case MTP_TYPE_INT8:
                    packet.putInt8(longValues[i]);
                    break;
                case MTP_TYPE_UINT8:
                    packet.putUInt8(longValues[i]);
                    break;
                case MTP_TYPE_INT16:
                    packet.putInt16(longValues[i]);
                    break;
                case MTP_TYPE_UINT16:
                    packet.putUInt16(longValues[i]);
                    break;
                case MTP_TYPE_INT32:
                    packet.putInt32(longValues[i]);
                    break;
                case MTP_TYPE_UINT32:
                    packet.putUInt32(longValues[i]);
                    break;
                case MTP_TYPE_INT64:
                    packet.putInt64(longValues[i]);
                    break;
                case MTP_TYPE_UINT64:
                    packet.putUInt64(longValues[i]);
                    break;
                case MTP_TYPE_INT128:
                    packet.putInt128(longValues[i]);
                    break;
                case MTP_TYPE_UINT128:
                    packet.putUInt128(longValues[i]);
                    break;
                case MTP_TYPE_STR: {
                    jstring value = (jstring)env->GetObjectArrayElement(stringValuesArray, i);
                    const char *valueStr = (value ? env->GetStringUTFChars(value, NULL) : NULL);
                    if (valueStr) {
                        packet.putString(valueStr);
                        env->ReleaseStringUTFChars(value, valueStr);
                    } else {
                        packet.putEmptyString();
                    }
                    env->DeleteLocalRef(value);
                    break;
                }
                default:
                    ALOGE("bad or unsupported data type in MyMtpDatabase::getObjectPropertyList");
                    break;
            }
        }

        env->ReleaseIntArrayElements(objectHandlesArray, objectHandles, 0);
        env->ReleaseIntArrayElements(propertyCodesArray, propertyCodes, 0);
        env->ReleaseIntArrayElements(dataTypesArray, dataTypes, 0);
        if (longValues)
            env->ReleaseLongArrayElements(longValuesArray, longValues, 0);

        env->DeleteLocalRef(objectHandlesArray);
        env->DeleteLocalRef(propertyCodesArray);
        env->DeleteLocalRef(dataTypesArray);
        if (longValuesArray)
            env->DeleteLocalRef(longValuesArray);
        if (stringValuesArray)
            env->DeleteLocalRef(stringValuesArray);
    }

    env->DeleteLocalRef(list);
    checkAndClearExceptionFromCallback(env, __FUNCTION__);
    return result;
}

static void foreachentry(ExifEntry *entry, void *user) {
    char buf[1024];
    ALOGI("entry %x, format %d, size %d: %s",
            entry->tag, entry->format, entry->size, exif_entry_get_value(entry, buf, sizeof(buf)));
}

static void foreachcontent(ExifContent *content, void *user) {
    ALOGI("content %d", exif_content_get_ifd(content));
    exif_content_foreach_entry(content, foreachentry, user);
}

static long getLongFromExifEntry(ExifEntry *e) {
    ExifByteOrder o = exif_data_get_byte_order(e->parent->parent);
    return exif_get_long(e->data, o);
}

MtpResponseCode MyMtpDatabase::getObjectInfo(MtpObjectHandle handle,
                                            MtpObjectInfo& info) {
    char            date[20];
    MtpString       path;
    int64_t         length;
    MtpObjectFormat format;

    MtpResponseCode result = getObjectFilePath(handle, path, length, format);
    if (result != MTP_RESPONSE_OK) {
        return result;
    }
    info.mCompressedSize = (length > 0xFFFFFFFFLL ? 0xFFFFFFFF : (uint32_t)length);

    JNIEnv* env = AndroidRuntime::getJNIEnv();
    if (!env->CallBooleanMethod(mDatabase, method_getObjectInfo,
                (jint)handle, mIntBuffer, mStringBuffer, mLongBuffer)) {
        return MTP_RESPONSE_INVALID_OBJECT_HANDLE;
    }

    jint* intValues = env->GetIntArrayElements(mIntBuffer, 0);
    info.mStorageID = intValues[0];
    info.mFormat = intValues[1];
    info.mParent = intValues[2];
    env->ReleaseIntArrayElements(mIntBuffer, intValues, 0);

    jlong* longValues = env->GetLongArrayElements(mLongBuffer, 0);
    info.mDateCreated = longValues[0];
    info.mDateModified = longValues[1];
    env->ReleaseLongArrayElements(mLongBuffer, longValues, 0);

//    info.mAssociationType = (format == MTP_FORMAT_ASSOCIATION ?
//                            MTP_ASSOCIATION_TYPE_GENERIC_FOLDER :
//                            MTP_ASSOCIATION_TYPE_UNDEFINED);
    info.mAssociationType = MTP_ASSOCIATION_TYPE_UNDEFINED;

    jchar* str = env->GetCharArrayElements(mStringBuffer, 0);
    MtpString temp(str);
    info.mName = strdup((const char *)temp);
    env->ReleaseCharArrayElements(mStringBuffer, str, 0);

    // read EXIF data for thumbnail information
    if (info.mFormat == MTP_FORMAT_EXIF_JPEG || info.mFormat == MTP_FORMAT_JFIF) {

        ExifData *exifdata = exif_data_new_from_file(path);
        if (exifdata) {
            //exif_data_foreach_content(exifdata, foreachcontent, NULL);

            // XXX get this from exif, or parse jpeg header instead?
            ExifEntry *w = exif_content_get_entry(
                    exifdata->ifd[EXIF_IFD_EXIF], EXIF_TAG_PIXEL_X_DIMENSION);
            ExifEntry *h = exif_content_get_entry(
                    exifdata->ifd[EXIF_IFD_EXIF], EXIF_TAG_PIXEL_Y_DIMENSION);
            info.mThumbCompressedSize = exifdata->data ? exifdata->size : 0;
            info.mThumbFormat = MTP_FORMAT_EXIF_JPEG;
            info.mImagePixWidth = w ? getLongFromExifEntry(w) : 0;
            info.mImagePixHeight = h ? getLongFromExifEntry(h) : 0;
            exif_data_unref(exifdata);
        }
    }

    checkAndClearExceptionFromCallback(env, __FUNCTION__);
    return MTP_RESPONSE_OK;
}

void* MyMtpDatabase::getThumbnail(MtpObjectHandle handle, size_t& outThumbSize) {
    MtpString path;
    int64_t length;
    MtpObjectFormat format;
    void* result = NULL;
    outThumbSize = 0;

    if (getObjectFilePath(handle, path, length, format) == MTP_RESPONSE_OK
            && (format == MTP_FORMAT_EXIF_JPEG || format == MTP_FORMAT_JFIF)) {

        ExifData *exifdata = exif_data_new_from_file(path);
        if (exifdata) {
            if (exifdata->data) {
                result = malloc(exifdata->size);
                if (result) {
                    memcpy(result, exifdata->data, exifdata->size);
                    outThumbSize = exifdata->size;
                }
            }
            exif_data_unref(exifdata);
        }
    }

    return result;
}

MtpResponseCode MyMtpDatabase::getObjectFilePath(MtpObjectHandle handle,
                                            MtpString& outFilePath,
                                            int64_t& outFileLength,
                                            MtpObjectFormat& outFormat) {
    JNIEnv* env = AndroidRuntime::getJNIEnv();
    jint result = env->CallIntMethod(mDatabase, method_getObjectFilePath,
                (jint)handle, mStringBuffer, mLongBuffer);
    if (result != MTP_RESPONSE_OK) {
        checkAndClearExceptionFromCallback(env, __FUNCTION__);
        return result;
    }

    jchar* str = env->GetCharArrayElements(mStringBuffer, 0);
    outFilePath.setTo(str, strlen16(str));
    env->ReleaseCharArrayElements(mStringBuffer, str, 0);

    jlong* longValues = env->GetLongArrayElements(mLongBuffer, 0);
    outFileLength = longValues[0];
    outFormat = longValues[1];
    env->ReleaseLongArrayElements(mLongBuffer, longValues, 0);

    checkAndClearExceptionFromCallback(env, __FUNCTION__);
    return result;
}

MtpResponseCode MyMtpDatabase::deleteFile(MtpObjectHandle handle) {
    JNIEnv* env = AndroidRuntime::getJNIEnv();
    MtpResponseCode result = env->CallIntMethod(mDatabase, method_deleteFile, (jint)handle);

    checkAndClearExceptionFromCallback(env, __FUNCTION__);
    return result;
}

struct PropertyTableEntry {
    MtpObjectProperty   property;
    int                 type;
};

static const PropertyTableEntry   kObjectPropertyTable[] = {
    {   MTP_PROPERTY_STORAGE_ID,        MTP_TYPE_UINT32     },
    {   MTP_PROPERTY_OBJECT_FORMAT,     MTP_TYPE_UINT16     },
    {   MTP_PROPERTY_PROTECTION_STATUS, MTP_TYPE_UINT16     },
    {   MTP_PROPERTY_OBJECT_SIZE,       MTP_TYPE_UINT64     },
    {   MTP_PROPERTY_OBJECT_FILE_NAME,  MTP_TYPE_STR        },
    {   MTP_PROPERTY_DATE_MODIFIED,     MTP_TYPE_STR        },
    {   MTP_PROPERTY_PARENT_OBJECT,     MTP_TYPE_UINT32     },
    {   MTP_PROPERTY_PERSISTENT_UID,    MTP_TYPE_UINT128    },
    {   MTP_PROPERTY_NAME,              MTP_TYPE_STR        },
    {   MTP_PROPERTY_DISPLAY_NAME,      MTP_TYPE_STR        },
    {   MTP_PROPERTY_DATE_ADDED,        MTP_TYPE_STR        },
    {   MTP_PROPERTY_ARTIST,            MTP_TYPE_STR        },
    {   MTP_PROPERTY_ALBUM_NAME,        MTP_TYPE_STR        },
    {   MTP_PROPERTY_ALBUM_ARTIST,      MTP_TYPE_STR        },
    {   MTP_PROPERTY_TRACK,             MTP_TYPE_UINT16     },
    {   MTP_PROPERTY_ORIGINAL_RELEASE_DATE, MTP_TYPE_STR    },
    {   MTP_PROPERTY_GENRE,             MTP_TYPE_STR        },
    {   MTP_PROPERTY_COMPOSER,          MTP_TYPE_STR        },
    {   MTP_PROPERTY_DURATION,          MTP_TYPE_UINT32     },
    {   MTP_PROPERTY_DESCRIPTION,       MTP_TYPE_STR        },
};

static const PropertyTableEntry   kDevicePropertyTable[] = {
    {   MTP_DEVICE_PROPERTY_SYNCHRONIZATION_PARTNER,    MTP_TYPE_STR },
    {   MTP_DEVICE_PROPERTY_DEVICE_FRIENDLY_NAME,       MTP_TYPE_STR },
    {   MTP_DEVICE_PROPERTY_IMAGE_SIZE,                 MTP_TYPE_STR },
    {   MTP_DEVICE_PROPERTY_BATTERY_LEVEL,              MTP_TYPE_UINT8 },
};

bool MyMtpDatabase::getObjectPropertyInfo(MtpObjectProperty property, int& type) {
    int count = sizeof(kObjectPropertyTable) / sizeof(kObjectPropertyTable[0]);
    const PropertyTableEntry* entry = kObjectPropertyTable;
    for (int i = 0; i < count; i++, entry++) {
        if (entry->property == property) {
            type = entry->type;
            return true;
        }
    }
    return false;
}

bool MyMtpDatabase::getDevicePropertyInfo(MtpDeviceProperty property, int& type) {
    int count = sizeof(kDevicePropertyTable) / sizeof(kDevicePropertyTable[0]);
    const PropertyTableEntry* entry = kDevicePropertyTable;
    for (int i = 0; i < count; i++, entry++) {
        if (entry->property == property) {
            type = entry->type;
            return true;
        }
    }
    return false;
}

MtpObjectHandleList* MyMtpDatabase::getObjectReferences(MtpObjectHandle handle) {
    JNIEnv* env = AndroidRuntime::getJNIEnv();
    jintArray array = (jintArray)env->CallObjectMethod(mDatabase, method_getObjectReferences,
                (jint)handle);
    if (!array)
        return NULL;
    MtpObjectHandleList* list = new MtpObjectHandleList();
    jint* handles = env->GetIntArrayElements(array, 0);
    jsize length = env->GetArrayLength(array);
    for (int i = 0; i < length; i++)
        list->push(handles[i]);
    env->ReleaseIntArrayElements(array, handles, 0);
    env->DeleteLocalRef(array);

    checkAndClearExceptionFromCallback(env, __FUNCTION__);
    return list;
}

MtpResponseCode MyMtpDatabase::setObjectReferences(MtpObjectHandle handle,
                                                    MtpObjectHandleList* references) {
    JNIEnv* env = AndroidRuntime::getJNIEnv();
    int count = references->size();
    jintArray array = env->NewIntArray(count);
    if (!array) {
        ALOGE("out of memory in setObjectReferences");
        return false;
    }
    jint* handles = env->GetIntArrayElements(array, 0);
     for (int i = 0; i < count; i++)
        handles[i] = (*references)[i];
    env->ReleaseIntArrayElements(array, handles, 0);
    MtpResponseCode result = env->CallIntMethod(mDatabase, method_setObjectReferences,
                (jint)handle, array);
    env->DeleteLocalRef(array);

    checkAndClearExceptionFromCallback(env, __FUNCTION__);
    return result;
}

MtpProperty* MyMtpDatabase::getObjectPropertyDesc(MtpObjectProperty property,
                                            MtpObjectFormat format) {
    static const int channelEnum[] = {
                                        1,  // mono
                                        2,  // stereo
                                        3,  // 2.1
                                        4,  // 3
                                        5,  // 3.1
                                        6,  // 4
                                        7,  // 4.1
                                        8,  // 5
                                        9,  // 5.1
                                    };
    static const int bitrateEnum[] = {
                                        1,  // fixed rate
                                        2,  // variable rate
                                     };

    MtpProperty* result = NULL;
    switch (property) {
        case MTP_PROPERTY_OBJECT_FORMAT:
            // use format as default value
            result = new MtpProperty(property, MTP_TYPE_UINT16, false, format);
            break;
        case MTP_PROPERTY_PROTECTION_STATUS:
        case MTP_PROPERTY_TRACK:
            result = new MtpProperty(property, MTP_TYPE_UINT16);
            break;
        case MTP_PROPERTY_STORAGE_ID:
        case MTP_PROPERTY_PARENT_OBJECT:
        case MTP_PROPERTY_DURATION:
        case MTP_PROPERTY_AUDIO_WAVE_CODEC:
            result = new MtpProperty(property, MTP_TYPE_UINT32);
            break;
        case MTP_PROPERTY_OBJECT_SIZE:
            result = new MtpProperty(property, MTP_TYPE_UINT64);
            break;
        case MTP_PROPERTY_PERSISTENT_UID:
            result = new MtpProperty(property, MTP_TYPE_UINT128);
            break;
        case MTP_PROPERTY_NAME:
        case MTP_PROPERTY_DISPLAY_NAME:
        case MTP_PROPERTY_ARTIST:
        case MTP_PROPERTY_ALBUM_NAME:
        case MTP_PROPERTY_ALBUM_ARTIST:
        case MTP_PROPERTY_GENRE:
        case MTP_PROPERTY_COMPOSER:
        case MTP_PROPERTY_DESCRIPTION:
            result = new MtpProperty(property, MTP_TYPE_STR);
            break;
        case MTP_PROPERTY_DATE_MODIFIED:
        case MTP_PROPERTY_DATE_ADDED:
        case MTP_PROPERTY_ORIGINAL_RELEASE_DATE:
            result = new MtpProperty(property, MTP_TYPE_STR);
            result->setFormDateTime();
            break;
        case MTP_PROPERTY_OBJECT_FILE_NAME:
            // We allow renaming files and folders
            result = new MtpProperty(property, MTP_TYPE_STR, true);
            break;
        case MTP_PROPERTY_BITRATE_TYPE:
             result = new MtpProperty(property, MTP_TYPE_UINT16);
            result->setFormEnum(bitrateEnum, sizeof(bitrateEnum)/sizeof(bitrateEnum[0]));
            break;
        case MTP_PROPERTY_AUDIO_BITRATE:
            result = new MtpProperty(property, MTP_TYPE_UINT32);
            result->setFormRange(1, 1536000, 1);
            break;
        case MTP_PROPERTY_NUMBER_OF_CHANNELS:
            result = new MtpProperty(property, MTP_TYPE_UINT16);
            result->setFormEnum(channelEnum, sizeof(channelEnum)/sizeof(channelEnum[0]));
            break;
        case MTP_PROPERTY_SAMPLE_RATE:
            result = new MtpProperty(property, MTP_TYPE_UINT32);
            result->setFormRange(8000, 48000, 1);
            break;
    }

    return result;
}

MtpProperty* MyMtpDatabase::getDevicePropertyDesc(MtpDeviceProperty property) {
    JNIEnv* env = AndroidRuntime::getJNIEnv();
    MtpProperty* result = NULL;
    bool writable = false;

    switch (property) {
        case MTP_DEVICE_PROPERTY_SYNCHRONIZATION_PARTNER:
        case MTP_DEVICE_PROPERTY_DEVICE_FRIENDLY_NAME:
            writable = true;
            // fall through
        case MTP_DEVICE_PROPERTY_IMAGE_SIZE: {
            result = new MtpProperty(property, MTP_TYPE_STR, writable);

            // get current value
            jint ret = env->CallIntMethod(mDatabase, method_getDeviceProperty,
                        (jint)property, mLongBuffer, mStringBuffer);
            if (ret == MTP_RESPONSE_OK) {
                jchar* str = env->GetCharArrayElements(mStringBuffer, 0);
                result->setCurrentValue(str);
                // for read-only properties it is safe to assume current value is default value
                if (!writable)
                    result->setDefaultValue(str);
                env->ReleaseCharArrayElements(mStringBuffer, str, 0);
            } else {
                ALOGE("unable to read device property, response: %04X", ret);
            }
            break;
        }
        case MTP_DEVICE_PROPERTY_BATTERY_LEVEL:
            result = new MtpProperty(property, MTP_TYPE_UINT8);
            result->setFormRange(0, env->GetIntField(mDatabase, field_batteryScale), 1);
            result->mCurrentValue.u.u8 = (uint8_t)env->GetIntField(mDatabase, field_batteryLevel);
            break;
    }

    checkAndClearExceptionFromCallback(env, __FUNCTION__);
    return result;
}

void MyMtpDatabase::sessionStarted() {
    JNIEnv* env = AndroidRuntime::getJNIEnv();
    env->CallVoidMethod(mDatabase, method_sessionStarted);
    checkAndClearExceptionFromCallback(env, __FUNCTION__);
}

void MyMtpDatabase::sessionEnded() {
    JNIEnv* env = AndroidRuntime::getJNIEnv();
    env->CallVoidMethod(mDatabase, method_sessionEnded);
    checkAndClearExceptionFromCallback(env, __FUNCTION__);
}

// ----------------------------------------------------------------------------

static void
android_mtp_MtpDatabase_setup(JNIEnv *env, jobject thiz)
{
    MyMtpDatabase* database = new MyMtpDatabase(env, thiz);
    env->SetLongField(thiz, field_context, (jlong)database);
    checkAndClearExceptionFromCallback(env, __FUNCTION__);
}

static void
android_mtp_MtpDatabase_finalize(JNIEnv *env, jobject thiz)
{
    MyMtpDatabase* database = (MyMtpDatabase *)env->GetLongField(thiz, field_context);
    database->cleanup(env);
    delete database;
    env->SetLongField(thiz, field_context, 0);
    checkAndClearExceptionFromCallback(env, __FUNCTION__);
}

static jstring
android_mtp_MtpPropertyGroup_format_date_time(JNIEnv *env, jobject /*thiz*/, jlong seconds)
{
    char    date[20];
    formatDateTime(seconds, date, sizeof(date));
    return env->NewStringUTF(date);
}

// ----------------------------------------------------------------------------

static JNINativeMethod gMtpDatabaseMethods[] = {
    {"native_setup",            "()V",  (void *)android_mtp_MtpDatabase_setup},
    {"native_finalize",         "()V",  (void *)android_mtp_MtpDatabase_finalize},
};

static JNINativeMethod gMtpPropertyGroupMethods[] = {
    {"format_date_time",        "(J)Ljava/lang/String;",
                                        (void *)android_mtp_MtpPropertyGroup_format_date_time},
};

static const char* const kClassPathName = "android/mtp/MtpDatabase";

int register_android_mtp_MtpDatabase(JNIEnv *env)
{
    jclass clazz;

    clazz = env->FindClass("android/mtp/MtpDatabase");
    if (clazz == NULL) {
        ALOGE("Can't find android/mtp/MtpDatabase");
        return -1;
    }
    method_beginSendObject = env->GetMethodID(clazz, "beginSendObject", "(Ljava/lang/String;IIIJJ)I");
    if (method_beginSendObject == NULL) {
        ALOGE("Can't find beginSendObject");
        return -1;
    }
    method_endSendObject = env->GetMethodID(clazz, "endSendObject", "(Ljava/lang/String;IIZ)V");
    if (method_endSendObject == NULL) {
        ALOGE("Can't find endSendObject");
        return -1;
    }
    method_getObjectList = env->GetMethodID(clazz, "getObjectList", "(III)[I");
    if (method_getObjectList == NULL) {
        ALOGE("Can't find getObjectList");
        return -1;
    }
    method_getNumObjects = env->GetMethodID(clazz, "getNumObjects", "(III)I");
    if (method_getNumObjects == NULL) {
        ALOGE("Can't find getNumObjects");
        return -1;
    }
    method_getSupportedPlaybackFormats = env->GetMethodID(clazz, "getSupportedPlaybackFormats", "()[I");
    if (method_getSupportedPlaybackFormats == NULL) {
        ALOGE("Can't find getSupportedPlaybackFormats");
        return -1;
    }
    method_getSupportedCaptureFormats = env->GetMethodID(clazz, "getSupportedCaptureFormats", "()[I");
    if (method_getSupportedCaptureFormats == NULL) {
        ALOGE("Can't find getSupportedCaptureFormats");
        return -1;
    }
    method_getSupportedObjectProperties = env->GetMethodID(clazz, "getSupportedObjectProperties", "(I)[I");
    if (method_getSupportedObjectProperties == NULL) {
        ALOGE("Can't find getSupportedObjectProperties");
        return -1;
    }
    method_getSupportedDeviceProperties = env->GetMethodID(clazz, "getSupportedDeviceProperties", "()[I");
    if (method_getSupportedDeviceProperties == NULL) {
        ALOGE("Can't find getSupportedDeviceProperties");
        return -1;
    }
    method_setObjectProperty = env->GetMethodID(clazz, "setObjectProperty", "(IIJLjava/lang/String;)I");
    if (method_setObjectProperty == NULL) {
        ALOGE("Can't find setObjectProperty");
        return -1;
    }
    method_getDeviceProperty = env->GetMethodID(clazz, "getDeviceProperty", "(I[J[C)I");
    if (method_getDeviceProperty == NULL) {
        ALOGE("Can't find getDeviceProperty");
        return -1;
    }
    method_setDeviceProperty = env->GetMethodID(clazz, "setDeviceProperty", "(IJLjava/lang/String;)I");
    if (method_setDeviceProperty == NULL) {
        ALOGE("Can't find setDeviceProperty");
        return -1;
    }
    method_getObjectPropertyList = env->GetMethodID(clazz, "getObjectPropertyList",
            "(JIJII)Landroid/mtp/MtpPropertyList;");
    if (method_getObjectPropertyList == NULL) {
        ALOGE("Can't find getObjectPropertyList");
        return -1;
    }
    method_getObjectInfo = env->GetMethodID(clazz, "getObjectInfo", "(I[I[C[J)Z");
    if (method_getObjectInfo == NULL) {
        ALOGE("Can't find getObjectInfo");
        return -1;
    }
    method_getObjectFilePath = env->GetMethodID(clazz, "getObjectFilePath", "(I[C[J)I");
    if (method_getObjectFilePath == NULL) {
        ALOGE("Can't find getObjectFilePath");
        return -1;
    }
    method_deleteFile = env->GetMethodID(clazz, "deleteFile", "(I)I");
    if (method_deleteFile == NULL) {
        ALOGE("Can't find deleteFile");
        return -1;
    }
    method_getObjectReferences = env->GetMethodID(clazz, "getObjectReferences", "(I)[I");
    if (method_getObjectReferences == NULL) {
        ALOGE("Can't find getObjectReferences");
        return -1;
    }
    method_setObjectReferences = env->GetMethodID(clazz, "setObjectReferences", "(I[I)I");
    if (method_setObjectReferences == NULL) {
        ALOGE("Can't find setObjectReferences");
        return -1;
    }
    method_sessionStarted = env->GetMethodID(clazz, "sessionStarted", "()V");
    if (method_sessionStarted == NULL) {
        ALOGE("Can't find sessionStarted");
        return -1;
    }
    method_sessionEnded = env->GetMethodID(clazz, "sessionEnded", "()V");
    if (method_sessionEnded == NULL) {
        ALOGE("Can't find sessionEnded");
        return -1;
    }

    field_context = env->GetFieldID(clazz, "mNativeContext", "J");
    if (field_context == NULL) {
        ALOGE("Can't find MtpDatabase.mNativeContext");
        return -1;
    }
    field_batteryLevel = env->GetFieldID(clazz, "mBatteryLevel", "I");
    if (field_batteryLevel == NULL) {
        ALOGE("Can't find MtpDatabase.mBatteryLevel");
        return -1;
    }
    field_batteryScale = env->GetFieldID(clazz, "mBatteryScale", "I");
    if (field_batteryScale == NULL) {
        ALOGE("Can't find MtpDatabase.mBatteryScale");
        return -1;
    }

    // now set up fields for MtpPropertyList class
    clazz = env->FindClass("android/mtp/MtpPropertyList");
    if (clazz == NULL) {
        ALOGE("Can't find android/mtp/MtpPropertyList");
        return -1;
    }
    field_mCount = env->GetFieldID(clazz, "mCount", "I");
    if (field_mCount == NULL) {
        ALOGE("Can't find MtpPropertyList.mCount");
        return -1;
    }
    field_mResult = env->GetFieldID(clazz, "mResult", "I");
    if (field_mResult == NULL) {
        ALOGE("Can't find MtpPropertyList.mResult");
        return -1;
    }
    field_mObjectHandles = env->GetFieldID(clazz, "mObjectHandles", "[I");
    if (field_mObjectHandles == NULL) {
        ALOGE("Can't find MtpPropertyList.mObjectHandles");
        return -1;
    }
    field_mPropertyCodes = env->GetFieldID(clazz, "mPropertyCodes", "[I");
    if (field_mPropertyCodes == NULL) {
        ALOGE("Can't find MtpPropertyList.mPropertyCodes");
        return -1;
    }
    field_mDataTypes = env->GetFieldID(clazz, "mDataTypes", "[I");
    if (field_mDataTypes == NULL) {
        ALOGE("Can't find MtpPropertyList.mDataTypes");
        return -1;
    }
    field_mLongValues = env->GetFieldID(clazz, "mLongValues", "[J");
    if (field_mLongValues == NULL) {
        ALOGE("Can't find MtpPropertyList.mLongValues");
        return -1;
    }
    field_mStringValues = env->GetFieldID(clazz, "mStringValues", "[Ljava/lang/String;");
    if (field_mStringValues == NULL) {
        ALOGE("Can't find MtpPropertyList.mStringValues");
        return -1;
    }

    if (AndroidRuntime::registerNativeMethods(env,
                "android/mtp/MtpDatabase", gMtpDatabaseMethods, NELEM(gMtpDatabaseMethods)))
        return -1;

    return AndroidRuntime::registerNativeMethods(env,
                "android/mtp/MtpPropertyGroup", gMtpPropertyGroupMethods, NELEM(gMtpPropertyGroupMethods));
}