static void android_os_Parcel_writeBlob(JNIEnv* env, jclass clazz, jlong nativePtr, jobject data,
                                        jint offset, jint length) {
    Parcel* parcel = reinterpret_cast<Parcel*>(nativePtr);
    if (parcel == NULL) {
        return;
    }

    if (data == NULL) {
        const status_t err = parcel->writeInt32(-1);
        if (err != NO_ERROR) {
            signalExceptionForError(env, clazz, err);
        }
        return;
    }

    const status_t err = parcel->writeInt32(length);
    if (err != NO_ERROR) {
        signalExceptionForError(env, clazz, err);
        return;
    }

    android::Parcel::WritableBlob blob;
    android::status_t err2 = parcel->writeBlob(length, &blob);
    if (err2 != NO_ERROR) {
        signalExceptionForError(env, clazz, err2);
        return;
    }

    jbyte* ar = (jbyte*)env->GetPrimitiveArrayCritical((jarray)data, 0);
    if (ar == NULL) {
        memset(blob.data(), 0, length);
    } else {
        memcpy(blob.data(), ar + offset, length);
        env->ReleasePrimitiveArrayCritical((jarray)data, ar, 0);
    }

    blob.release();
}
status_t CameraMetadata::writeToParcel(Parcel& data,
                                       const camera_metadata_t* metadata) {
    status_t res = OK;

    /**
     * Below is the camera metadata parcel layout:
     *
     * |--------------------------------------------|
     * |             arg0: blobSize                 |
     * |              (length = 4)                  |
     * |--------------------------------------------|<--Skip the rest if blobSize == 0.
     * |                                            |
     * |                                            |
     * |              arg1: blob                    |
     * | (length = variable, see arg1 layout below) |
     * |                                            |
     * |                                            |
     * |--------------------------------------------|
     * |              arg2: offset                  |
     * |              (length = 4)                  |
     * |--------------------------------------------|
     */

    // arg0 = blobSize (int32)
    if (metadata == NULL) {
        // Write zero blobSize for null metadata.
        return data.writeInt32(0);
    }

    /**
     * Always make the blob size sufficiently larger, as we need put alignment
     * padding and metadata into the blob. Since we don't know the alignment
     * offset before writeBlob. Then write the metadata to aligned offset.
     */
    const size_t metadataSize = get_camera_metadata_compact_size(metadata);
    const size_t alignment = get_camera_metadata_alignment();
    const size_t blobSize = metadataSize + alignment;
    res = data.writeInt32(static_cast<int32_t>(blobSize));
    if (res != OK) {
        return res;
    }

    size_t offset = 0;
    /**
     * arg1 = metadata (blob).
     *
     * The blob size is the sum of front padding size, metadata size and back padding
     * size, which is equal to metadataSize + alignment.
     *
     * The blob layout is:
     * |------------------------------------|<----Start address of the blob (unaligned).
     * |           front padding            |
     * |          (size = offset)           |
     * |------------------------------------|<----Aligned start address of metadata.
     * |                                    |
     * |                                    |
     * |            metadata                |
     * |       (size = metadataSize)        |
     * |                                    |
     * |                                    |
     * |------------------------------------|
     * |           back padding             |
     * |     (size = alignment - offset)    |
     * |------------------------------------|<----End address of blob.
     *                                            (Blob start address + blob size).
     */
    WritableBlob blob;
    do {
        res = data.writeBlob(blobSize, &blob);
        if (res != OK) {
            break;
        }
        const uintptr_t metadataStart = ALIGN_TO(blob.data(), alignment);
        offset = metadataStart - reinterpret_cast<uintptr_t>(blob.data());
        ALOGV("%s: alignment is: %zu, metadata start: %p, offset: %zu",
                __FUNCTION__, alignment,
                reinterpret_cast<const void *>(metadataStart), offset);
        copy_camera_metadata(reinterpret_cast<void*>(metadataStart), metadataSize, metadata);

        // Not too big of a problem since receiving side does hard validation
        // Don't check the size since the compact size could be larger
        if (validate_camera_metadata_structure(metadata, /*size*/NULL) != OK) {
            ALOGW("%s: Failed to validate metadata %p before writing blob",
                   __FUNCTION__, metadata);
        }

    } while(false);
    blob.release();

    // arg2 = offset (int32)
    res = data.writeInt32(static_cast<int32_t>(offset));

    return res;
}