/*
* Copyright (C) 2007 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.
*/
package java.nio;
import org.apache.harmony.luni.platform.PlatformAddress;
import org.apache.harmony.nio.internal.DirectBuffer;
/**
* A class allowing native code to access the underlying data of
* an NIO Buffer, breaking encapsulation in the name of efficiency.
*/
class NIOAccess {
/**
* Returns the underlying native pointer to the data of the given
* Buffer starting at the Buffer's current position, or 0 if the
* Buffer is not backed by native heap storage. Note that this is
* different than what the Harmony implementation calls a "base
* address."
*
* @param Buffer b the Buffer to be queried
* @return the native pointer to the Buffer's data at its current
* position, or 0 if there is none
*/
static long getBasePointer(Buffer b) {
if (b instanceof DirectBuffer) {
PlatformAddress address = ((DirectBuffer) b).getEffectiveAddress();
if (address == null) {
return 0L;
}
return address.toInt() + (b.position() << b._elementSizeShift);
}
return 0L;
}
/**
* Returns the number of bytes remaining in the given Buffer. That is,
* this scales <code>remaining()</code> by the byte-size of elements
* of this Buffer.
*
* @param Buffer b the Buffer to be queried
* @return the number of remaining bytes
*/
static int getRemainingBytes(Buffer b) {
return (b.limit - b.position) << b._elementSizeShift;
}
/**
* Returns the underlying Java array containing the data of the
* given Buffer, or null if the Buffer is not backed by a Java array.
*
* @param Buffer b the Buffer to be queried
* @return the Java array containing the Buffer's data, or null if
* there is none
*/
static Object getBaseArray(Buffer b) {
return b._array();
}
/**
* Returns the offset in bytes from the start of the underlying
* Java array object containing the data of the given Buffer to
* the actual start of the data. This method is only meaningful if
* getBaseArray() returns non-null.
*
* @param Buffer b the Buffer to be queried
* @return the data offset in bytes to the start of this Buffer's data
*/
static int getBaseArrayOffset(Buffer b) {
return b._arrayOffset() << b._elementSizeShift;
}
}