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A library for invoking native functions from java
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/*
 * Copyright (C) 2012 Wayne Meissner
 *
 * This file is part of the JNR 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 jnr.ffi.provider.converters;

import jnr.ffi.mapper.ToNativeContext;
import jnr.ffi.mapper.ToNativeConverter;
import jnr.ffi.provider.ParameterFlags;
import jnr.ffi.util.BufferUtil;

import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.nio.charset.Charset;

@ToNativeConverter.NoContext
@ToNativeConverter.Cacheable
public class StringBufferParameterConverter implements ToNativeConverter, ToNativeConverter.PostInvocation {
    private final Charset charset;
    private final int parameterFlags;

    private StringBufferParameterConverter(Charset charset, int parameterFlags) {
        this.charset = charset;
        this.parameterFlags = parameterFlags;
    }

    public Class nativeType() {
        return ByteBuffer.class;
    }

    public static StringBufferParameterConverter getInstance(int parameterFlags, ToNativeContext toNativeContext) {
        return new StringBufferParameterConverter(Charset.defaultCharset(), parameterFlags);
    }

    public static StringBufferParameterConverter getInstance(Charset charset, int parameterFlags, ToNativeContext toNativeContext) {
        return new StringBufferParameterConverter(charset, parameterFlags);
    }

    public ByteBuffer toNative(StringBuffer parameter, ToNativeContext context) {
        if (parameter == null) {
            return null;

        } else {
            ByteBuffer buf = ParameterFlags.isIn(parameterFlags)
                    ? charset.encode(CharBuffer.wrap(parameter))
                    : ByteBuffer.allocate(parameter.capacity() + 1);

            if ((ParameterFlags.isOut(parameterFlags) && buf.capacity() < parameter.capacity() + 1) || !buf.hasArray()) {
                byte[] array = new byte[parameter.capacity() + 1];
                buf.get(array, 0, buf.remaining());
                return ByteBuffer.wrap(array);

            } else {
                return buf;
            }
        }
    }

    public void postInvoke(StringBuffer stringBuffer, ByteBuffer buf, ToNativeContext context) {
        //
        // Copy the string back out if its an OUT parameter
        //
        if (ParameterFlags.isOut(parameterFlags) && stringBuffer != null && buf != null) {
            buf.limit(buf.capacity());
            stringBuffer.delete(0, stringBuffer.length()).append(BufferUtil.getCharSequence(buf, charset));
        }
    }
}