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Add WriteBufferDataHandle
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‎src/main/java/org/scijava/io/handle/WriteBufferDataHandle.java‎

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/*
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* #%L
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* SciJava Common shared library for SciJava software.
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* %%
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* Copyright (C) 2009 - 2017 Board of Regents of the University of
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* Wisconsin-Madison, Broad Institute of MIT and Harvard, Max Planck
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* Institute of Molecular Cell Biology and Genetics, University of
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* Konstanz, and KNIME GmbH.
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* %%
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are met:
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*
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* 1. Redistributions of source code must retain the above copyright notice,
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* this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright notice,
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* this list of conditions and the following disclaimer in the documentation
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* and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDERS OR CONTRIBUTORS BE
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* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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* #L%
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*/
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package org.scijava.io.handle;
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import java.io.EOFException;
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import java.io.IOException;
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import org.scijava.io.location.Location;
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/**
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* Wraps a {@link DataHandle} and acts as a write buffer.
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*
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* @author Gabriel Einsdorf
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*/
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public class WriteBufferDataHandle extends AbstractHigherOrderHandle<Location> {
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private static final int DEFAULT_BUFFERSIZE = 10_000;
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private long offset = 0;
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private int nextPos = 0;
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private byte[] buffer;
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private final int bufferSize;
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/**
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* Creates a {@link WriteBufferDataHandle} that wraps the given
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* {@link DataHandle}, the default size for the buffer is used
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* ({@value #DEFAULT_BUFFERSIZE} bytes).
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*
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* @param handle the handle to wrap
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*/
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public WriteBufferDataHandle(final DataHandle<Location> handle) {
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this(handle, DEFAULT_BUFFERSIZE);
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}
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/**
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* Creates a {@link WriteBufferDataHandle} that wraps the given
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* {@link DataHandle}
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*
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* @param handle the handle to wrap
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* @param bufferSize the size of the write buffer in bytes
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*/
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public WriteBufferDataHandle(final DataHandle<Location> handle,
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final int bufferSize)
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{
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super(handle);
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this.bufferSize = bufferSize;
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}
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@Override
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public void write(final int b) throws IOException {
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ensureOpen();
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// if buffer is full flush
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if (nextPos >= buffer.length) {
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flush();
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}
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// buffer the byte
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buffer[nextPos] = (byte) b;
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nextPos++;
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offset++;
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}
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@Override
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public void write(final byte[] b, final int off, final int len)
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throws IOException
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{
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ensureOpen();
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// ensure the range is valid
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if ((off < 0) || (off > b.length) || (len < 0) || ((off +
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len) > b.length) || ((off + len) < 0))
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{
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throw new IndexOutOfBoundsException();
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}
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else if (len == 0) {
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return; // nothing to do
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}
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// skip the buffering and write directly to the handle
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if (len > buffer.length) {
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flush();
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handle().write(b, off, len);
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offset += len;
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return;
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}
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// copy to buffer / flush if necessary
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int start = off;
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final int total = off + len;
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while (start < total) {
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final int numItems = Math.min(buffer.length - nextPos, total - start);
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System.arraycopy(b, start, buffer, nextPos, numItems);
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start += numItems;
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nextPos += numItems;
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if (nextPos >= buffer.length) {
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flush();
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}
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}
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}
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/**
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* Write the buffer content to the underlying handle
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*/
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private void flush() throws IOException {
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ensureOpen();
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if (nextPos == 0) return;
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handle().write(buffer, 0, nextPos);
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nextPos = 0;
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}
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@Override
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public long length() throws IOException {
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// data written out + data in the buffer
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return handle().length() + nextPos - 1;
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}
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@Override
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public void setLength(final long length) throws IOException {
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ensureOpen();
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handle().setLength(length);
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}
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@Override
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public boolean isReadable() {
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return false;
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}
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/**
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* @throws IOException if this handle has been closed
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*/
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@Override
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protected void ensureOpen() throws IOException {
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super.ensureOpen();
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if (buffer == null) {
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buffer = new byte[bufferSize];
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}
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}
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@Override
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public long offset() throws IOException {
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return offset;
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}
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@Override
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public void seek(final long pos) throws IOException {
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ensureOpen();
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if (pos >= length()) {
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throw new EOFException();
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}
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flush();
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offset = pos;
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handle().seek(offset);
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}
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@Override
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public long skip(final long n) throws IOException {
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throw new IOException("Operation 'skip' is not supported!");
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}
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@Override
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public byte readByte() throws IOException {
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throw DataHandles.writeOnlyException();
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}
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@Override
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public int read(final byte[] b, final int off, final int len)
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throws IOException
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{
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throw DataHandles.writeOnlyException();
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}
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@Override
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protected void cleanup() throws IOException {
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flush();
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buffer = null;
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}
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}

‎src/test/java/org/scijava/io/handle/WriteBufferDataHandleTest.java‎

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/*
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* #%L
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* SciJava Common shared library for SciJava software.
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* %%
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* Copyright (C) 2009 - 2017 Board of Regents of the University of
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* Wisconsin-Madison, Broad Institute of MIT and Harvard, Max Planck
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* Institute of Molecular Cell Biology and Genetics, University of
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* Konstanz, and KNIME GmbH.
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* %%
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are met:
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*
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* 1. Redistributions of source code must retain the above copyright notice,
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* this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright notice,
16+
* this list of conditions and the following disclaimer in the documentation
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* and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
21+
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDERS OR CONTRIBUTORS BE
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* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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* #L%
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*/
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package org.scijava.io.handle;
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import static org.junit.Assert.assertEquals;
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import java.io.ByteArrayOutputStream;
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import java.io.IOException;
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import org.junit.Test;
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import org.scijava.Context;
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import org.scijava.io.location.BytesLocation;
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import org.scijava.io.location.Location;
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public class WriteBufferDataHandleTest extends DataHandleTest {
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private Location loc;
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@Override
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public Class<? extends DataHandle<?>> getExpectedHandleType() {
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// not needed
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return null;
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}
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@Override
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@Test
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public void testDataHandle() throws IOException {
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final Context context = new Context(DataHandleService.class);
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final DataHandleService dataHandleService = context.service(
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DataHandleService.class);
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loc = createLocation();
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try (final DataHandle<Location> handle = //
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dataHandleService.create(loc);
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final DataHandle<Location> buffer = //
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new WriteBufferDataHandle(handle))
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{
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checkWrites(buffer);
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}
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}
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@Override
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public Location createLocation() throws IOException {
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final ByteArrayOutputStream out = new ByteArrayOutputStream();
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populateData(out);
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return new BytesLocation(out.toByteArray());
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}
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@Override
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protected <L extends Location> void checkWrites(final DataHandle<L> handle)
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throws IOException
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{
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final byte[] copy = BYTES.clone();
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// change the data
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handle.seek(7);
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final String splice = "there";
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for (int i = 0; i < splice.length(); i++) {
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final char c = splice.charAt(i);
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handle.write(c);
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copy[7 + i] = (byte) c;
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}
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handle.close();
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final Context context = new Context(DataHandleService.class);
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final DataHandleService dataHandleService = context.service(
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DataHandleService.class);
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try (final DataHandle<? extends Location> readHandle = //
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dataHandleService.create(loc))
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{
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readHandle.seek(0);
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for (int i = 0; i < copy.length; i++) {
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assertEquals(msg(i), 0xff & copy[i], readHandle.read());
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}
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}
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}
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}

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