Java tutorial
/* * Licensed to the Apache Software Foundation (ASF) under one or more * contributor license agreements. See the NOTICE file distributed with * this work for additional information regarding copyright ownership. * The ASF licenses this file to You 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 org.exist.util.io; import static org.apache.commons.io.IOUtils.EOF; import java.io.ByteArrayInputStream; import java.io.IOException; import java.io.InputStream; import java.io.OutputStream; import java.io.SequenceInputStream; import java.io.UnsupportedEncodingException; import java.nio.charset.Charset; import java.util.ArrayList; import java.util.Collections; import java.util.List; import net.jcip.annotations.NotThreadSafe; import org.apache.commons.io.input.ClosedInputStream; /** * NOTE this is a modified version of Apache * Commons IO 2.6 {@link org.apache.commons.io.output.ByteArrayOutputStream} * which removes the synchronization overhead for non-concurrent * access; as such this class is not thread-safe. * It also adds the method {@link FastByteArrayOutputStream#toFastByteInputStream()}. * * Modified by Adam Retter <adam@exist-db.org>. * Original Apache class header continues below: * * * This class implements an output stream in which the data is * written into a byte array. The buffer automatically grows as data * is written to it. * <p> * The data can be retrieved using <code>toByteArray()</code> and * <code>toString()</code>. * <p> * Closing a {@code ByteArrayOutputStream} has no effect. The methods in * this class can be called after the stream has been closed without * generating an {@code IOException}. * <p> * This is an alternative implementation of the {@link java.io.ByteArrayOutputStream} * class. The original implementation only allocates 32 bytes at the beginning. * As this class is designed for heavy duty it starts at 1024 bytes. In contrast * to the original it doesn't reallocate the whole memory block but allocates * additional buffers. This way no buffers need to be garbage collected and * the contents don't have to be copied to the new buffer. This class is * designed to behave exactly like the original. The only exception is the * deprecated toString(int) method that has been ignored. */ @NotThreadSafe public class FastByteArrayOutputStream extends OutputStream { static final int DEFAULT_SIZE = 1024; /** A singleton empty byte array. */ private static final byte[] EMPTY_BYTE_ARRAY = new byte[0]; /** The list of buffers, which grows and never reduces. */ private final List<byte[]> buffers = new ArrayList<>(); /** The index of the current buffer. */ private int currentBufferIndex; /** The total count of bytes in all the filled buffers. */ private int filledBufferSum; /** The current buffer. */ private byte[] currentBuffer; /** The total count of bytes written. */ private int count; /** Flag to indicate if the buffers can be reused after reset */ private boolean reuseBuffers = true; /** * Creates a new byte array output stream. The buffer capacity is * initially 1024 bytes, though its size increases if necessary. */ public FastByteArrayOutputStream() { this(DEFAULT_SIZE); } /** * Creates a new byte array output stream, with a buffer capacity of * the specified size, in bytes. * * @param size the initial size * @throws IllegalArgumentException if size is negative */ public FastByteArrayOutputStream(final int size) { if (size < 0) { throw new IllegalArgumentException("Negative initial size: " + size); } // synchronized (this) { needNewBuffer(size); // } } /** * Makes a new buffer available either by allocating * a new one or re-cycling an existing one. * * @param newcount the size of the buffer if one is created */ private void needNewBuffer(final int newcount) { if (currentBufferIndex < buffers.size() - 1) { //Recycling old buffer filledBufferSum += currentBuffer.length; currentBufferIndex++; currentBuffer = buffers.get(currentBufferIndex); } else { //Creating new buffer int newBufferSize; if (currentBuffer == null) { newBufferSize = newcount; filledBufferSum = 0; } else { newBufferSize = Math.max(currentBuffer.length << 1, newcount - filledBufferSum); filledBufferSum += currentBuffer.length; } currentBufferIndex++; currentBuffer = new byte[newBufferSize]; buffers.add(currentBuffer); } } /** * Write the bytes to byte array. * @param b the bytes to write * @param off The start offset * @param len The number of bytes to write */ @Override public void write(final byte[] b, final int off, final int len) { if ((off < 0) || (off > b.length) || (len < 0) || ((off + len) > b.length) || ((off + len) < 0)) { throw new IndexOutOfBoundsException(); } else if (len == 0) { return; } // synchronized (this) { final int newcount = count + len; int remaining = len; int inBufferPos = count - filledBufferSum; while (remaining > 0) { final int part = Math.min(remaining, currentBuffer.length - inBufferPos); System.arraycopy(b, off + len - remaining, currentBuffer, inBufferPos, part); remaining -= part; if (remaining > 0) { needNewBuffer(newcount); inBufferPos = 0; } } count = newcount; // } } /** * Write a byte to byte array. * @param b the byte to write */ @Override public /*synchronized*/ void write(final int b) { int inBufferPos = count - filledBufferSum; if (inBufferPos == currentBuffer.length) { needNewBuffer(count + 1); inBufferPos = 0; } currentBuffer[inBufferPos] = (byte) b; count++; } /** * Writes the entire contents of the specified input stream to this * byte stream. Bytes from the input stream are read directly into the * internal buffers of this streams. * * @param in the input stream to read from * @return total number of bytes read from the input stream * (and written to this stream) * @throws IOException if an I/O error occurs while reading the input stream * @since 1.4 */ public /*synchronized*/ int write(final InputStream in) throws IOException { int readCount = 0; int inBufferPos = count - filledBufferSum; int n = in.read(currentBuffer, inBufferPos, currentBuffer.length - inBufferPos); while (n != EOF) { readCount += n; inBufferPos += n; count += n; if (inBufferPos == currentBuffer.length) { needNewBuffer(currentBuffer.length); inBufferPos = 0; } n = in.read(currentBuffer, inBufferPos, currentBuffer.length - inBufferPos); } return readCount; } /** * Return the current size of the byte array. * @return the current size of the byte array */ public /*synchronized*/ int size() { return count; } /** * Closing a {@code ByteArrayOutputStream} has no effect. The methods in * this class can be called after the stream has been closed without * generating an {@code IOException}. * * @throws IOException never (this method should not declare this exception * but it has to now due to backwards compatibility) */ @Override public void close() throws IOException { //nop } /** * @see java.io.ByteArrayOutputStream#reset() */ public /*synchronized*/ void reset() { count = 0; filledBufferSum = 0; currentBufferIndex = 0; if (reuseBuffers) { currentBuffer = buffers.get(currentBufferIndex); } else { //Throw away old buffers currentBuffer = null; final int size = buffers.get(0).length; buffers.clear(); needNewBuffer(size); reuseBuffers = true; } } /** * Writes the entire contents of this byte stream to the * specified output stream. * * @param out the output stream to write to * @throws IOException if an I/O error occurs, such as if the stream is closed * @see java.io.ByteArrayOutputStream#writeTo(OutputStream) */ public /*synchronized*/ void writeTo(final OutputStream out) throws IOException { int remaining = count; for (final byte[] buf : buffers) { final int c = Math.min(buf.length, remaining); out.write(buf, 0, c); remaining -= c; if (remaining == 0) { break; } } } /** * Fetches entire contents of an <code>InputStream</code> and represent * same data as result InputStream. * <p> * This method is useful where, * <ul> * <li>Source InputStream is slow.</li> * <li>It has network resources associated, so we cannot keep it open for * long time.</li> * <li>It has network timeout associated.</li> * </ul> * It can be used in favor of {@link #toByteArray()}, since it * avoids unnecessary allocation and copy of byte[].<br> * This method buffers the input internally, so there is no need to use a * <code>BufferedInputStream</code>. * * @param input Stream to be fully buffered. * @return A fully buffered stream. * @throws IOException if an I/O error occurs * @since 2.0 */ public static InputStream toBufferedInputStream(final InputStream input) throws IOException { return toBufferedInputStream(input, 1024); } /** * Fetches entire contents of an <code>InputStream</code> and represent * same data as result InputStream. * <p> * This method is useful where, * <ul> * <li>Source InputStream is slow.</li> * <li>It has network resources associated, so we cannot keep it open for * long time.</li> * <li>It has network timeout associated.</li> * </ul> * It can be used in favor of {@link #toByteArray()}, since it * avoids unnecessary allocation and copy of byte[].<br> * This method buffers the input internally, so there is no need to use a * <code>BufferedInputStream</code>. * * @param input Stream to be fully buffered. * @param size the initial buffer size * @return A fully buffered stream. * @throws IOException if an I/O error occurs * @since 2.5 */ public static InputStream toBufferedInputStream(final InputStream input, final int size) throws IOException { // It does not matter if a ByteArrayOutputStream is not closed as close() is a no-op @SuppressWarnings("resource") final FastByteArrayOutputStream output = new FastByteArrayOutputStream(size); output.write(input); return output.toInputStream(); } /** * Gets the current contents of this byte stream as a Input Stream. The * returned stream is backed by buffers of <code>this</code> stream, * avoiding memory allocation and copy, thus saving space and time.<br> * * @return the current contents of this output stream. * @see java.io.ByteArrayOutputStream#toByteArray() * @see #reset() * @since 2.5 */ public /*synchronized*/ InputStream toInputStream() { int remaining = count; if (remaining == 0) { return new ClosedInputStream(); } final List<ByteArrayInputStream> list = new ArrayList<>(buffers.size()); for (final byte[] buf : buffers) { final int c = Math.min(buf.length, remaining); list.add(new ByteArrayInputStream(buf, 0, c)); remaining -= c; if (remaining == 0) { break; } } reuseBuffers = false; return new SequenceInputStream(Collections.enumeration(list)); } /** * Similar to {@link #toInputStream()} * but utilises {@link FastByteArrayInputStream} * as opposed to {@link java.io.ByteArrayInputStream}. */ public /*synchronized*/ InputStream toFastByteInputStream() { int remaining = count; if (remaining == 0) { return new ClosedInputStream(); } final List<FastByteArrayInputStream> list = new ArrayList<>(buffers.size()); for (final byte[] buf : buffers) { final int c = Math.min(buf.length, remaining); list.add(new FastByteArrayInputStream(buf, 0, c)); remaining -= c; if (remaining == 0) { break; } } reuseBuffers = false; return new SequenceInputStream(Collections.enumeration(list)); } /** * Gets the current contents of this byte stream as a byte array. * The result is independent of this stream. * * @return the current contents of this output stream, as a byte array * @see java.io.ByteArrayOutputStream#toByteArray() */ public /*synchronized*/ byte[] toByteArray() { int remaining = count; if (remaining == 0) { return EMPTY_BYTE_ARRAY; } final byte newbuf[] = new byte[remaining]; int pos = 0; for (final byte[] buf : buffers) { final int c = Math.min(buf.length, remaining); System.arraycopy(buf, 0, newbuf, pos, c); pos += c; remaining -= c; if (remaining == 0) { break; } } return newbuf; } /** * Gets the current contents of this byte stream as a string * using the platform default charset. * @return the contents of the byte array as a String * @see java.io.ByteArrayOutputStream#toString() * @deprecated 2.5 use {@link #toString(String)} instead */ @Override @Deprecated public String toString() { // make explicit the use of the default charset return new String(toByteArray(), Charset.defaultCharset()); } /** * Gets the current contents of this byte stream as a string * using the specified encoding. * * @param enc the name of the character encoding * @return the string converted from the byte array * @throws UnsupportedEncodingException if the encoding is not supported * @see java.io.ByteArrayOutputStream#toString(String) */ public String toString(final String enc) throws UnsupportedEncodingException { return new String(toByteArray(), enc); } /** * Gets the current contents of this byte stream as a string * using the specified encoding. * * @param charset the character encoding * @return the string converted from the byte array * @see java.io.ByteArrayOutputStream#toString(String) * @since 2.5 */ public String toString(final Charset charset) { return new String(toByteArray(), charset); } }