com.twelvemonkeys.imageio.stream.BufferedFileImageInputStream Maven / Gradle / Ivy
/*
* Copyright (c) 2021, Harald Kuhr
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* * Redistributions of source code must retain the above copyright notice, this
* list of conditions and the following disclaimer.
*
* * Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* * Neither the name of the copyright holder nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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package com.twelvemonkeys.imageio.stream;
import javax.imageio.stream.ImageInputStreamImpl;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import static com.twelvemonkeys.lang.Validate.notNull;
import static java.lang.Math.max;
/**
* A buffered replacement for {@link javax.imageio.stream.FileImageInputStream}
* that provides greatly improved performance for shorter reads, like single
* byte or bit reads.
* As with {@code javax.imageio.stream.FileImageInputStream}, either
* {@link File} or {@link RandomAccessFile} can be used as input.
*
* @see javax.imageio.stream.FileImageInputStream
*/
// TODO: Create a memory-mapped version?
// Or not... From java.nio.channels.FileChannel.map:
// For most operating systems, mapping a file into memory is more
// expensive than reading or writing a few tens of kilobytes of data via
// the usual {@link #read read} and {@link #write write} methods. From the
// standpoint of performance it is generally only worth mapping relatively
// large files into memory.
public final class BufferedFileImageInputStream extends ImageInputStreamImpl {
static final int DEFAULT_BUFFER_SIZE = 8192;
private byte[] buffer = new byte[DEFAULT_BUFFER_SIZE];
private int bufferPos;
private int bufferLimit;
private final ByteBuffer integralCache = ByteBuffer.allocate(8);
private final byte[] integralCacheArray = integralCache.array();
private RandomAccessFile raf;
/**
* Constructs a BufferedFileImageInputStream that will read from a given File.
*
* @param file a File to read from.
* @throws IllegalArgumentException if file is null.
* @throws FileNotFoundException if file is a directory or cannot be opened for reading
* for any reason.
*/
public BufferedFileImageInputStream(final File file) throws FileNotFoundException {
this(new RandomAccessFile(notNull(file, "file"), "r"));
}
/**
* Constructs a BufferedFileImageInputStream that will read from a given RandomAccessFile.
*
* @param raf a RandomAccessFile to read from.
* @throws IllegalArgumentException if raf is null.
*/
public BufferedFileImageInputStream(final RandomAccessFile raf) {
this.raf = notNull(raf, "raf");
}
@SuppressWarnings("BooleanMethodIsAlwaysInverted")
private boolean fillBuffer() throws IOException {
int length = raf.read(buffer, 0, buffer.length);
bufferPos = 0;
bufferLimit = max(length, 0);
return bufferLimit > 0;
}
private boolean bufferEmpty() {
return bufferPos >= bufferLimit;
}
@Override
public void setByteOrder(ByteOrder byteOrder) {
super.setByteOrder(byteOrder);
integralCache.order(byteOrder);
}
@Override
public int read() throws IOException {
checkClosed();
if (bufferEmpty() && !fillBuffer()) {
return -1;
}
bitOffset = 0;
streamPos++;
return buffer[bufferPos++] & 0xff;
}
@Override
public int read(final byte[] bytes, final int offset, final int length) throws IOException {
checkClosed();
bitOffset = 0;
if (bufferEmpty()) {
// Bypass buffer if buffer is empty for reads longer than buffer
if (length >= buffer.length) {
return readDirect(bytes, offset, length);
}
else if (!fillBuffer()) {
return -1;
}
}
int fromBuffer = readBuffered(bytes, offset, length);
if (length > fromBuffer) {
// Due to known bugs in certain JDK-bundled ImageIO plugins expecting read to behave as readFully,
// we'll read as much as possible from the buffer, and the rest directly after
return fromBuffer + max(0, readDirect(bytes, offset + fromBuffer, length - fromBuffer));
}
return fromBuffer;
}
private int readDirect(final byte[] bytes, final int offset, final int length) throws IOException {
// Invalidate the buffer, as its contents is no longer in sync with the stream's position.
bufferLimit = 0;
int read = raf.read(bytes, offset, length);
if (read > 0) {
streamPos += read;
}
return read;
}
private int readBuffered(final byte[] bytes, final int offset, final int length) {
// Read as much as possible from buffer
int available = Math.min(bufferLimit - bufferPos, length);
if (available > 0) {
System.arraycopy(buffer, bufferPos, bytes, offset, available);
bufferPos += available;
streamPos += available;
}
return available;
}
public long length() {
// WTF?! This method is allowed to throw IOException in the interface...
try {
checkClosed();
return raf.length();
}
catch (IOException ignore) {
}
return -1;
}
public void close() throws IOException {
super.close();
raf.close();
raf = null;
buffer = null;
}
// Need to override the readShort(), readInt() and readLong() methods,
// because the implementations in ImageInputStreamImpl expects the
// read(byte[], int, int) to always read the expected number of bytes,
// causing uninitialized values, alignment issues and EOFExceptions at
// random places...
// Notes:
// * readUnsignedXx() is covered by their signed counterparts
// * readChar() is covered by readShort()
// * readFloat() and readDouble() is covered by readInt() and readLong()
// respectively.
// * readLong() may be covered by two readInt()s, we'll override to be safe
@Override
public short readShort() throws IOException {
readFully(integralCacheArray, 0, 2);
return integralCache.getShort(0);
}
@Override
public int readInt() throws IOException {
readFully(integralCacheArray, 0, 4);
return integralCache.getInt(0);
}
@Override
public long readLong() throws IOException {
readFully(integralCacheArray, 0, 8);
return integralCache.getLong(0);
}
@Override
public void seek(long position) throws IOException {
checkClosed();
if (position < flushedPos) {
throw new IndexOutOfBoundsException("position < flushedPos!");
}
bitOffset = 0;
if (streamPos == position) {
return;
}
// Optimized to not invalidate buffer if new position is within current buffer
long newBufferPos = bufferPos + position - streamPos;
if (newBufferPos >= 0 && newBufferPos < bufferLimit) {
bufferPos = (int) newBufferPos;
}
else {
// Will invalidate buffer
bufferLimit = 0;
raf.seek(position);
}
streamPos = position;
}
}
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