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/*
* Copyright 2012-2021 the original author or authors.
* Copy from spring-boot-loader
*
* 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
*
* https://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 com.gitee.starblues.loader.jar;
import java.io.*;
/**
* {@link RandomAccessData} implementation backed by a {@link RandomAccessFile}.
*
* @author Phillip Webb
* @author Andy Wilkinson
* @since 1.0.0
*/
public class RandomAccessDataFile implements RandomAccessData{
private final FileAccess fileAccess;
private final long offset;
private final long length;
/**
* Create a new {@link RandomAccessDataFile} backed by the specified file.
* @param file the underlying file
* @throws IllegalArgumentException if the file is null or does not exist
*/
public RandomAccessDataFile(File file) {
if (file == null) {
throw new IllegalArgumentException("File must not be null");
}
this.fileAccess = new FileAccess(file);
this.offset = 0L;
this.length = file.length();
}
/**
* Private constructor used to create a {@link #getSubsection(long, long) subsection}.
* @param fileAccess provides access to the underlying file
* @param offset the offset of the section
* @param length the length of the section
*/
private RandomAccessDataFile(FileAccess fileAccess, long offset, long length) {
this.fileAccess = fileAccess;
this.offset = offset;
this.length = length;
}
/**
* Returns the underlying File.
* @return the underlying file
*/
public File getFile() {
return this.fileAccess.file;
}
@Override
public InputStream getInputStream() throws IOException {
return new DataInputStream();
}
@Override
public RandomAccessData getSubsection(long offset, long length) {
if (offset < 0 || length < 0 || offset + length > this.length) {
throw new IndexOutOfBoundsException();
}
return new RandomAccessDataFile(this.fileAccess, this.offset + offset, length);
}
@Override
public byte[] read() throws IOException {
return read(0, this.length);
}
@Override
public byte[] read(long offset, long length) throws IOException {
if (offset > this.length) {
throw new IndexOutOfBoundsException();
}
if (offset + length > this.length) {
throw new EOFException();
}
byte[] bytes = new byte[(int) length];
read(bytes, offset, 0, bytes.length);
return bytes;
}
private int readByte(long position) throws IOException {
if (position >= this.length) {
return -1;
}
return this.fileAccess.readByte(this.offset + position);
}
private int read(byte[] bytes, long position, int offset, int length) throws IOException {
if (position > this.length) {
return -1;
}
return this.fileAccess.read(bytes, this.offset + position, offset, length);
}
@Override
public long getSize() {
return this.length;
}
public void close() throws IOException {
this.fileAccess.close();
}
/**
* {@link InputStream} implementation for the {@link RandomAccessDataFile}.
*/
private class DataInputStream extends InputStream {
private int position;
@Override
public int read() throws IOException {
int read = RandomAccessDataFile.this.readByte(this.position);
if (read > -1) {
moveOn(1);
}
return read;
}
@Override
public int read(byte[] b) throws IOException {
return read(b, 0, (b != null) ? b.length : 0);
}
@Override
public int read(byte[] b, int off, int len) throws IOException {
if (b == null) {
throw new NullPointerException("Bytes must not be null");
}
return doRead(b, off, len);
}
/**
* Perform the actual read.
* @param b the bytes to read or {@code null} when reading a single byte
* @param off the offset of the byte array
* @param len the length of data to read
* @return the number of bytes read into {@code b} or the actual read byte if
* {@code b} is {@code null}. Returns -1 when the end of the stream is reached
* @throws IOException in case of I/O errors
*/
int doRead(byte[] b, int off, int len) throws IOException {
if (len == 0) {
return 0;
}
int cappedLen = cap(len);
if (cappedLen <= 0) {
return -1;
}
return (int) moveOn(RandomAccessDataFile.this.read(b, this.position, off, cappedLen));
}
@Override
public long skip(long n) throws IOException {
return (n <= 0) ? 0 : moveOn(cap(n));
}
/**
* Cap the specified value such that it cannot exceed the number of bytes
* remaining.
* @param n the value to cap
* @return the capped value
*/
private int cap(long n) {
return (int) Math.min(RandomAccessDataFile.this.length - this.position, n);
}
/**
* Move the stream position forwards the specified amount.
* @param amount the amount to move
* @return the amount moved
*/
private long moveOn(int amount) {
this.position += amount;
return amount;
}
}
private static final class FileAccess {
private final Object monitor = new Object();
private final File file;
private RandomAccessFile randomAccessFile;
private FileAccess(File file) {
this.file = file;
openIfNecessary();
}
private int read(byte[] bytes, long position, int offset, int length) throws IOException {
synchronized (this.monitor) {
openIfNecessary();
this.randomAccessFile.seek(position);
return this.randomAccessFile.read(bytes, offset, length);
}
}
private void openIfNecessary() {
if (this.randomAccessFile == null) {
try {
this.randomAccessFile = new RandomAccessFile(this.file, "r");
} catch (FileNotFoundException ex) {
throw new IllegalArgumentException(
String.format("File %s must exist", this.file.getAbsolutePath()));
}
}
}
private void close() throws IOException {
synchronized (this.monitor) {
if (this.randomAccessFile != null) {
this.randomAccessFile.close();
this.randomAccessFile = null;
}
}
}
private int readByte(long position) throws IOException {
synchronized (this.monitor) {
openIfNecessary();
this.randomAccessFile.seek(position);
return this.randomAccessFile.read();
}
}
}
}
