| /* |
| * Copyright (C) 2017, Google Inc. and others |
| * |
| * This program and the accompanying materials are made available under the |
| * terms of the Eclipse Distribution License v. 1.0 which is available at |
| * https://www.eclipse.org/org/documents/edl-v10.php. |
| * |
| * SPDX-License-Identifier: BSD-3-Clause |
| */ |
| |
| package org.eclipse.jgit.internal.storage.io; |
| |
| import java.io.FileInputStream; |
| import java.io.IOException; |
| import java.nio.ByteBuffer; |
| import java.nio.channels.FileChannel; |
| |
| /** |
| * Provides content blocks of file. |
| * <p> |
| * {@code BlockSource} implementations must decide if they will be thread-safe, |
| * or not. |
| */ |
| public abstract class BlockSource implements AutoCloseable { |
| /** |
| * Wrap a byte array as a {@code BlockSource}. |
| * |
| * @param content |
| * input file. |
| * @return block source to read from {@code content}. |
| */ |
| public static BlockSource from(byte[] content) { |
| return new BlockSource() { |
| @Override |
| public ByteBuffer read(long pos, int cnt) { |
| ByteBuffer buf = ByteBuffer.allocate(cnt); |
| if (pos < content.length) { |
| int p = (int) pos; |
| int n = Math.min(cnt, content.length - p); |
| buf.put(content, p, n); |
| } |
| return buf; |
| } |
| |
| @Override |
| public long size() { |
| return content.length; |
| } |
| |
| @Override |
| public void close() { |
| // Do nothing. |
| } |
| }; |
| } |
| |
| /** |
| * Read from a {@code FileInputStream}. |
| * <p> |
| * The returned {@code BlockSource} is not thread-safe, as it must seek the |
| * file channel to read a block. |
| * |
| * @param in |
| * the file. The {@code BlockSource} will close {@code in}. |
| * @return wrapper for {@code in}. |
| */ |
| public static BlockSource from(FileInputStream in) { |
| return from(in.getChannel()); |
| } |
| |
| /** |
| * Read from a {@code FileChannel}. |
| * <p> |
| * The returned {@code BlockSource} is not thread-safe, as it must seek the |
| * file channel to read a block. |
| * |
| * @param ch |
| * the file. The {@code BlockSource} will close {@code ch}. |
| * @return wrapper for {@code ch}. |
| */ |
| public static BlockSource from(FileChannel ch) { |
| return new BlockSource() { |
| @Override |
| public ByteBuffer read(long pos, int blockSize) throws IOException { |
| ByteBuffer b = ByteBuffer.allocate(blockSize); |
| ch.position(pos); |
| int n; |
| do { |
| n = ch.read(b); |
| } while (n > 0 && b.position() < blockSize); |
| return b; |
| } |
| |
| @Override |
| public long size() throws IOException { |
| return ch.size(); |
| } |
| |
| @Override |
| public void close() { |
| try { |
| ch.close(); |
| } catch (IOException e) { |
| // Ignore close failures of read-only files. |
| } |
| } |
| }; |
| } |
| |
| /** |
| * Read a block from the file. |
| * <p> |
| * To reduce copying, the returned ByteBuffer should have an accessible |
| * array and {@code arrayOffset() == 0}. The caller will discard the |
| * ByteBuffer and directly use the backing array. |
| * |
| * @param position |
| * position of the block in the file, specified in bytes from the |
| * beginning of the file. |
| * @param blockSize |
| * size to read. |
| * @return buffer containing the block content. |
| * @throws java.io.IOException |
| * if block cannot be read. |
| */ |
| public abstract ByteBuffer read(long position, int blockSize) |
| throws IOException; |
| |
| /** |
| * Determine the size of the file. |
| * |
| * @return total number of bytes in the file. |
| * @throws java.io.IOException |
| * if size cannot be obtained. |
| */ |
| public abstract long size() throws IOException; |
| |
| /** |
| * Advise the {@code BlockSource} a sequential scan is starting. |
| * |
| * @param startPos |
| * starting position. |
| * @param endPos |
| * ending position. |
| */ |
| public void adviseSequentialRead(long startPos, long endPos) { |
| // Do nothing by default. |
| } |
| |
| /** {@inheritDoc} */ |
| @Override |
| public abstract void close(); |
| } |