| /* ==================================================================== |
| 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.apache.poi.poifs.storage; |
| |
| /** |
| * Wraps a <tt>byte</tt> array and provides simple data input access. |
| * Internally, this class maintains a buffer read index, so that for the most part, primitive |
| * data can be read in a data-input-stream-like manner.<p/> |
| * |
| * Note - the calling class should call the {@link #available()} method to detect end-of-buffer |
| * and move to the next data block when the current is exhausted. |
| * For optimisation reasons, no error handling is performed in this class. Thus, mistakes in |
| * calling code ran may raise ugly exceptions here, like {@link ArrayIndexOutOfBoundsException}, |
| * etc .<p/> |
| * |
| * The multi-byte primitive input methods ({@link #readUShortLE()}, {@link #readIntLE()} and |
| * {@link #readLongLE()}) have corresponding 'spanning read' methods which (when required) perform |
| * a read across the block boundary. These spanning read methods take the previous |
| * {@link DataInputBlock} as a parameter. |
| * Reads of larger amounts of data (into <tt>byte</tt> array buffers) must be managed by the caller |
| * since these could conceivably involve more than two blocks. |
| * |
| * @author Josh Micich |
| */ |
| public final class DataInputBlock { |
| |
| /** |
| * Possibly any size (usually 512K or 64K). Assumed to be at least 8 bytes for all blocks |
| * before the end of the stream. The last block in the stream can be any size except zero. |
| */ |
| private final byte[] _buf; |
| private int _readIndex; |
| private int _maxIndex; |
| |
| DataInputBlock(byte[] data, int startOffset) { // NOSONAR |
| _buf = data; |
| _readIndex = startOffset; |
| _maxIndex = _buf.length; |
| } |
| public int available() { |
| return _maxIndex-_readIndex; |
| } |
| |
| public int readUByte() { |
| return _buf[_readIndex++] & 0xFF; |
| } |
| |
| /** |
| * Reads a <tt>short</tt> which was encoded in <em>little endian</em> format. |
| */ |
| public int readUShortLE() { |
| int i = _readIndex; |
| |
| int b0 = _buf[i++] & 0xFF; |
| int b1 = _buf[i++] & 0xFF; |
| _readIndex = i; |
| return (b1 << 8) + (b0 << 0); |
| } |
| |
| /** |
| * Reads a <tt>short</tt> which spans the end of <tt>prevBlock</tt> and the start of this block. |
| */ |
| public int readUShortLE(DataInputBlock prevBlock) { |
| // simple case - will always be one byte in each block |
| int i = prevBlock._buf.length-1; |
| |
| int b0 = prevBlock._buf[i] & 0xFF; |
| int b1 = _buf[_readIndex++] & 0xFF; |
| return (b1 << 8) + (b0 << 0); |
| } |
| |
| /** |
| * Reads an <tt>int</tt> which was encoded in <em>little endian</em> format. |
| */ |
| public int readIntLE() { |
| int i = _readIndex; |
| |
| int b0 = _buf[i++] & 0xFF; |
| int b1 = _buf[i++] & 0xFF; |
| int b2 = _buf[i++] & 0xFF; |
| int b3 = _buf[i++] & 0xFF; |
| _readIndex = i; |
| return (b3 << 24) + (b2 << 16) + (b1 << 8) + (b0 << 0); |
| } |
| |
| /** |
| * Reads an <tt>int</tt> which spans the end of <tt>prevBlock</tt> and the start of this block. |
| */ |
| public int readIntLE(DataInputBlock prevBlock, int prevBlockAvailable) { |
| byte[] buf = new byte[4]; |
| |
| readSpanning(prevBlock, prevBlockAvailable, buf); |
| int b0 = buf[0] & 0xFF; |
| int b1 = buf[1] & 0xFF; |
| int b2 = buf[2] & 0xFF; |
| int b3 = buf[3] & 0xFF; |
| return (b3 << 24) + (b2 << 16) + (b1 << 8) + (b0 << 0); |
| } |
| |
| /** |
| * Reads a <tt>long</tt> which was encoded in <em>little endian</em> format. |
| */ |
| public long readLongLE() { |
| int i = _readIndex; |
| |
| int b0 = _buf[i++] & 0xFF; |
| int b1 = _buf[i++] & 0xFF; |
| int b2 = _buf[i++] & 0xFF; |
| int b3 = _buf[i++] & 0xFF; |
| int b4 = _buf[i++] & 0xFF; |
| int b5 = _buf[i++] & 0xFF; |
| int b6 = _buf[i++] & 0xFF; |
| int b7 = _buf[i++] & 0xFF; |
| _readIndex = i; |
| return (((long)b7 << 56) + |
| ((long)b6 << 48) + |
| ((long)b5 << 40) + |
| ((long)b4 << 32) + |
| ((long)b3 << 24) + |
| (b2 << 16) + |
| (b1 << 8) + |
| (b0 << 0)); |
| } |
| |
| /** |
| * Reads a <tt>long</tt> which spans the end of <tt>prevBlock</tt> and the start of this block. |
| */ |
| public long readLongLE(DataInputBlock prevBlock, int prevBlockAvailable) { |
| byte[] buf = new byte[8]; |
| |
| readSpanning(prevBlock, prevBlockAvailable, buf); |
| |
| int b0 = buf[0] & 0xFF; |
| int b1 = buf[1] & 0xFF; |
| int b2 = buf[2] & 0xFF; |
| int b3 = buf[3] & 0xFF; |
| int b4 = buf[4] & 0xFF; |
| int b5 = buf[5] & 0xFF; |
| int b6 = buf[6] & 0xFF; |
| int b7 = buf[7] & 0xFF; |
| return (((long)b7 << 56) + |
| ((long)b6 << 48) + |
| ((long)b5 << 40) + |
| ((long)b4 << 32) + |
| ((long)b3 << 24) + |
| (b2 << 16) + |
| (b1 << 8) + |
| (b0 << 0)); |
| } |
| |
| /** |
| * Reads a small amount of data from across the boundary between two blocks. |
| * The {@link #_readIndex} of this (the second) block is updated accordingly. |
| * Note- this method (and other code) assumes that the second {@link DataInputBlock} |
| * always is big enough to complete the read without being exhausted. |
| */ |
| private void readSpanning(DataInputBlock prevBlock, int prevBlockAvailable, byte[] buf) { |
| System.arraycopy(prevBlock._buf, prevBlock._readIndex, buf, 0, prevBlockAvailable); |
| int secondReadLen = buf.length-prevBlockAvailable; |
| System.arraycopy(_buf, 0, buf, prevBlockAvailable, secondReadLen); |
| _readIndex = secondReadLen; |
| } |
| |
| /** |
| * Reads <tt>len</tt> bytes from this block into the supplied buffer. |
| */ |
| public void readFully(byte[] buf, int off, int len) { |
| System.arraycopy(_buf, _readIndex, buf, off, len); |
| _readIndex += len; |
| } |
| } |