/* ====================================================================
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Licensed to the Apache Software Foundation (ASF) under one or more
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contributor license agreements. See the NOTICE file distributed with
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this work for Additional information regarding copyright ownership.
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The ASF licenses this file to You under the Apache License, Version 2.0
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(the "License"); you may not use this file except in compliance with
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the License. You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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==================================================================== */
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using System;
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namespace HH.WMS.Utils.NPOI.POIFS.Storage
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{
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/**
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* Wraps a <c>byte</c> array and provides simple data input access.
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* Internally, this class maintains a buffer read index, so that for the most part, primitive
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* data can be read in a data-input-stream-like manner.<p/>
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*
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* Note - the calling class should call the {@link #available()} method to detect end-of-buffer
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* and Move to the next data block when the current is exhausted.
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* For optimisation reasons, no error handling is performed in this class. Thus, mistakes in
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* calling code ran may raise ugly exceptions here, like {@link ArrayIndexOutOfBoundsException},
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* etc .<p/>
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*
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* The multi-byte primitive input methods ({@link #readUshortLE()}, {@link #readIntLE()} and
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* {@link #readLongLE()}) have corresponding 'spanning Read' methods which (when required) perform
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* a read across the block boundary. These spanning read methods take the previous
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* {@link DataInputBlock} as a parameter.
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* Reads of larger amounts of data (into <c>byte</c> array buffers) must be managed by the caller
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* since these could conceivably involve more than two blocks.
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*
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* @author Josh Micich
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*/
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public class DataInputBlock
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{
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/**
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* Possibly any size (usually 512K or 64K). Assumed to be at least 8 bytes for all blocks
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* before the end of the stream. The last block in the stream can be any size except zero.
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*/
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private byte[] _buf;
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private int _readIndex;
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private int _maxIndex;
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internal DataInputBlock(byte[] data, int startOffset)
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{
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_buf = data;
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_readIndex = startOffset;
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_maxIndex = _buf.Length;
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}
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public int Available()
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{
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return _maxIndex - _readIndex;
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}
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public int ReadUByte()
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{
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return _buf[_readIndex++] & 0xFF;
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}
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/**
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* Reads a <c>short</c> which was encoded in <em>little endian</em> format.
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*/
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public int ReadUshortLE()
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{
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int i = _readIndex;
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int b0 = _buf[i++] & 0xFF;
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int b1 = _buf[i++] & 0xFF;
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_readIndex = i;
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return (b1 << 8) + (b0 << 0);
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}
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/**
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* Reads a <c>short</c> which spans the end of <c>prevBlock</c> and the start of this block.
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*/
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public int ReadUshortLE(DataInputBlock prevBlock)
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{
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// simple case - will always be one byte in each block
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int i = prevBlock._buf.Length - 1;
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int b0 = prevBlock._buf[i++] & 0xFF;
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int b1 = _buf[_readIndex++] & 0xFF;
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return (b1 << 8) + (b0 << 0);
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}
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/**
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* Reads an <c>int</c> which was encoded in <em>little endian</em> format.
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*/
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public int ReadIntLE()
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{
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int i = _readIndex;
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int b0 = _buf[i++] & 0xFF;
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int b1 = _buf[i++] & 0xFF;
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int b2 = _buf[i++] & 0xFF;
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int b3 = _buf[i++] & 0xFF;
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_readIndex = i;
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return (b3 << 24) + (b2 << 16) + (b1 << 8) + (b0 << 0);
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}
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/**
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* Reads an <c>int</c> which spans the end of <c>prevBlock</c> and the start of this block.
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*/
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public int ReadIntLE(DataInputBlock prevBlock, int prevBlockAvailable)
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{
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byte[] buf = new byte[4];
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ReadSpanning(prevBlock, prevBlockAvailable, buf);
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int b0 = buf[0] & 0xFF;
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int b1 = buf[1] & 0xFF;
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int b2 = buf[2] & 0xFF;
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int b3 = buf[3] & 0xFF;
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return (b3 << 24) + (b2 << 16) + (b1 << 8) + (b0 << 0);
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}
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/**
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* Reads a <c>long</c> which was encoded in <em>little endian</em> format.
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*/
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public long ReadLongLE()
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{
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int i = _readIndex;
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int b0 = _buf[i++] & 0xFF;
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int b1 = _buf[i++] & 0xFF;
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int b2 = _buf[i++] & 0xFF;
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int b3 = _buf[i++] & 0xFF;
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int b4 = _buf[i++] & 0xFF;
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int b5 = _buf[i++] & 0xFF;
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int b6 = _buf[i++] & 0xFF;
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int b7 = _buf[i++] & 0xFF;
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_readIndex = i;
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return (((long)b7 << 56) +
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((long)b6 << 48) +
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((long)b5 << 40) +
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((long)b4 << 32) +
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((long)b3 << 24) +
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(b2 << 16) +
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(b1 << 8) +
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(b0 << 0));
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}
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/**
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* Reads a <c>long</c> which spans the end of <c>prevBlock</c> and the start of this block.
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*/
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public long ReadLongLE(DataInputBlock prevBlock, int prevBlockAvailable)
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{
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byte[] buf = new byte[8];
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ReadSpanning(prevBlock, prevBlockAvailable, buf);
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int b0 = buf[0] & 0xFF;
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int b1 = buf[1] & 0xFF;
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int b2 = buf[2] & 0xFF;
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int b3 = buf[3] & 0xFF;
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int b4 = buf[4] & 0xFF;
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int b5 = buf[5] & 0xFF;
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int b6 = buf[6] & 0xFF;
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int b7 = buf[7] & 0xFF;
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return (((long)b7 << 56) +
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((long)b6 << 48) +
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((long)b5 << 40) +
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((long)b4 << 32) +
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((long)b3 << 24) +
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(b2 << 16) +
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(b1 << 8) +
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(b0 << 0));
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}
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/**
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* Reads a small amount of data from across the boundary between two blocks.
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* The {@link #_readIndex} of this (the second) block is updated accordingly.
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* Note- this method (and other code) assumes that the second {@link DataInputBlock}
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* always is big enough to complete the read without being exhausted.
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*/
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private void ReadSpanning(DataInputBlock prevBlock, int prevBlockAvailable, byte[] buf)
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{
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Array.Copy(prevBlock._buf, prevBlock._readIndex, buf, 0, prevBlockAvailable);
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int secondReadLen = buf.Length - prevBlockAvailable;
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Array.Copy(_buf, 0, buf, prevBlockAvailable, secondReadLen);
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_readIndex = secondReadLen;
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}
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/**
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* Reads <c>len</c> bytes from this block into the supplied buffer.
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*/
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public void ReadFully(byte[] buf, int off, int len)
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{
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Array.Copy(_buf, _readIndex, buf, off, len);
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_readIndex += len;
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}
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}
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}
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