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/*
* 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.
*/
using System;
namespace Lucene.Net.Store
{
/// <summary> A memory-resident <see cref="IndexInput" /> implementation.
///
/// </summary>
public class RAMInputStream : IndexInput
{
internal static readonly int BUFFER_SIZE;
private RAMFile file;
private long length;
private byte[] currentBuffer;
private int currentBufferIndex;
private int bufferPosition;
private long bufferStart;
private int bufferLength;
public /*internal*/ RAMInputStream(RAMFile f)
{
file = f;
length = file.length;
if (length / BUFFER_SIZE >= System.Int32.MaxValue)
{
throw new System.IO.IOException("Too large RAMFile! " + length);
}
// make sure that we switch to the
// first needed buffer lazily
currentBufferIndex = - 1;
currentBuffer = null;
}
protected override void Dispose(bool disposing)
{
// do nothing
}
public override long Length()
{
return length;
}
public override byte ReadByte()
{
if (bufferPosition >= bufferLength)
{
currentBufferIndex++;
SwitchCurrentBuffer(true);
}
return currentBuffer[bufferPosition++];
}
public override void ReadBytes(byte[] b, int offset, int len)
{
while (len > 0)
{
if (bufferPosition >= bufferLength)
{
currentBufferIndex++;
SwitchCurrentBuffer(true);
}
int remainInBuffer = bufferLength - bufferPosition;
int bytesToCopy = len < remainInBuffer?len:remainInBuffer;
Array.Copy(currentBuffer, bufferPosition, b, offset, bytesToCopy);
offset += bytesToCopy;
len -= bytesToCopy;
bufferPosition += bytesToCopy;
}
}
private void SwitchCurrentBuffer(bool enforceEOF)
{
if (currentBufferIndex >= file.NumBuffers())
{
// end of file reached, no more buffers left
if (enforceEOF)
throw new System.IO.IOException("Read past EOF");
else
{
// Force EOF if a read takes place at this position
currentBufferIndex--;
bufferPosition = BUFFER_SIZE;
}
}
else
{
currentBuffer = file.GetBuffer(currentBufferIndex);
bufferPosition = 0;
bufferStart = (long) BUFFER_SIZE * (long) currentBufferIndex;
long buflen = length - bufferStart;
bufferLength = buflen > BUFFER_SIZE?BUFFER_SIZE:(int) buflen;
}
}
public override long FilePointer
{
get { return currentBufferIndex < 0 ? 0 : bufferStart + bufferPosition; }
}
public override void Seek(long pos)
{
if (currentBuffer == null || pos < bufferStart || pos >= bufferStart + BUFFER_SIZE)
{
currentBufferIndex = (int) (pos / BUFFER_SIZE);
SwitchCurrentBuffer(false);
}
bufferPosition = (int) (pos % BUFFER_SIZE);
}
static RAMInputStream()
{
BUFFER_SIZE = RAMOutputStream.BUFFER_SIZE;
}
}
}
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