RAMOutputStream.cs

Go to the documentation of this file.

/* 
 * 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="IndexOutput" /> implementation.
    /// <para>For lucene internal use.</para>
    /// </summary>
    public class RAMOutputStream:IndexOutput
    {
        internal const int BUFFER_SIZE = 1024;
        
        private RAMFile file;
        
        private byte[] currentBuffer;
        private int currentBufferIndex;

        private bool isDisposed;

        private int bufferPosition;
        private long bufferStart;
        private int bufferLength;
        
        /// <summary>Construct an empty output buffer. </summary>
        public RAMOutputStream():this(new RAMFile())
        {
        }
        
        internal RAMOutputStream(RAMFile f)
        {
            file = f;
            
            // make sure that we switch to the
            // first needed buffer lazily
            currentBufferIndex = - 1;
            currentBuffer = null;
        }
        
        /// <summary>Copy the current contents of this buffer to the named output. </summary>
        public virtual void  WriteTo(IndexOutput out_Renamed)
        {
            Flush();
            long end = file.length;
            long pos = 0;
            int buffer = 0;
            while (pos < end)
            {
                int length = BUFFER_SIZE;
                long nextPos = pos + length;
                if (nextPos > end)
                {
                    // at the last buffer
                    length = (int) (end - pos);
                }
                out_Renamed.WriteBytes(file.GetBuffer(buffer++), length);
                pos = nextPos;
            }
        }
        
        /// <summary>Resets this to an empty buffer. </summary>
        public virtual void  Reset()
        {
            currentBuffer = null;
            currentBufferIndex = -1;
            bufferPosition = 0;
            bufferStart = 0;
            bufferLength = 0;
            
            file.Length = 0;
        }
        
        protected override void Dispose(bool disposing)
        {
            if (isDisposed) return;

            if (disposing)
            {
                Flush();
            }

            isDisposed = true;
        }
        
        public override void  Seek(long pos)
        {
            // set the file length in case we seek back
            // and flush() has not been called yet
            SetFileLength();
            if (pos < bufferStart || pos >= bufferStart + bufferLength)
            {
                currentBufferIndex = (int) (pos / BUFFER_SIZE);
                SwitchCurrentBuffer();
            }
            
            bufferPosition = (int) (pos % BUFFER_SIZE);
        }

        public override long Length
        {
            get { return file.length; }
        }

        public override void  WriteByte(byte b)
        {
            if (bufferPosition == bufferLength)
            {
                currentBufferIndex++;
                SwitchCurrentBuffer();
            }
            currentBuffer[bufferPosition++] = b;
        }
        
        public override void  WriteBytes(byte[] b, int offset, int len)
        {
            System.Diagnostics.Debug.Assert(b != null);
            while (len > 0)
            {
                if (bufferPosition == bufferLength)
                {
                    currentBufferIndex++;
                    SwitchCurrentBuffer();
                }
                
                int remainInBuffer = currentBuffer.Length - bufferPosition;
                int bytesToCopy = len < remainInBuffer?len:remainInBuffer;
                Array.Copy(b, offset, currentBuffer, bufferPosition, bytesToCopy);
                offset += bytesToCopy;
                len -= bytesToCopy;
                bufferPosition += bytesToCopy;
            }
        }
        
        private void  SwitchCurrentBuffer()
        {
            if (currentBufferIndex == file.NumBuffers())
            {
                currentBuffer = file.AddBuffer(BUFFER_SIZE);
            }
            else
            {
                currentBuffer = file.GetBuffer(currentBufferIndex);
            }
            bufferPosition = 0;
            bufferStart = (long) BUFFER_SIZE * (long) currentBufferIndex;
            bufferLength = currentBuffer.Length;
        }
        
        private void  SetFileLength()
        {
            long pointer = bufferStart + bufferPosition;
            if (pointer > file.length)
            {
                file.Length = pointer;
            }
        }
        
        public override void  Flush()
        {
            file.LastModified = (DateTime.UtcNow.Ticks / TimeSpan.TicksPerMillisecond);
            SetFileLength();
        }

        public override long FilePointer
        {
            get { return currentBufferIndex < 0 ? 0 : bufferStart + bufferPosition; }
        }

        /// <summary>Returns byte usage of all buffers. </summary>
        public virtual long SizeInBytes()
        {
            return file.NumBuffers() * BUFFER_SIZE;
        }
    }
}