/*

  * 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.giraph.utils.io;

 import org.apache.giraph.utils.ExtendedDataInput;

 import org.apache.giraph.utils.ExtendedDataOutput;

 import org.apache.giraph.utils.UnsafeByteArrayInputStream;

 import java.io.IOException;

 import java.util.ArrayList;

 import java.util.List;

 /**

  * Implementations of {@link ExtendedDataInput} are limited because they can

  * only handle up to 1GB of data. This {@link ExtendedDataInput} overcomes

  * that limitation, with almost no additional cost when data is not huge.

  *

  * Goes in pair with {@link BigDataOutput}

  */

 public class BigDataInput implements ExtendedDataInput {

   /** Empty data input */

   private static final ExtendedDataInput EMPTY_INPUT =

       new UnsafeByteArrayInputStream(new byte[0]);

   /** Input which we are currently reading from */

   private ExtendedDataInput currentInput;

   /** List of all data inputs which contain data */

   private final List<ExtendedDataInput> dataInputs;

   /** Which position within dataInputs are we currently reading from */

   private int currentPositionInInputs;

   /**

    * Constructor

    *

    * @param bigDataOutput {@link BigDataOutput} which we want to read data from

    */

   public BigDataInput(BigDataOutput bigDataOutput) {

     dataInputs = new ArrayList<ExtendedDataInput>(

         bigDataOutput.getNumberOfDataOutputs());

     for (ExtendedDataOutput dataOutput : bigDataOutput.getDataOutputs()) {

       dataInputs.add(bigDataOutput.getConf().createExtendedDataInput(

           dataOutput.getByteArray(), 0, dataOutput.getPos()));

     }

     currentPositionInInputs = -1;

     moveToNextDataInput();

   }

   /** Start reading the following data input */

   private void moveToNextDataInput() {

     currentPositionInInputs++;

     if (currentPositionInInputs < dataInputs.size()) {

       currentInput = dataInputs.get(currentPositionInInputs);

     } else {

       currentInput = EMPTY_INPUT;

     }

   }

   /**

    * Check if we read everything from the current data input, and move to the

    * next one if needed.

    */

   private void checkIfShouldMoveToNextDataInput() {

     if (currentInput.endOfInput()) {

       moveToNextDataInput();

     }

   }

   @Override

   public void readFully(byte[] b) throws IOException {

     readFully(b, 0, b.length);

   }

   @Override

   public void readFully(byte[] b, int off, int len) throws IOException {

     checkIfShouldMoveToNextDataInput();

     int available = currentInput.available();

     if (len <= available) {

       currentInput.readFully(b, off, len);

     } else {

       // When we are trying to read more bytes than there are in single chunk

       // we need to read part by part

       currentInput.readFully(b, off, available);

       readFully(b, off + available, len - available);

     }

   }

   @Override

   public boolean readBoolean() throws IOException {

     checkIfShouldMoveToNextDataInput();

     return currentInput.readBoolean();

   }

   @Override

   public byte readByte() throws IOException {

     checkIfShouldMoveToNextDataInput();

     return currentInput.readByte();

   }

   @Override

   public int readUnsignedByte() throws IOException {

     checkIfShouldMoveToNextDataInput();

     return currentInput.readUnsignedByte();

   }

   @Override

   public short readShort() throws IOException {

     checkIfShouldMoveToNextDataInput();

     return currentInput.readShort();

   }

   @Override

   public int readUnsignedShort() throws IOException {

     checkIfShouldMoveToNextDataInput();

     return currentInput.readUnsignedShort();

   }

   @Override

   public char readChar() throws IOException {

     checkIfShouldMoveToNextDataInput();

     return currentInput.readChar();

   }

   @Override

   public int readInt() throws IOException {

     checkIfShouldMoveToNextDataInput();

     return currentInput.readInt();

   }

   @Override

   public long readLong() throws IOException {

     checkIfShouldMoveToNextDataInput();

     return currentInput.readLong();

   }

   @Override

   public float readFloat() throws IOException {

     checkIfShouldMoveToNextDataInput();

     return currentInput.readFloat();

   }

   @Override

   public double readDouble() throws IOException {

     checkIfShouldMoveToNextDataInput();

     return currentInput.readDouble();

   }

   @Override

   public String readLine() throws IOException {

     checkIfShouldMoveToNextDataInput();

     return currentInput.readLine();

   }

   @Override

   public String readUTF() throws IOException {

     checkIfShouldMoveToNextDataInput();

     return currentInput.readUTF();

   }

   @Override

   public int skipBytes(int n) throws IOException {

     int bytesLeftToSkip = n;

     while (bytesLeftToSkip > 0) {

       int bytesSkipped = currentInput.skipBytes(bytesLeftToSkip);

       bytesLeftToSkip -= bytesSkipped;

       if (bytesLeftToSkip > 0) {

         moveToNextDataInput();

         if (endOfInput()) {

           break;

         }

       }

     }

     return n - bytesLeftToSkip;

   }

   @Override

   public int getPos() {

     int pos = 0;

     for (int i = 0; i <= currentPositionInInputs; i++) {

       pos += dataInputs.get(i).getPos();

     }

     return pos;

   }

   @Override

   public int available() {

     throw new UnsupportedOperationException("available: " +

         "Not supported with BigDataIO because overflow can happen");

   }

   @Override

   public boolean endOfInput() {

     return currentInput == EMPTY_INPUT ||

         (dataInputs.get(currentPositionInInputs).endOfInput() &&

             currentPositionInInputs == dataInputs.size() - 1);

   }

 }