/*
    * Copyright 2012 The Netty Project
    *
    * The Netty Project 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 io.netty.buffer;
  
  import io.netty.util.ReferenceCounted;
  
  import java.io.DataInput;
  import java.io.DataInputStream;
  import java.io.EOFException;
  import java.io.IOException;
  import java.io.InputStream;
  
  /**
   * An {@link InputStream} which reads data from a {@link ByteBuf}.
   * <p>
   * A read operation against this stream will occur at the {@code readerIndex}
   * of its underlying buffer and the {@code readerIndex} will increase during
   * the read operation.  Please note that it only reads up to the number of
   * readable bytes determined at the moment of construction.  Therefore,
   * updating {@link ByteBuf#writerIndex()} will not affect the return
   * value of {@link #available()}.
   * <p>
   * This stream implements {@link DataInput} for your convenience.
   * The endianness of the stream is not always big endian but depends on
   * the endianness of the underlying buffer.
   *
   * @see ByteBufOutputStream
   */
  public class ByteBufInputStream extends InputStream implements DataInput {
      private final ByteBuf buffer;
      private final int startIndex;
      private final int endIndex;
      private boolean closed;
      /**
       * To preserve backwards compatibility (which didn't transfer ownership) we support a conditional flag which
       * indicates if {@link #buffer} should be released when this {@link InputStream} is closed.
       * However in future releases ownership should always be transferred and callers of this class should call
       * {@link ReferenceCounted#retain()} if necessary.
       */
      private boolean releaseOnClose;
  
      /**
       * Creates a new stream which reads data from the specified {@code buffer}
       * starting at the current {@code readerIndex} and ending at the current
       * {@code writerIndex}.
       * @param buffer The buffer which provides the content for this {@link InputStream}.
       */
      public ByteBufInputStream(ByteBuf buffer) {
          this(buffer, buffer.readableBytes());
      }
  
      /**
       * Creates a new stream which reads data from the specified {@code buffer}
       * starting at the current {@code readerIndex} and ending at
       * {@code readerIndex + length}.
       * @param buffer The buffer which provides the content for this {@link InputStream}.
       * @param length The length of the buffer to use for this {@link InputStream}.
       * @throws IndexOutOfBoundsException
       *         if {@code readerIndex + length} is greater than
       *            {@code writerIndex}
       */
      public ByteBufInputStream(ByteBuf buffer, int length) {
          this(buffer, length, false);
      }
  
      /**
       * Creates a new stream which reads data from the specified {@code buffer}
       * starting at the current {@code readerIndex} and ending at the current
       * {@code writerIndex}.
       * @param buffer The buffer which provides the content for this {@link InputStream}.
       * @param releaseOnClose {@code true} means that when {@link #close()} is called then {@link ByteBuf#release()} will
       *                       be called on {@code buffer}.
       */
      public ByteBufInputStream(ByteBuf buffer, boolean releaseOnClose) {
          this(buffer, buffer.readableBytes(), releaseOnClose);
      }
  
      /**
       * Creates a new stream which reads data from the specified {@code buffer}
       * starting at the current {@code readerIndex} and ending at
       * {@code readerIndex + length}.
       * @param buffer The buffer which provides the content for this {@link InputStream}.
       * @param length The length of the buffer to use for this {@link InputStream}.
       * @param releaseOnClose {@code true} means that when {@link #close()} is called then {@link ByteBuf#release()} will
       *                       be called on {@code buffer}.
       * @throws IndexOutOfBoundsException
      *         if {@code readerIndex + length} is greater than
      *            {@code writerIndex}
      */
     public ByteBufInputStream(ByteBuf buffer, int length, boolean releaseOnClose) {
         if (buffer == null) {
             throw new NullPointerException("buffer");
         }
         if (length < 0) {
             if (releaseOnClose) {
                 buffer.release();
             }
             throw new IllegalArgumentException("length: " + length);
         }
         if (length > buffer.readableBytes()) {
             if (releaseOnClose) {
                 buffer.release();
             }
             throw new IndexOutOfBoundsException("Too many bytes to be read - Needs "
                     + length + ", maximum is " + buffer.readableBytes());
         }
 
         this.releaseOnClose = releaseOnClose;
         this.buffer = buffer;
         startIndex = buffer.readerIndex();
         endIndex = startIndex + length;
         buffer.markReaderIndex();
     }
 
     /**
      * Returns the number of read bytes by this stream so far.
      */
     public int readBytes() {
         return buffer.readerIndex() - startIndex;
     }
 
     @Override
     public void close() throws IOException {
         try {
             super.close();
         } finally {
             // The Closable interface says "If the stream is already closed then invoking this method has no effect."
             if (releaseOnClose && !closed) {
                 closed = true;
                 buffer.release();
             }
         }
     }
 
     @Override
     public int available() throws IOException {
         return endIndex - buffer.readerIndex();
     }
 
     @Override
     public void mark(int readlimit) {
         buffer.markReaderIndex();
     }
 
     @Override
     public boolean markSupported() {
         return true;
     }
 
     @Override
     public int read() throws IOException {
         if (!buffer.isReadable()) {
             return -1;
         }
         return buffer.readByte() & 0xff;
     }
 
     @Override
     public int read(byte[] b, int off, int len) throws IOException {
         int available = available();
         if (available == 0) {
             return -1;
         }
 
         len = Math.min(available, len);
         buffer.readBytes(b, off, len);
         return len;
     }
 
     @Override
     public void reset() throws IOException {
         buffer.resetReaderIndex();
     }
 
     @Override
     public long skip(long n) throws IOException {
         if (n > Integer.MAX_VALUE) {
             return skipBytes(Integer.MAX_VALUE);
         } else {
             return skipBytes((int) n);
         }
     }
 
     @Override
     public boolean readBoolean() throws IOException {
         checkAvailable(1);
         return read() != 0;
     }
 
     @Override
     public byte readByte() throws IOException {
         if (!buffer.isReadable()) {
             throw new EOFException();
         }
         return buffer.readByte();
     }
 
     @Override
     public char readChar() throws IOException {
         return (char) readShort();
     }
 
     @Override
     public double readDouble() throws IOException {
         return Double.longBitsToDouble(readLong());
     }
 
     @Override
     public float readFloat() throws IOException {
         return Float.intBitsToFloat(readInt());
     }
 
     @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 {
         checkAvailable(len);
         buffer.readBytes(b, off, len);
     }
 
     @Override
     public int readInt() throws IOException {
         checkAvailable(4);
         return buffer.readInt();
     }
 
     private final StringBuilder lineBuf = new StringBuilder();
 
     @Override
     public String readLine() throws IOException {
         lineBuf.setLength(0);
 
         loop: while (true) {
             if (!buffer.isReadable()) {
                 return lineBuf.length() > 0 ? lineBuf.toString() : null;
             }
 
             int c = buffer.readUnsignedByte();
             switch (c) {
                 case '\n':
                     break loop;
 
                 case '\r':
                     if (buffer.isReadable() && (char) buffer.getUnsignedByte(buffer.readerIndex()) == '\n') {
                         buffer.skipBytes(1);
                     }
                     break loop;
 
                 default:
                     lineBuf.append((char) c);
             }
         }
 
         return lineBuf.toString();
     }
 
     @Override
     public long readLong() throws IOException {
         checkAvailable(8);
         return buffer.readLong();
     }
 
     @Override
     public short readShort() throws IOException {
         checkAvailable(2);
         return buffer.readShort();
     }
 
     @Override
     public String readUTF() throws IOException {
         return DataInputStream.readUTF(this);
     }
 
     @Override
     public int readUnsignedByte() throws IOException {
         return readByte() & 0xff;
     }
 
     @Override
     public int readUnsignedShort() throws IOException {
         return readShort() & 0xffff;
     }
 
     @Override
     public int skipBytes(int n) throws IOException {
         int nBytes = Math.min(available(), n);
         buffer.skipBytes(nBytes);
         return nBytes;
     }
 
     private void checkAvailable(int fieldSize) throws IOException {
         if (fieldSize < 0) {
             throw new IndexOutOfBoundsException("fieldSize cannot be a negative number");
         }
         if (fieldSize > available()) {
             throw new EOFException("fieldSize is too long! Length is " + fieldSize
                     + ", but maximum is " + available());
         }
     }
 }