content: /*
   * Copyright (C) 2016 The Android Open Source Project
   *
   * Licensed 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 com.android.apksig.internal.util;
  
  import com.android.apksig.util.DataSink;
  import com.android.apksig.util.DataSource;
  import java.io.IOException;
  import java.nio.ByteBuffer;
  
  /**
   * {@link DataSource} backed by a {@link ByteBuffer}.
   */
  public class ByteBufferDataSource implements DataSource {
  
      private final ByteBuffer mBuffer;
      private final int mSize;
  
      /**
       * Constructs a new {@code ByteBufferDigestSource} based on the data contained in the provided
       * buffer between the buffer's position and limit.
       */
      public ByteBufferDataSource(ByteBuffer buffer) {
          this(buffer, true);
      }
  
      /**
       * Constructs a new {@code ByteBufferDigestSource} based on the data contained in the provided
       * buffer between the buffer's position and limit.
       */
      private ByteBufferDataSource(ByteBuffer buffer, boolean sliceRequired) {
          mBuffer = (sliceRequired) ? buffer.slice() : buffer;
          mSize = buffer.remaining();
      }
  
      @Override
      public long size() {
          return mSize;
      }
  
      @Override
      public ByteBuffer getByteBuffer(long offset, int size) {
          checkChunkValid(offset, size);
  
          // checkChunkValid ensures that it's OK to cast offset to int.
          int chunkPosition = (int) offset;
          int chunkLimit = chunkPosition + size;
          // Creating a slice of ByteBuffer modifies the state of the source ByteBuffer (position
          // and limit fields, to be more specific). We thus use synchronization around these
          // state-changing operations to make instances of this class thread-safe.
          synchronized (mBuffer) {
              // ByteBuffer.limit(int) and .position(int) check that that the position >= limit
              // invariant is not broken. Thus, the only way to safely change position and limit
              // without caring about their current values is to first set position to 0 or set the
              // limit to capacity.
              mBuffer.position(0);
  
              mBuffer.limit(chunkLimit);
              mBuffer.position(chunkPosition);
              return mBuffer.slice();
          }
      }
  
      @Override
      public void copyTo(long offset, int size, ByteBuffer dest) {
          dest.put(getByteBuffer(offset, size));
      }
  
      @Override
      public void feed(long offset, long size, DataSink sink) throws IOException {
          if ((size < 0) || (size > mSize)) {
              throw new IndexOutOfBoundsException("size: " + size + ", source size: " + mSize);
          }
          sink.consume(getByteBuffer(offset, (int) size));
      }
  
      @Override
      public ByteBufferDataSource slice(long offset, long size) {
          if ((offset == 0) && (size == mSize)) {
              return this;
          }
          if ((size < 0) || (size > mSize)) {
              throw new IndexOutOfBoundsException("size: " + size + ", source size: " + mSize);
          }
          return new ByteBufferDataSource(
                  getByteBuffer(offset, (int) size),
                  false // no need to slice -- it's already a slice
                  );
      }
  
      private void checkChunkValid(long offset, long size) {
          if (offset < 0) {
              throw new IndexOutOfBoundsException("offset: " + offset);
          }
          if (size < 0) {
              throw new IndexOutOfBoundsException("size: " + size);
          }
          if (offset > mSize) {
              throw new IndexOutOfBoundsException(
                      "offset (" + offset + ") > source size (" + mSize + ")");
          }
          long endOffset = offset + size;
          if (endOffset < offset) {
              throw new IndexOutOfBoundsException(
                      "offset (" + offset + ") + size (" + size + ") overflow");
          }
          if (endOffset > mSize) {
              throw new IndexOutOfBoundsException(
                      "offset (" + offset + ") + size (" + size + ") > source size (" + mSize  +")");
          }
      }
  }
  