content: /*
   *
   * 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.bookkeeper.bookie.storage.directentrylogger;
  
  import static com.google.common.base.Preconditions.checkArgument;
  import static org.apache.bookkeeper.common.util.ExceptionMessageHelper.exMsg;
  
  import io.netty.buffer.ByteBuf;
  import io.netty.buffer.ByteBufAllocator;
  import io.netty.util.ReferenceCountUtil;
  import java.io.IOException;
  import java.nio.ByteBuffer;
  import java.nio.ByteOrder;
  import java.util.Arrays;
  import org.apache.bookkeeper.common.util.nativeio.NativeIO;
  
  /**
   * A utility buffer class to be used with native calls.
   * <p/>
   * Buffers are page aligned (4k pages).
   * <p/>
   * The wrapper mostly handles writes between ByteBuffers and
   * ByteBufs. It also provides a method for padding the buffer to the next
   * alignment, so writes can have an aligned size also (as required by
   * direct I/O). The padding is done with 0xF0, so that if it is read as
   * an integer, or long, the value will be negative (assuming the read is
   * a java read, and thus a signed int).
   */
  class Buffer {
      /* Padding byte must have MSB set, so if read at the start
       * of an integer or long, the returned value is negative. */
      public static final byte PADDING_BYTE = (byte) 0xF0;
  
      /* Some machines can live with 512 alignment, but others
       * appear to require 4096, so go with 4096, which is page
       * alignment */
      public static final int ALIGNMENT = 4096;
      private static final int MAX_ALIGNMENT = Integer.MAX_VALUE & ~(ALIGNMENT - 1);
      static final byte[] PADDING = generatePadding();
  
      final NativeIO nativeIO;
      final int bufferSize;
      ByteBuf buffer;
      ByteBuffer byteBuffer;
      ByteBufAllocator allocator;
      long pointer = 0;
  
      Buffer(NativeIO nativeIO, ByteBufAllocator allocator, int bufferSize) throws IOException {
          checkArgument(isAligned(bufferSize),
                        "Buffer size not aligned %d", bufferSize);
  
          this.allocator = allocator;
          this.buffer = allocateAligned(ALIGNMENT, bufferSize);
          this.nativeIO = nativeIO;
          this.bufferSize = bufferSize;
          byteBuffer = buffer.nioBuffer(0, bufferSize);
          byteBuffer.order(ByteOrder.BIG_ENDIAN);
      }
  
      private ByteBuf allocateAligned(int alignment, int bufferSize) {
          ByteBuf buf = allocator.directBuffer(bufferSize + alignment);
          long addr = buf.memoryAddress();
          if ((addr & (alignment - 1)) == 0) {
              // The address is already aligned
              pointer = addr;
              return buf.slice(0, bufferSize);
          } else {
              int alignOffset = (int) (alignment - (addr & (alignment - 1)));
              pointer = addr + alignOffset;
              return buf.slice(alignOffset, bufferSize);
          }
      }
  
      /**
       * @return whether there is space in the buffer for size bytes.
       */
      boolean hasSpace(int size) throws IOException {
          if (size > bufferSize) {
              throw new IOException(exMsg("Write too large").kv("writeSize", size)
                                    .kv("maxSize", bufferSize).toString());
          }
          return byteBuffer.remaining() >= size;
      }
  
      /**
       * @return whether the buffer can honour a read of size at offset.
       */
      boolean hasData(int offset, int size) {
          return offset + size <= bufferSize;
      }
  
      /**
       * Write an integer to buffer. Progresses the position of the buffer by 4 bytes.
       */
      void writeInt(int value) throws IOException {
          byteBuffer.putInt(value);
      }
  
      /**
       * Write a btebuf to this buffer. Progresses the position of the buffer by the
       * number of readable bytes of the bytebuf. Progresses the readerIndex of the passed
       * bytebuf by the number of bytes read (i.e. to the end).
       */
      void writeByteBuf(ByteBuf bytebuf) throws IOException {
          int bytesWritten = bytebuf.readableBytes();
          ByteBuffer bytesToPut = bytebuf.nioBuffer();
          byteBuffer.put(bytesToPut);
          bytebuf.skipBytes(bytesWritten);
      }
  
      /**
       * Read an integer from the buffer at the given offset. The offset is in bytes.
       */
      int readInt(int offset) throws IOException {
          if (!hasData(offset, Integer.BYTES)) {
              throw new IOException(exMsg("Buffer cannot satisfy int read")
                                    .kv("offset", offset)
                                    .kv("bufferSize", bufferSize).toString());
          }
          try {
              return byteBuffer.getInt(offset);
          } catch (Exception e) {
              throw new IOException(exMsg("Error reading int")
                                    .kv("byteBuffer", byteBuffer.toString())
                                    .kv("offset", offset)
                                    .kv("bufferSize", bufferSize).toString(), e);
          }
      }
  
      /**
       * Read a long from the buffer at the given offset. The offset is in bytes.
       */
      long readLong(int offset) throws IOException {
          if (!hasData(offset, Long.BYTES)) {
              throw new IOException(exMsg("Buffer cannot satisfy long read")
                                    .kv("offset", offset)
                                    .kv("bufferSize", bufferSize).toString());
          }
          try {
              return byteBuffer.getLong(offset);
          } catch (Exception e) {
              throw new IOException(exMsg("Error reading long")
                                    .kv("byteBuffer", byteBuffer.toString())
                                    .kv("offset", offset)
                                    .kv("bufferSize", bufferSize).toString(), e);
          }
      }
  
      /**
       * Read a bytebuf of size from the buffer at the given offset.
       * If there are not enough bytes in the buffer to satisfy the read, some of the bytes are read
       * into the byte buffer and the number of bytes read is returned.
       */
      int readByteBuf(ByteBuf buffer, int offset, int size) throws IOException {
          int originalLimit = byteBuffer.limit();
          byteBuffer.position(offset);
          int bytesToRead = Math.min(size, byteBuffer.capacity() - offset);
          byteBuffer.limit(offset + bytesToRead);
          try {
              buffer.writeBytes(byteBuffer);
          } catch (Exception e) {
              throw new IOException(exMsg("Error reading buffer")
                                    .kv("byteBuffer", byteBuffer.toString())
                                    .kv("offset", offset).kv("size", size)
                                    .kv("bufferSize", bufferSize).toString(), e);
          } finally {
              byteBuffer.limit(originalLimit);
          }
          return bytesToRead;
      }
  
      /**
       * The data pointer object for the native buffer. This can be used
       * by JNI method which take a char* or void*.
       */
      long pointer() {
          return pointer;
      }
  
      long pointer(long offset, long expectedWrite) {
          if (offset == 0) {
              return pointer;
          } else {
              if (offset + expectedWrite > byteBuffer.capacity()) {
                  throw new IllegalArgumentException(
                          exMsg("Buffer overflow").kv("offset", offset).kv("expectedWrite", expectedWrite)
                          .kv("capacity", byteBuffer.capacity()).toString());
              }
  
              return pointer + offset;
          }
      }
      /**
       * @return the number of bytes which have been written to this buffer.
       */
      int position() {
          return byteBuffer.position();
      }
  
      /**
       * @return the size of the buffer (i.e. the max number of bytes writable, or the max offset readable)
       */
      int size() {
          return bufferSize;
      }
  
      /**
       * Pad the buffer to the next alignment position.
       * @return the position of the next alignment. This should be used as the size argument to make aligned writes.
       */
      int padToAlignment() {
          int bufferPos = byteBuffer.position();
          int nextAlignment = nextAlignment(bufferPos);
          byteBuffer.put(PADDING, 0, nextAlignment - bufferPos);
          return nextAlignment;
      }
  
      /**
       * Clear the bytes written. This doesn't actually destroy the data, but moves the position back to the start of
       * the buffer.
       */
      void reset() {
          byteBuffer.clear();
      }
  
      /**
       * Free the memory that backs this buffer.
       */
      void free() {
          ReferenceCountUtil.release(buffer);
          buffer = null;
          byteBuffer = null;
      }
      private static byte[] generatePadding() {
          byte[] padding = new byte[ALIGNMENT];
          Arrays.fill(padding, (byte) PADDING_BYTE);
          return padding;
      }
  
      static boolean isAligned(long size) {
          return size >= 0 && ((ALIGNMENT - 1) & size) == 0;
      }
  
      static int nextAlignment(int pos) {
          checkArgument(pos <= MAX_ALIGNMENT,
                        "position (0x%x) must be lower or equal to max alignment (0x%x)",
                         pos, MAX_ALIGNMENT);
          checkArgument(pos >= 0, "position (0x%x) must be positive", pos);
          return (pos + (ALIGNMENT - 1)) & ~(ALIGNMENT - 1);
      }
  }
  