/*
    * 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.commons.imaging.formats.tiff.itu_t4;
  
  import java.io.OutputStream;
  import java.util.Arrays;
  
  import org.apache.commons.imaging.common.Allocator;
  
  /**
   * Output stream writing to a byte array, and capable of writing 1 bit at a time, starting from the most significant bit.
   */
  final class BitArrayOutputStream extends OutputStream {
      private byte[] buffer;
      private int bytesWritten;
      private int cache;
      private int cacheMask = 0x80;
  
      BitArrayOutputStream() {
          buffer = new byte[16];
      }
  
      BitArrayOutputStream(final int size) {
          buffer = Allocator.byteArray(size);
      }
  
      @Override
      public void close() {
          flush();
      }
  
      @Override
      public void flush() {
          if (cacheMask != 0x80) {
              writeByte(cache);
              cache = 0;
              cacheMask = 0x80;
          }
      }
  
      public int getBitsAvailableInCurrentByte() {
          int count = 0;
          for (int mask = cacheMask; mask != 0; mask >>>= 1) {
              ++count;
          }
          return count;
      }
  
      public int size() {
          return bytesWritten;
      }
  
      public byte[] toByteArray() {
          flush();
          if (bytesWritten == buffer.length) {
              return buffer;
          }
          return Arrays.copyOf(buffer, bytesWritten);
      }
  
      @Override
      public void write(final int b) {
          flush();
          writeByte(b);
      }
  
      public void writeBit(final int bit) {
          if (bit != 0) {
              cache |= cacheMask;
          }
          cacheMask >>>= 1;
          if (cacheMask == 0) {
              flush();
          }
      }
  
      private void writeByte(final int b) {
          if (bytesWritten >= buffer.length) {
              final byte[] bigger = Allocator.byteArray(buffer.length * 2);
              System.arraycopy(buffer, 0, bigger, 0, bytesWritten);
              buffer = bigger;
          }
          buffer[bytesWritten++] = (byte) b;
      }
  }