using System.IO;

namespace Lucene.Net.Support.IO
{
    /*
	 * 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.
	 */

    public static class FileStreamExtensions
    {
        private static object _fsReadLock = new object();

        //Reads bytes from the Filestream into the bytebuffer
        public static int Read(this FileStream file, ByteBuffer dst, long position)
        {
            lock (_fsReadLock)
            {
                // TODO: check this logic, could probably optimize
                if (position >= file.Length)
                    return 0;

                var original = file.Position;

                file.Seek(position, SeekOrigin.Begin);

                int count = 0;

                for (int i = dst.Position; i < dst.Limit; i++)
                {
                    int v = file.ReadByte();
                    if (v == -1)
                        break;
                    dst.Put((byte) v);
                    count++;
                }

                file.Seek(original, SeekOrigin.Begin);

                return count;
            }
        }
    }
}