#region Disclaimer / License
// Copyright (C) 2011, Kenneth Skovhede
// http://www.hexad.dk, opensource@hexad.dk
// 
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public
// License as published by the Free Software Foundation; either
// version 2.1 of the License, or (at your option) any later version.
// 
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
// Lesser General Public License for more details.
// 
// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
// 
#endregion
using System;
using System.Collections.Generic;
using System.Text;

namespace Duplicati.Library.SharpRSync
{
    public static class Utility
    {
        /// <summary>
        /// Size of buffers for copying stream
        /// </summary>
        public static long DEFAULT_BUFFER_SIZE = 64 * 1024;

        /// <summary>
        /// Some streams can return a number that is less than the requested number of bytes.
        /// This is usually due to fragmentation, and is solved by issuing a new read.
        /// This function wraps that functionality.
        /// </summary>
        /// <param name="stream">The stream to read</param>
        /// <param name="buf">The buffer to read into</param>
        /// <returns>The actual number of bytes read</returns>
        public static int ForceStreamRead(System.IO.Stream stream, byte[] buf)
        {
            return ForceStreamRead(stream, buf, 0, buf.Length);
        }

        /// <summary>
        /// Some streams can return a number that is less than the requested number of bytes.
        /// This is usually due to fragmentation, and is solved by issuing a new read.
        /// This function wraps that functionality.
        /// </summary>
        /// <param name="stream">The stream to read</param>
        /// <param name="buf">The buffer to read into</param>
        /// <param name="count">The amout of bytes to read</param>
        /// <returns>The actual number of bytes read</returns>
        public static int ForceStreamRead(System.IO.Stream stream, byte[] buf, int count)
        {
            return ForceStreamRead(stream, buf, 0, count);
        }

        /// <summary>
        /// Some streams can return a number that is less than the requested number of bytes.
        /// This is usually due to fragmentation, and is solved by issuing a new read.
        /// This function wraps that functionality.
        /// </summary>
        /// <param name="stream">The stream to read</param>
        /// <param name="buf">The buffer to read into</param>
        /// <param name="index">The index into which the writing starts</param>
        /// <param name="count">The amout of bytes to read</param>
        /// <returns>The actual number of bytes read</returns>
        public static int ForceStreamRead(System.IO.Stream stream, byte[] buf, int index, int count)
        {
            //Non fragmenting streams skip here
            if (stream is System.IO.FileStream || stream is System.IO.MemoryStream)
                return stream.Read(buf, index, count);

            int a;
            int read = 0;
            do
            {
                a = stream.Read(buf, index, count);
                index += a;
                read += a;
                count -= a;
            }
            while (a != 0 && count > 0);

            return read;
        }

        /// <summary>
        /// Copies a number of bytes from one stream into another.
        /// </summary>
        /// <param name="input">The stream to read from</param>
        /// <param name="output">The stream to write to</param>
        /// <param name="count">The number of bytes to copy</param>
        public static void StreamCopy(System.IO.Stream input, System.IO.Stream output, long count)
        {
            byte[] buf = new byte[DEFAULT_BUFFER_SIZE];
            while (count > 0)
            {
                int a = input.Read(buf, 0, (int)Math.Min(count, buf.Length));
                if (a <= 0)
                    throw new Exception(Strings.Utility.UnexpectedEndOfStreamError);
                output.Write(buf, 0, a);
                count -= a;
            }
        }
    }
}