NativeStream.cs

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// Copyright (c) 2014 Silicon Studio Corp. (http://siliconstudio.co.jp)
// This file is distributed under GPL v3. See LICENSE.md for details.
using System;
using System.IO;

namespace SiliconStudio.Core.IO
{
    /// <summary>
    /// A <see cref="Stream"/> with additional methods for native read and write operations using <see cref="IntPtr"/>.
    /// </summary>
    public abstract class NativeStream : Stream
    {
        // Helper buffer for classes needing it.
        // If null, it should be initialized with NativeStreamBufferSize constant.
        protected byte[] nativeStreamBuffer;
        protected const int NativeStreamBufferSize = 1024;

        public virtual unsafe ushort ReadUInt16()
        {
            var temporaryBuffer = nativeStreamBuffer;
            if (temporaryBuffer == null)
                temporaryBuffer = nativeStreamBuffer = new byte[NativeStreamBufferSize];

            int currentReadSize = Read(temporaryBuffer, 0, sizeof(ushort));
            if (currentReadSize != sizeof(ushort))
                throw new InvalidOperationException("Reached end of stream.");

            fixed (byte* temporaryBufferStart = temporaryBuffer)
            {
                return *((ushort*)temporaryBufferStart);
            }
        }

        public virtual unsafe uint ReadUInt32()
        {
            var temporaryBuffer = nativeStreamBuffer;
            if (temporaryBuffer == null)
                temporaryBuffer = nativeStreamBuffer = new byte[NativeStreamBufferSize];

            int currentReadSize = Read(temporaryBuffer, 0, sizeof(uint));
            if (currentReadSize != sizeof(uint))
                throw new InvalidOperationException("Reached end of stream.");

            fixed (byte* temporaryBufferStart = temporaryBuffer)
            {
                return *((uint*)temporaryBufferStart);
            }
        }
        
        public virtual unsafe ulong ReadUInt64()
        {
            var temporaryBuffer = nativeStreamBuffer;
            if (temporaryBuffer == null)
                temporaryBuffer = nativeStreamBuffer = new byte[NativeStreamBufferSize];

            int currentReadSize = Read(temporaryBuffer, 0, sizeof(ulong));
            if (currentReadSize != sizeof(ulong))
                throw new InvalidOperationException("Reached end of stream.");

            fixed (byte* temporaryBufferStart = temporaryBuffer)
            {
                return *((ulong*)temporaryBufferStart);
            }
        }

        public virtual unsafe void Write(ushort i)
        {
            var temporaryBuffer = nativeStreamBuffer;
            if (temporaryBuffer == null)
                temporaryBuffer = nativeStreamBuffer = new byte[NativeStreamBufferSize];

            fixed (byte* temporaryBufferStart = temporaryBuffer)
                *((ushort*)temporaryBufferStart) = i;

            Write(temporaryBuffer, 0, sizeof(ushort));
        }
        
        public virtual unsafe void Write(uint i)
        {
            var temporaryBuffer = nativeStreamBuffer;
            if (temporaryBuffer == null)
                temporaryBuffer = nativeStreamBuffer = new byte[NativeStreamBufferSize];

            fixed (byte* temporaryBufferStart = temporaryBuffer)
                *((uint*)temporaryBufferStart) = i;

            Write(temporaryBuffer, 0, sizeof(uint));
        }

        public virtual unsafe void Write(ulong i)
        {
            var temporaryBuffer = nativeStreamBuffer;
            if (temporaryBuffer == null)
                temporaryBuffer = nativeStreamBuffer = new byte[NativeStreamBufferSize];

            fixed (byte* temporaryBufferStart = temporaryBuffer)
                *((ulong*)temporaryBufferStart) = i;

            Write(temporaryBuffer, 0, sizeof(ulong));
        }

        /// <summary>
        /// Reads a block of bytes from the stream and writes the data in a given buffer.
        /// </summary>
        /// <param name="buffer">When this method returns, contains the specified buffer with the values between 0 and (count - 1) replaced by the bytes read from the current source. </param>
        /// <param name="count">The maximum number of bytes to read. </param>
        /// <exception cref="ArgumentNullException">array is null. </exception>
        /// <returns>The total number of bytes read into the buffer. This might be less than the number of bytes requested if that number of bytes are not currently available, or zero if the end of the stream is reached.</returns>
        public virtual int Read(IntPtr buffer, int count)
        {
            var temporaryBuffer = nativeStreamBuffer;
            if (temporaryBuffer == null)
                temporaryBuffer = nativeStreamBuffer = new byte[NativeStreamBufferSize];

            int readSize = 0;

            for (int offset = 0; offset < count; offset += NativeStreamBufferSize, buffer += NativeStreamBufferSize)
            {
                // Compute missing bytes in this block
                int blockSize = count - offset;
                if (blockSize > NativeStreamBufferSize)
                    blockSize = NativeStreamBufferSize;


                int currentReadSize = Read(temporaryBuffer, 0, blockSize);
                readSize += currentReadSize;
                Utilities.Write(buffer, temporaryBuffer, 0, currentReadSize);

                // Reached end of stream?
                if (currentReadSize < blockSize)
                    break;
            }

            return readSize;
        }

        /// <summary>
        /// Writes a block of bytes to this stream using data from a buffer.
        /// </summary>
        /// <param name="buffer">The buffer containing data to write to the stream.</param>
        /// <param name="count">The number of bytes to be written to the current stream. </param>
        public unsafe virtual void Write(IntPtr buffer, int count)
        {
            var temporaryBuffer = nativeStreamBuffer;
            if (temporaryBuffer == null)
                temporaryBuffer = nativeStreamBuffer = new byte[NativeStreamBufferSize];

            for (int offset = 0; offset < count; offset += NativeStreamBufferSize, buffer += NativeStreamBufferSize)
            {
                // Compute missing bytes in this block
                int blockSize = count - offset;
                if (blockSize > NativeStreamBufferSize)
                    blockSize = NativeStreamBufferSize;

                fixed (byte* temporaryBufferStart = temporaryBuffer)
                    Utilities.CopyMemory((IntPtr)temporaryBufferStart, buffer, blockSize);

                Write(temporaryBuffer, 0, blockSize);
            }
        }
    }
}