458 lines
14 KiB
C#
458 lines
14 KiB
C#
/*
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* Copyright 2014 Google Inc. All rights reserved.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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// There are 2 #defines that have an impact on performance of this ByteBuffer implementation
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//
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// UNSAFE_BYTEBUFFER
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// This will use unsafe code to manipulate the underlying byte array. This
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// can yield a reasonable performance increase.
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//
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// BYTEBUFFER_NO_BOUNDS_CHECK
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// This will disable the bounds check asserts to the byte array. This can
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// yield a small performance gain in normal code..
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//
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// Using UNSAFE_BYTEBUFFER and BYTEBUFFER_NO_BOUNDS_CHECK together can yield a
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// performance gain of ~15% for some operations, however doing so is potentially
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// dangerous. Do so at your own risk!
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//
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using System;
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namespace FlatBuffers
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{
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/// <summary>
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/// Class to mimic Java's ByteBuffer which is used heavily in Flatbuffers.
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/// </summary>
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public class ByteBuffer
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{
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private readonly byte[] _buffer;
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private int _pos; // Must track start of the buffer.
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public int Length { get { return _buffer.Length; } }
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public byte[] Data { get { return _buffer; } }
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public ByteBuffer(byte[] buffer) : this(buffer, 0) { }
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public ByteBuffer(byte[] buffer, int pos)
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{
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_buffer = buffer;
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_pos = pos;
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}
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public int Position {
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get { return _pos; }
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set { _pos = value; }
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}
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public void Reset()
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{
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_pos = 0;
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}
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// Pre-allocated helper arrays for convertion.
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private float[] floathelper = new[] { 0.0f };
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private int[] inthelper = new[] { 0 };
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private double[] doublehelper = new[] { 0.0 };
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private ulong[] ulonghelper = new[] { 0UL };
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// Helper functions for the unsafe version.
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static public ushort ReverseBytes(ushort input)
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{
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return (ushort)(((input & 0x00FFU) << 8) |
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((input & 0xFF00U) >> 8));
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}
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static public uint ReverseBytes(uint input)
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{
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return ((input & 0x000000FFU) << 24) |
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((input & 0x0000FF00U) << 8) |
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((input & 0x00FF0000U) >> 8) |
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((input & 0xFF000000U) >> 24);
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}
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static public ulong ReverseBytes(ulong input)
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{
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return (((input & 0x00000000000000FFUL) << 56) |
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((input & 0x000000000000FF00UL) << 40) |
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((input & 0x0000000000FF0000UL) << 24) |
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((input & 0x00000000FF000000UL) << 8) |
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((input & 0x000000FF00000000UL) >> 8) |
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((input & 0x0000FF0000000000UL) >> 24) |
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((input & 0x00FF000000000000UL) >> 40) |
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((input & 0xFF00000000000000UL) >> 56));
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}
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#if !UNSAFE_BYTEBUFFER
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// Helper functions for the safe (but slower) version.
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protected void WriteLittleEndian(int offset, int count, ulong data)
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{
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if (BitConverter.IsLittleEndian)
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{
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for (int i = 0; i < count; i++)
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{
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_buffer[offset + i] = (byte)(data >> i * 8);
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}
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}
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else
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{
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for (int i = 0; i < count; i++)
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{
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_buffer[offset + count - 1 - i] = (byte)(data >> i * 8);
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}
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}
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}
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protected ulong ReadLittleEndian(int offset, int count)
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{
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AssertOffsetAndLength(offset, count);
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ulong r = 0;
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if (BitConverter.IsLittleEndian)
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{
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for (int i = 0; i < count; i++)
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{
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r |= (ulong)_buffer[offset + i] << i * 8;
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}
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}
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else
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{
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for (int i = 0; i < count; i++)
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{
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r |= (ulong)_buffer[offset + count - 1 - i] << i * 8;
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}
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}
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return r;
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}
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#endif // !UNSAFE_BYTEBUFFER
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private void AssertOffsetAndLength(int offset, int length)
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{
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#if !BYTEBUFFER_NO_BOUNDS_CHECK
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if (offset < 0 ||
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offset > _buffer.Length - length)
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throw new ArgumentOutOfRangeException();
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#endif
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}
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public void PutSbyte(int offset, sbyte value)
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{
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AssertOffsetAndLength(offset, sizeof(sbyte));
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_buffer[offset] = (byte)value;
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}
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public void PutByte(int offset, byte value)
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{
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AssertOffsetAndLength(offset, sizeof(byte));
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_buffer[offset] = value;
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}
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public void PutByte(int offset, byte value, int count)
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{
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AssertOffsetAndLength(offset, sizeof(byte) * count);
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for (var i = 0; i < count; ++i)
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_buffer[offset + i] = value;
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}
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// this method exists in order to conform with Java ByteBuffer standards
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public void Put(int offset, byte value)
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{
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PutByte(offset, value);
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}
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#if UNSAFE_BYTEBUFFER
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// Unsafe but more efficient versions of Put*.
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public void PutShort(int offset, short value)
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{
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PutUshort(offset, (ushort)value);
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}
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public unsafe void PutUshort(int offset, ushort value)
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{
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AssertOffsetAndLength(offset, sizeof(ushort));
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fixed (byte* ptr = _buffer)
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{
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*(ushort*)(ptr + offset) = BitConverter.IsLittleEndian
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? value
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: ReverseBytes(value);
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}
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}
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public void PutInt(int offset, int value)
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{
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PutUint(offset, (uint)value);
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}
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public unsafe void PutUint(int offset, uint value)
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{
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AssertOffsetAndLength(offset, sizeof(uint));
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fixed (byte* ptr = _buffer)
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{
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*(uint*)(ptr + offset) = BitConverter.IsLittleEndian
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? value
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: ReverseBytes(value);
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}
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}
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public unsafe void PutLong(int offset, long value)
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{
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PutUlong(offset, (ulong)value);
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}
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public unsafe void PutUlong(int offset, ulong value)
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{
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AssertOffsetAndLength(offset, sizeof(ulong));
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fixed (byte* ptr = _buffer)
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{
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*(ulong*)(ptr + offset) = BitConverter.IsLittleEndian
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? value
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: ReverseBytes(value);
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}
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}
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public unsafe void PutFloat(int offset, float value)
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{
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AssertOffsetAndLength(offset, sizeof(float));
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fixed (byte* ptr = _buffer)
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{
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if (BitConverter.IsLittleEndian)
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{
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*(float*)(ptr + offset) = value;
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}
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else
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{
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*(uint*)(ptr + offset) = ReverseBytes(*(uint*)(&value));
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}
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}
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}
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public unsafe void PutDouble(int offset, double value)
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{
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AssertOffsetAndLength(offset, sizeof(double));
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fixed (byte* ptr = _buffer)
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{
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if (BitConverter.IsLittleEndian)
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{
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*(double*)(ptr + offset) = value;
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}
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else
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{
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*(ulong*)(ptr + offset) = ReverseBytes(*(ulong*)(ptr + offset));
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}
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}
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}
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#else // !UNSAFE_BYTEBUFFER
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// Slower versions of Put* for when unsafe code is not allowed.
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public void PutShort(int offset, short value)
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{
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AssertOffsetAndLength(offset, sizeof(short));
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WriteLittleEndian(offset, sizeof(short), (ulong)value);
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}
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public void PutUshort(int offset, ushort value)
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{
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AssertOffsetAndLength(offset, sizeof(ushort));
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WriteLittleEndian(offset, sizeof(ushort), (ulong)value);
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}
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public void PutInt(int offset, int value)
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{
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AssertOffsetAndLength(offset, sizeof(int));
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WriteLittleEndian(offset, sizeof(int), (ulong)value);
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}
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public void PutUint(int offset, uint value)
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{
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AssertOffsetAndLength(offset, sizeof(uint));
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WriteLittleEndian(offset, sizeof(uint), (ulong)value);
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}
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public void PutLong(int offset, long value)
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{
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AssertOffsetAndLength(offset, sizeof(long));
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WriteLittleEndian(offset, sizeof(long), (ulong)value);
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}
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public void PutUlong(int offset, ulong value)
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{
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AssertOffsetAndLength(offset, sizeof(ulong));
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WriteLittleEndian(offset, sizeof(ulong), value);
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}
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public void PutFloat(int offset, float value)
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{
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AssertOffsetAndLength(offset, sizeof(float));
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floathelper[0] = value;
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Buffer.BlockCopy(floathelper, 0, inthelper, 0, sizeof(float));
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WriteLittleEndian(offset, sizeof(float), (ulong)inthelper[0]);
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}
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public void PutDouble(int offset, double value)
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{
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AssertOffsetAndLength(offset, sizeof(double));
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doublehelper[0] = value;
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Buffer.BlockCopy(doublehelper, 0, ulonghelper, 0, sizeof(double));
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WriteLittleEndian(offset, sizeof(double), ulonghelper[0]);
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}
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#endif // UNSAFE_BYTEBUFFER
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public sbyte GetSbyte(int index)
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{
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AssertOffsetAndLength(index, sizeof(sbyte));
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return (sbyte)_buffer[index];
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}
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public byte Get(int index)
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{
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AssertOffsetAndLength(index, sizeof(byte));
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return _buffer[index];
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}
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#if UNSAFE_BYTEBUFFER
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// Unsafe but more efficient versions of Get*.
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public short GetShort(int offset)
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{
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return (short)GetUshort(offset);
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}
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public unsafe ushort GetUshort(int offset)
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{
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AssertOffsetAndLength(offset, sizeof(ushort));
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fixed (byte* ptr = _buffer)
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{
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return BitConverter.IsLittleEndian
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? *(ushort*)(ptr + offset)
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: ReverseBytes(*(ushort*)(ptr + offset));
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}
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}
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public int GetInt(int offset)
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{
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return (int)GetUint(offset);
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}
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public unsafe uint GetUint(int offset)
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{
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AssertOffsetAndLength(offset, sizeof(uint));
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fixed (byte* ptr = _buffer)
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{
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return BitConverter.IsLittleEndian
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? *(uint*)(ptr + offset)
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: ReverseBytes(*(uint*)(ptr + offset));
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}
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}
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public long GetLong(int offset)
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{
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return (long)GetUlong(offset);
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}
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public unsafe ulong GetUlong(int offset)
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{
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AssertOffsetAndLength(offset, sizeof(ulong));
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fixed (byte* ptr = _buffer)
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{
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return BitConverter.IsLittleEndian
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? *(ulong*)(ptr + offset)
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: ReverseBytes(*(ulong*)(ptr + offset));
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}
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}
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public unsafe float GetFloat(int offset)
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{
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AssertOffsetAndLength(offset, sizeof(float));
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fixed (byte* ptr = _buffer)
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{
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if (BitConverter.IsLittleEndian)
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{
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return *(float*)(ptr + offset);
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}
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else
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{
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uint uvalue = ReverseBytes(*(uint*)(ptr + offset));
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return *(float*)(&uvalue);
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}
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}
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}
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public unsafe double GetDouble(int offset)
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{
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AssertOffsetAndLength(offset, sizeof(double));
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fixed (byte* ptr = _buffer)
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{
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if (BitConverter.IsLittleEndian)
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{
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return *(double*)(ptr + offset);
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}
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else
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{
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ulong uvalue = ReverseBytes(*(ulong*)(ptr + offset));
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return *(double*)(&uvalue);
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}
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}
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}
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#else // !UNSAFE_BYTEBUFFER
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// Slower versions of Get* for when unsafe code is not allowed.
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public short GetShort(int index)
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{
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return (short)ReadLittleEndian(index, sizeof(short));
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}
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public ushort GetUshort(int index)
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{
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return (ushort)ReadLittleEndian(index, sizeof(ushort));
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}
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public int GetInt(int index)
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{
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return (int)ReadLittleEndian(index, sizeof(int));
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}
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public uint GetUint(int index)
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{
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return (uint)ReadLittleEndian(index, sizeof(uint));
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}
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public long GetLong(int index)
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{
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return (long)ReadLittleEndian(index, sizeof(long));
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}
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public ulong GetUlong(int index)
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{
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return ReadLittleEndian(index, sizeof(ulong));
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}
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public float GetFloat(int index)
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{
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int i = (int)ReadLittleEndian(index, sizeof(float));
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inthelper[0] = i;
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Buffer.BlockCopy(inthelper, 0, floathelper, 0, sizeof(float));
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return floathelper[0];
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}
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public double GetDouble(int index)
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{
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ulong i = ReadLittleEndian(index, sizeof(double));
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// There's Int64BitsToDouble but it uses unsafe code internally.
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ulonghelper[0] = i;
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Buffer.BlockCopy(ulonghelper, 0, doublehelper, 0, sizeof(double));
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return doublehelper[0];
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}
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#endif // UNSAFE_BYTEBUFFER
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}
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}
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