#region Copyright notice and license
// Protocol Buffers - Google's data interchange format
// Copyright 2008 Google Inc. All rights reserved.
// https://developers.google.com/protocol-buffers/
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
// * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
// * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#endregion
using System;
using System.Buffers;
using System.Diagnostics;
namespace Google.Protobuf.Buffers
{
/// <summary>
/// Represents a heap-based, array-backed output sink into which <typeparam name="T"/> data can be written.
///
/// ArrayBufferWriter is originally from corefx, and has been contributed to Protobuf
/// https://github.com/dotnet/runtime/blob/071da4c41aa808c949a773b92dca6f88de9d11f3/src/libraries/Common/src/System/Buffers/ArrayBufferWriter.cs
/// </summary>
internal sealed class TestArrayBufferWriter<T> : IBufferWriter<T>
{
private T[] _buffer;
private int _index;
private const int DefaultInitialBufferSize = 256;
/// <summary>
/// Creates an instance of an <see cref="TestArrayBufferWriter{T}"/>, in which data can be written to,
/// with the default initial capacity.
/// </summary>
public TestArrayBufferWriter()
{
_buffer = new T[0];
_index = 0;
}
/// <summary>
/// Useful for testing writing to buffer writer with a lot of small segments.
/// If set, it limits the max number of bytes by which the buffer grows by at once.
/// </summary>
public int? MaxGrowBy { get; set; }
/// <summary>
/// Creates an instance of an <see cref="TestArrayBufferWriter{T}"/>, in which data can be written to,
/// with an initial capacity specified.
/// </summary>
/// <param name="initialCapacity">The minimum capacity with which to initialize the underlying buffer.</param>
/// <exception cref="ArgumentException">
/// Thrown when <paramref name="initialCapacity"/> is not positive (i.e. less than or equal to 0).
/// </exception>
public TestArrayBufferWriter(int initialCapacity)
{
if (initialCapacity <= 0)
throw new ArgumentException(nameof(initialCapacity));
_buffer = new T[initialCapacity];
_index = 0;
}
/// <summary>
/// Returns the data written to the underlying buffer so far, as a <see cref="ReadOnlyMemory{T}"/>.
/// </summary>
public ReadOnlyMemory<T> WrittenMemory => _buffer.AsMemory(0, _index);
/// <summary>
/// Returns the data written to the underlying buffer so far, as a <see cref="ReadOnlySpan{T}"/>.
/// </summary>
public ReadOnlySpan<T> WrittenSpan => _buffer.AsSpan(0, _index);
/// <summary>
/// Returns the amount of data written to the underlying buffer so far.
/// </summary>
public int WrittenCount => _index;
/// <summary>
/// Returns the total amount of space within the underlying buffer.
/// </summary>
public int Capacity => _buffer.Length;
/// <summary>
/// Returns the amount of space available that can still be written into without forcing the underlying buffer to grow.
/// </summary>
public int FreeCapacity => _buffer.Length - _index;
/// <summary>
/// Clears the data written to the underlying buffer.
/// </summary>
/// <remarks>
/// You must clear the <see cref="TestArrayBufferWriter{T}"/> before trying to re-use it.
/// </remarks>
public void Clear()
{
Debug.Assert(_buffer.Length >= _index);
_buffer.AsSpan(0, _index).Clear();
_index = 0;
}
/// <summary>
/// Notifies <see cref="IBufferWriter{T}"/> that <paramref name="count"/> amount of data was written to the output <see cref="Span{T}"/>/<see cref="Memory{T}"/>
/// </summary>
/// <exception cref="ArgumentException">
/// Thrown when <paramref name="count"/> is negative.
/// </exception>
/// <exception cref="InvalidOperationException">
/// Thrown when attempting to advance past the end of the underlying buffer.
/// </exception>
/// <remarks>
/// You must request a new buffer after calling Advance to continue writing more data and cannot write to a previously acquired buffer.
/// </remarks>
public void Advance(int count)
{
if (count < 0)
throw new ArgumentException(nameof(count));
if (_index > _buffer.Length - count)
throw new InvalidOperationException("Advanced past capacity.");
_index += count;
}
/// <summary>
/// Returns a <see cref="Memory{T}"/> to write to that is at least the requested length (specified by <paramref name="sizeHint"/>).
/// If no <paramref name="sizeHint"/> is provided (or it's equal to <code>0</code>), some non-empty buffer is returned.
/// </summary>
/// <exception cref="ArgumentException">
/// Thrown when <paramref name="sizeHint"/> is negative.
/// </exception>
/// <remarks>
/// This will never return an empty <see cref="Memory{T}"/>.
/// </remarks>
/// <remarks>
/// There is no guarantee that successive calls will return the same buffer or the same-sized buffer.
/// </remarks>
/// <remarks>
/// You must request a new buffer after calling Advance to continue writing more data and cannot write to a previously acquired buffer.
/// </remarks>
public Memory<T> GetMemory(int sizeHint = 0)
{
CheckAndResizeBuffer(sizeHint);
Debug.Assert(_buffer.Length > _index);
return _buffer.AsMemory(_index);
}
/// <summary>
/// Returns a <see cref="Span{T}"/> to write to that is at least the requested length (specified by <paramref name="sizeHint"/>).
/// If no <paramref name="sizeHint"/> is provided (or it's equal to <code>0</code>), some non-empty buffer is returned.
/// </summary>
/// <exception cref="ArgumentException">
/// Thrown when <paramref name="sizeHint"/> is negative.
/// </exception>
/// <remarks>
/// This will never return an empty <see cref="Span{T}"/>.
/// </remarks>
/// <remarks>
/// There is no guarantee that successive calls will return the same buffer or the same-sized buffer.
/// </remarks>
/// <remarks>
/// You must request a new buffer after calling Advance to continue writing more data and cannot write to a previously acquired buffer.
/// </remarks>
public Span<T> GetSpan(int sizeHint = 0)
{
CheckAndResizeBuffer(sizeHint);
Debug.Assert(_buffer.Length > _index);
return _buffer.AsSpan(_index);
}
private void CheckAndResizeBuffer(int sizeHint)
{
if (sizeHint < 0)
throw new ArgumentException(nameof(sizeHint));
if (sizeHint == 0)
{
sizeHint = 1;
}
if (sizeHint > FreeCapacity)
{
int growBy = Math.Max(sizeHint, _buffer.Length);
if (_buffer.Length == 0)
{
growBy = Math.Max(growBy, DefaultInitialBufferSize);
}
// enable tests that write to small buffer segments
if (MaxGrowBy.HasValue && growBy > MaxGrowBy.Value)
{
growBy = MaxGrowBy.Value;
}
int newSize = checked(_buffer.Length + growBy);
Array.Resize(ref _buffer, newSize);
}
Debug.Assert(FreeCapacity > 0 && FreeCapacity >= sizeHint);
}
}
}
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