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#region Copyright notice and license
// Protocol Buffers - Google's data interchange format
// Copyright 2008 Google Inc. All rights reserved.
//
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file or at
// https://developers.google.com/open-source/licenses/bsd
#endregion
using System;
using System.Buffers;
using System.Collections.Generic;
namespace Google.Protobuf
{
internal static class ReadOnlySequenceFactory
{
/// <summary>
/// Create a sequence from the specified data. The data will be divided up into segments in the sequence.
/// </summary>
public static ReadOnlySequence<byte> CreateWithContent(byte[] data, int segmentSize = 1, bool addEmptySegmentDelimiters = true)
{
var segments = new List<byte[]>();
if (addEmptySegmentDelimiters)
{
segments.Add(Array.Empty<byte>());
}
var currentIndex = 0;
while (currentIndex < data.Length)
{
var segment = new List<byte>();
while (segment.Count < segmentSize && currentIndex < data.Length)
{
segment.Add(data[currentIndex++]);
}
segments.Add(segment.ToArray());
if (addEmptySegmentDelimiters)
{
segments.Add(Array.Empty<byte>());
}
}
return CreateSegments(segments.ToArray());
}
/// <summary>
/// Originally from corefx, and has been contributed to Protobuf
/// https://github.com/dotnet/corefx/blob/e99ec129cfd594d53f4390bf97d1d736cff6f860/src/System.Memory/tests/ReadOnlyBuffer/ReadOnlySequenceFactory.byte.cs
/// </summary>
private static ReadOnlySequence<byte> CreateSegments(params byte[][] inputs)
{
if (inputs == null || inputs.Length == 0)
{
throw new InvalidOperationException();
}
int i = 0;
BufferSegment last = null;
BufferSegment first = null;
do
{
byte[] s = inputs[i];
int length = s.Length;
int dataOffset = length;
var chars = new byte[length * 2];
for (int j = 0; j < length; j++)
{
chars[dataOffset + j] = s[j];
}
// Create a segment that has offset relative to the OwnedMemory and OwnedMemory itself has offset relative to array
var memory = new Memory<byte>(chars).Slice(length, length);
if (first == null)
{
first = new BufferSegment(memory);
last = first;
}
else
{
last = last.Append(memory);
}
i++;
} while (i < inputs.Length);
return new ReadOnlySequence<byte>(first, 0, last, last.Memory.Length);
}
private class BufferSegment : ReadOnlySequenceSegment<byte>
{
public BufferSegment(Memory<byte> memory)
{
Memory = memory;
}
public BufferSegment Append(Memory<byte> memory)
{
var segment = new BufferSegment(memory)
{
RunningIndex = RunningIndex + Memory.Length
};
Next = segment;
return segment;
}
}
}
}