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using System;
namespace Hazel
{
/// <summary>
/// This is a minimal implementation of `System.Span` in .NET 5.0
/// </summary>
public struct ByteSpan
{
private readonly byte[] array_;
/// <summary>
/// Createa a new span object containing an entire array
/// </summary>
public ByteSpan(byte[] array)
{
if (array == null)
{
this.array_ = null;
this.Offset = 0;
this.Length = 0;
}
else
{
this.array_ = array;
this.Offset = 0;
this.Length = array.Length;
}
}
/// <summary>
/// Creates a new span object containing a subset of an array
/// </summary>
public ByteSpan(byte[] array, int offset, int length)
{
if (array == null)
{
if (offset != 0)
{
throw new ArgumentException("Invalid offset", nameof(offset));
}
if (length != 0)
{
throw new ArgumentException("Invalid length", nameof(offset));
}
this.array_ = null;
this.Offset = 0;
this.Length = 0;
}
else
{
if (offset < 0 || offset > array.Length)
{
throw new ArgumentException("Invalid offset", nameof(offset));
}
if (length < 0)
{
throw new ArgumentException($"Invalid length: {length}", nameof(length));
}
if ((offset + length) > array.Length)
{
throw new ArgumentException($"Invalid length. Length: {length} Offset: {offset} Array size: {array.Length}", nameof(length));
}
this.array_ = array;
this.Offset = offset;
this.Length = length;
}
}
/// <summary>
/// Returns the underlying array.
///
/// WARNING: This does not return the span, but the entire underlying storage block
/// </summary>
public byte[] GetUnderlyingArray()
{
return this.array_;
}
/// <summary>
/// Returns the offset into the underlying array
/// </summary>
public int Offset { get; }
/// <summary>
/// Returns the length of the current span
/// </summary>
public int Length { get; }
/// <summary>
/// Gets the span element at the specified index
/// </summary>
public byte this[int index]
{
get
{
if (index < 0 || index >= this.Length)
{
throw new IndexOutOfRangeException();
}
return this.array_[this.Offset + index];
}
set
{
if (index < 0 || index >= this.Length)
{
throw new IndexOutOfRangeException();
}
this.array_[this.Offset + index] = value;
}
}
/// <summary>
/// Create a new span that is a subset of this span [offset, this.Length-offset)
/// </summary>
public ByteSpan Slice(int offset)
{
return Slice(offset, this.Length - offset);
}
/// <summary>
/// Create a new span that is a subset of this span [offset, length)
/// </summary>
public ByteSpan Slice(int offset, int length)
{
return new ByteSpan(this.array_, this.Offset + offset, length);
}
/// <summary>
/// Copies the contents of the span to an array
/// </summary>
public void CopyTo(byte[] array, int offset)
{
CopyTo(new ByteSpan(array, offset, array.Length - offset));
}
/// <summary>
/// Copies the contents of the span to another span
/// </summary>
public void CopyTo(ByteSpan destination)
{
if (destination.Length < this.Length)
{
throw new ArgumentException("Destination span is shorter than source", nameof(destination));
}
if (Length > 0)
{
Buffer.BlockCopy(this.array_, this.Offset, destination.array_, destination.Offset, this.Length);
}
}
/// <summary>
/// Create a new array with the contents of this span
/// </summary>
public byte[] ToArray()
{
byte[] result = new byte[Length];
CopyTo(result);
return result;
}
public override string ToString()
{
return string.Join(" ", this.ToArray());
}
/// <summary>
/// Implicit conversion from byte[] -> ByteSpan
/// </summary>
public static implicit operator ByteSpan(byte[] array)
{
return new ByteSpan(array);
}
/// <summary>
/// Retuns an empty span object
/// </summary>
public static ByteSpan Empty
{
get
{
return new ByteSpan(null);
}
}
}
}
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