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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
using System;
using System.Numerics;
using System.Runtime.CompilerServices;
using System.Text;
namespace Internal.Text
{
public struct Utf8String : IEquatable<Utf8String>, IComparable<Utf8String>
{
private byte[] _value;
public Utf8String(byte[] underlyingArray)
{
_value = underlyingArray;
}
public Utf8String(string s)
{
_value = Encoding.UTF8.GetBytes(s);
}
// TODO: This should return ReadOnlySpan<byte> instead once available
public byte[] UnderlyingArray => _value;
public int Length => _value.Length;
// For now, define implicit conversions between string and Utf8String to aid the transition
// These conversions will be removed eventually
public static implicit operator Utf8String(string s)
{
return new Utf8String(s);
}
public override string ToString()
{
return Encoding.UTF8.GetString(_value);
}
public override bool Equals(object obj)
{
return (obj is Utf8String) && Equals((Utf8String)obj);
}
public unsafe override int GetHashCode()
{
int length = _value.Length;
uint hash = (uint)length;
fixed (byte* ap = _value)
{
byte* a = ap;
while (length >= 4)
{
hash = (hash + BitOperations.RotateLeft(hash, 5)) ^ *(uint*)a;
a += 4; length -= 4;
}
if (length >= 2)
{
hash = (hash + BitOperations.RotateLeft(hash, 5)) ^ *(ushort*)a;
a += 2; length -= 2;
}
if (length > 0)
{
hash = (hash + BitOperations.RotateLeft(hash, 5)) ^ *a;
}
hash += BitOperations.RotateLeft(hash, 7);
hash += BitOperations.RotateLeft(hash, 15);
return (int)hash;
}
}
public bool Equals(Utf8String other)
{
int length = _value.Length;
if (length != other.Length)
return false;
if (_value == other._value)
return true;
unsafe
{
fixed (byte* ap = _value) fixed (byte* bp = other._value)
{
byte* a = ap;
byte* b = bp;
while (length >= 4)
{
if (*(int*)a != *(int*)b) return false;
a += 4; b += 4; length -= 4;
}
if (length >= 2)
{
if (*(short*)a != *(short*)b) return false;
a += 2; b += 2; length -= 2;
}
if (length > 0)
{
if (*a != *b) return false;
}
return true;
}
}
}
private static int Compare(Utf8String strA, Utf8String strB)
{
int length = Math.Min(strA.Length, strB.Length);
unsafe
{
fixed (byte* ap = strA._value)
fixed (byte* bp = strB._value)
{
byte* a = ap;
byte* b = bp;
while (length > 0)
{
if (*a != *b)
return *a - *b;
a += 1;
b += 1;
length -= 1;
}
// At this point, we have compared all the characters in at least one string.
// The longer string will be larger.
// We could optimize and compare lengths before iterating strings, but we want
// Foo and Foo1 to be sorted adjacent to eachother.
return strA.Length - strB.Length;
}
}
}
public int CompareTo(Utf8String other)
{
return Compare(this, other);
}
}
}
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