67 lines
2.0 KiB
C#
67 lines
2.0 KiB
C#
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using System;
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using System.Buffers;
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using System.Collections.Generic;
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using System.Text;
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namespace Cysharp.Text
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{
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internal static class EnumUtil<T>
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// where T : Enum
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{
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const string InvalidName = "$";
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static readonly Dictionary<T, string> names;
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static readonly Dictionary<T, byte[]> utf8names;
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static EnumUtil()
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{
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var enumNames = Enum.GetNames(typeof(T));
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var values =
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#if NET7_0_OR_GREATER
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Enum.GetValuesAsUnderlyingType(typeof(T));
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#else
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Enum.GetValues(typeof(T));
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#endif
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names = new Dictionary<T, string>(enumNames.Length);
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utf8names = new Dictionary<T, byte[]>(enumNames.Length);
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for (int i = 0; i < enumNames.Length; i++)
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{
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var value = (T)values.GetValue(i)!;
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if (names.ContainsKey(value))
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{
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// already registered = invalid.
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names[value] = InvalidName;
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utf8names[value] = Array.Empty<byte>(); // byte[0] == Invalid.
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}
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else
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{
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names.Add(value, enumNames[i]);
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utf8names.Add(value, Encoding.UTF8.GetBytes(enumNames[i]));
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}
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}
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}
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public static bool TryFormatUtf16(T value, Span<char> dest, out int written, ReadOnlySpan<char> _)
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{
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if (!names.TryGetValue(value, out var v) || v == InvalidName)
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{
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v = value!.ToString(); // T is Enum, not null always
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}
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written = v.Length;
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return v.AsSpan().TryCopyTo(dest);
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}
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public static bool TryFormatUtf8(T value, Span<byte> dest, out int written, StandardFormat _)
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{
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if (!utf8names.TryGetValue(value, out var v) || v.Length == 0)
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{
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v = Encoding.UTF8.GetBytes(value!.ToString());
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}
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written = v.Length;
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return v.AsSpan().TryCopyTo(dest);
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}
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}
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}
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