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Add SepWriter.Col.FormatEnum since Format<T> allocates due to enum boxing #580

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Merged
nietras merged 4 commits into from
Aug 17, 2026
+98 −7
Merged

Add SepWriter.Col.FormatEnum since Format<T> allocates due to enum boxing #580

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e9fe7b7
Add SepWriter.Col.FormatEnum since Format<T> allocates due to enum bo…
nietras Aug 16, 2026
fdaca2e
extend testing
nietras Aug 16, 2026
9befb73
Merge branch 'main' into sepwriter-col-formatenum
nietras Aug 16, 2026
640761d
refactor bytes allocated asserts
nietras Aug 17, 2026
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4 changes: 4 additions & 0 deletions README.md
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Original file line number Diff line number Diff line change
Expand Up @@ -2633,6 +2633,10 @@ namespace nietras.SeparatedValues
where T : System.ISpanFormattable { }
public void Format<T>(T value, System.ReadOnlySpan<char> format)
where T : System.ISpanFormattable { }
public void FormatEnum<T>(T value)
where T : struct, System.Enum { }
public void FormatEnum<T>(T value, System.ReadOnlySpan<char> format)
where T : struct, System.Enum { }
public void Set(System.ReadOnlySpan<byte> utf8Span) { }
public void Set(System.ReadOnlySpan<char> span) { }
public void Set([System.Runtime.CompilerServices.InterpolatedStringHandlerArgument("")] ref nietras.SeparatedValues.SepWriter.Col.FormatInterpolatedStringHandler handler) { }
Expand Down
80 changes: 73 additions & 7 deletions src/Sep.Test/SepWriterColTest.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -22,13 +22,15 @@ public class SepWriterColTest
[TestMethod]
public async ValueTask SepWriterColTest_ColIndex()
{
await Run(col => Assert.AreEqual(0, col.ColIndex), null);
await Run(static col => Assert.AreEqual(0, col.ColIndex),
expectedColValue: null);
}

[TestMethod]
public async ValueTask SepWriterColTest_ColName()
{
await Run(col => Assert.AreEqual(ColName, col.ColName), null);
await Run(static col => Assert.AreEqual(ColName, col.ColName),
expectedColValue: null);
}

[TestMethod]
Expand All @@ -46,13 +48,15 @@ public async ValueTask SepWriterColTest_Set_String_Long()
[TestMethod]
public async ValueTask SepWriterColTest_Set_Utf8Span()
{
await Run(col => col.Set(Encoding.UTF8.GetBytes(ColText)));
var bytes = Encoding.UTF8.GetBytes(ColText);
await Run(col => col.Set(bytes));
}

[TestMethod]
public async ValueTask SepWriterColTest_Set_Utf8Span_Long()
{
await Run(col => col.Set(Encoding.UTF8.GetBytes(ColTextLong)), ColTextLong);
var bytes = Encoding.UTF8.GetBytes(ColTextLong);
await Run(col => col.Set(bytes), ColTextLong);
}

[TestMethod]
Expand Down Expand Up @@ -92,13 +96,15 @@ public async ValueTask SepWriterColTest_Set_InterpolatedString_F2()
[TestMethod]
public async ValueTask SepWriterColTest_Set_InterpolatedString_F2_CultureInfoAsConfig()
{
await Run(col => col.Set($"{ColValue:F2}"), ColText + ",00", CultureInfo.GetCultureInfo("da-DK"));
var cultureInfo = CultureInfo.GetCultureInfo("da-DK");
await Run(col => col.Set($"{ColValue:F2}"), ColText + ",00", cultureInfo);
}

[TestMethod]
public async ValueTask SepWriterColTest_Set_InterpolatedString_F2_CultureInfoAsParam()
{
await Run(col => col.Set(CultureInfo.GetCultureInfo("da-DK"), $"{ColValue:F2}"), ColText + ",00");
var cultureInfo = CultureInfo.GetCultureInfo("da-DK");
await Run(col => col.Set(cultureInfo, $"{ColValue:F2}"), ColText + ",00");
}

[TestMethod]
Expand Down Expand Up @@ -176,6 +182,52 @@ public async ValueTask SepWriterColTest_Format_Long()
await Run(col => col.Format(f), f.Text);
}

enum TestEnum { Aaaa = 42 }
[TestMethod]
public async ValueTask SepWriterColTest_Set_Enum()
{
await Run(col => col.Set($"{TestEnum.Aaaa}"), TestEnum.Aaaa.ToString(), expectedAllocatedBytes: 0);
}
[TestMethod]
public async ValueTask SepWriterColTest_Format_Enum()
{
// Unfortunately, formatting enum via T : ISpanFormatable allocates on
// each format, due to boxing enum. Prefer FormatEnum/Set(..) instead.
var expectedAllocatedBytes = System.Runtime.CompilerServices.Unsafe.SizeOf<nint>() * 3;
await Run(col => col.Format(TestEnum.Aaaa), TestEnum.Aaaa.ToString(),
expectedAllocatedBytes: expectedAllocatedBytes);
await Run(col => col.Format(TestEnum.Aaaa, "D"), ((int)TestEnum.Aaaa).ToString(),
expectedAllocatedBytes: expectedAllocatedBytes);
}
[TestMethod]
public async ValueTask SepWriterColTest_FormatEnum_Enum()
{
await Run(col => col.FormatEnum(TestEnum.Aaaa), TestEnum.Aaaa.ToString(), expectedAllocatedBytes: 0);
await Run(col => col.FormatEnum(TestEnum.Aaaa, "D"), ((int)TestEnum.Aaaa).ToString(), expectedAllocatedBytes: 0);
}

[Flags]
enum LongFlags
{
Flag000 = 1 << 0, Flag001 = 1 << 1, Flag002 = 1 << 2, Flag003 = 1 << 3,
Flag004 = 1 << 4, Flag005 = 1 << 5, Flag006 = 1 << 6, Flag007 = 1 << 7,
Flag008 = 1 << 8, Flag009 = 1 << 9, Flag010 = 1 << 10, Flag011 = 1 << 11,
Flag012 = 1 << 12, Flag013 = 1 << 13, Flag014 = 1 << 14, Flag015 = 1 << 15,
Flag016 = 1 << 16, Flag017 = 1 << 17, Flag018 = 1 << 18, Flag019 = 1 << 19,
Flag020 = 1 << 20, Flag021 = 1 << 21, Flag022 = 1 << 22, Flag023 = 1 << 23,
Flag024 = 1 << 24, Flag025 = 1 << 25, Flag026 = 1 << 26, Flag027 = 1 << 27,
Flag028 = 1 << 28, Flag029 = 1 << 29, Flag030 = 1 << 30,
}
[TestMethod]
public async ValueTask SepWriterColTest_FormatEnum_Enum_Long()
{
var value = (LongFlags)0x7FFFFFFF;
var expected = value.ToString();
Assert.IsGreaterThan(256, expected.Length);

await Run(col => col.FormatEnum(value), expected);
}

public class LongSpanFormattable : ISpanFormattable
{
public string Text { get; } = ColTextLong;
Expand Down Expand Up @@ -230,7 +282,8 @@ static void Assert(string expectedCol, SepWriter writer)
}
}

static async ValueTask Run(SepWriter.ColAction action, string? expectedColValue = ColText, CultureInfo? cultureInfo = null)
static async ValueTask Run(SepWriter.ColAction action, string? expectedColValue = ColText,
CultureInfo? cultureInfo = null, long? expectedAllocatedBytes = null)
{
Func<SepWriter>[] createWriters =
[
Expand All @@ -245,7 +298,20 @@ static async ValueTask Run(SepWriter.ColAction action, string? expectedColValue
using var writer = createWriter();
{
using var row = writer.NewRow();
// First row, first access will allocate ColImpl and supports, so warming up
action(row[ColName]);

var a0 = GC.GetAllocatedBytesForCurrentThread();
var col = row[ColName];
var a1 = GC.GetAllocatedBytesForCurrentThread();
action(col);
var a2 = GC.GetAllocatedBytesForCurrentThread();
// Getting col should always allocate zero bytes
Assert.AreEqual(0, a1 - a0);
if (expectedAllocatedBytes.HasValue)
{
Assert.AreEqual(expectedAllocatedBytes.Value, a2 - a1);
}
}
AssertCol(expectedColValue, writer);
}
Expand Down
21 changes: 21 additions & 0 deletions src/Sep/SepWriter.Col.cs
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Expand Up @@ -145,6 +145,27 @@ public void Format<T>(T value, ReadOnlySpan<char> format) where T : ISpanFormatt
MarkSet();
}

public void FormatEnum<T>(T value) where T : struct, Enum
{
FormatEnum(value, null);
}
public void FormatEnum<T>(T value, ReadOnlySpan<char> format) where T : struct, Enum
{
var impl = _impl;
impl.Clear();
if (Enum.TryFormat(value, impl._buffer, out var charsWritten, format))
{
impl._position = charsWritten;
}
else
{
var handler = new FormatInterpolatedStringHandler(0, 1, this);
handler.AppendFormatted(value);
handler.Finish();
}
MarkSet();
}

/// <summary>
/// Provides a handler used by the language compiler to append
/// interpolated strings into <see cref="Col"/> instances.
Expand Down