Add ToUpperOrdinal and ToLowerOrdinal casing APIs by tarekgh · Pull Request #130140 · dotnet/runtime

tarekgh · 2026-07-02T20:52:07Z

Implements the ordinal casing APIs approved in #90999.

APIs

char.ToUpperOrdinal(char) / char.ToLowerOrdinal(char)
Rune.ToUpperOrdinal(Rune) / Rune.ToLowerOrdinal(Rune)
string.ToUpperOrdinal() / string.ToLowerOrdinal()
MemoryExtensions.ToUpperOrdinal(ReadOnlySpan<char>, Span<char>) / ToLowerOrdinal(ReadOnlySpan<char>, Span<char>)

Notes

Ordinal casing uses the same simple, one-to-one mapping as OrdinalIgnoreCase comparisons. Two strings are OrdinalIgnoreCase-equal iff their ToUpperOrdinal results are ordinally equal.
Reuses the existing ordinal upper-casing tables and adds a mirrored lower-casing path. Six characters (U+0130, U+03F4, U+1E9E, U+2126, U+212A, U+212B) stay unchanged under lower casing to remain consistent with OrdinalIgnoreCase.
string.ToUpperOrdinal() / string.ToLowerOrdinal() return the same instance when an all-ASCII string is already in the requested case, avoiding an allocation.

Tests under System.Globalization.Tests validate the mappings against OrdinalIgnoreCase across the entire BMP.

Implement ordinal (simple, one-to-one) casing on Char, Rune, String, and MemoryExtensions, matching the mappings used by OrdinalIgnoreCase comparisons. String.ToUpperOrdinal/ToLowerOrdinal return the same instance when an all-ASCII string is already in the requested case.

dotnet-policy-service · 2026-07-02T20:53:21Z

Tagging subscribers to this area: @dotnet/area-system-globalization
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Copilot

Pull request overview

Adds new ordinal casing APIs across char, Rune, string, and span-based MemoryExtensions, implemented to match the StringComparison.OrdinalIgnoreCase folding behavior (one-to-one mapping, length-preserving), including a new ordinal lower-casing table path alongside the existing upper-casing tables.

Changes:

Introduces ToUpperOrdinal / ToLowerOrdinal APIs on char, Rune, string, and ReadOnlySpan<char> -> Span<char> transforms.
Implements ICU-backed ordinal lower-casing table initialization (native + managed), mirroring the existing upper-casing infrastructure and special-case handling.
Adds comprehensive System.Globalization.Tests coverage validating BMP-wide behavior and overload consistency.

Reviewed changes

Copilot reviewed 18 out of 18 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
src/native/libs/System.Globalization.Native/System.Globalization.Native.def	Exports the new native entrypoint for ordinal lower-casing page initialization.
src/native/libs/System.Globalization.Native/pal_common.c	Implements `GlobalizationNative_InitOrdinalLowerCasingPage` using ICU simple lower casing + special cases.
src/native/libs/System.Globalization.Native/pal_casing.h	Declares the new native PAL export for ordinal lower-casing page initialization.
src/native/libs/System.Globalization.Native/entrypoints.c	Registers the new entrypoint for DllImport resolution.
src/libraries/Common/src/Interop/Interop.Casing.cs	Adds managed `LibraryImport` for `GlobalizationNative_InitOrdinalLowerCasingPage`.
src/libraries/System.Private.CoreLib/src/System/Globalization/OrdinalCasing.Icu.cs	Adds a mirrored lower-casing table + lazy per-page initialization and span-based lower casing.
src/libraries/System.Private.CoreLib/src/System/Globalization/TextInfo.cs	Adds `TextInfo.ToLowerOrdinal(char)` routing based on globalization mode (Invariant / NLS / ICU).
src/libraries/System.Private.CoreLib/src/System/Globalization/Ordinal.cs	Adds span-based `Ordinal.ToLowerOrdinal` entrypoint consistent with existing `ToUpperOrdinal`.
src/libraries/System.Private.CoreLib/src/System/MemoryExtensions.Globalization.cs	Adds public span extension methods `ToUpperOrdinal` / `ToLowerOrdinal`.
src/libraries/System.Private.CoreLib/src/System/String.Manipulation.cs	Adds `string.ToUpperOrdinal()` / `string.ToLowerOrdinal()` with ASCII fast-path returning same instance when unchanged.
src/libraries/System.Private.CoreLib/src/System/Char.cs	Adds public `char.ToUpperOrdinal(char)` / `char.ToLowerOrdinal(char)`.
src/libraries/System.Private.CoreLib/src/System/Text/Rune.cs	Adds public `Rune.ToUpperOrdinal(Rune)` / `Rune.ToLowerOrdinal(Rune)` implementations.
src/libraries/System.Runtime/ref/System.Runtime.cs	Adds the new public APIs to the System.Runtime ref surface (`char`, `string`, `Rune`).
src/libraries/System.Memory/ref/System.Memory.cs	Adds the new public APIs to the System.Memory ref surface (`MemoryExtensions`).
src/libraries/System.Runtime/tests/System.Globalization.Tests/System/Globalization/OrdinalCasingTests.cs	New tests validating ordinal casing invariants and special-case behavior across the BMP and overloads.
src/libraries/System.Runtime/tests/System.Globalization.Tests/System.Globalization.Tests.csproj	Includes the new test file in the test project.
src/coreclr/vm/wasm/wasi/callhelpers-pinvoke.cpp	Adds the new native export for WASM/WASI callhelper pinvoke tables.
src/coreclr/vm/wasm/browser/callhelpers-pinvoke.cpp	Adds the new native export for WASM/browser callhelper pinvoke tables.

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tarekgh · 2026-07-02T21:27:35Z

CC @lewing to advise if we need to do anything more for WASM with this change?

CC @jkotas & @GrabYourPitchforks for awareness.

Copilot

Pull request overview

Copilot reviewed 18 out of 18 changed files in this pull request and generated 1 comment.

… modes Invariant and NLS simple lowering could move characters such as the Kelvin, Ohm and Angstrom signs out of their ordinal upper-casing class, so ToLowerOrdinal stopped being consistent with OrdinalIgnoreCase in those modes. Keep the original character when its simple lower mapping would change its ordinal upper-casing form, and extend the invariant-mode test to cover ToLowerOrdinal across the BMP.

…ecutor Guard the MICRO SIGN and GREEK SMALL FINAL SIGMA fold cases so they only run under ICU and invariant casing, since NLS does not treat them as OrdinalIgnoreCase-equal. Gate OrdinalIgnoreCase_Equivalence_HoldsInInvariantMode on RemoteExecutor.IsSupported so it is skipped on wasm and android instead of throwing PlatformNotSupportedException.

Copilot

Pull request overview

Copilot reviewed 18 out of 18 changed files in this pull request and generated 2 comments.

Copilot

Pull request overview

Copilot reviewed 18 out of 18 changed files in this pull request and generated no new comments.

Upper-case the source and lowered spans once each instead of calling TextInfo.ToUpperOrdinal per non-ASCII character, which is expensive under NLS.

Copilot

Pull request overview

Copilot reviewed 18 out of 18 changed files in this pull request and generated 1 comment.

Only a fixed set of five BMP scalars (Greek capital theta symbol, Latin capital sharp S, Ohm, Kelvin and Angstrom signs) fall out of their ordinal upper-casing class under simple invariant or NLS lowering. Scan the source once with SearchValues and skip the pass entirely when none are present, instead of upper-casing the whole span on every lowering.

MihaZupan · 2026-07-07T13:22:44Z

+            for (int i = 0; i < source.Length; i++)
+            {
+                char c = source[i];
+                if (c <= '\u00FF') // optimize ASCII/Latin


Can we call Ascii.ToLower first to quickly scan through any leading ASCII?

MihaZupan · 2026-07-07T13:41:35Z

+            int consumed;
+
+            // Fast path: scan the leading run of ASCII characters that is already in the
+            // requested case. If the entire string is ASCII and needs no change, return the
+            // same instance to avoid an allocation. This mirrors the behavior of
+            // TextInfo.ChangeCaseCommon used by ToUpper(Invariant)/ToLower.
+            fixed (char* pSource = this)
+            {
+                nuint currIdx = 0; // in chars
+
+                if (Length >= 2)
+                {
+                    nuint lastIndexWhereCanReadTwoChars = (uint)Length - 2;
+                    do
+                    {
+                        // Read 2 chars (one 32-bit integer) at a time.
+                        uint tempValue = Unsafe.ReadUnaligned<uint>(pSource + currIdx);
+                        if (!Utf16Utility.AllCharsInUInt32AreAscii(tempValue) ||
+                            (toUpper
+                                ? Utf16Utility.UInt32ContainsAnyLowercaseAsciiChar(tempValue)
+                                : Utf16Utility.UInt32ContainsAnyUppercaseAsciiChar(tempValue)))
+                        {
+                            goto MustChange;
+                        }
+
+                        currIdx += 2;
+                    } while (currIdx <= lastIndexWhereCanReadTwoChars);
+                }
+
+                // If there's a single character left, check it now.
+                if ((Length & 1) != 0)
+                {
+                    uint tempValue = pSource[currIdx];
+                    if (tempValue > 0x7Fu ||
+                        (toUpper
+                            ? ((tempValue - 'a') <= (uint)('z' - 'a'))
+                            : ((tempValue - 'A') <= (uint)('Z' - 'A'))))
+                    {
+                        goto MustChange;
+                    }
+                }
+
+                // The whole string is ASCII and already in the requested case.
+                return this;
+
+            MustChange:
+                consumed = (int)currIdx;
+            }


This seems like it could be written as something like this instead:

int skippedAscii = toUpper ? this.AsSpan().IndexOfAnyExcept(s_asciiExceptLower) : this.AsSpan().IndexOfAnyExcept(s_asciiExceptUpper); if (skippedAscii < 0) { return this; } private const string AsciiExceptLetters = "\u0000\u0001\u0002\u0003\u0004\u0005\u0006\u0007\u0008\u0009\u000A\u000B\u000C\u000D\u000E\u000F\u0010\u0011\u0012\u0013\u0014\u0015\u0016\u0017\u0018\u0019\u001A\u001B\u001C\u001D\u001E\u001F !\"#$%&'()*+,-./0123456789:;<=>?@[\\]^_`{|}~\u007F"; private static readonly SearchValues<char> s_asciiExceptLower = SearchValues.Create(AsciiExceptLetters + "ABCDEFGHIJKLMNOPQRSTUVWXYZ"); private static readonly SearchValues<char> s_asciiExceptUpper = SearchValues.Create(AsciiExceptLetters + "abcdefghijklmnopqrstuvwxyz");

And avoid the unsafe code

Copilot AI review requested due to automatic review settings July 2, 2026 20:52

github-actions Bot added the area-System.Globalization label Jul 2, 2026

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Copilot AI review requested due to automatic review settings July 2, 2026 21:23

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tarekgh added this to the 11.0.0 milestone Jul 2, 2026

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Comment thread ...s/System.Runtime/tests/System.Globalization.Tests/System/Globalization/OrdinalCasingTests.cs

Tarek Mahmoud Sayed added 2 commits July 2, 2026 14:40

Add param and returns XML docs to Rune.ToUpperOrdinal/ToLowerOrdinal

1e4789a

Copilot AI review requested due to automatic review settings July 6, 2026 19:40

Copilot started reviewing on behalf of tarekgh July 6, 2026 19:42 View session

Merge remote-tracking branch 'upstream/main' into ordinal-casing-apis

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Comment thread src/libraries/System.Private.CoreLib/src/System/Globalization/Ordinal.cs Outdated

Comment thread src/coreclr/vm/wasm/browser/callhelpers-pinvoke.cpp

Copilot AI review requested due to automatic review settings July 6, 2026 19:49

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Tarek Mahmoud Sayed added 2 commits July 6, 2026 13:46

Avoid per-character ToUpperOrdinal in PreserveOrdinalLowerCasingClass

691e2f1

Upper-case the source and lowered spans once each instead of calling TextInfo.ToUpperOrdinal per non-ASCII character, which is expensive under NLS.

Merge remote-tracking branch 'upstream/main' into ordinal-casing-apis

0a4a70e

Copilot AI review requested due to automatic review settings July 6, 2026 21:09

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Comment thread src/libraries/System.Private.CoreLib/src/System/Globalization/Ordinal.cs Outdated

build-analysis Bot mentioned this pull request Jul 7, 2026

[ci-scan] Test failure: System.Formats.Tar.Tests.TarFile_ExtractToDirectory_File_Tests.ExtractToDirectory_RejectsChainedSymlinkDirectoryTraversal_WithNestedFile #130177

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MihaZupan reviewed Jul 7, 2026

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tarekgh commented Jul 2, 2026

APIs

Notes

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tarekgh commented Jul 2, 2026 •

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