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Fix Regex.EnumerateSplits ranges for capture groups, RightToLeft and empty matches #642

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Merged
SimonCropp merged 1 commit into from
Oct 11, 2026
Merged

Fix Regex.EnumerateSplits ranges for capture groups, RightToLeft and empty matches #642

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4 changes: 2 additions & 2 deletions src/Polyfill/Regex/Polyfill_Regex.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -84,7 +84,7 @@ public static ValueMatchEnumerator EnumerateMatches(this Regex target, ReadOnlyS

//Link: https://learn.microsoft.com/en-us/dotnet/api/system.text.regularexpressions.regex.enumeratesplits?view=net-11.0#system-text-regularexpressions-regex-enumeratesplits(system-readonlyspan((system-char)))
public static ValueSplitEnumerator EnumerateSplits(this Regex regex, ReadOnlySpan<char> input) =>
new(input, regex, 0, 0);
new(input, regex, 0);

//Link: https://learn.microsoft.com/en-us/dotnet/api/system.text.regularexpressions.regex.enumeratesplits?view=net-11.0#system-text-regularexpressions-regex-enumeratesplits(system-readonlyspan((system-char))-system-int32)
public static ValueSplitEnumerator EnumerateSplits(this Regex regex, ReadOnlySpan<char> input, int count)
Expand All @@ -94,7 +94,7 @@ public static ValueSplitEnumerator EnumerateSplits(this Regex regex, ReadOnlySpa
throw new ArgumentOutOfRangeException(nameof(count), "Count must be non-negative.");
}

return new ValueSplitEnumerator(input, regex, count, 0);
return new ValueSplitEnumerator(input, regex, count);
}

//Link: https://learn.microsoft.com/en-us/dotnet/api/system.text.regularexpressions.regex.enumeratesplits?view=net-11.0#system-text-regularexpressions-regex-enumeratesplits(system-readonlyspan((system-char))-system-int32-system-int32)
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6 changes: 3 additions & 3 deletions src/Polyfill/Regex/RegexPolyfill.cs
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Expand Up @@ -115,21 +115,21 @@ public static ValueMatchEnumerator EnumerateMatches(ReadOnlySpan<char> input, st
public static ValueSplitEnumerator EnumerateSplits(ReadOnlySpan<char> input, string pattern)
{
var regex = new Regex(pattern);
return new ValueSplitEnumerator(input, regex, 0, 0);
return new ValueSplitEnumerator(input, regex, 0);
}

//Link: https://learn.microsoft.com/en-us/dotnet/api/system.text.regularexpressions.regex.enumeratesplits?view=net-11.0#system-text-regularexpressions-regex-enumeratesplits(system-readonlyspan((system-char))-system-string-system-text-regularexpressions-regexoptions)
public static ValueSplitEnumerator EnumerateSplits(ReadOnlySpan<char> input, string pattern, RegexOptions options)
{
var regex = new Regex(pattern, options);
return new ValueSplitEnumerator(input, regex, 0, 0);
return new ValueSplitEnumerator(input, regex, 0);
}

//Link: https://learn.microsoft.com/en-us/dotnet/api/system.text.regularexpressions.regex.enumeratesplits?view=net-11.0#system-text-regularexpressions-regex-enumeratesplits(system-readonlyspan((system-char))-system-string-system-text-regularexpressions-regexoptions-system-timespan)
public static ValueSplitEnumerator EnumerateSplits(ReadOnlySpan<char> input, string pattern, RegexOptions options, TimeSpan matchTimeout)
{
var regex = new Regex(pattern, options, matchTimeout);
return new ValueSplitEnumerator(input, regex, 0, 0);
return new ValueSplitEnumerator(input, regex, 0);
}

#endif
Expand Down
115 changes: 68 additions & 47 deletions src/Polyfill/Regex/ValueSplitEnumerator.cs
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Expand Up @@ -6,7 +6,6 @@

namespace System.Text.RegularExpressions;

using System.Collections.Generic;
using System;
using System.Runtime.CompilerServices;
using System.Diagnostics;
Expand All @@ -28,83 +27,105 @@ ref struct ValueSplitEnumerator
{
private readonly ReadOnlySpan<char> _input;
private readonly Regex _regex;
private readonly int _count;
private readonly int _startat;
private Range[]? _ranges;
private int _currentIndex;
private bool _initialized;
private int _remaining;
private Match? _match;
private int _previous;
private bool _completed;
private Range _current;

internal ValueSplitEnumerator(ReadOnlySpan<char> input, Regex regex, int count)
: this(input, regex, count, GetDefaultStartat(input, regex))
{
}

internal ValueSplitEnumerator(ReadOnlySpan<char> input, Regex regex, int count, int startat)
{
_input = input;
_regex = regex;
_count = count;
_startat = startat;
_ranges = null;
_currentIndex = -1;
_initialized = false;
}
_remaining = count;
if (count == 0)
{
_remaining = int.MaxValue;
}

public Range Current => _ranges![_currentIndex];
_match = null;
_previous = 0;
if (regex.RightToLeft)
{
_previous = input.Length;
}

public ValueSplitEnumerator GetEnumerator() => this;
_completed = false;
_current = default;
}

public bool MoveNext()
static int GetDefaultStartat(ReadOnlySpan<char> input, Regex regex)
{
if (!_initialized)
if (regex.RightToLeft)
{
Initialize();
_initialized = true;
return input.Length;
}

_currentIndex++;
return _currentIndex < _ranges!.Length;
return 0;
}

private void Initialize()
{
string inputString = _input.ToString();
string[] splits;
public readonly Range Current => _current;

if (_count == 0 && _startat == 0)
{
splits = _regex.Split(inputString);
}
else if (_startat == 0)
{
splits = _regex.Split(inputString, _count == 0 ? int.MaxValue : _count);
}
else
public readonly ValueSplitEnumerator GetEnumerator() => this;

public bool MoveNext()
{
if (_completed)
{
splits = _regex.Split(inputString, _count == 0 ? int.MaxValue : _count, _startat);
return false;
}

var ranges = new List<Range>();
int currentPos = 0;

for (int i = 0; i < splits.Length; i++)
// The last permitted split is always the remainder of the input, so only look for
// a further match when at least one more split is allowed after this one.
if (_remaining > 1)
{
int length = splits[i].Length;
int start = currentPos;
int end = currentPos + length;

ranges.Add(new Range(start, end));
Match match;
if (_match is null)
{
match = _regex.Match(_input.ToString(), _startat);
}
else
{
match = _match.NextMatch();
}

if (i < splits.Length - 1)
if (match.Success)
{
Match match = _regex.Match(inputString, end);
if (match.Success)
_match = match;
_remaining--;
if (_regex.RightToLeft)
{
currentPos = match.Index + match.Length;
_current = new Range(match.Index + match.Length, _previous);
_previous = match.Index;
}
else
{
currentPos = end;
_current = new Range(_previous, match.Index);
_previous = match.Index + match.Length;
}

return true;
}
}

_ranges = ranges.ToArray();
_completed = true;
if (_regex.RightToLeft)
{
_current = new Range(0, _previous);
}
else
{
_current = new Range(_previous, _input.Length);
}

return true;
}
}

Expand Down
4 changes: 2 additions & 2 deletions src/Split/net461/Regex/Polyfill_Regex.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -62,14 +62,14 @@ public static ValueMatchEnumerator EnumerateMatches(this Regex target, ReadOnlyS
#endif
#if FeatureMemory && FeatureValueTuple
public static ValueSplitEnumerator EnumerateSplits(this Regex regex, ReadOnlySpan<char> input) =>
new(input, regex, 0, 0);
new(input, regex, 0);
public static ValueSplitEnumerator EnumerateSplits(this Regex regex, ReadOnlySpan<char> input, int count)
{
if (count < 0)
{
throw new ArgumentOutOfRangeException(nameof(count), "Count must be non-negative.");
}
return new ValueSplitEnumerator(input, regex, count, 0);
return new ValueSplitEnumerator(input, regex, count);
}
public static ValueSplitEnumerator EnumerateSplits(this Regex regex, ReadOnlySpan<char> input, int count, int startat)
{
Expand Down
6 changes: 3 additions & 3 deletions src/Split/net461/Regex/RegexPolyfill.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -78,17 +78,17 @@ public static ValueMatchEnumerator EnumerateMatches(ReadOnlySpan<char> input, st
public static ValueSplitEnumerator EnumerateSplits(ReadOnlySpan<char> input, string pattern)
{
var regex = new Regex(pattern);
return new ValueSplitEnumerator(input, regex, 0, 0);
return new ValueSplitEnumerator(input, regex, 0);
}
public static ValueSplitEnumerator EnumerateSplits(ReadOnlySpan<char> input, string pattern, RegexOptions options)
{
var regex = new Regex(pattern, options);
return new ValueSplitEnumerator(input, regex, 0, 0);
return new ValueSplitEnumerator(input, regex, 0);
}
public static ValueSplitEnumerator EnumerateSplits(ReadOnlySpan<char> input, string pattern, RegexOptions options, TimeSpan matchTimeout)
{
var regex = new Regex(pattern, options, matchTimeout);
return new ValueSplitEnumerator(input, regex, 0, 0);
return new ValueSplitEnumerator(input, regex, 0);
}
#endif
}
Expand Down
103 changes: 60 additions & 43 deletions src/Split/net461/Regex/ValueSplitEnumerator.cs
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Expand Up @@ -2,7 +2,6 @@
#pragma warning disable
#if FeatureMemory && FeatureValueTuple
namespace System.Text.RegularExpressions;
using System.Collections.Generic;
using System;
using System.Runtime.CompilerServices;
using System.Diagnostics;
Expand All @@ -22,71 +21,89 @@ ref struct ValueSplitEnumerator
{
private readonly ReadOnlySpan<char> _input;
private readonly Regex _regex;
private readonly int _count;
private readonly int _startat;
private Range[]? _ranges;
private int _currentIndex;
private bool _initialized;
private int _remaining;
private Match? _match;
private int _previous;
private bool _completed;
private Range _current;
internal ValueSplitEnumerator(ReadOnlySpan<char> input, Regex regex, int count)
: this(input, regex, count, GetDefaultStartat(input, regex))
{
}
internal ValueSplitEnumerator(ReadOnlySpan<char> input, Regex regex, int count, int startat)
{
_input = input;
_regex = regex;
_count = count;
_startat = startat;
_ranges = null;
_currentIndex = -1;
_initialized = false;
}
public Range Current => _ranges![_currentIndex];
public ValueSplitEnumerator GetEnumerator() => this;
public bool MoveNext()
{
if (!_initialized)
_remaining = count;
if (count == 0)
{
Initialize();
_initialized = true;
_remaining = int.MaxValue;
}
_currentIndex++;
return _currentIndex < _ranges!.Length;
}
private void Initialize()
{
string inputString = _input.ToString();
string[] splits;
if (_count == 0 && _startat == 0)
_match = null;
_previous = 0;
if (regex.RightToLeft)
{
splits = _regex.Split(inputString);
_previous = input.Length;
}
else if (_startat == 0)
_completed = false;
_current = default;
}
static int GetDefaultStartat(ReadOnlySpan<char> input, Regex regex)
{
if (regex.RightToLeft)
{
splits = _regex.Split(inputString, _count == 0 ? int.MaxValue : _count);
return input.Length;
}
else
return 0;
}
public readonly Range Current => _current;
public readonly ValueSplitEnumerator GetEnumerator() => this;
public bool MoveNext()
{
if (_completed)
{
splits = _regex.Split(inputString, _count == 0 ? int.MaxValue : _count, _startat);
return false;
}
var ranges = new List<Range>();
int currentPos = 0;
for (int i = 0; i < splits.Length; i++)
if (_remaining > 1)
{
int length = splits[i].Length;
int start = currentPos;
int end = currentPos + length;
ranges.Add(new Range(start, end));
if (i < splits.Length - 1)
Match match;
if (_match is null)
{
match = _regex.Match(_input.ToString(), _startat);
}
else
{
match = _match.NextMatch();
}
if (match.Success)
{
Match match = _regex.Match(inputString, end);
if (match.Success)
_match = match;
_remaining--;
if (_regex.RightToLeft)
{
currentPos = match.Index + match.Length;
_current = new Range(match.Index + match.Length, _previous);
_previous = match.Index;
}
else
{
currentPos = end;
_current = new Range(_previous, match.Index);
_previous = match.Index + match.Length;
}
return true;
}
}
_ranges = ranges.ToArray();
_completed = true;
if (_regex.RightToLeft)
{
_current = new Range(0, _previous);
}
else
{
_current = new Range(_previous, _input.Length);
}
return true;
}
}
#endif
4 changes: 2 additions & 2 deletions src/Split/net462/Regex/Polyfill_Regex.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -62,14 +62,14 @@ public static ValueMatchEnumerator EnumerateMatches(this Regex target, ReadOnlyS
#endif
#if FeatureMemory && FeatureValueTuple
public static ValueSplitEnumerator EnumerateSplits(this Regex regex, ReadOnlySpan<char> input) =>
new(input, regex, 0, 0);
new(input, regex, 0);
public static ValueSplitEnumerator EnumerateSplits(this Regex regex, ReadOnlySpan<char> input, int count)
{
if (count < 0)
{
throw new ArgumentOutOfRangeException(nameof(count), "Count must be non-negative.");
}
return new ValueSplitEnumerator(input, regex, count, 0);
return new ValueSplitEnumerator(input, regex, count);
}
public static ValueSplitEnumerator EnumerateSplits(this Regex regex, ReadOnlySpan<char> input, int count, int startat)
{
Expand Down
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