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⚡ Optimize Ansi parsing using ReadOnlySpan<char> #133

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Merged
johnstrand merged 2 commits into from
Aug 21, 2026
Merged

⚡ Optimize Ansi parsing using ReadOnlySpan<char> #133

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a857a55
⚡ Optimize Ansi parsing to use ReadOnlySpan<char>
google-labs-jules[bot] Aug 21, 2026
43774a4
Merge branch 'master' into perf/ansi-span-parsing-7603647255921967973
johnstrand Aug 21, 2026
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106 changes: 71 additions & 35 deletions src/GameUtils/Term/Ansi.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -278,11 +278,12 @@ public static string WriteLine(string text, params object[] args)
public static string Format(string text)
{
var result = new StringBuilder();
var span = text.AsSpan();
var i = 0;

while (i < text.Length)
while (i < span.Length)
{
var c = text[i];
var c = span[i];

if (c != '[')
{
Expand All @@ -291,76 +292,77 @@ public static string Format(string text)
continue;
}

if (text.TryGet(i + 1, out var next) && next == '[')
if (i + 1 < span.Length && span[i + 1] == '[')
{
result.Append('[');
i += 2;
continue;
}

var endOfSequence = text.IndexOf(']', i);
var endOfSequence = span[i..].IndexOf(']');

if (endOfSequence == -1)
{
throw new ArgumentException($"Invalid ANSI sequence starting at position {i}");
}

var sequence = text.Substring(i + 1, endOfSequence - i - 1);
endOfSequence += i;
var sequence = span.Slice(i + 1, endOfSequence - i - 1);
i = endOfSequence + 1;

if (sequence is "/" or "")
if (sequence.Equals("/", StringComparison.Ordinal) || sequence.IsEmpty)
{
result.Append(Reset);
continue;
}

if (_foregroundColors.ContainsKey(sequence))
{
result.Append(Foreground(sequence));
continue;
}

if (sequence is "bold" or "b")
if (sequence.Equals("bold", StringComparison.Ordinal) || sequence.Equals("b", StringComparison.Ordinal))
{
result.Append(Bold);
continue;
}

if (sequence is "faint" or "f")
if (sequence.Equals("faint", StringComparison.Ordinal) || sequence.Equals("f", StringComparison.Ordinal))
{
result.Append(Faint);
continue;
}

if (sequence is "italic" or "i")
if (sequence.Equals("italic", StringComparison.Ordinal) || sequence.Equals("i", StringComparison.Ordinal))
{
result.Append(Italic);
continue;
}

if (sequence is "underline" or "u")
if (sequence.Equals("underline", StringComparison.Ordinal) || sequence.Equals("u", StringComparison.Ordinal))
{
result.Append(Underline);
continue;
}

if (sequence.StartsWith("fg:"))
if (sequence.StartsWith("fg:", StringComparison.Ordinal))
{
result.Append(Foreground(sequence[3..]));
continue;
var colorSpan = sequence[3..];
if (TryGetNamedColor(_foregroundColors, colorSpan, out var colorCode))
{
result.Append(CreateSequence("m", colorCode));
continue;
}
}

if (sequence.StartsWith("bg:"))
if (sequence.StartsWith("bg:", StringComparison.Ordinal))
{
result.Append(Background(sequence[3..]));
continue;
var colorSpan = sequence[3..];
if (TryGetNamedColor(_backgroundColors, colorSpan, out var colorCode))
{
result.Append(CreateSequence("m", colorCode));
continue;
}
}

if (sequence.StartsWith("#fg:"))
if (sequence.StartsWith("#fg:", StringComparison.Ordinal))
{
var rgb = sequence[4..].Split(',');

if (rgb.Length != 3 || !byte.TryParse(rgb[0], out var r) || !byte.TryParse(rgb[1], out var g) || !byte.TryParse(rgb[2], out var b))
if (!TryParseRgbSpan(sequence[4..], out var r, out var g, out var b))
{
throw new ArgumentException($"Invalid RGB color sequence starting at position {i}");
}
Expand All @@ -369,11 +371,9 @@ public static string Format(string text)
continue;
}

if (sequence.StartsWith("#bg:"))
if (sequence.StartsWith("#bg:", StringComparison.Ordinal))
{
var rgb = sequence[4..].Split(',');

if (rgb.Length != 3 || !byte.TryParse(rgb[0], out var r) || !byte.TryParse(rgb[1], out var g) || !byte.TryParse(rgb[2], out var b))
if (!TryParseRgbSpan(sequence[4..], out var r, out var g, out var b))
{
throw new ArgumentException($"Invalid RGB color sequence starting at position {i}");
}
Expand All @@ -382,11 +382,9 @@ public static string Format(string text)
continue;
}

if (sequence[0] == '#')
if (sequence.Length > 0 && sequence[0] == '#')
{
var rgb = sequence[1..].Split(',');

if (rgb.Length != 3 || !byte.TryParse(rgb[0], out var r) || !byte.TryParse(rgb[1], out var g) || !byte.TryParse(rgb[2], out var b))
if (!TryParseRgbSpan(sequence[1..], out var r, out var g, out var b))
{
throw new ArgumentException($"Invalid RGB color sequence starting at position {i}");
}
Expand All @@ -395,9 +393,47 @@ public static string Format(string text)
continue;
}

throw new ArgumentException($"Unknown ANSI sequence '{sequence}' starting at position {i}");
if (TryGetNamedColor(_foregroundColors, sequence, out var fgCode))
{
result.Append(CreateSequence("m", fgCode));
continue;
}

throw new ArgumentException($"Unknown ANSI sequence '{sequence.ToString()}' starting at position {i}");
}

return result.ToString();
}

private static bool TryGetNamedColor(Dictionary<string, int> colorDict, ReadOnlySpan<char> nameSpan, out int code)
{
foreach (var kvp in colorDict)
{
if (nameSpan.Equals(kvp.Key, StringComparison.Ordinal))
{
code = kvp.Value;
return true;
}
}
code = 0;
return false;
}

private static bool TryParseRgbSpan(ReadOnlySpan<char> span, out byte r, out byte g, out byte b)
{
r = g = b = 0;
var comma1 = span.IndexOf(',');
if (comma1 == -1) return false;

var part1 = span[..comma1];
var remaining = span[(comma1 + 1)..];

var comma2 = remaining.IndexOf(',');
if (comma2 == -1) return false;

var part2 = remaining[..comma2];
var part3 = remaining[(comma2 + 1)..];

return byte.TryParse(part1, out r) && byte.TryParse(part2, out g) && byte.TryParse(part3, out b);
}
}
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