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Reduce allocations in the ImageElementConverter and ImageIdConverter Read methods #78881

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Merged
merged 2 commits into from
Jun 10, 2025
Merged

Reduce allocations in the ImageElementConverter and ImageIdConverter Read methods #78881

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890fa01
Reduce allocations in the ImageElementConverter and ImageIdConverter …
ToddGrun Jun 9, 2025
356eb83
Fix analyzer complaint about not doing anaimplicit conversion from st…
ToddGrun Jun 10, 2025
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19 changes: 16 additions & 3 deletions src/LanguageServer/Protocol/Protocol/Internal/Converters/ImageElementConverter.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -9,6 +9,7 @@
using Roslyn.Text.Adornments;

namespace Roslyn.LanguageServer.Protocol;

internal sealed class ImageElementConverter : JsonConverter<ImageElement>
{
public static readonly ImageElementConverter Instance = new();
Expand All @@ -20,6 +21,8 @@ public override ImageElement Read(ref Utf8JsonReader reader, Type typeToConvert,
ImageId? imageId = null;
string? automationName = null;

Span<char> scratchChars = stackalloc char[64];

while (reader.Read())
{
if (reader.TokenType == JsonTokenType.EndObject)
Expand All @@ -30,7 +33,11 @@ public override ImageElement Read(ref Utf8JsonReader reader, Type typeToConvert,

if (reader.TokenType == JsonTokenType.PropertyName)
{
var propertyName = reader.GetString();
var valueLength = reader.HasValueSequence ? reader.ValueSequence.Length : reader.ValueSpan.Length;

var propertyNameLength = valueLength <= scratchChars.Length ? reader.CopyString(scratchChars) : -1;
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talked with Todd offline and sounds like we can't do have a helper to or if/else here, so fine with this.

var propertyName = propertyNameLength >= 0 ? scratchChars[..propertyNameLength] : reader.GetString().AsSpan();

reader.Read();
switch (propertyName)
{
Expand All @@ -41,7 +48,10 @@ public override ImageElement Read(ref Utf8JsonReader reader, Type typeToConvert,
automationName = reader.GetString();
break;
case ObjectContentConverter.TypeProperty:
if (reader.GetString() != nameof(ImageElement))
var typePropertyLength = valueLength <= scratchChars.Length ? reader.CopyString(scratchChars) : -1;
var typeProperty = typePropertyLength >= 0 ? scratchChars[..typePropertyLength] : reader.GetString().AsSpan();

if (!typeProperty.SequenceEqual(nameof(ImageElement).AsSpan()))
throw new JsonException($"Expected {ObjectContentConverter.TypeProperty} property value {nameof(ImageElement)}");
break;
default:
Expand All @@ -60,7 +70,10 @@ public override void Write(Utf8JsonWriter writer, ImageElement value, JsonSerial
writer.WriteStartObject();
writer.WritePropertyName(nameof(ImageElement.ImageId));
ImageIdConverter.Instance.Write(writer, value.ImageId, options);
writer.WriteString(nameof(ImageElement.AutomationName), value.AutomationName);

if (value.AutomationName != null)
writer.WriteString(nameof(ImageElement.AutomationName), value.AutomationName);

writer.WriteString(ObjectContentConverter.TypeProperty, nameof(ImageElement));
writer.WriteEndObject();
}
Expand Down
57 changes: 45 additions & 12 deletions src/LanguageServer/Protocol/Protocol/Internal/Converters/ImageIdConverter.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -8,6 +8,7 @@
using Roslyn.Core.Imaging;

namespace Roslyn.LanguageServer.Protocol;

internal sealed class ImageIdConverter : JsonConverter<ImageId>
{
public static readonly ImageIdConverter Instance = new();
Expand All @@ -16,21 +17,53 @@ public override ImageId Read(ref Utf8JsonReader reader, Type objectType, JsonSer
{
if (reader.TokenType == JsonTokenType.StartObject)
{
using var document = JsonDocument.ParseValue(ref reader);
var root = document.RootElement;
if (root.TryGetProperty(ObjectContentConverter.TypeProperty, out var typeProperty) && typeProperty.GetString() != nameof(ImageId))
Guid? guid = null;
int? id = null;

Span<char> scratchChars = stackalloc char[64];

while (reader.Read())
{
throw new JsonException($"Expected {ObjectContentConverter.TypeProperty} property value {nameof(ImageId)}");
}
if (reader.TokenType == JsonTokenType.EndObject)
{
if (guid is null || id is null)
throw new JsonException("Expected properties Guid and Id to be present");

var guid = root.GetProperty(nameof(ImageId.Guid)).GetString() ?? throw new JsonException();
var id = root.GetProperty(nameof(ImageId.Id)).GetInt32();
return new ImageId(new Guid(guid), id);
}
else
{
throw new JsonException("Expected start object or null tokens");
return new ImageId(guid.Value, id.Value);
}

if (reader.TokenType == JsonTokenType.PropertyName)
{
var valueLength = reader.HasValueSequence ? reader.ValueSequence.Length : reader.ValueSpan.Length;

var propertyNameLength = valueLength <= scratchChars.Length ? reader.CopyString(scratchChars) : -1;
var propertyName = propertyNameLength >= 0 ? scratchChars[..propertyNameLength] : reader.GetString().AsSpan();

reader.Read();
switch (propertyName)
{
case nameof(ImageId.Guid):
guid = reader.GetGuid();
break;
case nameof(ImageId.Id):
id = reader.GetInt32();
break;
case ObjectContentConverter.TypeProperty:
var typePropertyLength = valueLength <= scratchChars.Length ? reader.CopyString(scratchChars) : -1;
var typeProperty = typePropertyLength >= 0 ? scratchChars[..typePropertyLength] : reader.GetString().AsSpan();

if (!typeProperty.SequenceEqual(nameof(ImageId).AsSpan()))
throw new JsonException($"Expected {ObjectContentConverter.TypeProperty} property value {nameof(ImageId)}");
break;
default:
reader.Skip();
break;
}
}
}
}

throw new JsonException("Expected start object or null tokens");
}

public override void Write(Utf8JsonWriter writer, ImageId value, JsonSerializerOptions options)
Expand Down
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