Class PooledArrayConverter<T>

Namespace

MassiveDotNet.Serialization

Assembly

MassiveDotNet.dll

Reads a JSON array into a pooled buffer and copies it out once, so materializing a large result page allocates the array it returns and nothing else.

public sealed class PooledArrayConverter<T> : JsonConverter<T[]>

Type Parameters

T

The element type, resolved through the serializer's source-generated context.

Inheritance

object

JsonConverter

JsonConverter<T[]>

PooledArrayConverter<T>

Inherited Members

JsonConverter<T[]>.CanConvert(Type)

JsonConverter<T[]>.Read(ref Utf8JsonReader, Type, JsonSerializerOptions)

JsonConverter<T[]>.ReadAsPropertyName(ref Utf8JsonReader, Type, JsonSerializerOptions)

JsonConverter<T[]>.Write(Utf8JsonWriter, T[], JsonSerializerOptions)

JsonConverter<T[]>.WriteAsPropertyName(Utf8JsonWriter, T[], JsonSerializerOptions)

JsonConverter<T[]>.HandleNull

JsonConverter<T[]>.Type

JsonConverter.CanConvert(Type)

JsonConverter.Type

object.Equals(object)

object.Equals(object, object)

object.GetHashCode()

object.GetType()

object.ReferenceEquals(object, object)

object.ToString()

Remarks

System.Text.Json builds an array by filling a List<T> and calling ToArray. List<T> doubles its backing array as it grows, so every intermediate buffer is discarded. For a class element each discarded slot is an 8-byte reference and the churn disappears against the objects themselves; for an 88-byte readonly record struct row (decision D4) each slot is the whole value, and a 50,000-row response allocated 8.8 times the array it returned.

Renting the growth buffers instead means they are reused rather than collected, which leaves the returned array as very nearly the only allocation on the path. The buffer is returned in a finally so a malformed body cannot leak it out of the pool, and cleared on return only when T carries references, since clearing a block of numeric structs costs a memset for no benefit.

Applied by the generator as a property attribute rather than registered as a JsonConverterFactory: a factory has to build its converter through MakeGenericType, which is reflection over a generic instantiation the trimmer cannot see, and constitution rules 3 and 4 rule that out. An attribute names the closed type at compile time, so every instantiation is rooted in the generated code.

Methods

Read(ref Utf8JsonReader, Type, JsonSerializerOptions)

Reads and converts the JSON to type T.

public override T[]? Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)

Parameters

reader Utf8JsonReader

The reader.

typeToConvert Type

The type to convert.

options JsonSerializerOptions

An object that specifies serialization options to use.

Returns

T[]

The converted value.

Write(Utf8JsonWriter, T[], JsonSerializerOptions)

Writes a specified value as JSON.

public override void Write(Utf8JsonWriter writer, T[] value, JsonSerializerOptions options)

Parameters

writer Utf8JsonWriter

The writer to write to.

value T[]

The value to convert to JSON.

options JsonSerializerOptions

An object that specifies serialization options to use.