API Reference — dna/JSONStreamReader

DefaultInstanceCreator<dna::JSONStreamReader>

Policy specialization that maps pma's generic construction mechanism to JSONStreamReader's create() factory method.

Why this exists

pma uses DefaultInstanceCreator<T> as a customization point so that managed containers and scoped helpers can construct any type without calling new directly. This specialization tells pma to use FactoryCreate<dna::JSONStreamReader> — which delegates to JSONStreamReader::create() — rather than a raw constructor. Without this specialization, pma infrastructure could not safely manage JSONStreamReader instances.

Fields

Name Type Description
type pma::FactoryCreate<dna::JSONStreamReader> required — the factory creator type used by pma to construct JSONStreamReader instances

Relationships

  • JSONStreamReader — the type this policy governs construction of
  • DefaultInstanceDestroyer<dna::JSONStreamReader> — paired destruction policy
  • pma::FactoryCreate — the underlying creator implementation

DefaultInstanceDestroyer<dna::JSONStreamReader>

Policy specialization that maps pma's generic destruction mechanism to JSONStreamReader's destroy() factory method.

Why this exists

pma uses DefaultInstanceDestroyer<T> as a customization point so that managed scopes and containers can release any type without calling delete directly. This specialization tells pma to use FactoryDestroy<dna::JSONStreamReader> — which delegates to JSONStreamReader::destroy() — ensuring destruction always goes through the correct factory path and avoids mismatched allocator teardown.

Fields

Name Type Description
type pma::FactoryDestroy<dna::JSONStreamReader> required — the factory destroyer type used by pma to release JSONStreamReader instances

Relationships

  • JSONStreamReader — the type this policy governs destruction of
  • DefaultInstanceCreator<dna::JSONStreamReader> — paired construction policy
  • pma::FactoryDestroy — the underlying destroyer implementation

class JSONStreamReader : public StreamReader

Factory-managed stream reader that deserializes DNA data from a JSON-formatted source. Use this when your DNA asset is stored in JSON format rather than the binary format handled by BinaryStreamReader.

When to use this

Reach for this when your DNA pipeline produces or stores assets as JSON — for example, during development or tooling workflows where human-readable output matters. For production runtime loading, prefer BinaryStreamReader: it is faster and produces smaller in-memory representations. Both classes share the same StreamReader interface, so switching between them requires only a factory-call change.

Example

// Open a JSON DNA file and read it into the runtime structure
auto* stream = pma::makeScoped<dna::FileStream>("character.dna", dna::FileStream::AccessMode::Read);
auto* reader = dna::JSONStreamReader::create(stream.get());
reader->read();
// Use reader via the StreamReader interface...
dna::JSONStreamReader::destroy(reader);

Parameters

Name Type Description
stream BoundedIOStream* required — the JSON-formatted source stream to read DNA data from
memRes MemoryResource* optional — custom memory resource for internal allocations; uses the default allocator when nullptr

Returns

JSONStreamReader* — a heap-allocated reader instance. The caller owns this pointer and must release it by calling destroy().

Watch out for

  • The returned pointer is caller-owned. Failing to call destroy(instance) leaks memory. Do not delete it with delete — always use the paired destroy() static method.
  • memRes governs only internal allocations made by the reader. The stream lifetime must exceed the reader's lifetime; the reader does not take ownership of the stream.

type

Type alias that resolves to pma::FactoryCreate<dna::JSONStreamReader>, the factory creator policy used by pma managed infrastructure to construct JSONStreamReader instances.

Why this exists

The pma customization-point protocol requires a nested type alias inside each DefaultInstanceCreator specialization. This alias is the single token that pma reads when it needs to know how to construct a T — here, delegating to JSONStreamReader::create().

Relationships

  • DefaultInstanceCreator<dna::JSONStreamReader> — the enclosing policy struct that declares this alias
  • pma::FactoryCreate<dna::JSONStreamReader> — the resolved type