Interface ISymbolIndex

Namespace

DatabentoDotNet.Dbn

Assembly

DatabentoDotNet.Dbn.dll

Resolves a symbol for a decoded record, without the caller having to know which timestamp the record indexes on or which kind of symbol map is answering. Implemented by TsSymbolMap and PitSymbolMap.

public interface ISymbolIndex

Remarks

Port of upstream's SymbolIndex trait (symbol_map.rs:79-83). It exists so code can be written against "a symbol map" rather than against one of the two: a live session keeps a PitSymbolMap updated record by record, a historical request builds a TsSymbolMap from metadata, and a consumer that wants a symbol for the record in front of it should not have to care which it was handed.

The two implementations answer differently, and that is the design. TsSymbolMap keys on the record's own index date; PitSymbolMap ignores the record's timestamp entirely and keys on the instrument ID alone, because the caller already committed to one date when the map was built. Both match upstream's own impls (symbol_map.rs:165-171, 336-340). A PitSymbolMap that started consulting the record's date would not be a point-in-time map any more.

There is no indexer, deliberately. Upstream pairs get_for_rec with Index<&R> impls (symbol_map.rs:342-364) that unwrap(), so a miss panics; a C# indexer carries the same expectation, since that is what Dictionary<TKey, TValue> does. But a miss here is routine, not exceptional — a live stream resolves nothing for an instrument until its mapping record arrives, and a timeseries map holds nothing for a date outside the query's range. An indexer would make the ordinary case throw, so the whole surface is Try*.

Methods

TryGetSymbol(RecordRef, out string?)

Looks up the symbol for a decoded record.

bool TryGetSymbol(RecordRef record, out string? symbol)

Parameters

record RecordRef

The record to resolve.

symbol string

Receives the resolved symbol, or null when the map has no mapping for this record.

Returns

bool

true if a mapping was found.

Remarks

This is the overload a decoder loop uses, since RecordRef is what TryNextRecord hands out and no downcast is needed to resolve a symbol.

TryGetSymbol<TRecord>(in TRecord, out string?)

Looks up the symbol for a decoded record of a known type.

bool TryGetSymbol<TRecord>(in TRecord record, out string? symbol) where TRecord : unmanaged, IRecord<TRecord>

Parameters

record TRecord

The record to resolve.

symbol string

Receives the resolved symbol, or null when the map has no mapping for this record.

Returns

bool

true if a mapping was found.

Type Parameters

TRecord

The record struct.

Remarks

For a record that has been downcast or copied out of the read buffer — one held in a collection, say, where no RecordRef survives to call the other overload with. Takes the record by in so a 520-byte InstrumentDefMsg is read in place rather than copied to be asked its symbol.