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package antlr
var BasePredictionContextEMPTY = &PredictionContext{
cachedHash: calculateEmptyHash(),
pcType: PredictionContextEmpty,
returnState: BasePredictionContextEmptyReturnState,
}
// PredictionContextCache is Used to cache [PredictionContext] objects. It is used for the shared
// context cash associated with contexts in DFA states. This cache
// can be used for both lexers and parsers.
type PredictionContextCache struct {
cache *JMap[*PredictionContext, *PredictionContext, Comparator[*PredictionContext]]
}
func NewPredictionContextCache() *PredictionContextCache {
return &PredictionContextCache{
cache: NewJMap[*PredictionContext, *PredictionContext, Comparator[*PredictionContext]](pContextEqInst, PredictionContextCacheCollection, "NewPredictionContextCache()"),
}
}
// Add a context to the cache and return it. If the context already exists,
// return that one instead and do not add a new context to the cache.
// Protect shared cache from unsafe thread access.
func (p *PredictionContextCache) add(ctx *PredictionContext) *PredictionContext {
if ctx.isEmpty() {
return BasePredictionContextEMPTY
}
// Put will return the existing entry if it is present (note this is done via Equals, not whether it is
// the same pointer), otherwise it will add the new entry and return that.
//
existing, present := p.cache.Get(ctx)
if present {
return existing
}
p.cache.Put(ctx, ctx)
return ctx
}
func (p *PredictionContextCache) Get(ctx *PredictionContext) (*PredictionContext, bool) {
pc, exists := p.cache.Get(ctx)
return pc, exists
}
func (p *PredictionContextCache) length() int {
return p.cache.Len()
}
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