ArcIterator< GrammarFst > Class Template Reference

This is the overridden template for class ArcIterator for GrammarFst. More...

#include <grammar-fst.h>

Collaboration diagram for ArcIterator< GrammarFst >:

Public Types
using	Arc = typename GrammarFst::Arc
using	BaseArc = StdArc
using	StateId = typename Arc::StateId
using	BaseStateId = typename StdArc::StateId
using	ExpandedState = GrammarFst::ExpandedState

Public Member Functions
	ArcIterator (const GrammarFst &fst_in, StateId s)
bool	Done ()
void	Next ()
const Arc &	Value () const

Private Member Functions
void	CopyArcToTemp ()

Private Attributes
ArcIteratorData< StdArc >	data_
int32	dest_instance_
size_t	i_
Arc	arc_

Detailed Description

template<>
class fst::ArcIterator< GrammarFst >

This is the overridden template for class ArcIterator for GrammarFst.

This is only used in the decoder, and the GrammarFst is not a "real" FST (it just has a very similar-looking interface), so we don't need to implement all the functionality that the regular ArcIterator has.

Definition at line 496 of file grammar-fst.h.

Member Typedef Documentation

Arc

using Arc = typename GrammarFst::Arc

Definition at line 498 of file grammar-fst.h.

BaseArc

using BaseArc = StdArc

Definition at line 499 of file grammar-fst.h.

BaseStateId

using BaseStateId = typename StdArc::StateId

Definition at line 501 of file grammar-fst.h.

ExpandedState

using ExpandedState = GrammarFst::ExpandedState

Definition at line 502 of file grammar-fst.h.

StateId

using StateId = typename Arc::StateId

Definition at line 500 of file grammar-fst.h.

Constructor & Destructor Documentation

ArcIterator()

ArcIterator ( const GrammarFst &  fst_in, StateId  s  )

inline

Definition at line 506 of file grammar-fst.h.

References GrammarFst::ExpandedState::arcs, data_, GrammarFst::ExpandedState::dest_fst_instance, GrammarFst::FstInstance::fst, GrammarFst::GetExpandedState(), GrammarFst::instances_, and KALDI_GRAMMAR_FST_SPECIAL_WEIGHT.

                                                          {
    GrammarFst &fst = const_cast<GrammarFst&>(fst_in);
    // 'instance_id' is the high order bits of the state.
    int32 instance_id = s >> 32;
    // 'base_state' is low order bits of the state.  It's important to
    // explicitly say int32 below, not BaseStateId == int, which might on some
    // compilers be a 64-bit type.
    BaseStateId base_state = static_cast<int32>(s);
    const GrammarFst::FstInstance &instance = fst.instances_[instance_id];
    const ConstFst<StdArc> *base_fst = instance.fst;
    if (base_fst->Final(base_state).Value() != KALDI_GRAMMAR_FST_SPECIAL_WEIGHT) {
      // A normal state
      dest_instance_ = instance_id;
      base_fst->InitArcIterator(s, &data_);
      i_ = 0;
    } else {
      // A special state
      ExpandedState *expanded_state = fst.GetExpandedState(instance_id,
                                                           base_state);
      dest_instance_ = expanded_state->dest_fst_instance;
      // it's ok to leave the other members of data_ uninitialized, as they will
      // never be interrogated.
      data_.arcs = &(expanded_state->arcs[0]);
      data_.narcs = expanded_state->arcs.size();
      i_ = 0;
    }
    // Ideally we want to call CopyArcToTemp() now, but we rely on the fact that
    // the calling code needs to call Done() before accessing Value(); we call
    // CopyArcToTemp() from Done().  Of course this is slightly against the
    // semantics of Done(), but it's more efficient to have Done() call
    // CopyArcToTemp() than this function or Next(), as Done() already has to
    // test that the arc-iterator has not reached the end.
  }

Member Function Documentation

CopyArcToTemp()

void CopyArcToTemp ( )

inlineprivate

Definition at line 564 of file grammar-fst.h.

References data_.

                              {
    const StdArc &src = data_.arcs[i_];
    arc_.ilabel = src.ilabel;
    arc_.olabel = src.olabel;
    arc_.weight = src.weight;
    arc_.nextstate = (static_cast<int64>(dest_instance_) << 32) |
        src.nextstate;
  }

Done()

bool Done ( )

inline

Definition at line 540 of file grammar-fst.h.

References data_.

Referenced by fst::CopyToVectorFst().

                     {
    if (i_ < data_.narcs) {
      CopyArcToTemp();
      return false;
    } else {
      return true;
    }
  }

Next()

void Next ( )

inline

Definition at line 549 of file grammar-fst.h.

Referenced by fst::CopyToVectorFst().

                     {
    i_++;
    // Note: logically, at this point we should do:
    // if (i_ < data_.size)
    //  CopyArcToTemp();
    // Instead we move this CopyArcToTemp() invocation into Done(), which we
    // know will always be called after Next() and before Value(), because the
    // user has no other way of knowing whether the iterator is still valid.
    // This is for efficiency.
  }

Value()

const Arc& Value ( ) const

inline

Definition at line 560 of file grammar-fst.h.

Referenced by fst::CopyToVectorFst().

{ return arc_; }

Member Data Documentation

arc_

Arc arc_

private

Definition at line 583 of file grammar-fst.h.

data_

ArcIteratorData<StdArc> data_

private

Definition at line 576 of file grammar-fst.h.

dest_instance_

int32 dest_instance_

private

Definition at line 579 of file grammar-fst.h.

i_

size_t i_

private

Definition at line 581 of file grammar-fst.h.

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The documentation for this class was generated from the following file:

• decoder/grammar-fst.h