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// See www.openfst.org for extensive documentation on this weighted
// finite-state transducer library.
//
// Functions and classes for the recursive replacement of FSTs.
#ifndef FST_REPLACE_H_
#define FST_REPLACE_H_
#include <set>
#include <string>
#include <unordered_map>
#include <utility>
#include <vector>
#include <fst/log.h>
#include <fst/cache.h>
#include <fst/expanded-fst.h>
#include <fst/fst-decl.h> // For optional argument declarations.
#include <fst/fst.h>
#include <fst/matcher.h>
#include <fst/replace-util.h>
#include <fst/state-table.h>
#include <fst/test-properties.h>
namespace fst {
// Replace state tables have the form:
//
// template <class Arc, class P>
// class ReplaceStateTable {
// public:
// using Label = typename Arc::Label Label;
// using StateId = typename Arc::StateId;
//
// using PrefixId = P;
// using StateTuple = ReplaceStateTuple<StateId, PrefixId>;
// using StackPrefix = ReplaceStackPrefix<Label, StateId>;
//
// // Required constructor.
// ReplaceStateTable(
// const std::vector<std::pair<Label, const Fst<Arc> *>> &fst_list,
// Label root);
//
// // Required copy constructor that does not copy state.
// ReplaceStateTable(const ReplaceStateTable<Arc, PrefixId> &table);
//
// // Looks up state ID by tuple, adding it if it doesn't exist.
// StateId FindState(const StateTuple &tuple);
//
// // Looks up state tuple by ID.
// const StateTuple &Tuple(StateId id) const;
//
// // Lookus up prefix ID by stack prefix, adding it if it doesn't exist.
// PrefixId FindPrefixId(const StackPrefix &stack_prefix);
//
// // Looks up stack prefix by ID.
// const StackPrefix &GetStackPrefix(PrefixId id) const;
// };
// Tuple that uniquely defines a state in replace.
template <class S, class P>
struct ReplaceStateTuple {
using StateId = S;
using PrefixId = P;
ReplaceStateTuple(PrefixId prefix_id = -1, StateId fst_id = kNoStateId,
StateId fst_state = kNoStateId)
: prefix_id(prefix_id), fst_id(fst_id), fst_state(fst_state) {}
PrefixId prefix_id; // Index in prefix table.
StateId fst_id; // Current FST being walked.
StateId fst_state; // Current state in FST being walked (not to be
// confused with the thse StateId of the combined FST).
};
// Equality of replace state tuples.
template <class StateId, class PrefixId>
inline bool operator==(const ReplaceStateTuple<StateId, PrefixId> &x,
const ReplaceStateTuple<StateId, PrefixId> &y) {
return x.prefix_id == y.prefix_id && x.fst_id == y.fst_id &&
x.fst_state == y.fst_state;
}
// Functor returning true for tuples corresponding to states in the root FST.
template <class StateId, class PrefixId>
class ReplaceRootSelector {
public:
bool operator()(const ReplaceStateTuple<StateId, PrefixId> &tuple) const {
return tuple.prefix_id == 0;
}
};
// Functor for fingerprinting replace state tuples.
template <class StateId, class PrefixId>
class ReplaceFingerprint {
public:
explicit ReplaceFingerprint(const std::vector<uint64> *size_array)
: size_array_(size_array) {}
uint64 operator()(const ReplaceStateTuple<StateId, PrefixId> &tuple) const {
return tuple.prefix_id * size_array_->back() +
size_array_->at(tuple.fst_id - 1) + tuple.fst_state;
}
private:
const std::vector<uint64> *size_array_;
};
// Useful when the fst_state uniquely define the tuple.
template <class StateId, class PrefixId>
class ReplaceFstStateFingerprint {
public:
uint64 operator()(const ReplaceStateTuple<StateId, PrefixId> &tuple) const {
return tuple.fst_state;
}
};
// A generic hash function for replace state tuples.
template <typename S, typename P>
class ReplaceHash {
public:
size_t operator()(const ReplaceStateTuple<S, P>& t) const {
static constexpr size_t prime0 = 7853;
static constexpr size_t prime1 = 7867;
return t.prefix_id + t.fst_id * prime0 + t.fst_state * prime1;
}
};
// Container for stack prefix.
template <class Label, class StateId>
class ReplaceStackPrefix {
public:
struct PrefixTuple {
PrefixTuple(Label fst_id = kNoLabel, StateId nextstate = kNoStateId)
: fst_id(fst_id), nextstate(nextstate) {}
Label fst_id;
StateId nextstate;
};
ReplaceStackPrefix() {}
ReplaceStackPrefix(const ReplaceStackPrefix &other)
: prefix_(other.prefix_) {}
void Push(StateId fst_id, StateId nextstate) {
prefix_.push_back(PrefixTuple(fst_id, nextstate));
}
void Pop() { prefix_.pop_back(); }
const PrefixTuple &Top() const { return prefix_[prefix_.size() - 1]; }
size_t Depth() const { return prefix_.size(); }
public:
std::vector<PrefixTuple> prefix_;
};
// Equality stack prefix classes.
template <class Label, class StateId>
inline bool operator==(const ReplaceStackPrefix<Label, StateId> &x,
const ReplaceStackPrefix<Label, StateId> &y) {
if (x.prefix_.size() != y.prefix_.size()) return false;
for (size_t i = 0; i < x.prefix_.size(); ++i) {
if (x.prefix_[i].fst_id != y.prefix_[i].fst_id ||
x.prefix_[i].nextstate != y.prefix_[i].nextstate) {
return false;
}
}
return true;
}
// Hash function for stack prefix to prefix id.
template <class Label, class StateId>
class ReplaceStackPrefixHash {
public:
size_t operator()(const ReplaceStackPrefix<Label, StateId> &prefix) const {
size_t sum = 0;
for (const auto &pair : prefix.prefix_) {
static constexpr size_t prime = 7863;
sum += pair.fst_id + pair.nextstate * prime;
}
return sum;
}
};
// Replace state tables.
// A two-level state table for replace. Warning: calls CountStates to compute
// the number of states of each component FST.
template <class Arc, class P = ssize_t>
class VectorHashReplaceStateTable {
public:
using Label = typename Arc::Label;
using StateId = typename Arc::StateId;
using PrefixId = P;
using StateTuple = ReplaceStateTuple<StateId, PrefixId>;
using StateTable =
VectorHashStateTable<ReplaceStateTuple<StateId, PrefixId>,
ReplaceRootSelector<StateId, PrefixId>,
ReplaceFstStateFingerprint<StateId, PrefixId>,
ReplaceFingerprint<StateId, PrefixId>>;
using StackPrefix = ReplaceStackPrefix<Label, StateId>;
using StackPrefixTable =
CompactHashBiTable<PrefixId, StackPrefix,
ReplaceStackPrefixHash<Label, StateId>>;
VectorHashReplaceStateTable(
const std::vector<std::pair<Label, const Fst<Arc> *>> &fst_list,
Label root)
: root_size_(0) {
size_array_.push_back(0);
for (const auto &fst_pair : fst_list) {
if (fst_pair.first == root) {
root_size_ = CountStates(*(fst_pair.second));
size_array_.push_back(size_array_.back());
} else {
size_array_.push_back(size_array_.back() +
CountStates(*(fst_pair.second)));
}
}
state_table_.reset(
new StateTable(new ReplaceRootSelector<StateId, PrefixId>,
new ReplaceFstStateFingerprint<StateId, PrefixId>,
new ReplaceFingerprint<StateId, PrefixId>(&size_array_),
root_size_, root_size_ + size_array_.back()));
}
VectorHashReplaceStateTable(
const VectorHashReplaceStateTable<Arc, PrefixId> &table)
: root_size_(table.root_size_),
size_array_(table.size_array_),
prefix_table_(table.prefix_table_) {
state_table_.reset(
new StateTable(new ReplaceRootSelector<StateId, PrefixId>,
new ReplaceFstStateFingerprint<StateId, PrefixId>,
new ReplaceFingerprint<StateId, PrefixId>(&size_array_),
root_size_, root_size_ + size_array_.back()));
}
StateId FindState(const StateTuple &tuple) {
return state_table_->FindState(tuple);
}
const StateTuple &Tuple(StateId id) const { return state_table_->Tuple(id); }
PrefixId FindPrefixId(const StackPrefix &prefix) {
return prefix_table_.FindId(prefix);
}
const StackPrefix& GetStackPrefix(PrefixId id) const {
return prefix_table_.FindEntry(id);
}
private:
StateId root_size_;
std::vector<uint64> size_array_;
std::unique_ptr<StateTable> state_table_;
StackPrefixTable prefix_table_;
};
// Default replace state table.
template <class Arc, class P /* = size_t */>
class DefaultReplaceStateTable
: public CompactHashStateTable<ReplaceStateTuple<typename Arc::StateId, P>,
ReplaceHash<typename Arc::StateId, P>> {
public:
using Label = typename Arc::Label;
using StateId = typename Arc::StateId;
using PrefixId = P;
using StateTuple = ReplaceStateTuple<StateId, PrefixId>;
using StateTable =
CompactHashStateTable<StateTuple, ReplaceHash<StateId, PrefixId>>;
using StackPrefix = ReplaceStackPrefix<Label, StateId>;
using StackPrefixTable =
CompactHashBiTable<PrefixId, StackPrefix,
ReplaceStackPrefixHash<Label, StateId>>;
using StateTable::FindState;
using StateTable::Tuple;
DefaultReplaceStateTable(
const std::vector<std::pair<Label, const Fst<Arc> *>> &, Label) {}
DefaultReplaceStateTable(const DefaultReplaceStateTable<Arc, PrefixId> &table)
: StateTable(), prefix_table_(table.prefix_table_) {}
PrefixId FindPrefixId(const StackPrefix &prefix) {
return prefix_table_.FindId(prefix);
}
const StackPrefix &GetStackPrefix(PrefixId id) const {
return prefix_table_.FindEntry(id);
}
private:
StackPrefixTable prefix_table_;
};
// By default ReplaceFst will copy the input label of the replace arc.
// The call_label_type and return_label_type options specify how to manage
// the labels of the call arc and the return arc of the replace FST
template <class Arc, class StateTable = DefaultReplaceStateTable<Arc>,
class CacheStore = DefaultCacheStore<Arc>>
struct ReplaceFstOptions : CacheImplOptions<CacheStore> {
using Label = typename Arc::Label;
// Index of root rule for expansion.
Label root;
// How to label call arc.
ReplaceLabelType call_label_type = REPLACE_LABEL_INPUT;
// How to label return arc.
ReplaceLabelType return_label_type = REPLACE_LABEL_NEITHER;
// Specifies output label to put on call arc; if kNoLabel, use existing label
// on call arc. Otherwise, use this field as the output label.
Label call_output_label = kNoLabel;
// Specifies label to put on return arc.
Label return_label = 0;
// Take ownership of input FSTs?
bool take_ownership = false;
// Pointer to optional pre-constructed state table.
StateTable *state_table = nullptr;
explicit ReplaceFstOptions(const CacheImplOptions<CacheStore> &opts,
Label root = kNoLabel)
: CacheImplOptions<CacheStore>(opts), root(root) {}
explicit ReplaceFstOptions(const CacheOptions &opts, Label root = kNoLabel)
: CacheImplOptions<CacheStore>(opts), root(root) {}
// FIXME(kbg): There are too many constructors here. Come up with a consistent
// position for call_output_label (probably the very end) so that it is
// possible to express all the remaining constructors with a single
// default-argument constructor. Also move clients off of the "backwards
// compatibility" constructor, for good.
explicit ReplaceFstOptions(Label root) : root(root) {}
explicit ReplaceFstOptions(Label root, ReplaceLabelType call_label_type,
ReplaceLabelType return_label_type,
Label return_label)
: root(root),
call_label_type(call_label_type),
return_label_type(return_label_type),
return_label(return_label) {}
explicit ReplaceFstOptions(Label root, ReplaceLabelType call_label_type,
ReplaceLabelType return_label_type,
Label call_output_label, Label return_label)
: root(root),
call_label_type(call_label_type),
return_label_type(return_label_type),
call_output_label(call_output_label),
return_label(return_label) {}
explicit ReplaceFstOptions(const ReplaceUtilOptions &opts)
: ReplaceFstOptions(opts.root, opts.call_label_type,
opts.return_label_type, opts.return_label) {}
ReplaceFstOptions() : root(kNoLabel) {}
// For backwards compatibility.
ReplaceFstOptions(int64 root, bool epsilon_replace_arc)
: root(root),
call_label_type(epsilon_replace_arc ? REPLACE_LABEL_NEITHER
: REPLACE_LABEL_INPUT),
call_output_label(epsilon_replace_arc ? 0 : kNoLabel) {}
};
// Forward declaration.
template <class Arc, class StateTable, class CacheStore>
class ReplaceFstMatcher;
template <class Arc>
using FstList = std::vector<std::pair<typename Arc::Label, const Fst<Arc> *>>;
// Returns true if label type on arc results in epsilon input label.
inline bool EpsilonOnInput(ReplaceLabelType label_type) {
return label_type == REPLACE_LABEL_NEITHER ||
label_type == REPLACE_LABEL_OUTPUT;
}
// Returns true if label type on arc results in epsilon input label.
inline bool EpsilonOnOutput(ReplaceLabelType label_type) {
return label_type == REPLACE_LABEL_NEITHER ||
label_type == REPLACE_LABEL_INPUT;
}
// Returns true if for either the call or return arc ilabel != olabel.
template <class Label>
bool ReplaceTransducer(ReplaceLabelType call_label_type,
ReplaceLabelType return_label_type,
Label call_output_label) {
return call_label_type == REPLACE_LABEL_INPUT ||
call_label_type == REPLACE_LABEL_OUTPUT ||
(call_label_type == REPLACE_LABEL_BOTH &&
call_output_label != kNoLabel) ||
return_label_type == REPLACE_LABEL_INPUT ||
return_label_type == REPLACE_LABEL_OUTPUT;
}
template <class Arc>
uint64 ReplaceFstProperties(typename Arc::Label root_label,
const FstList<Arc> &fst_list,
ReplaceLabelType call_label_type,
ReplaceLabelType return_label_type,
typename Arc::Label call_output_label,
bool *sorted_and_non_empty) {
using Label = typename Arc::Label;
std::vector<uint64> inprops;
bool all_ilabel_sorted = true;
bool all_olabel_sorted = true;
bool all_non_empty = true;
// All nonterminals are negative?
bool all_negative = true;
// All nonterminals are positive and form a dense range containing 1?
bool dense_range = true;
Label root_fst_idx = 0;
for (Label i = 0; i < fst_list.size(); ++i) {
const auto label = fst_list[i].first;
if (label >= 0) all_negative = false;
if (label > fst_list.size() || label <= 0) dense_range = false;
if (label == root_label) root_fst_idx = i;
const auto *fst = fst_list[i].second;
if (fst->Start() == kNoStateId) all_non_empty = false;
if (!fst->Properties(kILabelSorted, false)) all_ilabel_sorted = false;
if (!fst->Properties(kOLabelSorted, false)) all_olabel_sorted = false;
inprops.push_back(fst->Properties(kCopyProperties, false));
}
const auto props = ReplaceProperties(
inprops, root_fst_idx, EpsilonOnInput(call_label_type),
EpsilonOnInput(return_label_type), EpsilonOnOutput(call_label_type),
EpsilonOnOutput(return_label_type),
ReplaceTransducer(call_label_type, return_label_type, call_output_label),
all_non_empty, all_ilabel_sorted, all_olabel_sorted,
all_negative || dense_range);
const bool sorted = props & (kILabelSorted | kOLabelSorted);
*sorted_and_non_empty = all_non_empty && sorted;
return props;
}
namespace internal {
// The replace implementation class supports a dynamic expansion of a recursive
// transition network represented as label/FST pairs with dynamic replacable
// arcs.
template <class Arc, class StateTable, class CacheStore>
class ReplaceFstImpl
: public CacheBaseImpl<typename CacheStore::State, CacheStore> {
public:
using Label = typename Arc::Label;
using StateId = typename Arc::StateId;
using Weight = typename Arc::Weight;
using State = typename CacheStore::State;
using CacheImpl = CacheBaseImpl<State, CacheStore>;
using PrefixId = typename StateTable::PrefixId;
using StateTuple = ReplaceStateTuple<StateId, PrefixId>;
using StackPrefix = ReplaceStackPrefix<Label, StateId>;
using NonTerminalHash = std::unordered_map<Label, Label>;
using FstImpl<Arc>::SetType;
using FstImpl<Arc>::SetProperties;
using FstImpl<Arc>::WriteHeader;
using FstImpl<Arc>::SetInputSymbols;
using FstImpl<Arc>::SetOutputSymbols;
using FstImpl<Arc>::InputSymbols;
using FstImpl<Arc>::OutputSymbols;
using CacheImpl::PushArc;
using CacheImpl::HasArcs;
using CacheImpl::HasFinal;
using CacheImpl::HasStart;
using CacheImpl::SetArcs;
using CacheImpl::SetFinal;
using CacheImpl::SetStart;
friend class ReplaceFstMatcher<Arc, StateTable, CacheStore>;
ReplaceFstImpl(const FstList<Arc> &fst_list,
const ReplaceFstOptions<Arc, StateTable, CacheStore> &opts)
: CacheImpl(opts),
call_label_type_(opts.call_label_type),
return_label_type_(opts.return_label_type),
call_output_label_(opts.call_output_label),
return_label_(opts.return_label),
state_table_(opts.state_table ? opts.state_table
: new StateTable(fst_list, opts.root)) {
SetType("replace");
// If the label is epsilon, then all replace label options are equivalent,
// so we set the label types to NEITHER for simplicity.
if (call_output_label_ == 0) call_label_type_ = REPLACE_LABEL_NEITHER;
if (return_label_ == 0) return_label_type_ = REPLACE_LABEL_NEITHER;
if (!fst_list.empty()) {
SetInputSymbols(fst_list[0].second->InputSymbols());
SetOutputSymbols(fst_list[0].second->OutputSymbols());
}
fst_array_.push_back(nullptr);
for (Label i = 0; i < fst_list.size(); ++i) {
const auto label = fst_list[i].first;
const auto *fst = fst_list[i].second;
nonterminal_hash_[label] = fst_array_.size();
nonterminal_set_.insert(label);
fst_array_.emplace_back(opts.take_ownership ? fst : fst->Copy());
if (i) {
if (!CompatSymbols(InputSymbols(), fst->InputSymbols())) {
FSTERROR() << "ReplaceFstImpl: Input symbols of FST " << i
<< " do not match input symbols of base FST (0th FST)";
SetProperties(kError, kError);
}
if (!CompatSymbols(OutputSymbols(), fst->OutputSymbols())) {
FSTERROR() << "ReplaceFstImpl: Output symbols of FST " << i
<< " do not match output symbols of base FST (0th FST)";
SetProperties(kError, kError);
}
}
}
const auto nonterminal = nonterminal_hash_[opts.root];
if ((nonterminal == 0) && (fst_array_.size() > 1)) {
FSTERROR() << "ReplaceFstImpl: No FST corresponding to root label "
<< opts.root << " in the input tuple vector";
SetProperties(kError, kError);
}
root_ = (nonterminal > 0) ? nonterminal : 1;
bool all_non_empty_and_sorted = false;
SetProperties(ReplaceFstProperties(opts.root, fst_list, call_label_type_,
return_label_type_, call_output_label_,
&all_non_empty_and_sorted));
// Enables optional caching as long as sorted and all non-empty.
always_cache_ = !all_non_empty_and_sorted;
VLOG(2) << "ReplaceFstImpl::ReplaceFstImpl: always_cache = "
<< (always_cache_ ? "true" : "false");
}
ReplaceFstImpl(const ReplaceFstImpl &impl)
: CacheImpl(impl),
call_label_type_(impl.call_label_type_),
return_label_type_(impl.return_label_type_),
call_output_label_(impl.call_output_label_),
return_label_(impl.return_label_),
always_cache_(impl.always_cache_),
state_table_(new StateTable(*(impl.state_table_))),
nonterminal_set_(impl.nonterminal_set_),
nonterminal_hash_(impl.nonterminal_hash_),
root_(impl.root_) {
SetType("replace");
SetProperties(impl.Properties(), kCopyProperties);
SetInputSymbols(impl.InputSymbols());
SetOutputSymbols(impl.OutputSymbols());
fst_array_.reserve(impl.fst_array_.size());
fst_array_.emplace_back(nullptr);
for (Label i = 1; i < impl.fst_array_.size(); ++i) {
fst_array_.emplace_back(impl.fst_array_[i]->Copy(true));
}
}
// Computes the dependency graph of the replace class and returns
// true if the dependencies are cyclic. Cyclic dependencies will result
// in an un-expandable FST.
bool CyclicDependencies() const {
const ReplaceUtilOptions opts(root_);
ReplaceUtil<Arc> replace_util(fst_array_, nonterminal_hash_, opts);
return replace_util.CyclicDependencies();
}
StateId Start() {
if (!HasStart()) {
if (fst_array_.size() == 1) {
SetStart(kNoStateId);
return kNoStateId;
} else {
const auto fst_start = fst_array_[root_]->Start();
if (fst_start == kNoStateId) return kNoStateId;
const auto prefix = GetPrefixId(StackPrefix());
const auto start =
state_table_->FindState(StateTuple(prefix, root_, fst_start));
SetStart(start);
return start;
}
} else {
return CacheImpl::Start();
}
}
Weight Final(StateId s) {
if (HasFinal(s)) return CacheImpl::Final(s);
const auto &tuple = state_table_->Tuple(s);
auto weight = Weight::Zero();
if (tuple.prefix_id == 0) {
const auto fst_state = tuple.fst_state;
weight = fst_array_[tuple.fst_id]->Final(fst_state);
}
if (always_cache_ || HasArcs(s)) SetFinal(s, weight);
return weight;
}
size_t NumArcs(StateId s) {
if (HasArcs(s)) {
return CacheImpl::NumArcs(s);
} else if (always_cache_) { // If always caching, expands and caches state.
Expand(s);
return CacheImpl::NumArcs(s);
} else { // Otherwise computes the number of arcs without expanding.
const auto tuple = state_table_->Tuple(s);
if (tuple.fst_state == kNoStateId) return 0;
auto num_arcs = fst_array_[tuple.fst_id]->NumArcs(tuple.fst_state);
if (ComputeFinalArc(tuple, nullptr)) ++num_arcs;
return num_arcs;
}
}
// Returns whether a given label is a non-terminal.
bool IsNonTerminal(Label label) const {
if (label < *nonterminal_set_.begin() ||
label > *nonterminal_set_.rbegin()) {
return false;
} else {
return nonterminal_hash_.count(label);
}
// TODO(allauzen): be smarter and take advantage of all_dense or
// all_negative. Also use this in ComputeArc. This would require changes to
// Replace so that recursing into an empty FST lead to a non co-accessible
// state instead of deleting the arc as done currently. The current use
// correct, since labels are sorted if all_non_empty is true.
}
size_t NumInputEpsilons(StateId s) {
if (HasArcs(s)) {
return CacheImpl::NumInputEpsilons(s);
} else if (always_cache_ || !Properties(kILabelSorted)) {
// If always caching or if the number of input epsilons is too expensive
// to compute without caching (i.e., not ilabel-sorted), then expands and
// caches state.
Expand(s);
return CacheImpl::NumInputEpsilons(s);
} else {
// Otherwise, computes the number of input epsilons without caching.
const auto tuple = state_table_->Tuple(s);
if (tuple.fst_state == kNoStateId) return 0;
size_t num = 0;
if (!EpsilonOnInput(call_label_type_)) {
// If EpsilonOnInput(c) is false, all input epsilon arcs
// are also input epsilons arcs in the underlying machine.
num = fst_array_[tuple.fst_id]->NumInputEpsilons(tuple.fst_state);
} else {
// Otherwise, one need to consider that all non-terminal arcs
// in the underlying machine also become input epsilon arc.
ArcIterator<Fst<Arc>> aiter(*fst_array_[tuple.fst_id], tuple.fst_state);
for (; !aiter.Done() && ((aiter.Value().ilabel == 0) ||
IsNonTerminal(aiter.Value().olabel));
aiter.Next()) {
++num;
}
}
if (EpsilonOnInput(return_label_type_) &&
ComputeFinalArc(tuple, nullptr)) {
++num;
}
return num;
}
}
size_t NumOutputEpsilons(StateId s) {
if (HasArcs(s)) {
return CacheImpl::NumOutputEpsilons(s);
} else if (always_cache_ || !Properties(kOLabelSorted)) {
// If always caching or if the number of output epsilons is too expensive
// to compute without caching (i.e., not olabel-sorted), then expands and
// caches state.
Expand(s);
return CacheImpl::NumOutputEpsilons(s);
} else {
// Otherwise, computes the number of output epsilons without caching.
const auto tuple = state_table_->Tuple(s);
if (tuple.fst_state == kNoStateId) return 0;
size_t num = 0;
if (!EpsilonOnOutput(call_label_type_)) {
// If EpsilonOnOutput(c) is false, all output epsilon arcs are also
// output epsilons arcs in the underlying machine.
num = fst_array_[tuple.fst_id]->NumOutputEpsilons(tuple.fst_state);
} else {
// Otherwise, one need to consider that all non-terminal arcs in the
// underlying machine also become output epsilon arc.
ArcIterator<Fst<Arc>> aiter(*fst_array_[tuple.fst_id], tuple.fst_state);
for (; !aiter.Done() && ((aiter.Value().olabel == 0) ||
IsNonTerminal(aiter.Value().olabel));
aiter.Next()) {
++num;
}
}
if (EpsilonOnOutput(return_label_type_) &&
ComputeFinalArc(tuple, nullptr)) {
++num;
}
return num;
}
}
uint64 Properties() const override { return Properties(kFstProperties); }
// Sets error if found, and returns other FST impl properties.
uint64 Properties(uint64 mask) const override {
if (mask & kError) {
for (Label i = 1; i < fst_array_.size(); ++i) {
if (fst_array_[i]->Properties(kError, false)) {
SetProperties(kError, kError);
}
}
}
return FstImpl<Arc>::Properties(mask);
}
// Returns the base arc iterator, and if arcs have not been computed yet,
// extends and recurses for new arcs.
void InitArcIterator(StateId s, ArcIteratorData<Arc> *data) {
if (!HasArcs(s)) Expand(s);
CacheImpl::InitArcIterator(s, data);
// TODO(allauzen): Set behaviour of generic iterator.
// Warning: ArcIterator<ReplaceFst<A>>::InitCache() relies on current
// behaviour.
}
// Extends current state (walk arcs one level deep).
void Expand(StateId s) {
const auto tuple = state_table_->Tuple(s);
if (tuple.fst_state == kNoStateId) { // Local FST is empty.
SetArcs(s);
return;
}
ArcIterator<Fst<Arc>> aiter(*fst_array_[tuple.fst_id], tuple.fst_state);
Arc arc;
// Creates a final arc when needed.
if (ComputeFinalArc(tuple, &arc)) PushArc(s, arc);
// Expands all arcs leaving the state.
for (; !aiter.Done(); aiter.Next()) {
if (ComputeArc(tuple, aiter.Value(), &arc)) PushArc(s, arc);
}
SetArcs(s);
}
void Expand(StateId s, const StateTuple &tuple,
const ArcIteratorData<Arc> &data) {
if (tuple.fst_state == kNoStateId) { // Local FST is empty.
SetArcs(s);
return;
}
ArcIterator<Fst<Arc>> aiter(data);
Arc arc;
// Creates a final arc when needed.
if (ComputeFinalArc(tuple, &arc)) AddArc(s, arc);
// Expands all arcs leaving the state.
for (; !aiter.Done(); aiter.Next()) {
if (ComputeArc(tuple, aiter.Value(), &arc)) AddArc(s, arc);
}
SetArcs(s);
}
// If acpp is null, only returns true if a final arcp is required, but does
// not actually compute it.
bool ComputeFinalArc(const StateTuple &tuple, Arc *arcp,
uint32 flags = kArcValueFlags) {
const auto fst_state = tuple.fst_state;
if (fst_state == kNoStateId) return false;
// If state is final, pops the stack.
if (fst_array_[tuple.fst_id]->Final(fst_state) != Weight::Zero() &&
tuple.prefix_id) {
if (arcp) {
arcp->ilabel = (EpsilonOnInput(return_label_type_)) ? 0 : return_label_;
arcp->olabel =
(EpsilonOnOutput(return_label_type_)) ? 0 : return_label_;
if (flags & kArcNextStateValue) {
const auto &stack = state_table_->GetStackPrefix(tuple.prefix_id);
const auto prefix_id = PopPrefix(stack);
const auto &top = stack.Top();
arcp->nextstate = state_table_->FindState(
StateTuple(prefix_id, top.fst_id, top.nextstate));
}
if (flags & kArcWeightValue) {
arcp->weight = fst_array_[tuple.fst_id]->Final(fst_state);
}
}
return true;
} else {
return false;
}
}
// Computes an arc in the FST corresponding to one in the underlying machine.
// Returns false if the underlying arc corresponds to no arc in the resulting
// FST.
bool ComputeArc(const StateTuple &tuple, const Arc &arc, Arc *arcp,
uint32 flags = kArcValueFlags) {
if (!EpsilonOnInput(call_label_type_) &&
(flags == (flags & (kArcILabelValue | kArcWeightValue)))) {
*arcp = arc;
return true;
}
if (arc.olabel == 0 || arc.olabel < *nonterminal_set_.begin() ||
arc.olabel > *nonterminal_set_.rbegin()) { // Expands local FST.
const auto nextstate =
flags & kArcNextStateValue
? state_table_->FindState(
StateTuple(tuple.prefix_id, tuple.fst_id, arc.nextstate))
: kNoStateId;
*arcp = Arc(arc.ilabel, arc.olabel, arc.weight, nextstate);
} else {
// Checks for non-terminal.
const auto it = nonterminal_hash_.find(arc.olabel);
if (it != nonterminal_hash_.end()) { // Recurses into non-terminal.
const auto nonterminal = it->second;
const auto nt_prefix =
PushPrefix(state_table_->GetStackPrefix(tuple.prefix_id),
tuple.fst_id, arc.nextstate);
// If the start state is valid, replace; othewise, the arc is implicitly
// deleted.
const auto nt_start = fst_array_[nonterminal]->Start();
if (nt_start != kNoStateId) {
const auto nt_nextstate = flags & kArcNextStateValue
? state_table_->FindState(StateTuple(
nt_prefix, nonterminal, nt_start))
: kNoStateId;
const auto ilabel =
(EpsilonOnInput(call_label_type_)) ? 0 : arc.ilabel;
const auto olabel =
(EpsilonOnOutput(call_label_type_))
? 0
: ((call_output_label_ == kNoLabel) ? arc.olabel
: call_output_label_);
*arcp = Arc(ilabel, olabel, arc.weight, nt_nextstate);
} else {
return false;
}
} else {
const auto nextstate =
flags & kArcNextStateValue
? state_table_->FindState(
StateTuple(tuple.prefix_id, tuple.fst_id, arc.nextstate))
: kNoStateId;
*arcp = Arc(arc.ilabel, arc.olabel, arc.weight, nextstate);
}
}
return true;
}
// Returns the arc iterator flags supported by this FST.
uint32 ArcIteratorFlags() const {
uint32 flags = kArcValueFlags;
if (!always_cache_) flags |= kArcNoCache;
return flags;
}
StateTable *GetStateTable() const { return state_table_.get(); }
const Fst<Arc> *GetFst(Label fst_id) const {
return fst_array_[fst_id].get();
}
Label GetFstId(Label nonterminal) const {
const auto it = nonterminal_hash_.find(nonterminal);
if (it == nonterminal_hash_.end()) {
FSTERROR() << "ReplaceFstImpl::GetFstId: Nonterminal not found: "
<< nonterminal;
}
return it->second;
}
// Returns true if label type on call arc results in epsilon input label.
bool EpsilonOnCallInput() { return EpsilonOnInput(call_label_type_); }
private:
// The unique index into stack prefix table.
PrefixId GetPrefixId(const StackPrefix &prefix) {
return state_table_->FindPrefixId(prefix);
}
// The prefix ID after a stack pop.
PrefixId PopPrefix(StackPrefix prefix) {
prefix.Pop();
return GetPrefixId(prefix);
}
// The prefix ID after a stack push.
PrefixId PushPrefix(StackPrefix prefix, Label fst_id, StateId nextstate) {
prefix.Push(fst_id, nextstate);
return GetPrefixId(prefix);
}
// Runtime options
ReplaceLabelType call_label_type_; // How to label call arc.
ReplaceLabelType return_label_type_; // How to label return arc.
int64 call_output_label_; // Specifies output label to put on call arc
int64 return_label_; // Specifies label to put on return arc.
bool always_cache_; // Disable optional caching of arc iterator?
// State table.
std::unique_ptr<StateTable> state_table_;
// Replace components.
std::set<Label> nonterminal_set_;
NonTerminalHash nonterminal_hash_;
std::vector<std::unique_ptr<const Fst<Arc>>> fst_array_;
Label root_;
};
} // namespace internal
//
// ReplaceFst supports dynamic replacement of arcs in one FST with another FST.
// This replacement is recursive. ReplaceFst can be used to support a variety of
// delayed constructions such as recursive
// transition networks, union, or closure. It is constructed with an array of
// FST(s). One FST represents the root (or topology) machine. The root FST
// refers to other FSTs by recursively replacing arcs labeled as non-terminals
// with the matching non-terminal FST. Currently the ReplaceFst uses the output
// symbols of the arcs to determine whether the arc is a non-terminal arc or
// not. A non-terminal can be any label that is not a non-zero terminal label in
// the output alphabet.
//
// Note that the constructor uses a vector of pairs. These correspond to the
// tuple of non-terminal Label and corresponding FST. For example to implement
// the closure operation we need 2 FSTs. The first root FST is a single
// self-loop arc on the start state.
//
// The ReplaceFst class supports an optionally caching arc iterator.
//
// The ReplaceFst needs to be built such that it is known to be ilabel- or
// olabel-sorted (see usage below).
//
// Observe that Matcher<Fst<A>> will use the optionally caching arc iterator
// when available (the FST is ilabel-sorted and matching on the input, or the
// FST is olabel -orted and matching on the output). In order to obtain the
// most efficient behaviour, it is recommended to set call_label_type to
// REPLACE_LABEL_INPUT or REPLACE_LABEL_BOTH and return_label_type to
// REPLACE_LABEL_OUTPUT or REPLACE_LABEL_NEITHER. This means that the call arc
// does not have epsilon on the input side and the return arc has epsilon on the
// input side) and matching on the input side.
//
// This class attaches interface to implementation and handles reference
// counting, delegating most methods to ImplToFst.
template <class A, class T /* = DefaultReplaceStateTable<A> */,
class CacheStore /* = DefaultCacheStore<A> */>
class ReplaceFst
: public ImplToFst<internal::ReplaceFstImpl<A, T, CacheStore>> {
public:
using Arc = A;
using Label = typename Arc::Label;
using StateId = typename Arc::StateId;
using Weight = typename Arc::Weight;
using StateTable = T;
using Store = CacheStore;
using State = typename CacheStore::State;
using Impl = internal::ReplaceFstImpl<Arc, StateTable, CacheStore>;
using CacheImpl = internal::CacheBaseImpl<State, CacheStore>;
using ImplToFst<Impl>::Properties;
friend class ArcIterator<ReplaceFst<Arc, StateTable, CacheStore>>;
friend class StateIterator<ReplaceFst<Arc, StateTable, CacheStore>>;
friend class ReplaceFstMatcher<Arc, StateTable, CacheStore>;
ReplaceFst(const std::vector<std::pair<Label, const Fst<Arc> *>> &fst_array,
Label root)
: ImplToFst<Impl>(std::make_shared<Impl>(
fst_array, ReplaceFstOptions<Arc, StateTable, CacheStore>(root))) {}
ReplaceFst(const std::vector<std::pair<Label, const Fst<Arc> *>> &fst_array,
const ReplaceFstOptions<Arc, StateTable, CacheStore> &opts)
: ImplToFst<Impl>(std::make_shared<Impl>(fst_array, opts)) {}
// See Fst<>::Copy() for doc.
ReplaceFst(const ReplaceFst<Arc, StateTable, CacheStore> &fst,
bool safe = false)
: ImplToFst<Impl>(fst, safe) {}
// Get a copy of this ReplaceFst. See Fst<>::Copy() for further doc.
ReplaceFst<Arc, StateTable, CacheStore> *Copy(
bool safe = false) const override {
return new ReplaceFst<Arc, StateTable, CacheStore>(*this, safe);
}
inline void InitStateIterator(StateIteratorData<Arc> *data) const override;
void InitArcIterator(StateId s, ArcIteratorData<Arc> *data) const override {
GetMutableImpl()->InitArcIterator(s, data);
}
MatcherBase<Arc> *InitMatcher(MatchType match_type) const override {
if ((GetImpl()->ArcIteratorFlags() & kArcNoCache) &&
((match_type == MATCH_INPUT && Properties(kILabelSorted, false)) ||
(match_type == MATCH_OUTPUT && Properties(kOLabelSorted, false)))) {
return new ReplaceFstMatcher<Arc, StateTable, CacheStore>
(this, match_type);
} else {
VLOG(2) << "Not using replace matcher";
return nullptr;
}
}
bool CyclicDependencies() const { return GetImpl()->CyclicDependencies(); }
const StateTable &GetStateTable() const {
return *GetImpl()->GetStateTable();
}
const Fst<Arc> &GetFst(Label nonterminal) const {
return *GetImpl()->GetFst(GetImpl()->GetFstId(nonterminal));
}
private:
using ImplToFst<Impl>::GetImpl;
using ImplToFst<Impl>::GetMutableImpl;
ReplaceFst &operator=(const ReplaceFst &) = delete;
};
// Specialization for ReplaceFst.
template <class Arc, class StateTable, class CacheStore>
class StateIterator<ReplaceFst<Arc, StateTable, CacheStore>>
: public CacheStateIterator<ReplaceFst<Arc, StateTable, CacheStore>> {
public:
explicit StateIterator(const ReplaceFst<Arc, StateTable, CacheStore> &fst)
: CacheStateIterator<ReplaceFst<Arc, StateTable, CacheStore>>(
fst, fst.GetMutableImpl()) {}
};
// Specialization for ReplaceFst, implementing optional caching. It is be used
// as follows:
//
// ReplaceFst<A> replace;
// ArcIterator<ReplaceFst<A>> aiter(replace, s);
// // Note: ArcIterator< Fst<A>> is always a caching arc iterator.
// aiter.SetFlags(kArcNoCache, kArcNoCache);
// // Uses the arc iterator, no arc will be cached, no state will be expanded.
// // Arc flags can be used to decide which component of the arc need to be
// computed.
// aiter.SetFlags(kArcILabelValue, kArcValueFlags);
// // Wants the ilabel for this arc.
// aiter.Value(); // Does not compute the destination state.
// aiter.Next();
// aiter.SetFlags(kArcNextStateValue, kArcNextStateValue);
// // Wants the ilabel and next state for this arc.
// aiter.Value(); // Does compute the destination state and inserts it
// // in the replace state table.
// // No additional arcs have been cached at this point.
template <class Arc, class StateTable, class CacheStore>
class ArcIterator<ReplaceFst<Arc, StateTable, CacheStore>> {
public:
using StateId = typename Arc::StateId;
using StateTuple = typename StateTable::StateTuple;
ArcIterator(const ReplaceFst<Arc, StateTable, CacheStore> &fst, StateId s)
: fst_(fst),
s_(s),
pos_(0),
offset_(0),
flags_(kArcValueFlags),
arcs_(nullptr),
data_flags_(0),
final_flags_(0) {
cache_data_.ref_count = nullptr;
local_data_.ref_count = nullptr;
// If FST does not support optional caching, forces caching.
if (!(fst_.GetImpl()->ArcIteratorFlags() & kArcNoCache) &&
!(fst_.GetImpl()->HasArcs(s_))) {
fst_.GetMutableImpl()->Expand(s_);
}
// If state is already cached, use cached arcs array.
if (fst_.GetImpl()->HasArcs(s_)) {
(fst_.GetImpl())
->internal::template CacheBaseImpl<
typename CacheStore::State,
CacheStore>::InitArcIterator(s_, &cache_data_);
num_arcs_ = cache_data_.narcs;
arcs_ = cache_data_.arcs; // arcs_ is a pointer to the cached arcs.
data_flags_ = kArcValueFlags; // All the arc member values are valid.
} else { // Otherwise delay decision until Value() is called.
tuple_ = fst_.GetImpl()->GetStateTable()->Tuple(s_);
if (tuple_.fst_state == kNoStateId) {
num_arcs_ = 0;
} else {
// The decision to cache or not to cache has been defered until Value()
// or
// SetFlags() is called. However, the arc iterator is set up now to be
// ready for non-caching in order to keep the Value() method simple and
// efficient.
const auto *rfst = fst_.GetImpl()->GetFst(tuple_.fst_id);
rfst->InitArcIterator(tuple_.fst_state, &local_data_);
// arcs_ is a pointer to the arcs in the underlying machine.
arcs_ = local_data_.arcs;
// Computes the final arc (but not its destination state) if a final arc
// is required.
bool has_final_arc = fst_.GetMutableImpl()->ComputeFinalArc(
tuple_, &final_arc_, kArcValueFlags & ~kArcNextStateValue);
// Sets the arc value flags that hold for final_arc_.
final_flags_ = kArcValueFlags & ~kArcNextStateValue;
// Computes the number of arcs.
num_arcs_ = local_data_.narcs;
if (has_final_arc) ++num_arcs_;
// Sets the offset between the underlying arc positions and the
// positions
// in the arc iterator.
offset_ = num_arcs_ - local_data_.narcs;
// Defers the decision to cache or not until Value() or SetFlags() is
// called.
data_flags_ = 0;
}
}
}
~ArcIterator() {
if (cache_data_.ref_count) --(*cache_data_.ref_count);
if (local_data_.ref_count) --(*local_data_.ref_count);
}
void ExpandAndCache() const {
// TODO(allauzen): revisit this.
// fst_.GetImpl()->Expand(s_, tuple_, local_data_);
// (fst_.GetImpl())->CacheImpl<A>*>::InitArcIterator(s_,
// &cache_data_);
//
fst_.InitArcIterator(s_, &cache_data_); // Expand and cache state.
arcs_ = cache_data_.arcs; // arcs_ is a pointer to the cached arcs.
data_flags_ = kArcValueFlags; // All the arc member values are valid.
offset_ = 0; // No offset.
}
void Init() {
if (flags_ & kArcNoCache) { // If caching is disabled
// arcs_ is a pointer to the arcs in the underlying machine.
arcs_ = local_data_.arcs;
// Sets the arcs value flags that hold for arcs_.
data_flags_ = kArcWeightValue;
if (!fst_.GetMutableImpl()->EpsilonOnCallInput()) {
data_flags_ |= kArcILabelValue;
}
// Sets the offset between the underlying arc positions and the positions
// in the arc iterator.
offset_ = num_arcs_ - local_data_.narcs;
} else {
ExpandAndCache();
}
}
bool Done() const { return pos_ >= num_arcs_; }
const Arc &Value() const {
// If data_flags_ is 0, non-caching was not requested.
if (!data_flags_) {
// TODO(allauzen): Revisit this.
if (flags_ & kArcNoCache) {
// Should never happen.
FSTERROR() << "ReplaceFst: Inconsistent arc iterator flags";
}
ExpandAndCache();
}
if (pos_ - offset_ >= 0) { // The requested arc is not the final arc.
const auto &arc = arcs_[pos_ - offset_];
if ((data_flags_ & flags_) == (flags_ & kArcValueFlags)) {
// If the value flags match the recquired value flags then returns the
// arc.
return arc;
} else {
// Otherwise, compute the corresponding arc on-the-fly.
fst_.GetMutableImpl()->ComputeArc(tuple_, arc, &arc_,
flags_ & kArcValueFlags);
return arc_;
}
} else { // The requested arc is the final arc.
if ((final_flags_ & flags_) != (flags_ & kArcValueFlags)) {
// If the arc value flags that hold for the final arc do not match the
// requested value flags, then
// final_arc_ needs to be updated.
fst_.GetMutableImpl()->ComputeFinalArc(tuple_, &final_arc_,
flags_ & kArcValueFlags);
final_flags_ = flags_ & kArcValueFlags;
}
return final_arc_;
}
}
void Next() { ++pos_; }
size_t Position() const { return pos_; }
void Reset() { pos_ = 0; }
void Seek(size_t pos) { pos_ = pos; }
uint32 Flags() const { return flags_; }
void SetFlags(uint32 flags, uint32 mask) {
// Updates the flags taking into account what flags are supported
// by the FST.
flags_ &= ~mask;
flags_ |= (flags & fst_.GetImpl()->ArcIteratorFlags());
// If non-caching is not requested (and caching has not already been
// performed), then flush data_flags_ to request caching during the next
// call to Value().
if (!(flags_ & kArcNoCache) && data_flags_ != kArcValueFlags) {
if (!fst_.GetImpl()->HasArcs(s_)) data_flags_ = 0;
}
// If data_flags_ has been flushed but non-caching is requested before
// calling Value(), then set up the iterator for non-caching.
if ((flags & kArcNoCache) && (!data_flags_)) Init();
}
private:
const ReplaceFst<Arc, StateTable, CacheStore> &fst_; // Reference to the FST.
StateId s_; // State in the FST.
mutable StateTuple tuple_; // Tuple corresponding to state_.
ssize_t pos_; // Current position.
mutable ssize_t offset_; // Offset between position in iterator and in arcs_.
ssize_t num_arcs_; // Number of arcs at state_.
uint32 flags_; // Behavorial flags for the arc iterator
mutable Arc arc_; // Memory to temporarily store computed arcs.
mutable ArcIteratorData<Arc> cache_data_; // Arc iterator data in cache.
mutable ArcIteratorData<Arc> local_data_; // Arc iterator data in local FST.
mutable const Arc *arcs_; // Array of arcs.
mutable uint32 data_flags_; // Arc value flags valid for data in arcs_.
mutable Arc final_arc_; // Final arc (when required).
mutable uint32 final_flags_; // Arc value flags valid for final_arc_.
ArcIterator(const ArcIterator &) = delete;
ArcIterator &operator=(const ArcIterator &) = delete;
};
template <class Arc, class StateTable, class CacheStore>
class ReplaceFstMatcher : public MatcherBase<Arc> {
public:
using Label = typename Arc::Label;
using StateId = typename Arc::StateId;
using Weight = typename Arc::Weight;
using FST = ReplaceFst<Arc, StateTable, CacheStore>;
using LocalMatcher = MultiEpsMatcher<Matcher<Fst<Arc>>>;
using StateTuple = typename StateTable::StateTuple;
// This makes a copy of the FST.
ReplaceFstMatcher(const ReplaceFst<Arc, StateTable, CacheStore> &fst,
MatchType match_type)
: owned_fst_(fst.Copy()),
fst_(*owned_fst_),
impl_(fst_.GetMutableImpl()),
s_(fst::kNoStateId),
match_type_(match_type),
current_loop_(false),
final_arc_(false),
loop_(kNoLabel, 0, Weight::One(), kNoStateId) {
if (match_type_ == fst::MATCH_OUTPUT) {
std::swap(loop_.ilabel, loop_.olabel);
}
InitMatchers();
}
// This doesn't copy the FST.
ReplaceFstMatcher(const ReplaceFst<Arc, StateTable, CacheStore> *fst,
MatchType match_type)
: fst_(*fst),
impl_(fst_.GetMutableImpl()),
s_(fst::kNoStateId),
match_type_(match_type),
current_loop_(false),
final_arc_(false),
loop_(kNoLabel, 0, Weight::One(), kNoStateId) {
if (match_type_ == fst::MATCH_OUTPUT) {
std::swap(loop_.ilabel, loop_.olabel);
}
InitMatchers();
}
// This makes a copy of the FST.
ReplaceFstMatcher(
const ReplaceFstMatcher<Arc, StateTable, CacheStore> &matcher,
bool safe = false)
: owned_fst_(matcher.fst_.Copy(safe)),
fst_(*owned_fst_),
impl_(fst_.GetMutableImpl()),
s_(fst::kNoStateId),
match_type_(matcher.match_type_),
current_loop_(false),
final_arc_(false),
loop_(fst::kNoLabel, 0, Weight::One(), fst::kNoStateId) {
if (match_type_ == fst::MATCH_OUTPUT) {
std::swap(loop_.ilabel, loop_.olabel);
}
InitMatchers();
}
// Creates a local matcher for each component FST in the RTN. LocalMatcher is
// a multi-epsilon wrapper matcher. MultiEpsilonMatcher is used to match each
// non-terminal arc, since these non-terminal
// turn into epsilons on recursion.
void InitMatchers() {
const auto &fst_array = impl_->fst_array_;
matcher_.resize(fst_array.size());
for (Label i = 0; i < fst_array.size(); ++i) {
if (fst_array[i]) {
matcher_[i].reset(
new LocalMatcher(*fst_array[i], match_type_, kMultiEpsList));
auto it = impl_->nonterminal_set_.begin();
for (; it != impl_->nonterminal_set_.end(); ++it) {
matcher_[i]->AddMultiEpsLabel(*it);
}
}
}
}
ReplaceFstMatcher<Arc, StateTable, CacheStore> *Copy(
bool safe = false) const override {
return new ReplaceFstMatcher<Arc, StateTable, CacheStore>(*this, safe);
}
MatchType Type(bool test) const override {
if (match_type_ == MATCH_NONE) return match_type_;
const auto true_prop =
match_type_ == MATCH_INPUT ? kILabelSorted : kOLabelSorted;
const auto false_prop =
match_type_ == MATCH_INPUT ? kNotILabelSorted : kNotOLabelSorted;
const auto props = fst_.Properties(true_prop | false_prop, test);
if (props & true_prop) {
return match_type_;
} else if (props & false_prop) {
return MATCH_NONE;
} else {
return MATCH_UNKNOWN;
}
}
const Fst<Arc> &GetFst() const override { return fst_; }
uint64 Properties(uint64 props) const override { return props; }
// Sets the state from which our matching happens.
void SetState(StateId s) final {
if (s_ == s) return;
s_ = s;
tuple_ = impl_->GetStateTable()->Tuple(s_);
if (tuple_.fst_state == kNoStateId) {
done_ = true;
return;
}
// Gets current matcher, used for non-epsilon matching.
current_matcher_ = matcher_[tuple_.fst_id].get();
current_matcher_->SetState(tuple_.fst_state);
loop_.nextstate = s_;
final_arc_ = false;
}
// Searches for label from previous set state. If label == 0, first
// hallucinate an epsilon loop; otherwise use the underlying matcher to
// search for the label or epsilons. Note since the ReplaceFst recursion
// on non-terminal arcs causes epsilon transitions to be created we use
// MultiEpsilonMatcher to search for possible matches of non-terminals. If the
// component FST
// reaches a final state we also need to add the exiting final arc.
bool Find(Label label) final {
bool found = false;
label_ = label;
if (label_ == 0 || label_ == kNoLabel) {
// Computes loop directly, avoiding Replace::ComputeArc.
if (label_ == 0) {
current_loop_ = true;
found = true;
}
// Searches for matching multi-epsilons.
final_arc_ = impl_->ComputeFinalArc(tuple_, nullptr);
found = current_matcher_->Find(kNoLabel) || final_arc_ || found;
} else {
// Searches on a sub machine directly using sub machine matcher.
found = current_matcher_->Find(label_);
}
return found;
}
bool Done() const final {
return !current_loop_ && !final_arc_ && current_matcher_->Done();
}
const Arc &Value() const final {
if (current_loop_) return loop_;
if (final_arc_) {
impl_->ComputeFinalArc(tuple_, &arc_);
return arc_;
}
const auto &component_arc = current_matcher_->Value();
impl_->ComputeArc(tuple_, component_arc, &arc_);
return arc_;
}
void Next() final {
if (current_loop_) {
current_loop_ = false;
return;
}
if (final_arc_) {
final_arc_ = false;
return;
}
current_matcher_->Next();
}
ssize_t Priority(StateId s) final { return fst_.NumArcs(s); }
private:
std::unique_ptr<const ReplaceFst<Arc, StateTable, CacheStore>> owned_fst_;
const ReplaceFst<Arc, StateTable, CacheStore> &fst_;
internal::ReplaceFstImpl<Arc, StateTable, CacheStore> *impl_;
LocalMatcher *current_matcher_;
std::vector<std::unique_ptr<LocalMatcher>> matcher_;
StateId s_; // Current state.
Label label_; // Current label.
MatchType match_type_; // Supplied by caller.
mutable bool done_;
mutable bool current_loop_; // Current arc is the implicit loop.
mutable bool final_arc_; // Current arc for exiting recursion.
mutable StateTuple tuple_; // Tuple corresponding to state_.
mutable Arc arc_;
Arc loop_;
ReplaceFstMatcher &operator=(const ReplaceFstMatcher &) = delete;
};
template <class Arc, class StateTable, class CacheStore>
inline void ReplaceFst<Arc, StateTable, CacheStore>::InitStateIterator(
StateIteratorData<Arc> *data) const {
data->base =
new StateIterator<ReplaceFst<Arc, StateTable, CacheStore>>(*this);
}
using StdReplaceFst = ReplaceFst<StdArc>;
// Recursively replaces arcs in the root FSTs with other FSTs.
// This version writes the result of replacement to an output MutableFst.
//
// Replace supports replacement of arcs in one Fst with another FST. This
// replacement is recursive. Replace takes an array of FST(s). One FST
// represents the root (or topology) machine. The root FST refers to other FSTs
// by recursively replacing arcs labeled as non-terminals with the matching
// non-terminal FST. Currently Replace uses the output symbols of the arcs to
// determine whether the arc is a non-terminal arc or not. A non-terminal can be
// any label that is not a non-zero terminal label in the output alphabet.
//
// Note that input argument is a vector of pairs. These correspond to the tuple
// of non-terminal Label and corresponding FST.
template <class Arc>
void Replace(const std::vector<std::pair<typename Arc::Label, const Fst<Arc> *>>
&ifst_array,
MutableFst<Arc> *ofst,
ReplaceFstOptions<Arc> opts = ReplaceFstOptions<Arc>()) {
opts.gc = true;
opts.gc_limit = 0; // Caches only the last state for fastest copy.
*ofst = ReplaceFst<Arc>(ifst_array, opts);
}
template <class Arc>
void Replace(const std::vector<std::pair<typename Arc::Label, const Fst<Arc> *>>
&ifst_array,
MutableFst<Arc> *ofst, const ReplaceUtilOptions &opts) {
Replace(ifst_array, ofst, ReplaceFstOptions<Arc>(opts));
}
// For backwards compatibility.
template <class Arc>
void Replace(const std::vector<std::pair<typename Arc::Label, const Fst<Arc> *>>
&ifst_array,
MutableFst<Arc> *ofst, typename Arc::Label root,
bool epsilon_on_replace) {
Replace(ifst_array, ofst, ReplaceFstOptions<Arc>(root, epsilon_on_replace));
}
template <class Arc>
void Replace(const std::vector<std::pair<typename Arc::Label, const Fst<Arc> *>>
&ifst_array,
MutableFst<Arc> *ofst, typename Arc::Label root) {
Replace(ifst_array, ofst, ReplaceFstOptions<Arc>(root));
}
} // namespace fst
#endif // FST_REPLACE_H_
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