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tools/openfst-1.6.7/include/fst/string.h
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// See www.openfst.org for extensive documentation on this weighted
// finite-state transducer library.
//
// Utilities to convert strings into FSTs.
#ifndef FST_STRING_H_
#define FST_STRING_H_
#include <memory>
#include <sstream>
#include <string>
#include <vector>
#include <fst/flags.h>
#include <fst/log.h>
#include <fst/compact-fst.h>
#include <fst/icu.h>
#include <fst/mutable-fst.h>
#include <fst/util.h>
DECLARE_string(fst_field_separator);
namespace fst {
enum StringTokenType { SYMBOL = 1, BYTE = 2, UTF8 = 3 };
namespace internal {
template <class Label>
bool ConvertSymbolToLabel(const char *str, const SymbolTable *syms,
Label unknown_label, bool allow_negative,
Label *output) {
int64 n;
if (syms) {
n = syms->Find(str);
if ((n == -1) && (unknown_label != kNoLabel)) n = unknown_label;
if (n == -1 || (!allow_negative && n < 0)) {
VLOG(1) << "ConvertSymbolToLabel: Symbol \"" << str
<< "\" is not mapped to any integer label, symbol table = "
<< syms->Name();
return false;
}
} else {
char *p;
n = strtoll(str, &p, 10);
if (p < str + strlen(str) || (!allow_negative && n < 0)) {
VLOG(1) << "ConvertSymbolToLabel: Bad label integer "
<< "= \"" << str << "\"";
return false;
}
}
*output = n;
return true;
}
template <class Label>
bool ConvertStringToLabels(const string &str, StringTokenType token_type,
const SymbolTable *syms, Label unknown_label,
bool allow_negative, std::vector<Label> *labels) {
labels->clear();
if (token_type == StringTokenType::BYTE) {
for (const char c : str) labels->push_back(c);
} else if (token_type == StringTokenType::UTF8) {
return UTF8StringToLabels(str, labels);
} else {
std::unique_ptr<char[]> c_str(new char[str.size() + 1]);
str.copy(c_str.get(), str.size());
c_str[str.size()] = 0;
std::vector<char *> vec;
const string separator = "
" + FLAGS_fst_field_separator;
SplitString(c_str.get(), separator.c_str(), &vec, true);
for (const char *c : vec) {
Label label;
if (!ConvertSymbolToLabel(c, syms, unknown_label, allow_negative,
&label)) {
return false;
}
labels->push_back(label);
}
}
return true;
}
} // namespace internal
// Functor for compiling a string in an FST.
template <class Arc>
class StringCompiler {
public:
using Label = typename Arc::Label;
using StateId = typename Arc::StateId;
using Weight = typename Arc::Weight;
explicit StringCompiler(StringTokenType token_type,
const SymbolTable *syms = nullptr,
Label unknown_label = kNoLabel,
bool allow_negative = false)
: token_type_(token_type),
syms_(syms),
unknown_label_(unknown_label),
allow_negative_(allow_negative) {}
// Compiles string into an FST.
template <class FST>
bool operator()(const string &str, FST *fst) const {
std::vector<Label> labels;
if (!internal::ConvertStringToLabels(str, token_type_, syms_,
unknown_label_, allow_negative_,
&labels)) {
return false;
}
Compile(labels, fst);
return true;
}
template <class FST>
bool operator()(const string &str, FST *fst, Weight weight) const {
std::vector<Label> labels;
if (!internal::ConvertStringToLabels(str, token_type_, syms_,
unknown_label_, allow_negative_,
&labels)) {
return false;
}
Compile(labels, fst, std::move(weight));
return true;
}
private:
void Compile(const std::vector<Label> &labels, MutableFst<Arc> *fst,
Weight weight = Weight::One()) const {
fst->DeleteStates();
while (fst->NumStates() <= labels.size()) fst->AddState();
for (StateId i = 0; i < labels.size(); ++i) {
fst->AddArc(i, Arc(labels[i], labels[i], Weight::One(), i + 1));
}
fst->SetStart(0);
fst->SetFinal(labels.size(), std::move(weight));
}
template <class Unsigned>
void Compile(const std::vector<Label> &labels,
CompactStringFst<Arc, Unsigned> *fst) const {
fst->SetCompactElements(labels.begin(), labels.end());
}
template <class Unsigned>
void Compile(const std::vector<Label> &labels,
CompactWeightedStringFst<Arc, Unsigned> *fst,
const Weight &weight = Weight::One()) const {
std::vector<std::pair<Label, Weight>> compacts;
compacts.reserve(labels.size() + 1);
for (StateId i = 0; i < static_cast<StateId>(labels.size()) - 1; ++i) {
compacts.emplace_back(labels[i], Weight::One());
}
compacts.emplace_back(!labels.empty() ? labels.back() : kNoLabel, weight);
fst->SetCompactElements(compacts.begin(), compacts.end());
}
const StringTokenType token_type_;
const SymbolTable *syms_; // Symbol table (used when token type is symbol).
const Label unknown_label_; // Label for token missing from symbol table.
const bool allow_negative_; // Negative labels allowed?
StringCompiler(const StringCompiler &) = delete;
StringCompiler &operator=(const StringCompiler &) = delete;
};
// Functor for printing a string FST as a string.
template <class Arc>
class StringPrinter {
public:
using Label = typename Arc::Label;
using StateId = typename Arc::StateId;
using Weight = typename Arc::Weight;
explicit StringPrinter(StringTokenType token_type,
const SymbolTable *syms = nullptr)
: token_type_(token_type), syms_(syms) {}
// Converts the FST into a string.
bool operator()(const Fst<Arc> &fst, string *result) {
if (!FstToLabels(fst)) {
VLOG(1) << "StringPrinter::operator(): FST is not a string";
return false;
}
result->clear();
if (token_type_ == StringTokenType::SYMBOL) {
std::stringstream sstrm;
for (size_t i = 0; i < labels_.size(); ++i) {
if (i) sstrm << *(FLAGS_fst_field_separator.rbegin());
if (!PrintLabel(labels_[i], sstrm)) return false;
}
*result = sstrm.str();
} else if (token_type_ == StringTokenType::BYTE) {
result->reserve(labels_.size());
for (size_t i = 0; i < labels_.size(); ++i) result->push_back(labels_[i]);
} else if (token_type_ == StringTokenType::UTF8) {
return LabelsToUTF8String(labels_, result);
} else {
VLOG(1) << "StringPrinter::operator(): Unknown token type: "
<< token_type_;
return false;
}
return true;
}
private:
bool FstToLabels(const Fst<Arc> &fst) {
labels_.clear();
auto s = fst.Start();
if (s == kNoStateId) {
VLOG(2) << "StringPrinter::FstToLabels: Invalid starting state for "
<< "string FST";
return false;
}
while (fst.Final(s) == Weight::Zero()) {
ArcIterator<Fst<Arc>> aiter(fst, s);
if (aiter.Done()) {
VLOG(2) << "StringPrinter::FstToLabels: String FST traversal does "
<< "not reach final state";
return false;
}
const auto &arc = aiter.Value();
labels_.push_back(arc.olabel);
s = arc.nextstate;
if (s == kNoStateId) {
VLOG(2) << "StringPrinter::FstToLabels: Transition to invalid state";
return false;
}
aiter.Next();
if (!aiter.Done()) {
VLOG(2) << "StringPrinter::FstToLabels: State with multiple "
<< "outgoing arcs found";
return false;
}
}
return true;
}
bool PrintLabel(Label label, std::ostream &ostrm) {
if (syms_) {
const auto symbol = syms_->Find(label);
if (symbol == "") {
VLOG(2) << "StringPrinter::PrintLabel: Integer " << label << " is not "
<< "mapped to any textual symbol, symbol table = "
<< syms_->Name();
return false;
}
ostrm << symbol;
} else {
ostrm << label;
}
return true;
}
const StringTokenType token_type_;
const SymbolTable *syms_; // Symbol table (used when token type is symbol).
std::vector<Label> labels_; // Input FST labels.
StringPrinter(const StringPrinter &) = delete;
StringPrinter &operator=(const StringPrinter &) = delete;
};
} // namespace fst
#endif // FST_STRING_H_
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