/usr/include/fst/extensions/linear/trie.h is in libfst-dev 1.6.3-2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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// finite-state transducer library.
#ifndef FST_EXTENSIONS_LINEAR_TRIE_H_
#define FST_EXTENSIONS_LINEAR_TRIE_H_
#include <unordered_map>
#include <utility>
#include <vector>
#include <fst/compat.h>
#include <fst/util.h>
namespace fst {
const int kNoTrieNodeId = -1;
// Forward declarations of all available trie topologies.
template <class L, class H>
class NestedTrieTopology;
template <class L, class H>
class FlatTrieTopology;
// A pair of parent node id and label, part of a trie edge
template <class L>
struct ParentLabel {
int parent;
L label;
ParentLabel() {}
ParentLabel(int p, L l) : parent(p), label(l) {}
bool operator==(const ParentLabel &that) const {
return parent == that.parent && label == that.label;
}
std::istream &Read(std::istream &strm) { // NOLINT
ReadType(strm, &parent);
ReadType(strm, &label);
return strm;
}
std::ostream &Write(std::ostream &strm) const { // NOLINT
WriteType(strm, parent);
WriteType(strm, label);
return strm;
}
};
template <class L, class H>
struct ParentLabelHash {
size_t operator()(const ParentLabel<L> &pl) const {
return static_cast<size_t>(pl.parent * 7853 + H()(pl.label));
}
};
// The trie topology in a nested tree of hash maps; allows efficient
// iteration over children of a specific node.
template <class L, class H>
class NestedTrieTopology {
public:
typedef L Label;
typedef H Hash;
typedef std::unordered_map<L, int, H> NextMap;
class const_iterator {
public:
typedef std::forward_iterator_tag iterator_category;
typedef std::pair<ParentLabel<L>, int> value_type;
typedef std::ptrdiff_t difference_type;
typedef const value_type *pointer;
typedef const value_type &reference;
friend class NestedTrieTopology<L, H>;
const_iterator() : ptr_(nullptr), cur_node_(kNoTrieNodeId), cur_edge_() {}
reference operator*() {
UpdateStub();
return stub_;
}
pointer operator->() {
UpdateStub();
return &stub_;
}
const_iterator &operator++();
const_iterator &operator++(int); // NOLINT
bool operator==(const const_iterator &that) const {
return ptr_ == that.ptr_ && cur_node_ == that.cur_node_ &&
cur_edge_ == that.cur_edge_;
}
bool operator!=(const const_iterator &that) const {
return !(*this == that);
}
private:
const_iterator(const NestedTrieTopology *ptr, int cur_node)
: ptr_(ptr), cur_node_(cur_node) {
SetProperCurEdge();
}
void SetProperCurEdge() {
if (cur_node_ < ptr_->NumNodes())
cur_edge_ = ptr_->nodes_[cur_node_]->begin();
else
cur_edge_ = ptr_->nodes_[0]->begin();
}
void UpdateStub() {
stub_.first = ParentLabel<L>(cur_node_, cur_edge_->first);
stub_.second = cur_edge_->second;
}
const NestedTrieTopology *ptr_;
int cur_node_;
typename NextMap::const_iterator cur_edge_;
value_type stub_;
};
NestedTrieTopology();
NestedTrieTopology(const NestedTrieTopology &that);
~NestedTrieTopology();
void swap(NestedTrieTopology &that);
NestedTrieTopology &operator=(const NestedTrieTopology &that);
bool operator==(const NestedTrieTopology &that) const;
bool operator!=(const NestedTrieTopology &that) const;
int Root() const { return 0; }
size_t NumNodes() const { return nodes_.size(); }
int Insert(int parent, const L &label);
int Find(int parent, const L &label) const;
const NextMap &ChildrenOf(int parent) const { return *nodes_[parent]; }
std::istream &Read(std::istream &strm); // NOLINT
std::ostream &Write(std::ostream &strm) const; // NOLINT
const_iterator begin() const { return const_iterator(this, 0); }
const_iterator end() const { return const_iterator(this, NumNodes()); }
private:
std::vector<NextMap *>
nodes_; // Use pointers to avoid copying the maps when the
// vector grows
};
template <class L, class H>
NestedTrieTopology<L, H>::NestedTrieTopology() {
nodes_.push_back(new NextMap);
}
template <class L, class H>
NestedTrieTopology<L, H>::NestedTrieTopology(const NestedTrieTopology &that) {
nodes_.reserve(that.nodes_.size());
for (size_t i = 0; i < that.nodes_.size(); ++i) {
NextMap *node = that.nodes_[i];
nodes_.push_back(new NextMap(*node));
}
}
template <class L, class H>
NestedTrieTopology<L, H>::~NestedTrieTopology() {
for (size_t i = 0; i < nodes_.size(); ++i) {
NextMap *node = nodes_[i];
delete node;
}
}
// TODO(wuke): std::swap compatibility
template <class L, class H>
inline void NestedTrieTopology<L, H>::swap(NestedTrieTopology &that) {
nodes_.swap(that.nodes_);
}
template <class L, class H>
inline NestedTrieTopology<L, H> &NestedTrieTopology<L, H>::operator=(
const NestedTrieTopology &that) {
NestedTrieTopology copy(that);
swap(copy);
return *this;
}
template <class L, class H>
inline bool NestedTrieTopology<L, H>::operator==(
const NestedTrieTopology &that) const {
if (NumNodes() != that.NumNodes()) return false;
for (int i = 0; i < NumNodes(); ++i)
if (ChildrenOf(i) != that.ChildrenOf(i)) return false;
return true;
}
template <class L, class H>
inline bool NestedTrieTopology<L, H>::operator!=(
const NestedTrieTopology &that) const {
return !(*this == that);
}
template <class L, class H>
inline int NestedTrieTopology<L, H>::Insert(int parent, const L &label) {
int ret = Find(parent, label);
if (ret == kNoTrieNodeId) {
ret = NumNodes();
(*nodes_[parent])[label] = ret;
nodes_.push_back(new NextMap);
}
return ret;
}
template <class L, class H>
inline int NestedTrieTopology<L, H>::Find(int parent, const L &label) const {
typename NextMap::const_iterator it = nodes_[parent]->find(label);
return it == nodes_[parent]->end() ? kNoTrieNodeId : it->second;
}
template <class L, class H>
inline std::istream &NestedTrieTopology<L, H>::Read(
std::istream &strm) { // NOLINT
NestedTrieTopology new_trie;
size_t num_nodes;
if (!ReadType(strm, &num_nodes)) return strm;
for (size_t i = 1; i < num_nodes; ++i) new_trie.nodes_.push_back(new NextMap);
for (size_t i = 0; i < num_nodes; ++i) ReadType(strm, new_trie.nodes_[i]);
if (strm) swap(new_trie);
return strm;
}
template <class L, class H>
inline std::ostream &NestedTrieTopology<L, H>::Write(
std::ostream &strm) const { // NOLINT
WriteType(strm, NumNodes());
for (size_t i = 0; i < NumNodes(); ++i) WriteType(strm, *nodes_[i]);
return strm;
}
template <class L, class H>
inline typename NestedTrieTopology<L, H>::const_iterator
&NestedTrieTopology<L, H>::const_iterator::operator++() {
++cur_edge_;
if (cur_edge_ == ptr_->nodes_[cur_node_]->end()) {
++cur_node_;
while (cur_node_ < ptr_->NumNodes() && ptr_->nodes_[cur_node_]->empty())
++cur_node_;
SetProperCurEdge();
}
return *this;
}
template <class L, class H>
inline typename NestedTrieTopology<L, H>::const_iterator
&NestedTrieTopology<L, H>::const_iterator::operator++(int) { // NOLINT
const_iterator save(*this);
++(*this);
return save;
}
// The trie topology in a single hash map; only allows iteration over
// all the edges in arbitrary order.
template <class L, class H>
class FlatTrieTopology {
private:
typedef std::unordered_map<ParentLabel<L>, int, ParentLabelHash<L, H>>
NextMap;
public:
// Iterator over edges as std::pair<ParentLabel<L>, int>
typedef typename NextMap::const_iterator const_iterator;
typedef L Label;
typedef H Hash;
FlatTrieTopology() {}
FlatTrieTopology(const FlatTrieTopology &that) : next_(that.next_) {}
template <class T>
explicit FlatTrieTopology(const T &that);
// TODO(wuke): std::swap compatibility
void swap(FlatTrieTopology &that) { next_.swap(that.next_); }
bool operator==(const FlatTrieTopology &that) const {
return next_ == that.next_;
}
bool operator!=(const FlatTrieTopology &that) const {
return !(*this == that);
}
int Root() const { return 0; }
size_t NumNodes() const { return next_.size() + 1; }
int Insert(int parent, const L &label);
int Find(int parent, const L &label) const;
std::istream &Read(std::istream &strm) { // NOLINT
return ReadType(strm, &next_);
}
std::ostream &Write(std::ostream &strm) const { // NOLINT
return WriteType(strm, next_);
}
const_iterator begin() const { return next_.begin(); }
const_iterator end() const { return next_.end(); }
private:
NextMap next_;
};
template <class L, class H>
template <class T>
FlatTrieTopology<L, H>::FlatTrieTopology(const T &that)
: next_(that.begin(), that.end()) {}
template <class L, class H>
inline int FlatTrieTopology<L, H>::Insert(int parent, const L &label) {
int ret = Find(parent, label);
if (ret == kNoTrieNodeId) {
ret = NumNodes();
next_[ParentLabel<L>(parent, label)] = ret;
}
return ret;
}
template <class L, class H>
inline int FlatTrieTopology<L, H>::Find(int parent, const L &label) const {
typename NextMap::const_iterator it =
next_.find(ParentLabel<L>(parent, label));
return it == next_.end() ? kNoTrieNodeId : it->second;
}
// A collection of implementations of the trie data structure. The key
// is a sequence of type `L` which must be hashable. The value is of
// `V` which must be default constructible and copyable. In addition,
// a value object is stored for each node in the trie therefore
// copying `V` should be cheap.
//
// One can access the store values with an integer node id, using the
// [] operator. A valid node id can be obtained by the following ways:
//
// 1. Using the `Root()` method to get the node id of the root.
//
// 2. Iterating through 0 to `NumNodes() - 1`. The node ids are dense
// so every integer in this range is a valid node id.
//
// 3. Using the node id returned from a successful `Insert()` or
// `Find()` call.
//
// 4. Iterating over the trie edges with an `EdgeIterator` and using
// the node ids returned from its `Parent()` and `Child()` methods.
//
// Below is an example of inserting keys into the trie:
//
// const string words[] = {"hello", "health", "jello"};
// Trie<char, bool> dict;
// for (auto word : words) {
// int cur = dict.Root();
// for (char c : word) {
// cur = dict.Insert(cur, c);
// }
// dict[cur] = true;
// }
//
// And the following is an example of looking up the longest prefix of
// a string using the trie constructed above:
//
// string query = "healed";
// size_t prefix_length = 0;
// int cur = dict.Find(dict.Root(), query[prefix_length]);
// while (prefix_length < query.size() &&
// cur != Trie<char, bool>::kNoNodeId) {
// ++prefix_length;
// cur = dict.Find(cur, query[prefix_length]);
// }
template <class L, class V, class T>
class MutableTrie {
public:
template <class LL, class VV, class TT>
friend class MutableTrie;
typedef L Label;
typedef V Value;
typedef T Topology;
// Constructs a trie with only the root node.
MutableTrie() {}
// Conversion from another trie of a possiblly different
// topology. The underlying topology must supported conversion.
template <class S>
explicit MutableTrie(const MutableTrie<L, V, S> &that)
: topology_(that.topology_), values_(that.values_) {}
// TODO(wuke): std::swap compatibility
void swap(MutableTrie &that) {
topology_.swap(that.topology_);
values_.swap(that.values_);
DCHECK_EQ(topology_.NumNodes(), values_.size());
}
int Root() const { return topology_.Root(); }
size_t NumNodes() const { return topology_.NumNodes(); }
// Inserts an edge with given `label` at node `parent`. Returns the
// child node id. If the node already exists, returns the node id
// right away.
int Insert(int parent, const L &label) {
int ret = topology_.Insert(parent, label);
values_.resize(NumNodes());
return ret;
}
// Finds the node id of the node from `parent` via `label`. Returns
// `kNoTrieNodeId` when such a node does not exist.
int Find(int parent, const L &label) const {
return topology_.Find(parent, label);
}
const T &TrieTopology() const { return topology_; }
// Accesses the value stored for the given node.
V &operator[](int node_id) { return values_[node_id]; }
const V &operator[](int node_id) const { return values_[node_id]; }
// Comparison by content
bool operator==(const MutableTrie &that) const {
return topology_ == that.topology_ && values_ == that.values_;
}
bool operator!=(const MutableTrie &that) const { return !(*this == that); }
std::istream &Read(std::istream &strm) { // NOLINT
ReadType(strm, &topology_);
ReadType(strm, &values_);
return strm;
}
std::ostream &Write(std::ostream &strm) const { // NOLINT
WriteType(strm, topology_);
WriteType(strm, values_);
return strm;
}
private:
T topology_;
std::vector<V> values_;
};
} // namespace fst
#endif // FST_EXTENSIONS_LINEAR_TRIE_H_
|