/usr/include/fst/bi-table.h is in libfst-dev 1.5.3+r3-2.
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// finite-state transducer library.
//
// Classes for representing a bijective mapping between an arbitrary entry
// of type T and a signed integral ID.
#ifndef FST_LIB_BI_TABLE_H_
#define FST_LIB_BI_TABLE_H_
#include <deque>
#include <memory>
#include <functional>
#include <unordered_map>
#include <unordered_set>
#include <vector>
#include <fst/memory.h>
namespace fst {
// BI TABLES - these determine a bijective mapping between an
// arbitrary entry of type T and an signed integral ID of type I. The IDs are
// allocated starting from 0 in order.
//
// template <class I, class T>
// class BiTable {
// public:
//
// // Required constructors.
// BiTable();
//
// // Lookup integer ID from entry. If it doesn't exist and 'insert'
// / is true, then add it. Otherwise return -1.
// I FindId(const T &entry, bool insert = true);
// // Lookup entry from integer ID.
// const T &FindEntry(I) const;
// // # of stored entries.
// I Size() const;
// };
// An implementation using a hash map for the entry to ID mapping.
// H is the hash function and E is the equality function.
// If passed to the constructor, ownership is given to this class.
template <class I, class T, class H, class E = std::equal_to<T>>
class HashBiTable {
public:
// Reserves space for 'table_size' elements. If passing H and E to the
// constructor, this class owns them.
explicit HashBiTable(size_t table_size = 0, H *h = nullptr, E *e = nullptr) :
hash_func_(h ? h : new H()), hash_equal_(e ? e : new E()),
entry2id_(table_size, *h, *e) {
if (table_size) id2entry_.reserve(table_size);
}
HashBiTable(const HashBiTable<I, T, H, E> &table)
: hash_func_(new H(*table.hash_func_)),
hash_equal_(new E(*table.hash_equal_)),
entry2id_(table.entry2id_.begin(), table.entry2id_.end(),
table.entry2id_.size(), *hash_func_, *hash_equal_),
id2entry_(table.id2entry_) {}
I FindId(const T &entry, bool insert = true) {
if (!insert) {
const auto it = entry2id_.find(entry);
return it == entry2id_.end() ? -1 : it->second - 1;
}
I &id_ref = entry2id_[entry];
if (id_ref == 0) { // T not found store and assign it a new ID
id2entry_.push_back(entry);
id_ref = id2entry_.size();
}
return id_ref - 1; // NB: id_ref = ID + 1
}
const T &FindEntry(I s) const { return id2entry_[s]; }
I Size() const { return id2entry_.size(); }
// TODO(riley): Add fancy clear-to-size as in CompactHashBiTable.
void Clear() {
entry2id_.clear();
id2entry_.clear();
}
private:
std::unique_ptr<H> hash_func_;
std::unique_ptr<E> hash_equal_;
std::unordered_map<T, I, H, E> entry2id_;
std::vector<T> id2entry_;
void operator=(const HashBiTable<I, T, H, E> &table); // disallow
};
// Enables alternative hash set representations below.
typedef enum { HS_STL = 0, HS_DENSE = 1, HS_SPARSE = 2 } HSType;
// Default hash set is STL hash_set
template <class K, class H, class E, HSType>
struct HashSet : public std::unordered_set<K, H, E, PoolAllocator<K>> {
HashSet(size_t n = 0, const H &h = H(), const E &e = E())
: std::unordered_set<K, H, E, PoolAllocator<K>>(n, h, e) {}
void rehash(size_t n) {}
};
// An implementation using a hash set for the entry to ID mapping.
// The hash set holds 'keys' which are either the ID or kCurrentKey.
// These keys can be mapped to entrys either by looking up in the
// entry vector or, if kCurrentKey, in current_entry_ member. The hash
// and key equality functions map to entries first. H
// is the hash function and E is the equality function. If passed to
// the constructor, ownership is given to this class.
template <class I, class T, class H, class E = std::equal_to<T>,
HSType HS = HS_DENSE>
class CompactHashBiTable {
public:
friend class HashFunc;
friend class HashEqual;
// Reserves space for 'table_size' elements. If passing H and E to the
// constructor, this class owns them.
explicit CompactHashBiTable(size_t table_size = 0, H *h = nullptr,
E *e = nullptr) :
hash_func_(h ? h : new H()), hash_equal_(e ? e : new E()),
compact_hash_func_(*this), compact_hash_equal_(*this),
keys_(table_size, compact_hash_func_, compact_hash_equal_) {
if (table_size) id2entry_.reserve(table_size);
}
CompactHashBiTable(const CompactHashBiTable<I, T, H, E, HS> &table)
: hash_func_(new H(*table.hash_func_)),
hash_equal_(new E(*table.hash_equal_)),
compact_hash_func_(*this), compact_hash_equal_(*this),
keys_(table.keys_.size(), compact_hash_func_, compact_hash_equal_),
id2entry_(table.id2entry_) {
keys_.insert(table.keys_.begin(), table.keys_.end());
}
I FindId(const T &entry, bool insert = true) {
current_entry_ = &entry;
const auto it = keys_.find(kCurrentKey);
if (it == keys_.end()) { // T not found
if (insert) { // store and assign it a new ID
I key = id2entry_.size();
id2entry_.push_back(entry);
keys_.insert(key);
return key;
} else {
return -1;
}
} else {
return *it;
}
}
const T &FindEntry(I s) const { return id2entry_[s]; }
I Size() const { return id2entry_.size(); }
// Clear content. With argument, erases last n IDs.
void Clear(ssize_t n = -1) {
if (n < 0 || n >= id2entry_.size()) { // Clear completely.
keys_.clear();
id2entry_.clear();
} else if (n == id2entry_.size() - 1) { // Leave only key 0
const T entry = FindEntry(0);
keys_.clear();
id2entry_.clear();
FindId(entry, true);
} else {
while (n-- > 0) {
I key = id2entry_.size() - 1;
keys_.erase(key);
id2entry_.pop_back();
}
keys_.rehash(0);
}
}
private:
static const I kCurrentKey; // -1
static const I kEmptyKey; // -2
static const I kDeletedKey; // -3
class HashFunc {
public:
HashFunc(const CompactHashBiTable &ht) : ht_(&ht) {}
size_t operator()(I k) const {
if (k >= kCurrentKey) {
return (*ht_->hash_func_)(ht_->Key2Entry(k));
} else {
return 0;
}
}
private:
const CompactHashBiTable *ht_;
};
class HashEqual {
public:
HashEqual(const CompactHashBiTable &ht) : ht_(&ht) {}
bool operator()(I k1, I k2) const {
if (k1 >= kCurrentKey && k2 >= kCurrentKey) {
return (*ht_->hash_equal_)(ht_->Key2Entry(k1), ht_->Key2Entry(k2));
} else {
return k1 == k2;
}
}
private:
const CompactHashBiTable *ht_;
};
typedef HashSet<I, HashFunc, HashEqual, HS> KeyHashSet;
const T &Key2Entry(I k) const {
if (k == kCurrentKey)
return *current_entry_;
else
return id2entry_[k];
}
std::unique_ptr<H> hash_func_;
std::unique_ptr<E> hash_equal_;
HashFunc compact_hash_func_;
HashEqual compact_hash_equal_;
KeyHashSet keys_;
std::vector<T> id2entry_;
const T *current_entry_;
void operator=(const CompactHashBiTable<I, T, H, E, HS> &table); // disallow
};
template <class I, class T, class H, class E, HSType HS>
const I CompactHashBiTable<I, T, H, E, HS>::kCurrentKey = -1;
template <class I, class T, class H, class E, HSType HS>
const I CompactHashBiTable<I, T, H, E, HS>::kEmptyKey = -2;
template <class I, class T, class H, class E, HSType HS>
const I CompactHashBiTable<I, T, H, E, HS>::kDeletedKey = -3;
// An implementation using a vector for the entry to ID mapping.
// It is passed a function object FP that should fingerprint entries
// uniquely to an integer that can used as a vector index. Normally,
// VectorBiTable constructs the FP object. The user can instead
// pass in this object; in that case, VectorBiTable takes its
// ownership.
template <class I, class T, class FP>
class VectorBiTable {
public:
// Reserves space for 'table_size' elements. If passing FP argument to the
// constructor, this class owns it.
explicit VectorBiTable(FP *fp = nullptr, size_t table_size = 0) :
fp_(fp ? fp : new FP()) {
if (table_size) id2entry_.reserve(table_size);
}
VectorBiTable(const VectorBiTable<I, T, FP> &table)
: fp_(new FP(*table.fp_)), fp2id_(table.fp2id_),
id2entry_(table.id2entry_) {}
I FindId(const T &entry, bool insert = true) {
ssize_t fp = (*fp_)(entry);
if (fp >= fp2id_.size()) fp2id_.resize(fp + 1);
I &id_ref = fp2id_[fp];
if (id_ref == 0) { // T not found
if (insert) { // store and assign it a new ID
id2entry_.push_back(entry);
id_ref = id2entry_.size();
} else {
return -1;
}
}
return id_ref - 1; // NB: id_ref = ID + 1
}
const T &FindEntry(I s) const { return id2entry_[s]; }
I Size() const { return id2entry_.size(); }
const FP &Fingerprint() const { return *fp_; }
private:
std::unique_ptr<FP> fp_;
std::vector<I> fp2id_;
std::vector<T> id2entry_;
void operator=(const VectorBiTable<I, T, FP> &table); // disallow
};
// An implementation using a vector and a compact hash table. The
// selecting functor S returns true for entries to be hashed in the
// vector. The fingerprinting functor FP returns a unique fingerprint
// for each entry to be hashed in the vector (these need to be
// suitable for indexing in a vector). The hash functor H is used
// when hashing entry into the compact hash table. If passed to the
// constructor, ownership is given to this class.
template <class I, class T, class S, class FP, class H, HSType HS = HS_DENSE>
class VectorHashBiTable {
public:
friend class HashFunc;
friend class HashEqual;
explicit VectorHashBiTable(S *s, FP *fp, H *h, size_t vector_size = 0,
size_t entry_size = 0)
: selector_(s), fp_(fp), h_(h), hash_func_(*this), hash_equal_(*this),
keys_(0, hash_func_, hash_equal_) {
if (vector_size) fp2id_.reserve(vector_size);
if (entry_size) id2entry_.reserve(entry_size);
}
VectorHashBiTable(const VectorHashBiTable<I, T, S, FP, H, HS> &table)
: selector_(new S(table.s_)), fp_(new FP(*table.fp_)),
h_(new H(*table.h_)), id2entry_(table.id2entry_),
fp2id_(table.fp2id_), hash_func_(*this), hash_equal_(*this),
keys_(table.keys_.size(), hash_func_, hash_equal_) {
keys_.insert(table.keys_.begin(), table.keys_.end());
}
I FindId(const T &entry, bool insert = true) {
if ((*selector_)(entry)) { // Use the vector if 'selector_(entry) == true'
uint64 fp = (*fp_)(entry);
if (fp2id_.size() <= fp) fp2id_.resize(fp + 1, 0);
if (fp2id_[fp] == 0) { // T not found
if (insert) { // store and assign it a new ID
id2entry_.push_back(entry);
fp2id_[fp] = id2entry_.size();
} else {
return -1;
}
}
return fp2id_[fp] - 1; // NB: assoc_value = ID + 1
} else { // Use the hash table otherwise.
current_entry_ = &entry;
const auto it = keys_.find(kCurrentKey);
if (it == keys_.end()) {
if (insert) {
I key = id2entry_.size();
id2entry_.push_back(entry);
keys_.insert(key);
return key;
} else {
return -1;
}
} else {
return *it;
}
}
}
const T &FindEntry(I s) const { return id2entry_[s]; }
I Size() const { return id2entry_.size(); }
const S &Selector() const { return *selector_; }
const FP &Fingerprint() const { return *fp_; }
const H &Hash() const { return *h_; }
private:
static const I kCurrentKey; // -1
static const I kEmptyKey; // -2
class HashFunc {
public:
HashFunc(const VectorHashBiTable &ht) : ht_(&ht) {}
size_t operator()(I k) const {
if (k >= kCurrentKey) {
return (*(ht_->h_))(ht_->Key2Entry(k));
} else {
return 0;
}
}
private:
const VectorHashBiTable *ht_;
};
class HashEqual {
public:
HashEqual(const VectorHashBiTable &ht) : ht_(&ht) {}
bool operator()(I k1, I k2) const {
if (k1 >= kCurrentKey && k2 >= kCurrentKey) {
return ht_->Key2Entry(k1) == ht_->Key2Entry(k2);
} else {
return k1 == k2;
}
}
private:
const VectorHashBiTable *ht_;
};
typedef HashSet<I, HashFunc, HashEqual, HS> KeyHashSet;
const T &Key2Entry(I k) const {
if (k == kCurrentKey)
return *current_entry_;
else
return id2entry_[k];
}
std::unique_ptr<S> selector_; // Returns true if entry hashed into vector.
std::unique_ptr<FP> fp_; // Fingerprint used when hashing into vector.
std::unique_ptr<H> h_; // Hash fnc used when hashing into hash_set.
std::vector<T> id2entry_; // Maps state IDs to entry
std::vector<I> fp2id_; // Maps entry fingerprints to IDs
// Compact implementation of the hash table mapping entrys to
// state IDs using the hash function 'h_'
HashFunc hash_func_;
HashEqual hash_equal_;
KeyHashSet keys_;
const T *current_entry_;
// disallow
void operator=(const VectorHashBiTable<I, T, S, FP, H, HS> &table);
};
template <class I, class T, class S, class FP, class H, HSType HS>
const I VectorHashBiTable<I, T, S, FP, H, HS>::kCurrentKey = -1;
template <class I, class T, class S, class FP, class H, HSType HS>
const I VectorHashBiTable<I, T, S, FP, H, HS>::kEmptyKey = -3;
// An implementation using a hash map for the entry to ID
// mapping. This version permits erasing of arbitrary states. The
// entry T must have == defined and its default constructor must
// produce a entry that will never be seen. F is the hash function.
template <class I, class T, class F>
class ErasableBiTable {
public:
ErasableBiTable() : first_(0) {}
I FindId(const T &entry, bool insert = true) {
I &id_ref = entry2id_[entry];
if (id_ref == 0) { // T not found
if (insert) { // store and assign it a new ID
id2entry_.push_back(entry);
id_ref = id2entry_.size() + first_;
} else {
return -1;
}
}
return id_ref - 1; // NB: id_ref = ID + 1
}
const T &FindEntry(I s) const { return id2entry_[s - first_]; }
I Size() const { return id2entry_.size(); }
void Erase(I s) {
T &entry = id2entry_[s - first_];
const auto it = entry2id_.find(entry);
entry2id_.erase(it);
id2entry_[s - first_] = empty_entry_;
while (!id2entry_.empty() && id2entry_.front() == empty_entry_) {
id2entry_.pop_front();
++first_;
}
}
private:
std::unordered_map<T, I, F> entry2id_;
std::deque<T> id2entry_;
const T empty_entry_;
I first_; // I of first element in the deque;
// disallow
void operator=(const ErasableBiTable<I, T, F> &table); // disallow
};
} // namespace fst
#endif // FST_LIB_BI_TABLE_H__
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