project.h revision 8fc5a7f51e62cb4ae44a27bdf4176d04adc80ede
1// project.h 2// 3// Licensed under the Apache License, Version 2.0 (the "License"); 4// you may not use this file except in compliance with the License. 5// You may obtain a copy of the License at 6// 7// http://www.apache.org/licenses/LICENSE-2.0 8// 9// Unless required by applicable law or agreed to in writing, software 10// distributed under the License is distributed on an "AS IS" BASIS, 11// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12// See the License for the specific language governing permissions and 13// limitations under the License. 14// 15// 16// \file 17// Functions and classes to project an Fst on to its domain or range. 18 19#ifndef FST_LIB_PROJECT_H__ 20#define FST_LIB_PROJECT_H__ 21 22#include "fst/lib/map.h" 23#include "fst/lib/mutable-fst.h" 24 25namespace fst { 26 27// This specifies whether to project on input or output. 28enum ProjectType { PROJECT_INPUT = 1, PROJECT_OUTPUT = 2 }; 29 30 31// Mapper to implement projection per arc. 32template <class A> class ProjectMapper { 33 public: 34 explicit ProjectMapper(ProjectType project_type) 35 : project_type_(project_type) {} 36 37 A operator()(const A &arc) { 38 typename A::Label label = project_type_ == PROJECT_INPUT 39 ? arc.ilabel : arc.olabel; 40 return A(label, label, arc.weight, arc.nextstate); 41 } 42 43 uint64 Properties(uint64 props) { 44 return ProjectProperties(props, project_type_ == PROJECT_INPUT); 45 } 46 47 MapFinalAction FinalAction() const { return MAP_NO_SUPERFINAL; } 48 49 private: 50 ProjectType project_type_; 51}; 52 53 54// Projects an FST onto its domain or range by either copying each arcs' 55// input label to the output label or vice versa. This version modifies 56// its input. 57// 58// Complexity: 59// - Time: O(V + E) 60// - Space: O(1) 61// where V = # of states and E = # of arcs. 62template<class Arc> inline 63void Project(MutableFst<Arc> *fst, ProjectType project_type) { 64 Map(fst, ProjectMapper<Arc>(project_type)); 65} 66 67 68// Projects an FST onto its domain or range by either copying each arc's 69// input label to the output label or vice versa. This version is a delayed 70// Fst. 71// 72// Complexity: 73// - Time: O(v + e) 74// - Space: O(1) 75// where v = # of states visited, e = # of arcs visited. Constant 76// time and to visit an input state or arc is assumed and exclusive 77// of caching. 78template <class A> 79class ProjectFst : public MapFst<A, A, ProjectMapper<A> > { 80 public: 81 typedef A Arc; 82 typedef ProjectMapper<A> C; 83 84 ProjectFst(const Fst<A> &fst, ProjectType project_type) 85 : MapFst<A, A, C>(fst, C(project_type)) {} 86 87 ProjectFst(const ProjectFst<A> &fst) : MapFst<A, A, C>(fst) {} 88 89 virtual ProjectFst<A> *Copy() const { return new ProjectFst(*this); } 90}; 91 92 93// Specialization for ProjectFst. 94template <class A> 95class StateIterator< ProjectFst<A> > 96 : public StateIterator< MapFst<A, A, ProjectMapper<A> > > { 97 public: 98 explicit StateIterator(const ProjectFst<A> &fst) 99 : StateIterator< MapFst<A, A, ProjectMapper<A> > >(fst) {} 100}; 101 102 103// Specialization for ProjectFst. 104template <class A> 105class ArcIterator< ProjectFst<A> > 106 : public ArcIterator< MapFst<A, A, ProjectMapper<A> > > { 107 public: 108 ArcIterator(const ProjectFst<A> &fst, typename A::StateId s) 109 : ArcIterator< MapFst<A, A, ProjectMapper<A> > >(fst, s) {} 110}; 111 112 113// Useful alias when using StdArc. 114typedef ProjectFst<StdArc> StdProjectFst; 115 116} // namespace fst 117 118#endif // FST_LIB_PROJECT_H__ 119