1 //===-- SequenceToOffsetTable.h - Compress similar sequences ----*- C++ -*-===//
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
7 //===----------------------------------------------------------------------===//
9 // SequenceToOffsetTable can be used to emit a number of null-terminated
10 // sequences as one big array. Use the same memory when a sequence is a suffix
13 //===----------------------------------------------------------------------===//
15 #ifndef LLVM_UTILS_TABLEGEN_SEQUENCETOOFFSETTABLE_H
16 #define LLVM_UTILS_TABLEGEN_SEQUENCETOOFFSETTABLE_H
18 #include "llvm/Support/raw_ostream.h"
27 /// SequenceToOffsetTable - Collect a number of terminated sequences of T.
28 /// Compute the layout of a table that contains all the sequences, possibly by
31 /// @tparam SeqT The sequence container. (vector or string).
32 /// @tparam Less A stable comparator for SeqT elements.
33 template<typename SeqT, typename Less = std::less<typename SeqT::value_type> >
34 class SequenceToOffsetTable {
35 typedef typename SeqT::value_type ElemT;
37 // Define a comparator for SeqT that sorts a suffix immediately before a
38 // sequence with that suffix.
41 bool operator()(const SeqT &A, const SeqT &B) const {
42 return std::lexicographical_compare(A.rbegin(), A.rend(),
43 B.rbegin(), B.rend(), L);
47 // Keep sequences ordered according to SeqLess so suffixes are easy to find.
48 // Map each sequence to its offset in the table.
49 typedef std::map<SeqT, unsigned, SeqLess> SeqMap;
51 // Sequences added so far, with suffixes removed.
54 // Entries in the final table, or 0 before layout was called.
57 // isSuffix - Returns true if A is a suffix of B.
58 static bool isSuffix(const SeqT &A, const SeqT &B) {
59 return A.size() <= B.size() && std::equal(A.rbegin(), A.rend(), B.rbegin());
63 SequenceToOffsetTable() : Entries(0) {}
65 /// add - Add a sequence to the table.
66 /// This must be called before layout().
67 void add(const SeqT &Seq) {
68 assert(Entries == 0 && "Cannot call add() after layout()");
69 typename SeqMap::iterator I = Seqs.lower_bound(Seq);
71 // If SeqMap contains a sequence that has Seq as a suffix, I will be
73 if (I != Seqs.end() && isSuffix(Seq, I->first))
76 I = Seqs.insert(I, std::make_pair(Seq, 0u));
78 // The entry before I may be a suffix of Seq that can now be erased.
79 if (I != Seqs.begin() && isSuffix((--I)->first, Seq))
83 bool empty() const { return Seqs.empty(); }
85 unsigned size() const {
86 assert(Entries && "Call layout() before size()");
90 /// layout - Computes the final table layout.
92 assert(Entries == 0 && "Can only call layout() once");
93 // Lay out the table in Seqs iteration order.
94 for (typename SeqMap::iterator I = Seqs.begin(), E = Seqs.end(); I != E;
97 // Include space for a terminator.
98 Entries += I->first.size() + 1;
102 /// get - Returns the offset of Seq in the final table.
103 unsigned get(const SeqT &Seq) const {
104 assert(Entries && "Call layout() before get()");
105 typename SeqMap::const_iterator I = Seqs.lower_bound(Seq);
106 assert(I != Seqs.end() && isSuffix(Seq, I->first) &&
107 "get() called with sequence that wasn't added first");
108 return I->second + (I->first.size() - Seq.size());
111 /// emit - Print out the table as the body of an array initializer.
112 /// Use the Print function to print elements.
113 void emit(raw_ostream &OS,
114 void (*Print)(raw_ostream&, ElemT),
115 const char *Term = "0") const {
116 assert(Entries && "Call layout() before emit()");
117 for (typename SeqMap::const_iterator I = Seqs.begin(), E = Seqs.end();
119 OS << " /* " << I->second << " */ ";
120 for (typename SeqT::const_iterator SI = I->first.begin(),
121 SE = I->first.end(); SI != SE; ++SI) {
130 // Helper function for SequenceToOffsetTable<string>.
131 static inline void printChar(raw_ostream &OS, char C) {
133 if (isalnum(UC) || ispunct(UC)) {
135 if (C == '\\' || C == '\'')
143 } // end namespace llvm