1 //===-- SequenceToOffsetTable.h - Compress similar sequences ----*- C++ -*-===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // SequenceToOffsetTable can be used to emit a number of null-terminated
11 // sequences as one big array. Use the same memory when a sequence is a suffix
12 // of another.
13 //
14 //===----------------------------------------------------------------------===//
15
16 #ifndef LLVM_UTILS_TABLEGEN_SEQUENCETOOFFSETTABLE_H
17 #define LLVM_UTILS_TABLEGEN_SEQUENCETOOFFSETTABLE_H
18
19 #include "llvm/Support/raw_ostream.h"
20 #include <algorithm>
21 #include <cassert>
22 #include <cctype>
23 #include <functional>
24 #include <map>
25
26 namespace llvm {
27
28 /// SequenceToOffsetTable - Collect a number of terminated sequences of T.
29 /// Compute the layout of a table that contains all the sequences, possibly by
30 /// reusing entries.
31 ///
32 /// @tparam SeqT The sequence container. (vector or string).
33 /// @tparam Less A stable comparator for SeqT elements.
34 template<typename SeqT, typename Less = std::less<typename SeqT::value_type> >
35 class SequenceToOffsetTable {
36 typedef typename SeqT::value_type ElemT;
37
38 // Define a comparator for SeqT that sorts a suffix immediately before a
39 // sequence with that suffix.
40 struct SeqLess : public std::binary_function<SeqT, SeqT, bool> {
41 Less L;
operatorSeqLess42 bool operator()(const SeqT &A, const SeqT &B) const {
43 return std::lexicographical_compare(A.rbegin(), A.rend(),
44 B.rbegin(), B.rend(), L);
45 }
46 };
47
48 // Keep sequences ordered according to SeqLess so suffixes are easy to find.
49 // Map each sequence to its offset in the table.
50 typedef std::map<SeqT, unsigned, SeqLess> SeqMap;
51
52 // Sequences added so far, with suffixes removed.
53 SeqMap Seqs;
54
55 // Entries in the final table, or 0 before layout was called.
56 unsigned Entries;
57
58 // isSuffix - Returns true if A is a suffix of B.
isSuffix(const SeqT & A,const SeqT & B)59 static bool isSuffix(const SeqT &A, const SeqT &B) {
60 return A.size() <= B.size() && std::equal(A.rbegin(), A.rend(), B.rbegin());
61 }
62
63 public:
SequenceToOffsetTable()64 SequenceToOffsetTable() : Entries(0) {}
65
66 /// add - Add a sequence to the table.
67 /// This must be called before layout().
add(const SeqT & Seq)68 void add(const SeqT &Seq) {
69 assert(Entries == 0 && "Cannot call add() after layout()");
70 typename SeqMap::iterator I = Seqs.lower_bound(Seq);
71
72 // If SeqMap contains a sequence that has Seq as a suffix, I will be
73 // pointing to it.
74 if (I != Seqs.end() && isSuffix(Seq, I->first))
75 return;
76
77 I = Seqs.insert(I, std::make_pair(Seq, 0u));
78
79 // The entry before I may be a suffix of Seq that can now be erased.
80 if (I != Seqs.begin() && isSuffix((--I)->first, Seq))
81 Seqs.erase(I);
82 }
83
empty()84 bool empty() const { return Seqs.empty(); }
85
size()86 unsigned size() const {
87 assert(Entries && "Call layout() before size()");
88 return Entries;
89 }
90
91 /// layout - Computes the final table layout.
layout()92 void layout() {
93 assert(Entries == 0 && "Can only call layout() once");
94 // Lay out the table in Seqs iteration order.
95 for (typename SeqMap::iterator I = Seqs.begin(), E = Seqs.end(); I != E;
96 ++I) {
97 I->second = Entries;
98 // Include space for a terminator.
99 Entries += I->first.size() + 1;
100 }
101 }
102
103 /// get - Returns the offset of Seq in the final table.
get(const SeqT & Seq)104 unsigned get(const SeqT &Seq) const {
105 assert(Entries && "Call layout() before get()");
106 typename SeqMap::const_iterator I = Seqs.lower_bound(Seq);
107 assert(I != Seqs.end() && isSuffix(Seq, I->first) &&
108 "get() called with sequence that wasn't added first");
109 return I->second + (I->first.size() - Seq.size());
110 }
111
112 /// emit - Print out the table as the body of an array initializer.
113 /// Use the Print function to print elements.
114 void emit(raw_ostream &OS,
115 void (*Print)(raw_ostream&, ElemT),
116 const char *Term = "0") const {
117 assert(Entries && "Call layout() before emit()");
118 for (typename SeqMap::const_iterator I = Seqs.begin(), E = Seqs.end();
119 I != E; ++I) {
120 OS << " /* " << I->second << " */ ";
121 for (typename SeqT::const_iterator SI = I->first.begin(),
122 SE = I->first.end(); SI != SE; ++SI) {
123 Print(OS, *SI);
124 OS << ", ";
125 }
126 OS << Term << ",\n";
127 }
128 }
129 };
130
131 // Helper function for SequenceToOffsetTable<string>.
printChar(raw_ostream & OS,char C)132 static inline void printChar(raw_ostream &OS, char C) {
133 unsigned char UC(C);
134 if (isalnum(UC) || ispunct(UC)) {
135 OS << '\'';
136 if (C == '\\' || C == '\'')
137 OS << '\\';
138 OS << C << '\'';
139 } else {
140 OS << unsigned(UC);
141 }
142 }
143
144 } // end namespace llvm
145
146 #endif
147