1 //===-- StringTableBuilder.cpp - String table building utility ------------===//
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 #include "llvm/MC/StringTableBuilder.h"
11 #include "llvm/ADT/STLExtras.h"
12 #include "llvm/Support/COFF.h"
13 #include "llvm/Support/Endian.h"
14
15 #include <vector>
16
17 using namespace llvm;
18
StringTableBuilder(Kind K)19 StringTableBuilder::StringTableBuilder(Kind K) : K(K) {}
20
21 typedef std::pair<StringRef, size_t> StringPair;
22
23 // Returns the character at Pos from end of a string.
charTailAt(StringPair * P,size_t Pos)24 static int charTailAt(StringPair *P, size_t Pos) {
25 StringRef S = P->first;
26 if (Pos >= S.size())
27 return -1;
28 return (unsigned char)S[S.size() - Pos - 1];
29 }
30
31 // Three-way radix quicksort. This is much faster than std::sort with strcmp
32 // because it does not compare characters that we already know the same.
multikey_qsort(StringPair ** Begin,StringPair ** End,int Pos)33 static void multikey_qsort(StringPair **Begin, StringPair **End, int Pos) {
34 tailcall:
35 if (End - Begin <= 1)
36 return;
37
38 // Partition items. Items in [Begin, P) are greater than the pivot,
39 // [P, Q) are the same as the pivot, and [Q, End) are less than the pivot.
40 int Pivot = charTailAt(*Begin, Pos);
41 StringPair **P = Begin;
42 StringPair **Q = End;
43 for (StringPair **R = Begin + 1; R < Q;) {
44 int C = charTailAt(*R, Pos);
45 if (C > Pivot)
46 std::swap(*P++, *R++);
47 else if (C < Pivot)
48 std::swap(*--Q, *R);
49 else
50 R++;
51 }
52
53 multikey_qsort(Begin, P, Pos);
54 multikey_qsort(Q, End, Pos);
55 if (Pivot != -1) {
56 // qsort(P, Q, Pos + 1), but with tail call optimization.
57 Begin = P;
58 End = Q;
59 ++Pos;
60 goto tailcall;
61 }
62 }
63
finalize()64 void StringTableBuilder::finalize() {
65 std::vector<std::pair<StringRef, size_t> *> Strings;
66 Strings.reserve(StringIndexMap.size());
67 for (std::pair<StringRef, size_t> &P : StringIndexMap)
68 Strings.push_back(&P);
69
70 if (!Strings.empty())
71 multikey_qsort(&Strings[0], &Strings[0] + Strings.size(), 0);
72
73 switch (K) {
74 case RAW:
75 break;
76 case ELF:
77 case MachO:
78 // Start the table with a NUL byte.
79 StringTable += '\x00';
80 break;
81 case WinCOFF:
82 // Make room to write the table size later.
83 StringTable.append(4, '\x00');
84 break;
85 }
86
87 StringRef Previous;
88 for (std::pair<StringRef, size_t> *P : Strings) {
89 StringRef S = P->first;
90 if (K == WinCOFF)
91 assert(S.size() > COFF::NameSize && "Short string in COFF string table!");
92
93 if (Previous.endswith(S)) {
94 P->second = StringTable.size() - S.size() - (K != RAW);
95 continue;
96 }
97
98 P->second = StringTable.size();
99 StringTable += S;
100 if (K != RAW)
101 StringTable += '\x00';
102 Previous = S;
103 }
104
105 switch (K) {
106 case RAW:
107 case ELF:
108 break;
109 case MachO:
110 // Pad to multiple of 4.
111 while (StringTable.size() % 4)
112 StringTable += '\x00';
113 break;
114 case WinCOFF:
115 // Write the table size in the first word.
116 assert(StringTable.size() <= std::numeric_limits<uint32_t>::max());
117 uint32_t Size = static_cast<uint32_t>(StringTable.size());
118 support::endian::write<uint32_t, support::little, support::unaligned>(
119 StringTable.data(), Size);
120 break;
121 }
122
123 Size = StringTable.size();
124 }
125
clear()126 void StringTableBuilder::clear() {
127 StringTable.clear();
128 StringIndexMap.clear();
129 }
130
getOffset(StringRef S) const131 size_t StringTableBuilder::getOffset(StringRef S) const {
132 assert(isFinalized());
133 auto I = StringIndexMap.find(S);
134 assert(I != StringIndexMap.end() && "String is not in table!");
135 return I->second;
136 }
137
add(StringRef S)138 size_t StringTableBuilder::add(StringRef S) {
139 assert(!isFinalized());
140 auto P = StringIndexMap.insert(std::make_pair(S, Size));
141 if (P.second)
142 Size += S.size() + (K != RAW);
143 return P.first->second;
144 }
145