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/SmallVector.h"
12 #include "llvm/Support/COFF.h"
13 #include "llvm/Support/Endian.h"
14
15 using namespace llvm;
16
compareBySuffix(StringRef a,StringRef b)17 static bool compareBySuffix(StringRef a, StringRef b) {
18 size_t sizeA = a.size();
19 size_t sizeB = b.size();
20 size_t len = std::min(sizeA, sizeB);
21 for (size_t i = 0; i < len; ++i) {
22 char ca = a[sizeA - i - 1];
23 char cb = b[sizeB - i - 1];
24 if (ca != cb)
25 return ca > cb;
26 }
27 return sizeA > sizeB;
28 }
29
finalize(Kind kind)30 void StringTableBuilder::finalize(Kind kind) {
31 SmallVector<StringRef, 8> Strings;
32 Strings.reserve(StringIndexMap.size());
33
34 for (auto i = StringIndexMap.begin(), e = StringIndexMap.end(); i != e; ++i)
35 Strings.push_back(i->getKey());
36
37 std::sort(Strings.begin(), Strings.end(), compareBySuffix);
38
39 switch (kind) {
40 case ELF:
41 case MachO:
42 // Start the table with a NUL byte.
43 StringTable += '\x00';
44 break;
45 case WinCOFF:
46 // Make room to write the table size later.
47 StringTable.append(4, '\x00');
48 break;
49 }
50
51 StringRef Previous;
52 for (StringRef s : Strings) {
53 if (kind == WinCOFF)
54 assert(s.size() > COFF::NameSize && "Short string in COFF string table!");
55
56 if (Previous.endswith(s)) {
57 StringIndexMap[s] = StringTable.size() - 1 - s.size();
58 continue;
59 }
60
61 StringIndexMap[s] = StringTable.size();
62 StringTable += s;
63 StringTable += '\x00';
64 Previous = s;
65 }
66
67 switch (kind) {
68 case ELF:
69 break;
70 case MachO:
71 // Pad to multiple of 4.
72 while (StringTable.size() % 4)
73 StringTable += '\x00';
74 break;
75 case WinCOFF:
76 // Write the table size in the first word.
77 assert(StringTable.size() <= std::numeric_limits<uint32_t>::max());
78 uint32_t size = static_cast<uint32_t>(StringTable.size());
79 support::endian::write<uint32_t, support::little, support::unaligned>(
80 StringTable.data(), size);
81 break;
82 }
83 }
84
clear()85 void StringTableBuilder::clear() {
86 StringTable.clear();
87 StringIndexMap.clear();
88 }
89