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 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 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 85 void StringTableBuilder::clear() { 86 StringTable.clear(); 87 StringIndexMap.clear(); 88 } 89