145 lines
3.7 KiB
C++
145 lines
3.7 KiB
C++
//===-- StringTableBuilder.cpp - String table building utility ------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/MC/StringTableBuilder.h"
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#include "llvm/ADT/STLExtras.h"
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#include "llvm/Support/COFF.h"
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#include "llvm/Support/Endian.h"
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#include <vector>
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using namespace llvm;
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StringTableBuilder::StringTableBuilder(Kind K) : K(K) {}
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typedef std::pair<StringRef, size_t> StringPair;
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// Returns the character at Pos from end of a string.
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static int charTailAt(StringPair *P, size_t Pos) {
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StringRef S = P->first;
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if (Pos >= S.size())
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return -1;
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return (unsigned char)S[S.size() - Pos - 1];
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}
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// Three-way radix quicksort. This is much faster than std::sort with strcmp
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// because it does not compare characters that we already know the same.
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static void multikey_qsort(StringPair **Begin, StringPair **End, int Pos) {
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tailcall:
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if (End - Begin <= 1)
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return;
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// Partition items. Items in [Begin, P) are greater than the pivot,
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// [P, Q) are the same as the pivot, and [Q, End) are less than the pivot.
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int Pivot = charTailAt(*Begin, Pos);
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StringPair **P = Begin;
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StringPair **Q = End;
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for (StringPair **R = Begin + 1; R < Q;) {
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int C = charTailAt(*R, Pos);
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if (C > Pivot)
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std::swap(*P++, *R++);
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else if (C < Pivot)
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std::swap(*--Q, *R);
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else
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R++;
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}
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multikey_qsort(Begin, P, Pos);
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multikey_qsort(Q, End, Pos);
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if (Pivot != -1) {
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// qsort(P, Q, Pos + 1), but with tail call optimization.
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Begin = P;
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End = Q;
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++Pos;
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goto tailcall;
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}
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}
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void StringTableBuilder::finalize() {
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std::vector<std::pair<StringRef, size_t> *> Strings;
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Strings.reserve(StringIndexMap.size());
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for (std::pair<StringRef, size_t> &P : StringIndexMap)
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Strings.push_back(&P);
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if (!Strings.empty())
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multikey_qsort(&Strings[0], &Strings[0] + Strings.size(), 0);
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switch (K) {
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case RAW:
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break;
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case ELF:
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case MachO:
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// Start the table with a NUL byte.
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StringTable += '\x00';
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break;
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case WinCOFF:
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// Make room to write the table size later.
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StringTable.append(4, '\x00');
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break;
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}
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StringRef Previous;
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for (std::pair<StringRef, size_t> *P : Strings) {
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StringRef S = P->first;
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if (K == WinCOFF)
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assert(S.size() > COFF::NameSize && "Short string in COFF string table!");
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if (Previous.endswith(S)) {
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P->second = StringTable.size() - S.size() - (K != RAW);
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continue;
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}
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P->second = StringTable.size();
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StringTable += S;
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if (K != RAW)
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StringTable += '\x00';
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Previous = S;
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}
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switch (K) {
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case RAW:
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case ELF:
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break;
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case MachO:
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// Pad to multiple of 4.
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while (StringTable.size() % 4)
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StringTable += '\x00';
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break;
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case WinCOFF:
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// Write the table size in the first word.
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assert(StringTable.size() <= std::numeric_limits<uint32_t>::max());
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uint32_t Size = static_cast<uint32_t>(StringTable.size());
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support::endian::write<uint32_t, support::little, support::unaligned>(
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StringTable.data(), Size);
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break;
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}
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Size = StringTable.size();
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}
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void StringTableBuilder::clear() {
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StringTable.clear();
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StringIndexMap.clear();
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}
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size_t StringTableBuilder::getOffset(StringRef S) const {
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assert(isFinalized());
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auto I = StringIndexMap.find(S);
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assert(I != StringIndexMap.end() && "String is not in table!");
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return I->second;
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}
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size_t StringTableBuilder::add(StringRef S) {
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assert(!isFinalized());
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auto P = StringIndexMap.insert(std::make_pair(S, Size));
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if (P.second)
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Size += S.size() + (K != RAW);
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return P.first->second;
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}
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