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