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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/ADT/CachedHashString.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/MC/StringTableBuilder.h"
#include "llvm/Support/COFF.h"
#include "llvm/Support/Endian.h"
#include "llvm/Support/MathExtras.h"
#include "llvm/Support/raw_ostream.h"
#include <cassert>
#include <cstddef>
#include <cstdint>
#include <cstring>
#include <utility>
#include <vector>
using namespace llvm;
StringTableBuilder::~StringTableBuilder() = default;
void StringTableBuilder::initSize() {
// Account for leading bytes in table so that offsets returned from add are
// correct.
switch (K) {
case RAW:
Size = 0;
break;
case MachO:
case ELF:
// Start the table with a NUL byte.
Size = 1;
break;
case WinCOFF:
// Make room to write the table size later.
Size = 4;
break;
}
}
StringTableBuilder::StringTableBuilder(Kind K, unsigned Alignment)
: K(K), Alignment(Alignment) {
initSize();
}
void StringTableBuilder::write(raw_ostream &OS) const {
assert(isFinalized());
SmallString<0> Data;
Data.resize(getSize());
write((uint8_t *)Data.data());
OS << Data;
}
using StringPair = std::pair<CachedHashStringRef, size_t>;
void StringTableBuilder::write(uint8_t *Buf) const {
assert(isFinalized());
for (const StringPair &P : StringIndexMap) {
StringRef Data = P.first.val();
if (!Data.empty())
memcpy(Buf + P.second, Data.data(), Data.size());
}
if (K != WinCOFF)
return;
support::endian::write32le(Buf, Size);
}
// Returns the character at Pos from end of a string.
static int charTailAt(StringPair *P, size_t Pos) {
StringRef S = P->first.val();
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() {
finalizeStringTable(/*Optimize=*/true);
}
void StringTableBuilder::finalizeInOrder() {
finalizeStringTable(/*Optimize=*/false);
}
void StringTableBuilder::finalizeStringTable(bool Optimize) {
Finalized = true;
if (Optimize) {
std::vector<StringPair *> Strings;
Strings.reserve(StringIndexMap.size());
for (StringPair &P : StringIndexMap)
Strings.push_back(&P);
if (!Strings.empty()) {
// If we're optimizing, sort by name. If not, sort by previously assigned
// offset.
multikey_qsort(&Strings[0], &Strings[0] + Strings.size(), 0);
}
initSize();
StringRef Previous;
for (StringPair *P : Strings) {
StringRef S = P->first.val();
if (Previous.endswith(S)) {
size_t Pos = Size - S.size() - (K != RAW);
if (!(Pos & (Alignment - 1))) {
P->second = Pos;
continue;
}
}
Size = alignTo(Size, Alignment);
P->second = Size;
Size += S.size();
if (K != RAW)
++Size;
Previous = S;
}
}
if (K == MachO)
Size = alignTo(Size, 4); // Pad to multiple of 4.
}
void StringTableBuilder::clear() {
Finalized = false;
StringIndexMap.clear();
}
size_t StringTableBuilder::getOffset(CachedHashStringRef 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(CachedHashStringRef S) {
if (K == WinCOFF)
assert(S.size() > COFF::NameSize && "Short string in COFF string table!");
assert(!isFinalized());
auto P = StringIndexMap.insert(std::make_pair(S, 0));
if (P.second) {
size_t Start = alignTo(Size, Alignment);
P.first->second = Start;
Size = Start + S.size() + (K != RAW);
}
return P.first->second;
}
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