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//===--- PPCaching.cpp - Handle caching lexed tokens ----------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements pieces of the Preprocessor interface that manage the
// caching of lexed tokens.
//
//===----------------------------------------------------------------------===//
#include "clang/Lex/Preprocessor.h"
using namespace clang;
/// EnableBacktrackAtThisPos - From the point that this method is called, and
/// until CommitBacktrackedTokens() or Backtrack() is called, the Preprocessor
/// keeps track of the lexed tokens so that a subsequent Backtrack() call will
/// make the Preprocessor re-lex the same tokens.
///
/// Nested backtracks are allowed, meaning that EnableBacktrackAtThisPos can
/// be called multiple times and CommitBacktrackedTokens/Backtrack calls will
/// be combined with the EnableBacktrackAtThisPos calls in reverse order.
void Preprocessor::EnableBacktrackAtThisPos() {
CacheTokens = true;
BacktrackPositions.push_back(CachedLexPos);
EnterCachingLexMode();
}
/// CommitBacktrackedTokens - Disable the last EnableBacktrackAtThisPos call.
void Preprocessor::CommitBacktrackedTokens() {
assert(!BacktrackPositions.empty()
&& "EnableBacktrackAtThisPos was not called!");
BacktrackPositions.pop_back();
CacheTokens = !BacktrackPositions.empty();
}
/// Backtrack - Make Preprocessor re-lex the tokens that were lexed since
/// EnableBacktrackAtThisPos() was previously called.
void Preprocessor::Backtrack() {
assert(!BacktrackPositions.empty()
&& "EnableBacktrackAtThisPos was not called!");
CachedLexPos = BacktrackPositions.back();
BacktrackPositions.pop_back();
CacheTokens = !BacktrackPositions.empty();
}
void Preprocessor::CachingLex(Token &Result) {
if (CachedLexPos < CachedTokens.size()) {
Result = CachedTokens[CachedLexPos++];
return;
}
ExitCachingLexMode();
Lex(Result);
if (!CacheTokens) {
// All cached tokens were consumed.
CachedTokens.clear();
CachedLexPos = 0;
return;
}
// We should cache the lexed token.
EnterCachingLexMode();
if (Result.isNot(tok::eof)) {
CachedTokens.push_back(Result);
++CachedLexPos;
}
}
void Preprocessor::EnterCachingLexMode() {
if (InCachingLexMode())
return;
IncludeMacroStack.push_back(IncludeStackInfo(CurLexer, CurDirLookup,
CurTokenLexer));
CurLexer = 0;
CurTokenLexer = 0;
}
const Token &Preprocessor::PeekAhead(unsigned N) {
assert(CachedLexPos + N > CachedTokens.size() && "Confused caching.");
ExitCachingLexMode();
for (unsigned C = CachedLexPos + N - CachedTokens.size(); C > 0; --C) {
CachedTokens.push_back(Token());
Lex(CachedTokens.back());
}
EnterCachingLexMode();
return CachedTokens.back();
}
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