Check in LLVM r95781.
diff --git a/lib/Lex/PPCaching.cpp b/lib/Lex/PPCaching.cpp
new file mode 100644
index 0000000..6aeb6fa
--- /dev/null
+++ b/lib/Lex/PPCaching.cpp
@@ -0,0 +1,112 @@
+//===--- 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() {
+ BacktrackPositions.push_back(CachedLexPos);
+ EnterCachingLexMode();
+}
+
+/// CommitBacktrackedTokens - Disable the last EnableBacktrackAtThisPos call.
+void Preprocessor::CommitBacktrackedTokens() {
+ assert(!BacktrackPositions.empty()
+ && "EnableBacktrackAtThisPos was not called!");
+ BacktrackPositions.pop_back();
+}
+
+/// 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();
+}
+
+void Preprocessor::CachingLex(Token &Result) {
+ if (CachedLexPos < CachedTokens.size()) {
+ Result = CachedTokens[CachedLexPos++];
+ return;
+ }
+
+ ExitCachingLexMode();
+ Lex(Result);
+
+ if (!isBacktrackEnabled()) {
+ // 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;
+
+ PushIncludeMacroStack();
+}
+
+
+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();
+}
+
+void Preprocessor::AnnotatePreviousCachedTokens(const Token &Tok) {
+ assert(Tok.isAnnotation() && "Expected annotation token");
+ assert(CachedLexPos != 0 && "Expected to have some cached tokens");
+ assert(CachedTokens[CachedLexPos-1].getLastLoc() == Tok.getAnnotationEndLoc()
+ && "The annotation should be until the most recent cached token");
+
+ // Start from the end of the cached tokens list and look for the token
+ // that is the beginning of the annotation token.
+ for (CachedTokensTy::size_type i = CachedLexPos; i != 0; --i) {
+ CachedTokensTy::iterator AnnotBegin = CachedTokens.begin() + i-1;
+ if (AnnotBegin->getLocation() == Tok.getLocation()) {
+ assert((BacktrackPositions.empty() || BacktrackPositions.back() < i) &&
+ "The backtrack pos points inside the annotated tokens!");
+ // Replace the cached tokens with the single annotation token.
+ if (i < CachedLexPos)
+ CachedTokens.erase(AnnotBegin + 1, CachedTokens.begin() + CachedLexPos);
+ *AnnotBegin = Tok;
+ CachedLexPos = i;
+ return;
+ }
+ }
+}