Allow the preprocessor to cache the lexed tokens, so that we can do efficient lookahead and backtracking.
1) New public methods added:
-EnableBacktrackAtThisPos
-DisableBacktrack
-Backtrack
-isBacktrackEnabled
2) LookAhead() implementation is replaced with a more efficient one.
3) LookNext() is removed.
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@54611 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Lex/PPCaching.cpp b/lib/Lex/PPCaching.cpp
new file mode 100644
index 0000000..794e9c4
--- /dev/null
+++ b/lib/Lex/PPCaching.cpp
@@ -0,0 +1,63 @@
+//===--- 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;
+
+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();
+}