Allow nested backtracks.
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@55204 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Lex/PPCaching.cpp b/lib/Lex/PPCaching.cpp
index 794e9c4..e69eac6 100644
--- a/lib/Lex/PPCaching.cpp
+++ b/lib/Lex/PPCaching.cpp
@@ -15,6 +15,38 @@
#include "clang/Lex/Preprocessor.h"
using namespace clang;
+/// EnableBacktrackAtThisPos - From the point that this method is called, and
+/// until DisableBacktrack() 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 DisableBacktrack/Backtrack calls will be
+/// combined with the EnableBacktrackAtThisPos calls in reverse order.
+void Preprocessor::EnableBacktrackAtThisPos() {
+ CacheTokens = true;
+ BacktrackPositions.push_back(CachedLexPos);
+ EnterCachingLexMode();
+}
+
+/// DisableBacktrack - Disable the last EnableBacktrackAtThisPos() call.
+void Preprocessor::DisableBacktrack() {
+ 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++];