1 files changed, 113 insertions, 0 deletions
diff --git a/lib/Lex/PPCaching.cpp b/lib/Lex/PPCaching.cpp
new file mode 100644
index 0000000..53aa09c
--- /dev/null
+++ b/lib/Lex/PPCaching.cpp
@@ -0,0 +1,113 @@
+//===--- 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].getLocation() == 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.
+      CachedTokens.erase(AnnotBegin + 1, CachedTokens.begin() + CachedLexPos);
+      *AnnotBegin = Tok;
+      CachedLexPos = i;
+      return;
+    }
+  }
+
+  assert(0&&"Didn't find the first token represented by the annotation token!");
+}