Rewriter: Output RewriteRope contents efficiently

This avoids allocation of temporary std::strings for file contents, instead
writing chunks directly to the output stream.

The old character-based B-tree iterator remains intact for the time being.

llvm-svn: 196119

1 files changed, 5 insertions, 2 deletions

diff --git a/clang/lib/Rewrite/Core/Rewriter.cpp b/clang/lib/Rewrite/Core/Rewriter.cpp
index afb1080c66a..51af83954c5 100644
--- a/clang/lib/Rewrite/Core/Rewriter.cpp
+++ b/clang/lib/Rewrite/Core/Rewriter.cpp
@@ -26,8 +26,11 @@
 using namespace clang;
 
 raw_ostream &RewriteBuffer::write(raw_ostream &os) const {
-  // FIXME: eliminate the copy by writing out each chunk at a time
-  os << std::string(begin(), end());
+  // Walk RewriteRope chunks efficiently using MoveToNextPiece() instead of the
+  // character iterator.
+  for (RopePieceBTreeIterator I = begin(), E = end(); I != E;
+       I.MoveToNextPiece())
+    os << I.piece();
   return os;
 }