[clang-format] Add comment manipulation header

Summary:
Introduces a separate target for comment manipulation.
Currently, comment manipulation is in BreakableComment.cpp.
Towards implementing comment reflowing, we want to factor out the
comment-related functionality, so it can be reused.
Start simple by just moving out getLineCommentIndentPrefix.

Patch by Krasimir Georgiev!

Reviewers: djasper

Subscribers: klimek, beanz, mgorny, modocache

Differential Revision: https://reviews.llvm.org/D25725

llvm-svn: 284573

1 files changed, 36 insertions, 0 deletions

diff --git a/clang/lib/Format/Comments.cpp b/clang/lib/Format/Comments.cpp
new file mode 100644
index 00000000000..1b27f5b30a6
--- /dev/null
+++ b/clang/lib/Format/Comments.cpp
@@ -0,0 +1,36 @@
+//===--- Comments.cpp - Comment Manipulation  -------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// \brief Implements comment manipulation.
+///
+//===----------------------------------------------------------------------===//
+
+#include "Comments.h"
+
+namespace clang {
+namespace format {
+
+StringRef getLineCommentIndentPrefix(StringRef Comment) {
+  static const char *const KnownPrefixes[] = {"///", "//", "//!"};
+  StringRef LongestPrefix;
+  for (StringRef KnownPrefix : KnownPrefixes) {
+    if (Comment.startswith(KnownPrefix)) {
+      size_t PrefixLength = KnownPrefix.size();
+      while (PrefixLength < Comment.size() && Comment[PrefixLength] == ' ')
+        ++PrefixLength;
+      if (PrefixLength > LongestPrefix.size())
+        LongestPrefix = Comment.substr(0, PrefixLength);
+    }
+  }
+  return LongestPrefix;
+}
+
+} // namespace format
+} // namespace clang