From a26be4a946ded0d328473e3842f2df45e896488f Mon Sep 17 00:00:00 2001
From: Douglas Katzman <dougk@google.com>
Date: Wed, 2 Sep 2015 21:02:10 +0000
Subject: [PATCH] Move twice-repeated clang path operation into a new function.

And make it more robust in the edge case of exactly "./" as input.

llvm-svn: 246711
---
 llvm/include/llvm/Support/Path.h |  6 ++++++
 llvm/lib/Support/Path.cpp        | 12 ++++++++++--
 llvm/unittests/Support/Path.cpp  | 10 ++++++++++
 3 files changed, 26 insertions(+), 2 deletions(-)

diff --git a/llvm/include/llvm/Support/Path.h b/llvm/include/llvm/Support/Path.h
index 6fedb93d2376..0853f916b580 100644
--- a/llvm/include/llvm/Support/Path.h
+++ b/llvm/include/llvm/Support/Path.h
@@ -401,6 +401,12 @@ bool is_absolute(const Twine &path);
 /// @result True if the path is relative, false if it is not.
 bool is_relative(const Twine &path);
 
+/// @brief Remove redundant leading "./" pieces and consecutive separators.
+///
+/// @param path Input path.
+/// @result The cleaned-up \a path.
+StringRef remove_leading_dotslash(StringRef path);
+
 } // end namespace path
 } // end namespace sys
 } // end namespace llvm
diff --git a/llvm/lib/Support/Path.cpp b/llvm/lib/Support/Path.cpp
index 54daf24daba0..aa96074554e4 100644
--- a/llvm/lib/Support/Path.cpp
+++ b/llvm/lib/Support/Path.cpp
@@ -661,8 +661,16 @@ bool is_absolute(const Twine &path) {
   return rootDir && rootName;
 }
 
-bool is_relative(const Twine &path) {
-  return !is_absolute(path);
+bool is_relative(const Twine &path) { return !is_absolute(path); }
+
+StringRef remove_leading_dotslash(StringRef Path) {
+  // Remove leading "./" (or ".//" or "././" etc.)
+  while (Path.size() > 2 && Path[0] == '.' && is_separator(Path[1])) {
+    Path = Path.substr(2);
+    while (Path.size() > 0 && is_separator(Path[0]))
+      Path = Path.substr(1);
+  }
+  return Path;
 }
 
 } // end namespace path
diff --git a/llvm/unittests/Support/Path.cpp b/llvm/unittests/Support/Path.cpp
index 11d53c83419d..cfba227dbe93 100644
--- a/llvm/unittests/Support/Path.cpp
+++ b/llvm/unittests/Support/Path.cpp
@@ -789,4 +789,14 @@ TEST(Support, NormalizePath) {
 
 #undef EXPECT_PATH_IS
 }
+
+TEST(Support, RemoveLeadingDotSlash) {
+  StringRef Path1("././/foolz/wat");
+  StringRef Path2("./////");
+
+  Path1 = path::remove_leading_dotslash(Path1);
+  EXPECT_EQ(Path1, "foolz/wat");
+  Path2 = path::remove_leading_dotslash(Path2);
+  EXPECT_EQ(Path2, "");
+}
 } // anonymous namespace