[PATCH] Refactor the code in clang to find a file in a PATH like environment variable into a helper function

[Ehsan Akhgari]

Hi hans,

http://reviews.llvm.org/D4201

Files:
  include/llvm/Support/Program.h
  lib/Support/Program.cpp

Index: include/llvm/Support/Program.h
===================================================================
--- include/llvm/Support/Program.h
+++ include/llvm/Support/Program.h
@@ -15,6 +15,7 @@
 #define LLVM_SUPPORT_PROGRAM_H
 
 #include "llvm/ADT/ArrayRef.h"
+#include "llvm/ADT/Optional.h"
 #include "llvm/Support/Path.h"
 #include <system_error>
 
@@ -146,6 +147,13 @@
       ///< string is non-empty upon return an error occurred while invoking the
       ///< program.
       );
+
+  /// This function searches for an existing file in the list of directories
+  /// in a PATH like environment variable, and returns the first file found,
+  /// according to the order of the entries in the PATH like environment
+  /// variable.
+  Optional<std::string> FindInEnvPath(const std::string& EnvName,
+                                      const std::string& FileName);
   }
 }
 
Index: lib/Support/Program.cpp
===================================================================
--- lib/Support/Program.cpp
+++ lib/Support/Program.cpp
@@ -12,7 +12,10 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/Support/Program.h"
+#include "llvm/ADT/StringExtras.h"
 #include "llvm/Config/config.h"
+#include "llvm/Support/FileSystem.h"
+#include "llvm/Support/Process.h"
 #include <system_error>
 using namespace llvm;
 using namespace sys;
@@ -59,6 +62,33 @@
   return PI;
 }
 
+Optional<std::string> sys::FindInEnvPath(const std::string& EnvName,
+                                         const std::string& FileName)
+{
+  Optional<std::string> FoundPath;
+  Optional<std::string> OptPath = Process::GetEnv(EnvName);
+  if (!OptPath.hasValue())
+    return FoundPath;
+
+  const char EnvPathSeparatorStr[] = {EnvPathSeparator, '\0'};
+  SmallVector<StringRef, 8> Dirs;
+  SplitString(OptPath.getValue(), Dirs, EnvPathSeparatorStr);
+
+  for (const auto &Dir : Dirs) {
+    if (Dir.empty())
+      continue;
+
+    SmallString<128> FilePath(Dir);
+    path::append(FilePath, FileName);
+    if (fs::exists(Twine(FilePath))) {
+      FoundPath = FilePath.str();
+      break;
+    }
+  }
+
+  return FoundPath;
+}
+
 // Include the platform-specific parts of this class.
 #ifdef LLVM_ON_UNIX
 #include "Unix/Program.inc"
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