add a simplified lexer ctor that sets up the lexer to raw-lex an
entire file.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@62414 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Lex/Lexer.cpp b/lib/Lex/Lexer.cpp
index e898150..704c4db 100644
--- a/lib/Lex/Lexer.cpp
+++ b/lib/Lex/Lexer.cpp
@@ -127,7 +127,6 @@
              const char *BufPtr, const char *BufEnd,
              const llvm::MemoryBuffer *FromFile)
   : FileLoc(fileloc), Features(features) {
-      
 
   // If a MemoryBuffer was specified, use its start as BufferStart. This affects
   // the source location objects produced by this lexer.
@@ -140,6 +139,20 @@
   LexingRawMode = true;
 }
 
+/// Lexer constructor - Create a new raw lexer object.  This object is only
+/// suitable for calls to 'LexRawToken'.  This lexer assumes that the text
+/// range will outlive it, so it doesn't take ownership of it.
+Lexer::Lexer(FileID FID, const SourceManager &SM, const LangOptions &features)
+  : FileLoc(SM.getLocForStartOfFile(FID)), Features(features) {
+  const llvm::MemoryBuffer *FromFile = SM.getBuffer(FID);
+
+  InitLexer(FromFile->getBufferStart(), FromFile->getBufferStart(), 
+            FromFile->getBufferEnd());
+  
+  // We *are* in raw mode.
+  LexingRawMode = true;
+}
+
 
 /// Stringify - Convert the specified string into a C string, with surrounding
 /// ""'s, and with escaped \ and " characters.