[Object] Define Archive::isEmpty().

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@282884 91177308-0d34-0410-b5e6-96231b3b80d8

Author: rui314

include/llvm/Object/Archive.h

@@ -239,6 +239,7 @@ class Archive : public Binary {
   // check if a symbol is in the archive
   Expected<Optional<Child>> findSym(StringRef name) const;
 
+  bool isEmpty() const;
   bool hasSymbolTable() const;
   StringRef getSymbolTable() const { return SymbolTable; }
   StringRef getStringTable() const { return StringTable; }

lib/Object/Archive.cpp

@@ -752,7 +752,7 @@ Archive::Archive(MemoryBufferRef Source, Error &Err)
 
 Archive::child_iterator Archive::child_begin(Error &Err,
                                              bool SkipInternal) const {
-  if (Data.getBufferSize() == 8) // empty archive.
+  if (isEmpty())
     return child_end();
 
   if (SkipInternal)
@@ -968,4 +968,7 @@ Expected<Optional<Archive::Child>> Archive::findSym(StringRef name) const {
   return Optional<Child>();
 }
 
+// Returns true if archive file contains no member file.
+bool Archive::isEmpty() const { return Data.getBufferSize() == 8; }
+
 bool Archive::hasSymbolTable() const { return !SymbolTable.empty(); }