Object: Teach llvm-ar to create symbol table for COFF short import files.

COFF short import files are special kind of files that contains only
DLL-exported symbol names. That's different from object files because
it has no data except symbol names.

This change implements a SymbolicFile interface for the short import
files so that symbol names can be accessed through that interface.
llvm-ar is now able to read the file and create symbol table entries
for short import files.

llvm-svn: 246276

1 files changed, 46 insertions, 1 deletions

diff --git a/llvm/lib/Object/SymbolicFile.cpp b/llvm/lib/Object/SymbolicFile.cpp
index 854e68e40f4..c3106319c7f 100644
--- a/llvm/lib/Object/SymbolicFile.cpp
+++ b/llvm/lib/Object/SymbolicFile.cpp
@@ -11,14 +11,58 @@
 //
 //===----------------------------------------------------------------------===//
 
+#include "llvm/Object/COFF.h"
 #include "llvm/Object/IRObjectFile.h"
 #include "llvm/Object/ObjectFile.h"
 #include "llvm/Object/SymbolicFile.h"
+#include "llvm/Support/COFF.h"
 #include "llvm/Support/MemoryBuffer.h"
 
 using namespace llvm;
 using namespace object;
 
+// COFF short import file is a special kind of file which contains
+// only symbol names for DLL-exported symbols. This class implements
+// SymbolicFile interface for the file.
+namespace {
+class COFFImportFile : public SymbolicFile {
+public:
+  COFFImportFile(MemoryBufferRef Source)
+      : SymbolicFile(sys::fs::file_magic::coff_import_library, Source) {}
+
+  void moveSymbolNext(DataRefImpl &Symb) const override { ++Symb.p; }
+
+  std::error_code printSymbolName(raw_ostream &OS,
+                                  DataRefImpl Symb) const override {
+    if (Symb.p == 1)
+      OS << "__imp_";
+    OS << StringRef(Data.getBufferStart() + sizeof(coff_import_header));
+    return std::error_code();
+  }
+
+  uint32_t getSymbolFlags(DataRefImpl Symb) const override {
+    return SymbolRef::SF_Global;
+  }
+
+  basic_symbol_iterator symbol_begin_impl() const override {
+    return BasicSymbolRef(DataRefImpl(), this);
+  }
+
+  basic_symbol_iterator symbol_end_impl() const override {
+    DataRefImpl Symb;
+    Symb.p = isCode() ? 2 : 1;
+    return BasicSymbolRef(Symb, this);
+  }
+
+private:
+  bool isCode() const {
+    auto *Import = reinterpret_cast<const coff_import_header *>(
+        Data.getBufferStart());
+    return Import->getType() == llvm::COFF::IMPORT_CODE;
+  }
+};
+} // anonymous namespace
+
 SymbolicFile::SymbolicFile(unsigned int Type, MemoryBufferRef Source)
     : Binary(Type, Source) {}
 
@@ -54,9 +98,10 @@ ErrorOr<std::unique_ptr<SymbolicFile>> SymbolicFile::createSymbolicFile(
   case sys::fs::file_magic::macho_dynamically_linked_shared_lib_stub:
   case sys::fs::file_magic::macho_dsym_companion:
   case sys::fs::file_magic::macho_kext_bundle:
-  case sys::fs::file_magic::coff_import_library:
   case sys::fs::file_magic::pecoff_executable:
     return ObjectFile::createObjectFile(Object, Type);
+  case sys::fs::file_magic::coff_import_library:
+    return std::unique_ptr<SymbolicFile>(new COFFImportFile(Object));
   case sys::fs::file_magic::elf_relocatable:
   case sys::fs::file_magic::macho_object:
   case sys::fs::file_magic::coff_object: {