[llvm-objcopy][Support] move writeToOutput helper function to Support.

writeToOutput function is useful when it is necessary to create different kinds
of streams(based on stream name) and when we need to use a temporary file
while writing(which would be renamed into the resulting file in a success case).
This patch moves the writeToStream helper into the Support library.

Differential Revision: https://reviews.llvm.org/D98426

llvm/include/llvm/Support/raw_ostream.h

@@ -714,6 +714,17 @@ public:
   ~buffer_unique_ostream() override { *OS << str(); }
 };
 
+class Error;
+
+/// This helper creates an output stream and then passes it to \p Write.
+/// The stream created is based on the specified \p OutputFileName:
+/// llvm::outs for "-", raw_null_ostream for "/dev/null", and raw_fd_ostream
+/// for other names. For raw_fd_ostream instances, the stream writes to
+/// a temporary file. The final output file is atomically replaced with the
+/// temporary file after the \p Write function is finished.
+Error writeToOutput(StringRef OutputFileName,
+                    std::function<Error(raw_ostream &)> Write);
+
 } // end namespace llvm
 
 #endif // LLVM_SUPPORT_RAW_OSTREAM_H

llvm/lib/Support/raw_ostream.cpp

@@ -989,3 +989,31 @@ void raw_pwrite_stream::anchor() {}
 void buffer_ostream::anchor() {}
 
 void buffer_unique_ostream::anchor() {}
+
+Error llvm::writeToOutput(StringRef OutputFileName,
+                          std::function<Error(raw_ostream &)> Write) {
+  if (OutputFileName == "-")
+    return Write(outs());
+
+  if (OutputFileName == "/dev/null") {
+    raw_null_ostream Out;
+    return Write(Out);
+  }
+
+  unsigned Mode = sys::fs::all_read | sys::fs::all_write | sys::fs::all_exe;
+  Expected<sys::fs::TempFile> Temp =
+      sys::fs::TempFile::create(OutputFileName + ".temp-stream-%%%%%%", Mode);
+  if (!Temp)
+    return createFileError(OutputFileName, Temp.takeError());
+
+  raw_fd_ostream Out(Temp->FD, false);
+
+  if (Error E = Write(Out)) {
+    if (Error DiscardError = Temp->discard())
+      return joinErrors(std::move(E), std::move(DiscardError));
+    return E;
+  }
+  Out.flush();
+
+  return Temp->keep(OutputFileName);
+}

llvm/tools/llvm-objcopy/llvm-objcopy.cpp

@@ -57,34 +57,6 @@
 namespace llvm {
 namespace objcopy {
 
-Error writeToFile(StringRef OutputFileName,
-                  std::function<Error(raw_ostream &)> Write) {
-  if (OutputFileName == "-")
-    return Write(outs());
-
-  if (OutputFileName == "/dev/null") {
-    raw_null_ostream Out;
-    return Write(Out);
-  }
-
-  unsigned Mode = sys::fs::all_read | sys::fs::all_write | sys::fs::all_exe;
-  Expected<sys::fs::TempFile> Temp =
-      sys::fs::TempFile::create(OutputFileName + ".temp-objcopy-%%%%%%", Mode);
-  if (!Temp)
-    return createFileError(OutputFileName, Temp.takeError());
-
-  raw_fd_ostream Out(Temp->FD, false);
-
-  if (Error E = Write(Out)) {
-    if (Error DiscardError = Temp->discard())
-      return joinErrors(std::move(E), std::move(DiscardError));
-    return E;
-  }
-  Out.flush();
-
-  return Temp->keep(OutputFileName);
-}
-
 // The name this program was invoked as.
 StringRef ToolName;
 
@@ -369,21 +341,21 @@ static Error executeObjcopy(CopyConfig &Config) {
     if (Config.SplitDWO.empty()) {
       // Apply transformations described by Config and store result into
       // Config.OutputFilename using specified ObjcopyFunc function.
-      if (Error E = writeToFile(Config.OutputFilename, ObjcopyFunc))
+      if (Error E = writeToOutput(Config.OutputFilename, ObjcopyFunc))
         return E;
     } else {
       Config.ExtractDWO = true;
       Config.StripDWO = false;
       // Copy .dwo tables from the Config.InputFilename into Config.SplitDWO
       // file using specified ObjcopyFunc function.
-      if (Error E = writeToFile(Config.SplitDWO, ObjcopyFunc))
+      if (Error E = writeToOutput(Config.SplitDWO, ObjcopyFunc))
         return E;
       Config.ExtractDWO = false;
       Config.StripDWO = true;
       // Apply transformations described by Config, remove .dwo tables and
       // store result into Config.OutputFilename using specified ObjcopyFunc
       // function.
-      if (Error E = writeToFile(Config.OutputFilename, ObjcopyFunc))
+      if (Error E = writeToOutput(Config.OutputFilename, ObjcopyFunc))
         return E;
     }
   }

llvm/tools/llvm-objcopy/llvm-objcopy.h

@@ -27,14 +27,6 @@ struct CopyConfig;
 Expected<std::vector<NewArchiveMember>>
 createNewArchiveMembers(CopyConfig &Config, const object::Archive &Ar);
 
-/// A writeToFile helper creates an output stream, based on the specified
-/// \p OutputFileName: std::outs for the "-", raw_null_ostream for
-/// the "/dev/null", temporary file in the same directory as the final output
-/// file for other names. The final output file is atomically replaced with
-/// the temporary file after \p Write handler is finished.
-Error writeToFile(StringRef OutputFileName,
-                  std::function<Error(raw_ostream &)> Write);
-
 } // end namespace objcopy
 } // end namespace llvm
 

llvm/unittests/Support/raw_ostream_test.cpp

@@ -8,8 +8,11 @@
 
 #include "llvm/ADT/SmallString.h"
 #include "llvm/Support/FileSystem.h"
+#include "llvm/Support/FileUtilities.h"
 #include "llvm/Support/Format.h"
+#include "llvm/Support/MemoryBuffer.h"
 #include "llvm/Support/raw_ostream.h"
+#include "llvm/Testing/Support/Error.h"
 #include "gtest/gtest.h"
 
 using namespace llvm;
@@ -469,4 +472,75 @@ TEST(raw_ostreamTest, reserve_stream) {
   OS.flush();
   EXPECT_EQ("11111111111111111111hello1world", Str);
 }
+
+static void checkFileData(StringRef FileName, StringRef GoldenData) {
+  ErrorOr<std::unique_ptr<MemoryBuffer>> BufOrErr =
+      MemoryBuffer::getFileOrSTDIN(FileName);
+  EXPECT_FALSE(BufOrErr.getError());
+
+  EXPECT_EQ((*BufOrErr)->getBufferSize(), GoldenData.size());
+  EXPECT_EQ(memcmp((*BufOrErr)->getBufferStart(), GoldenData.data(),
+                   GoldenData.size()),
+            0);
+}
+
+TEST(raw_ostreamTest, writeToOutputFile) {
+  SmallString<64> Path;
+  int FD;
+  ASSERT_FALSE(sys::fs::createTemporaryFile("foo", "bar", FD, Path));
+  FileRemover Cleanup(Path);
+
+  ASSERT_THAT_ERROR(writeToOutput(Path,
+                                  [](raw_ostream &Out) -> Error {
+                                    Out << "HelloWorld";
+                                    return Error::success();
+                                  }),
+                    Succeeded());
+  checkFileData(Path, "HelloWorld");
+}
+
+TEST(raw_ostreamTest, writeToNonexistingPath) {
+  StringRef FileName = "/_bad/_path";
+  std::string ErrorMessage = toString(createFileError(
+      FileName, make_error_code(errc::no_such_file_or_directory)));
+
+  EXPECT_THAT_ERROR(writeToOutput(FileName,
+                                  [](raw_ostream &Out) -> Error {
+                                    Out << "HelloWorld";
+                                    return Error::success();
+                                  }),
+                    FailedWithMessage(ErrorMessage));
+}
+
+TEST(raw_ostreamTest, writeToDevNull) {
+  bool DevNullIsUsed = false;
+
+  EXPECT_THAT_ERROR(
+      writeToOutput("/dev/null",
+                    [&](raw_ostream &Out) -> Error {
+                      DevNullIsUsed =
+                          testing::internal::CheckedDowncastToActualType<
+                              raw_null_ostream, raw_ostream>(&Out);
+                      return Error::success();
+                    }),
+      Succeeded());
+
+  EXPECT_TRUE(DevNullIsUsed);
+}
+
+TEST(raw_ostreamTest, writeToStdOut) {
+  outs().flush();
+  testing::internal::CaptureStdout();
+
+  EXPECT_THAT_ERROR(writeToOutput("-",
+                                  [](raw_ostream &Out) -> Error {
+                                    Out << "HelloWorld";
+                                    return Error::success();
+                                  }),
+                    Succeeded());
+  outs().flush();
+
+  std::string CapturedStdOut = testing::internal::GetCapturedStdout();
+  EXPECT_EQ(CapturedStdOut, "HelloWorld");
+}
 }