[GitHub] [arrow] cyb70289 commented on a diff in pull request #13354: ARROW-16799: [C++] Create a self-pipe abstraction

[GitBox <gi...@apache.org>]

cyb70289 commented on code in PR #13354:
URL: https://github.com/apache/arrow/pull/13354#discussion_r894088698


##########
cpp/src/arrow/util/io_util.h:
##########
@@ -124,14 +125,46 @@ Result<bool> DeleteFile(const PlatformFilename& file_path, bool allow_not_found
 ARROW_EXPORT
 Result<bool> FileExists(const PlatformFilename& path);
 
+// TODO expose this more publicly to make it available from io/file.h?
+/// A RAII wrapper for a file descriptor.

Review Comment:
   nit nit: `An RAII`?



##########
cpp/src/arrow/util/io_util_test.cc:
##########
@@ -159,6 +170,282 @@ TEST(WinErrorFromStatus, Basics) {
 }
 #endif
 
+class TestFileDescriptor : public ::testing::Test {
+ public:
+  Result<int> NewFileDescriptor() {
+    // Make a new fd by dup'ing C stdout (why not?)
+    int new_fd = dup(1);
+    if (new_fd < 0) {
+      return IOErrorFromErrno(errno, "Failed to dup() C stdout");
+    }
+    return new_fd;
+  }
+
+  void AssertValidFileDescriptor(int fd) {
+    ASSERT_FALSE(FileIsClosed(fd)) << "Not a valid file descriptor: " << fd;
+  }
+
+  void AssertInvalidFileDescriptor(int fd) {
+    ASSERT_TRUE(FileIsClosed(fd)) << "Unexpectedly valid file descriptor: " << fd;
+  }
+};
+
+TEST_F(TestFileDescriptor, Basics) {
+  int new_fd, new_fd2;
+
+  // Default initialization
+  FileDescriptor a;
+  ASSERT_EQ(a.fd(), -1);
+  ASSERT_TRUE(a.closed());
+  ASSERT_OK(a.Close());
+  ASSERT_OK(a.Close());
+
+  // Assignment
+  ASSERT_OK_AND_ASSIGN(new_fd, NewFileDescriptor());
+  AssertValidFileDescriptor(new_fd);
+  a = FileDescriptor(new_fd);
+  ASSERT_FALSE(a.closed());
+  ASSERT_GT(a.fd(), 2);

Review Comment:
   Will it fail if `stdin` or `stderr` is closed? Though I don't think it will happen.



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