libos: Add os:: print(), println(), eprint(), and eprintln()

libluna/include/luna/String.h

@@ -38,6 +38,7 @@ class String
 
     static Result<String> format(const String& fmt, ...);
     static Result<String> format(StringView fmt, ...);
+    static Result<String> vformat(StringView fmt, va_list ap);
 
     static Result<String> from_cstring(const char* str);
 
@@ -94,6 +95,4 @@ class String
     usize m_length { 0 };
 
     void empty();
-
-    static Result<String> vformat(StringView fmt, va_list ap);
 };

libos/include/os/File.h

@@ -66,4 +66,9 @@ namespace os
 
         int m_fd { -1 };
     };
+
+    Result<void> print(StringView fmt, ...);
+    Result<void> println(StringView fmt, ...);
+    Result<void> eprint(StringView fmt, ...);
+    Result<void> eprintln(StringView fmt, ...);
 }

libos/src/File.cpp

@@ -193,4 +193,63 @@ namespace os
     {
         fcntl(m_fd, F_SETFD, FD_CLOEXEC);
     }
+
+    // FIXME: Do not allocate memory for printing.
+    Result<void> print_impl(SharedPtr<File> f, StringView fmt, va_list ap)
+    {
+        auto str = TRY(String::vformat(fmt, ap));
+        return f->write(str.view());
+    }
+
+    Result<void> print(StringView fmt, ...)
+    {
+        va_list ap;
+        va_start(ap, fmt);
+
+        auto rc = print_impl(File::standard_output(), fmt, ap);
+
+        va_end(ap);
+
+        return rc;
+    }
+
+    Result<void> println(StringView fmt, ...)
+    {
+        va_list ap;
+        va_start(ap, fmt);
+
+        auto rc = print_impl(File::standard_output(), fmt, ap);
+
+        va_end(ap);
+
+        TRY(rc);
+
+        return File::standard_output()->write("\n"_sv);
+    }
+
+    Result<void> eprint(StringView fmt, ...)
+    {
+        va_list ap;
+        va_start(ap, fmt);
+
+        auto rc = print_impl(File::standard_error(), fmt, ap);
+
+        va_end(ap);
+
+        return rc;
+    }
+
+    Result<void> eprintln(StringView fmt, ...)
+    {
+        va_list ap;
+        va_start(ap, fmt);
+
+        auto rc = print_impl(File::standard_error(), fmt, ap);
+
+        va_end(ap);
+
+        TRY(rc);
+
+        return File::standard_error()->write("\n"_sv);
+    }
 }