libos: Add ways to format output to a File

libos/include/os/File.h

@@ -9,6 +9,7 @@
 
 #pragma once
 #include <fcntl.h>
+#include <luna/Attributes.h>
 #include <luna/Buffer.h>
 #include <luna/Result.h>
 #include <luna/SharedPtr.h>
@@ -126,6 +127,24 @@ namespace os
          */
         Result<void> write(const Buffer& buf);
 
+        /**
+         * @brief Write a formatted string to this File.
+         *
+         * @param format The format string.
+         * @param ... The format arguments.
+         * @return Result<void> Whether the operation succeeded.
+         */
+        Result<usize> write_formatted(const char* format, ...) _format(2, 3);
+
+        /**
+         * @brief Write a formatted string to this File.
+         *
+         * @param format The format string.
+         * @param args The format arguments.
+         * @return Result<void> Whether the operation succeeded.
+         */
+        Result<usize> write_vformatted(const char* format, va_list args);
+
         /**
          * @brief Read a line from this File.
          *
@@ -247,36 +266,36 @@ namespace os
     /**
      * @brief Print a formatted string to standard output.
      *
-     * @param fmt The format string (in the same format as printf(3)).
+     * @param format The format string (in the same format as printf(3)).
      * @param ... The format arguments.
      * @return Result<void> Whether the operation succeeded.
      */
-    Result<void> print(StringView fmt, ...);
+    Result<void> print(const char* format, ...) _format(1, 2);
 
     /**
      * @brief Print a newline-terminated formatted string to standard output.
      *
-     * @param fmt The format string (in the same format as printf(3)).
+     * @param format The format string (in the same format as printf(3)).
      * @param ... The format arguments.
      * @return Result<void> Whether the operation succeeded.
      */
-    Result<void> println(StringView fmt, ...);
+    Result<void> println(const char* format, ...) _format(1, 2);
 
     /**
      * @brief Print a formatted string to standard error.
      *
-     * @param fmt The format string (in the same format as printf(3)).
+     * @param format The format string (in the same format as printf(3)).
      * @param ... The format arguments.
      * @return Result<void> Whether the operation succeeded.
      */
-    Result<void> eprint(StringView fmt, ...);
+    Result<void> eprint(const char* format, ...) _format(1, 2);
 
     /**
      * @brief Print a newline-terminated formatted string to standard error.
      *
-     * @param fmt The format string (in the same format as printf(3)).
+     * @param format The format string (in the same format as printf(3)).
      * @param ... The format arguments.
      * @return Result<void> Whether the operation succeeded.
      */
-    Result<void> eprintln(StringView fmt, ...);
+    Result<void> eprintln(const char* format, ...) _format(1, 2);
 }

libos/src/File.cpp

@@ -8,6 +8,7 @@
  */
 
 #include <errno.h>
+#include <luna/Format.h>
 #include <luna/StringBuilder.h>
 #include <os/File.h>
 #include <unistd.h>
@@ -141,6 +142,33 @@ namespace os
         return {};
     }
 
+    Result<usize> File::write_formatted(const char* format, ...)
+    {
+        va_list ap;
+        va_start(ap, format);
+
+        auto result = write_vformatted(format, ap);
+
+        va_end(ap);
+
+        return result;
+    }
+
+    Result<usize> File::write_vformatted(const char* format, va_list args)
+    {
+        auto rc = TRY(cstyle_format(
+            format,
+            [](char c, void* f) -> Result<void> {
+                TRY(((File*)f)->raw_write((const u8*)&c, 1));
+                return {};
+            },
+            this, args));
+
+        flush();
+
+        return rc;
+    }
+
     Result<String> File::read_line()
     {
         Vector<char> data;
@@ -246,64 +274,57 @@ namespace os
         setvbuf(m_file, NULL, mode, 0);
     }
 
-    // FIXME: Do not allocate memory for printing.
+    Result<void> print(const char* format, ...)
-    Result<void> print_impl(SharedPtr<File> f, StringView fmt, va_list ap)
-    {
-        auto str = TRY(String::vformat(fmt, ap));
-        auto rc = f->write(str.view());
-        f->flush();
-        return rc;
-    }
-
-    Result<void> print(StringView fmt, ...)
     {
         va_list ap;
-        va_start(ap, fmt);
+        va_start(ap, format);
 
-        auto rc = print_impl(File::standard_output(), fmt, ap);
+        TRY(File::standard_output()->write_vformatted(format, ap));
 
         va_end(ap);
 
-        return rc;
+        return {};
     }
 
-    Result<void> println(StringView fmt, ...)
+    Result<void> println(const char* format, ...)
     {
         va_list ap;
-        va_start(ap, fmt);
+        va_start(ap, format);
 
-        auto rc = print_impl(File::standard_output(), fmt, ap);
+        auto file = File::standard_output();
+
+        TRY(file->write_vformatted(format, ap));
+        TRY(file->write("\n"_sv));
 
         va_end(ap);
 
-        TRY(rc);
+        return {};
-
-        return File::standard_output()->write("\n"_sv);
     }
 
-    Result<void> eprint(StringView fmt, ...)
+    Result<void> eprint(const char* format, ...)
     {
         va_list ap;
-        va_start(ap, fmt);
+        va_start(ap, format);
 
-        auto rc = print_impl(File::standard_error(), fmt, ap);
+        TRY(File::standard_error()->write_vformatted(format, ap));
 
         va_end(ap);
 
-        return rc;
+        return {};
     }
 
-    Result<void> eprintln(StringView fmt, ...)
+    Result<void> eprintln(const char* format, ...)
     {
         va_list ap;
-        va_start(ap, fmt);
+        va_start(ap, format);
 
-        auto rc = print_impl(File::standard_error(), fmt, ap);
+        auto file = File::standard_error();
+
+        TRY(file->write_vformatted(format, ap));
+        TRY(file->write("\n"_sv));
 
         va_end(ap);
 
-        TRY(rc);
+        return {};
-
-        return File::standard_error()->write("\n"_sv);
     }
 }