feat: implement kernel logging and formatted output subsystems

1 files changed, 68 insertions, 0 deletions

diff --git a/na/lib/kprintf.cc b/na/lib/kprintf.cc
new file mode 100644
index 0000000..ddd2e59
--- /dev/null
+++ b/na/lib/kprintf.cc
@@ -0,0 +1,68 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/* Copyright (C) 2026 Richard Qin */
+
+/*
+ * kprintf.cc — Kernel formatted output
+ *
+ * Uses mpaland/printf's vsnprintf_ as the core formatting engine.
+ * All kernel output ultimately goes through this module.
+ *
+ * Architecture:
+ *   vsnprintf_()  ← pure formatting, writes to buffer
+ *       ↓
+ *   kprintf()     ← format + emit to UART via early_putc
+ *   kvprintf()    ← va_list variant
+ *   ksnprintf()   ← format into caller's buffer
+ */
+
+#include <lume/kprintf.h>
+#include <lume/console.h>
+#include "printf.h"
+
+/* ------------------------------------------------------------------ */
+/*  _putchar: required by mpaland/printf for printf_() / vprintf_()   */
+/* ------------------------------------------------------------------ */
+
+void _putchar(char character)
+{
+    early_putc(character);
+}
+
+/* ------------------------------------------------------------------ */
+/*  Public API                                                        */
+/* ------------------------------------------------------------------ */
+
+extern "C" int kprintf(const char* fmt, ...)
+{
+    char buf[256];
+    va_list va;
+    va_start(va, fmt);
+    int len = vsnprintf_(buf, sizeof(buf), fmt, va);
+    va_end(va);
+
+    /* Emit to console */
+    for (int i = 0; i < len && buf[i] != '\0'; ++i) {
+        early_putc(buf[i]);
+    }
+    return len;
+}
+
+extern "C" int kvprintf(const char* fmt, va_list va)
+{
+    char buf[256];
+    int len = vsnprintf_(buf, sizeof(buf), fmt, va);
+
+    for (int i = 0; i < len && buf[i] != '\0'; ++i) {
+        early_putc(buf[i]);
+    }
+    return len;
+}
+
+extern "C" int ksnprintf(char* buf, int count, const char* fmt, ...)
+{
+    va_list va;
+    va_start(va, fmt);
+    int ret = vsnprintf_(buf, (size_t)count, fmt, va);
+    va_end(va);
+    return ret;
+}