Say hello, kernel!

src/Console.cc

@@ -32,20 +32,64 @@ makeVGAEntry(char c,
 
 Console::Console()
     : mBase(reinterpret_cast<uint16_t *>(0xB8000)),
-      mCursor{0, 0}
+      mCursor{0, 0},
+      mColor(makeVGAColor(Console::Color::LightGray, Console::Color::Black))
 { }
 
 
 void
 Console::clear(Console::Color color)
 {
-    const uint16_t vgaColor = makeVGAColor(Color::LightGray, color);
+    setColor(Color::LightGray, color);
     for (size_t y = 0; y < Console::Height; y++) {
         for (size_t x = 0; x < Console::Width; x++) {
-            const size_t index = y * Console::Width + x;
-            mBase[index] = makeVGAEntry(' ', vgaColor);
+            putEntryAt(x, y, ' ', mColor);
         }
     }
 }
 
+
+void
+Console::writeChar(char c)
+{
+    putEntryAt(mCursor.col, mCursor.row, c, mColor);
+    if (++mCursor.col == Console::Width) {
+        mCursor.col = 0;
+        if (++mCursor.row == Console::Height) {
+            mCursor.row = 0;
+        }
+    }
+}
+
+void
+Console::writeString(const char *str)
+{
+    // XXX: THIS IS VERY UNSAFE. PUT DOWN THE POINTER ERYN. NO BAD ERYN DONT YOU DARE.
+    const char *cur = str;
+    while (*cur != '\0') {
+        writeChar(*cur++);
+    }
+}
+
+void
+Console::setColor(Console::Color fg,
+                  Console::Color bg)
+{
+    mColor = makeVGAColor(fg, bg);
+}
+
+/*
+ * Private
+ */
+
+void
+Console::putEntryAt(size_t x,
+                    size_t y,
+                    char c,
+                    uint8_t color)
+{
+    const size_t index = y * Console::Width + x;
+    mBase[index] = makeVGAEntry(c, color);
+}
+
 } /* namespace kernel */

src/Console.hh

@@ -46,9 +46,20 @@ struct Console
     /** Clear the console to the provided color. */
     void clear(Color color = Color::Black);
 
+    /** Write a character to the terminal at the current cursor position. */
+    void writeChar(char c);
+
+    /** Write a string to the terminal at the current cursor position. */
+    void writeString(const char *str);
+
+    void setColor(Color fg, Color bg);
+
 private:
     uint16_t *const mBase;
     Cursor mCursor;
+    uint8_t mColor;
+
+    void putEntryAt(size_t x, size_t y, char c, uint8_t color);
 };
 
 } /* namespace kernel */

src/Main.cc

@@ -1,5 +1,6 @@
 #include <stddef.h>
 #include <stdint.h>
+#include "Console.hh"
 
 #if defined(__linux__)
 #error "This file should be compiled with a cross-compiler, not the Linux system compiler!"
@@ -13,7 +14,11 @@
 extern "C"
 void
 kearly()
-{ }
+{
+    kernel::Console console;
+    console.clear(kernel::Console::Color::Blue);
+    console.writeString("Hello world!");
+}
 
 
 /** The beginning of the world... */

src/SConscript

@@ -9,7 +9,7 @@ files = [
     'boot.s',
     'crti.s',
     'crtn.s',
-    'main.cc',
+    'Main.cc',
     'Console.cc'
 ]