Add console, klog, and writef modules.

They are not complete, but adding to checkpoint progress.

src/hulk/console.d

@@ -0,0 +1,72 @@
+/**
+ * HULK Console functionality.
+ */
+module hulk.console;
+
+import hulk.framebuffer;
+import hulk.kfont;
+
+struct Console
+{
+    Framebuffer * m_fb;
+    size_t m_width;
+    size_t m_height;
+    size_t m_x;
+    size_t m_y;
+
+    public void initialize(Framebuffer * fb)
+    {
+        m_fb = fb;
+        m_width = fb.width / kfont.advance;
+        m_height = fb.height / kfont.line_height;
+    }
+
+    public void clear()
+    {
+        m_fb.clear();
+        m_x = 0u;
+        m_y = 0u;
+    }
+
+    public void write(char ch)
+    {
+        if (ch == '\n')
+        {
+            m_x = 0u;
+            m_y++;
+        }
+        else
+        {
+            render_char(m_x, m_y, ch);
+            m_x++;
+            if (m_x == m_width)
+            {
+                m_x = 0u;
+                m_y++;
+            }
+        }
+        if (m_y == m_height)
+        {
+            m_y--;
+            m_fb.copy_rows_up(fb_y(m_height - 1u),
+                    (m_height - 1u) * kfont.line_height,
+                    kfont.line_height);
+        }
+    }
+
+    private void render_char(size_t x, size_t y, char ch)
+    {
+        const(CharInfo) * ci = &kfont.chars[ch];
+        m_fb.blit_alpha_bitmap(fb_x(x) + ci.left, fb_y(y) + ci.top - ci.height, ci.bitmap, ci.width, ci.height);
+    }
+
+    private size_t fb_x(size_t x)
+    {
+        return x * kfont.advance;
+    }
+
+    private size_t fb_y(size_t y)
+    {
+        return m_fb.height - ((y + 1u) * kfont.line_height);
+    }
+}

src/hulk/framebuffer.d

@@ -28,6 +28,22 @@ struct Framebuffer
     /** Number of pixels in the frame buffer (whether visible or not). */
     private uint m_buffer_size;
 
+    /**
+     * Get the framebuffer width.
+     */
+    public @property uint width()
+    {
+        return m_width;
+    }
+
+    /**
+     * Get the framebuffer height.
+     */
+    public @property uint height()
+    {
+        return m_height;
+    }
+
     /**
      * Initialize a frame buffer.
      *
@@ -168,6 +184,52 @@ struct Framebuffer
         blend_alpha_bitmap(x, y, alpha_bitmap.ptr, width, height, color);
     }
 
+    /**
+     * Blit an 8-bit alpha bitmap to the framebuffer.
+     * The foreground will be white (based on the alpha value), and the
+     * background black.
+     *
+     * @param x X coordinate of left side of target location.
+     * @param y Y coordinate of bottom side of target location.
+     * @param alpha_bitmap 8-bit alpha-channel bitmap.
+     * @param width Bitmap width.
+     * @param height Bitmap height.
+     */
+    void blit_alpha_bitmap(size_t x, size_t y, const(ubyte) * alpha_bitmap,
+            size_t width, size_t height)
+    {
+        y += height - 1u;
+        size_t bitmap_index;
+        for (size_t iy = 0u; iy < height; iy++)
+        {
+            for (size_t ix = 0u; ix < width; ix++)
+            {
+                size_t buffer_index = buffer_index(x + ix, y);
+                ubyte alpha = alpha_bitmap[bitmap_index];
+                m_buffer[buffer_index] = (alpha << 16u) | (alpha << 8u) | alpha;
+                bitmap_index++;
+            }
+            y--;
+        }
+    }
+
+    /**
+     * Blit an 8-bit alpha bitmap to the framebuffer.
+     * The foreground will be white (based on the alpha value), and the
+     * background black.
+     *
+     * @param x X coordinate of left side of target location.
+     * @param y Y coordinate of bottom side of target location.
+     * @param alpha_bitmap 8-bit alpha-channel bitmap.
+     * @param width Bitmap width.
+     * @param height Bitmap height.
+     */
+    void blit_alpha_bitmap(size_t x, size_t y, const(ubyte)[] alpha_bitmap,
+            size_t width, size_t height)
+    {
+        blit_alpha_bitmap(x, y, alpha_bitmap.ptr, width, height);
+    }
+
     /**
      * Copy framebuffer rows up in the framebuffer.
      *

src/hulk/hulk.d

@@ -6,11 +6,14 @@ module hulk.hulk;
 import hulk.header;
 import hulk.bootinfo;
 import hulk.framebuffer;
+import hulk.console;
 import hos.memory;
 import ldc.attributes;
 import hulk.kfont;
+static import hulk.klog;
 
 private __gshared Framebuffer fb;
+private __gshared Console console;
 
 extern extern(C) __gshared ubyte _hulk_total_size;
 
@@ -44,6 +47,15 @@ extern(C) void hulk_start(ulong rdi, ulong rsi, ulong rdx, BootInfo * bootinfo)
         x += kfont.advance;
     }
 
+    console.initialize(&fb);
+    console.clear();
+    hulk.klog.initialize(&console);
+
+    for (size_t i = 1u; i != 0u; i++)
+    {
+        hulk.klog.writef("Hello! i = %010u\n", i);
+    }
+
     for (;;)
     {
     }

src/hulk/klog.d

@@ -0,0 +1,76 @@
+/**
+ * HULK Kernel Log buffer.
+ */
+module hulk.klog;
+
+import core.stdc.stdarg;
+import hulk.console;
+static import hulk.writef;
+
+/**
+ * Kernel buffer size log.
+ * 16 gives a kernel buffer size of 64KB.
+ */
+enum size_t KLOG_SIZE_LOG = 16u;
+
+/** Kernel buffer size.  */
+enum size_t KLOG_SIZE = 1u << KLOG_SIZE_LOG;
+
+/** Kernel log buffer. */
+private __gshared align(4096) char[KLOG_SIZE] klog_buffer;
+
+/** Write index in the kernel log buffer. */
+private __gshared size_t klog_index;
+
+/** Pointer to the console to use for kernel log output. */
+private __gshared Console * console;
+
+/**
+ * Initialize the klog module.
+ *
+ * @param console Pointer to the Console to use for kernel output.
+ */
+void initialize(Console * console)
+{
+    .console = console;
+}
+
+/**
+ * Write a formatted string to the kernel log.
+ *
+ * @param s Format string.
+ * @param args Variable arguments structure.
+ */
+void writef(string s, va_list args)
+{
+    hulk.writef.writef(s, args, function void(ubyte ch) {
+                console.write(ch);
+            });
+}
+
+/**
+ * Write a formatted string to the kernel log.
+ *
+ * @param s Format string.
+ */
+extern (C) void writef(string s, ...)
+{
+    va_list args;
+    va_start(args, s);
+    writef(s, args);
+    va_end(args);
+}
+
+/**
+ * Write a formatted string and newline to the console.
+ *
+ * @param s Format string.
+ */
+extern (C) void writefln(string s, ...)
+{
+    va_list args;
+    va_start(args, s);
+    writef(s, args);
+    writef("\n", args);
+    va_end(args);
+}

src/hulk/writef.d

@@ -0,0 +1,151 @@
+/**
+ * HULK Formatted stream writing support.
+ */
+module hulk.writef;
+
+import core.stdc.stdarg;
+
+alias ch_out_fn = void function(ubyte);
+
+/**
+ * Format a string and write characters to the given output function.
+ *
+ * @param s Format string.
+ * @param args Variable arguments structure.
+ * @param ch_out Character output function.
+ *
+ * @return Number of characters written.
+ */
+size_t writef(string s, va_list args, ch_out_fn ch_out)
+{
+    size_t length_written;
+    bool escape = false;
+    char pad = ' ';
+    size_t width;
+    foreach (char c; s)
+    {
+        if (escape)
+        {
+            if (c == 'x')
+            {
+                ulong v;
+                va_arg(args, v);
+                length_written += write_hex(v, false, pad, width, ch_out);
+                escape = false;
+            }
+            else if (c == 'X')
+            {
+                ulong v;
+                va_arg(args, v);
+                length_written += write_hex(v, true, pad, width, ch_out);
+                escape = false;
+            }
+            else if (c == 'u')
+            {
+                ulong v;
+                va_arg(args, v);
+                length_written += write_udec(v, pad, width, ch_out);
+                escape = false;
+            }
+            else if ((c == '0') && (width == 0u))
+            {
+                pad = '0';
+            }
+            else if (('0' <= c) && (c <= '9'))
+            {
+                width = (width * 10u) + (c - '0');
+            }
+            else
+            {
+                ch_out(c);
+                escape = false;
+            }
+        }
+        else if (c == '%')
+        {
+            escape = true;
+            pad = ' ';
+            width = 0u;
+        }
+        else
+        {
+            ch_out(c);
+        }
+    }
+    return length_written;
+}
+
+/**
+ * Format a value in hexadecimal to the given output function.
+ *
+ * @param v Value to format.
+ * @param upper Whether to use uppercase letters.
+ * @param pad Pad character to use.
+ * @param width Field width.
+ * @param ch_out Character output function.
+ *
+ * @return Number of characters written.
+ */
+private size_t write_hex(ulong v, bool upper, char pad, size_t width, ch_out_fn ch_out)
+{
+    string hex_chars_lower = "0123456789abcdef";
+    string hex_chars_upper = "0123456789ABCDEF";
+    char[16] buf;
+    size_t i;
+    do
+    {
+        ulong n = v & 0xFu;
+        buf[i] = upper ? hex_chars_upper[n] : hex_chars_lower[n];
+        v >>= 4u;
+        i++;
+    } while (v != 0u);
+    size_t length_written = i;
+    while (width > i)
+    {
+        ch_out(pad);
+        width--;
+        length_written++;
+    }
+    do
+    {
+        i--;
+        ch_out(buf[i]);
+    } while (i != 0u);
+    return length_written;
+}
+
+/**
+ * Format a value in decimal to the given output function.
+ *
+ * @param v Value to format.
+ * @param pad Pad character to use.
+ * @param width Field width.
+ * @param ch_out Character output function.
+ *
+ * @return Number of characters written.
+ */
+private size_t write_udec(ulong v, char pad, size_t width, ch_out_fn ch_out)
+{
+    char[20] buf;
+    size_t i;
+    do
+    {
+        ulong d = v % 10u;
+        buf[i] = cast(char)(d + '0');
+        v /= 10u;
+        i++;
+    } while (v != 0u);
+    size_t length_written = i;
+    while (width > i)
+    {
+        ch_out(pad);
+        width--;
+        length_written++;
+    }
+    do
+    {
+        i--;
+        ch_out(buf[i]);
+    } while (i != 0u);
+    return length_written;
+}