From c2f48fb5df0981df1df23de2b277274f9fe75080 Mon Sep 17 00:00:00 2001
From: Benji Dial <benji@benjidial.net>
Date: Mon, 8 Jan 2024 22:28:41 -0500
Subject: first commit

---
 kernel/terminal.cpp | 106 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 106 insertions(+)
 create mode 100644 kernel/terminal.cpp

(limited to 'kernel/terminal.cpp')

diff --git a/kernel/terminal.cpp b/kernel/terminal.cpp
new file mode 100644
index 0000000..f017cad
--- /dev/null
+++ b/kernel/terminal.cpp
@@ -0,0 +1,106 @@
+#include <mercury/kernel/framebuffer.hpp>
+#include <mercury/kernel/terminal.hpp>
+
+namespace mercury::kernel::terminal {
+
+  uint8_t *termfont;
+  uint64_t termfont_len;
+
+  int width;
+  int height;
+
+  int cursor_x;
+  int cursor_y;
+
+  framebuffer::color bg_color;
+  framebuffer::color fg_color;
+
+  static uint8_t glyph_height;
+
+  void init_terminal() {
+    //TODO - verify that termfont fits inside termfont_len (i.e. that no other
+    //       functions in this file will try to access memory outside termfont)
+    //TODO - check magic header to verify that this is actually a font and to
+    //       see whether this is a psf1 font or a psf2 font.
+    //TODO - support psf2 fonts. currently psf1 is assumed.
+    //TODO - read unicode table if there is one. currently it is assumed that
+    //       all 256 codepoints have glyphs, and that they appear in order.
+
+    glyph_height = termfont[3];
+    width = framebuffer::width / 8;
+    height = framebuffer::height / glyph_height;
+    cursor_x = 0;
+    cursor_y = 0;
+    bg_color = framebuffer::encode_color(0, 0, 0);
+    fg_color = framebuffer::encode_color(255, 255, 255);
+
+  }
+
+  static void cursor_down() {
+    if (++cursor_y == height) {
+      --cursor_y;
+      framebuffer::move_region(
+        0, glyph_height, width * 8, height * glyph_height, 0, 0);
+      framebuffer::fill_region(0, (height - 1) * glyph_height,
+        width * 8, height * glyph_height, bg_color);
+    }
+  }
+
+  static void cursor_right() {
+    if (++cursor_x == width) {
+      cursor_x = 0;
+      cursor_down();
+    }
+  }
+
+  void draw_char(char ch, int x, int y) {
+    const uint8_t *glyph = termfont + 4 + glyph_height * (unsigned)ch;
+    for (int i = 0; i < glyph_height; ++i)
+      for (int j = 0; j < 8; ++j)
+        framebuffer::set_pixel(x * 8 + j, y * glyph_height + i,
+          ((glyph[i] << j) & 0x80) ? fg_color : bg_color);
+  }
+
+  void put_char(char ch) {
+    switch (ch) {
+    case '\n':
+      cursor_x = 0;
+      cursor_down();
+      break;
+    default:
+      draw_char(ch, cursor_x, cursor_y);
+      cursor_right();
+      break;
+    }
+  }
+
+  void put_string_sz(const char *str) {
+    for (int i = 0; str[i]; ++i)
+      put_char(str[i]);
+  }
+
+  void put_int_decimal(uint64_t n, bool with_commas) {
+
+    if (n == 0) {
+      put_char('0');
+      return;
+    }
+
+    uint64_t d = 1;
+    int i = 0;
+    while (d <= n / 10) {
+      d *= 10;
+      ++i;
+    }
+
+    while (d) {
+      put_char('0' + ((n / d) % 10));
+      d /= 10;
+      if (with_commas && (i % 3 == 0) && (i != 0))
+        put_char(',');
+      --i;
+    }
+
+  }
+
+}
-- 
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