1 files changed, 145 insertions, 0 deletions
diff --git a/src/kernel/graphics/vga.c b/src/kernel/graphics/vga.c
new file mode 100644
index 0000000..86c00ff
--- /dev/null
+++ b/src/kernel/graphics/vga.c
@@ -0,0 +1,145 @@
+#include <stddef.h>
+#include <stdint.h>
+#include "../io/io.h"
+#include "../lib/lib.h"
+#include "../commands/command.h"
+#include "../interrupts/interrupts.h"
+
+// Hardware text mode color constants
+enum vga_color {
+    VGA_COLOR_BLACK = 0,
+    VGA_COLOR_BLUE = 1,
+    VGA_COLOR_GREEN = 2,
+    VGA_COLOR_CYAN = 3,
+    VGA_COLOR_RED = 4,
+    VGA_COLOR_MAGENTA = 5,
+    VGA_COLOR_BROWN = 6,
+    VGA_COLOR_LIGHT_GREY = 7,
+    VGA_COLOR_DARK_GREY = 8,
+    VGA_COLOR_LIGHT_BLUE = 9,
+    VGA_COLOR_LIGHT_GREEN = 10,
+    VGA_COLOR_LIGHT_CYAN = 11,
+    VGA_COLOR_LIGHT_RED = 12,
+    VGA_COLOR_LIGHT_MAGENTA = 13,
+    VGA_COLOR_LIGHT_BROWN = 14,
+    VGA_COLOR_WHITE = 15,
+};
+
+static inline uint8_t vga_entry_color(enum vga_color fg, enum vga_color bg) {
+    return fg | bg << 4;
+}
+
+static inline uint16_t vga_entry(unsigned char uc, uint8_t color) {
+    return (uint16_t) uc | (uint16_t) color << 8;
+}
+
+static const size_t VGA_WIDTH = 80;
+static const size_t VGA_HEIGHT = 25;
+
+size_t terminal_row;
+size_t terminal_column;
+uint8_t terminal_color;
+uint16_t *terminal_buffer;
+
+char text[1024] = {0};
+
+void terminal_clear() {
+    for (size_t y = 0; y < VGA_HEIGHT; y++) {
+        for (size_t x = 0; x < VGA_WIDTH; x++) {
+            const size_t index = y * VGA_WIDTH + x;
+            terminal_buffer[index] = vga_entry(' ', terminal_color);
+        }
+    }
+}
+
+void terminal_enable_cursor(uint8_t cursor_start, uint8_t cursor_end) {
+    send(0x3D4, 0x0A);
+    send(0x3D5, (receive(0x3D5) & 0xC0) | cursor_start);
+    send(0x3D4, 0x0B);
+    send(0x3D5, (receive(0x3D5) & 0xE0) | cursor_end);
+}
+
+void terminal_update_cursor(void) {
+    unsigned temp = terminal_row * VGA_WIDTH + terminal_column;
+    send(0x3D4, 14);
+    send(0x3D5, temp >> 8);
+    send(0x3D4, 15);
+    send(0x3D5, temp);
+}
+
+void terminal_initialize(void) {
+    terminal_enable_cursor(0, 15);
+    terminal_row = 0;
+    terminal_column = 0;
+    terminal_color = vga_entry_color(VGA_COLOR_LIGHT_GREY, VGA_COLOR_BLACK);
+    terminal_buffer = (uint16_t *) 0xB8000;
+    terminal_clear();
+}
+
+void terminal_scroll(void) {
+    if (terminal_row >= VGA_HEIGHT) {
+        terminal_row = VGA_HEIGHT - 1;
+        for (size_t x = 0; x < VGA_WIDTH; x++)
+            for (size_t y = 0; y < VGA_HEIGHT; y++) {
+                uint16_t c = terminal_buffer[y * VGA_WIDTH + x];
+                terminal_buffer[(y - 1) * VGA_WIDTH + x] = c;
+                terminal_buffer[y * VGA_WIDTH + x] = vga_entry(' ', terminal_color);
+            }
+    }
+}
+
+void terminal_set_color(uint8_t color) {
+    terminal_color = color;
+}
+
+void terminal_put_entry_at(char c, uint8_t color, size_t x, size_t y) {
+    const size_t index = y * VGA_WIDTH + x;
+    terminal_buffer[index] = vga_entry(c, color);
+}
+
+void terminal_put_char(char c) {
+    if (c == 0x08) {
+        if (terminal_column != 0) terminal_column--;
+    } else if (c == 0x09) {
+        terminal_column = (terminal_column + 8) & ~(8 - 1);
+    } else if (c == '\r') {
+        terminal_column = 0;
+    } else if (c == '\n') {
+        if (irq_is_installed(1)) exec_command(text);
+        memory_set(text, 0, sizeof(text));
+        terminal_column = 0;
+        terminal_row++;
+        terminal_scroll();
+        terminal_put_entry_at('$', terminal_color, terminal_column, terminal_row);
+        terminal_column = 2;
+    } else if (c >= ' ') { // Any printable character
+        strcat(text, &c);
+        terminal_put_entry_at(c, terminal_color, terminal_column, terminal_row);
+        terminal_column++;
+    }
+
+    // Add new line on overflow
+    if (terminal_column >= VGA_WIDTH) {
+        terminal_column = 0;
+        terminal_row++;
+    }
+
+    terminal_scroll();
+    terminal_update_cursor();
+}
+
+void terminal_write(const char *data, size_t size) {
+    for (size_t i = 0; i < size; i++)
+        terminal_put_char(data[i]);
+}
+
+void terminal_write_string(const char *data) {
+    terminal_write(data, strlen(data));
+}
+
+void terminal_write_line(const char *data) {
+    terminal_row++;
+    terminal_column = 0;
+    terminal_write_string(data);
+    terminal_column = 0;
+}