...

src/boot/console.c

@@ -0,0 +1,168 @@
+#include "console.h"
+#include <string.h>
+
+#define ROWS 25
+#define COLUMNS 80
+
+typedef struct {
+    u8 character;
+    u8 color;
+} vga_char_t;
+
+static vga_char_t *vga_buffer = (vga_char_t *)0xb8000;
+static u8 cursor_row = 0;
+static u8 cursor_col = 0;
+
+void console_putchar(char c, u8 color) {
+    switch (c) {
+    case '\n': {
+        cursor_row += 1;
+        cursor_col = 0;
+        break;
+    }
+    case '\r': {
+        cursor_col = 0;
+        break;
+    }
+    case '\t': {
+        u8 remainder = 4 - (cursor_col % 4);
+        cursor_col += remainder;
+        break;
+    }
+    case '\b': {
+        if (cursor_col > 0) {
+            cursor_col -= 1;
+        } else if (cursor_row > 0) {
+            cursor_row -= 1;
+
+            cursor_col = 0;
+            for (int col = COLUMNS - 1; col >= 0; col--) {
+                vga_char_t cell = vga_buffer[cursor_row * COLUMNS + col];
+                if (cell.character != ' ') {
+                    cursor_col = col;
+                    break;
+                }
+            }
+        }
+
+        vga_buffer[cursor_row * COLUMNS + cursor_col] = (vga_char_t){
+            .character = ' ',
+            .color = VGA_DEFAULT_COLOR,
+        };
+        break;
+    }
+    default: {
+        vga_buffer[COLUMNS * cursor_row + cursor_col] = (vga_char_t){
+            .character = c,
+            .color = color,
+        };
+        cursor_col += 1;
+        break;
+    }
+    }
+
+    if (cursor_col >= COLUMNS) {
+        cursor_col = 0;
+        cursor_row += 1;
+    }
+
+    if (cursor_row >= ROWS) {
+        for (size_t row = 1; row < ROWS; row++) {
+            for (size_t col = 0; col < COLUMNS; col++) {
+                vga_buffer[COLUMNS * (row - 1) + col] = vga_buffer[COLUMNS * row + col];
+            }
+        }
+
+        for (size_t col = 0; col < COLUMNS; col++) {
+            vga_buffer[COLUMNS * (ROWS - 1) + col] = (vga_char_t){
+                .character = ' ',
+                .color = VGA_DEFAULT_COLOR,
+            };
+        };
+
+        cursor_row = ROWS - 1;
+    }
+}
+
+void console_clear() {
+    for (size_t row = 0; row < ROWS; row++) {
+        for (size_t col = 0; col < COLUMNS; col++) {
+            vga_buffer[COLUMNS * row + col] = (vga_char_t){
+                .character = ' ',
+                .color = VGA_DEFAULT_COLOR,
+            };
+        }
+    }
+
+    cursor_row = 0;
+    cursor_col = 0;
+}
+
+// Supported formats:
+//     - `d`: i32     (decimal)
+//     - `u`: u32     (decimal)
+//     - `x`: u32     (hex)
+//     - `c`: char    (ascii)
+//     - `s`: char*   (ascii string)
+//
+// ```c
+// printf(
+//     "The answer is %d is located at offset %x in file %s",
+//      42,
+//      0x2000
+//      "hitchhiker.txt"
+// );
+// ```
+void kprintf(const char *fmt, ...) {
+    va_list args;
+    va_start(args, fmt);
+
+    bool should_format = false;
+
+    for (size_t i = 0; fmt[i] != '\0'; i++) {
+        if (should_format) {
+            should_format = false;
+
+            if (fmt[i] == '%') {
+                console_putchar('%', VGA_DEFAULT_COLOR);
+            } else if (fmt[i] == 's') {
+                const char *str = va_arg(args, const char *);
+                for (size_t j = 0; str[j] != '\0'; j++) {
+                    console_putchar(str[j], VGA_DEFAULT_COLOR);
+                }
+            } else if (fmt[i] == 'c') {
+                char character = (char)va_arg(args, u32);
+                console_putchar(character, VGA_DEFAULT_COLOR);
+            } else if (fmt[i] == 'd') {
+                u32 val = va_arg(args, u32);
+                char buf[21];
+                itoa(val, buf);
+                for (size_t j = 0; buf[j] != '\0'; j++) {
+                    console_putchar(buf[j], VGA_DEFAULT_COLOR);
+                }
+            } else if (fmt[i] == 'u') {
+                u32 val = va_arg(args, u32);
+                char buf[21];
+                uitoa(val, buf);
+                for (size_t j = 0; buf[j] != '\0'; j++) {
+                    console_putchar(buf[j], VGA_DEFAULT_COLOR);
+                }
+            } else if (fmt[i] == 'x') {
+                u32 val = va_arg(args, u32);
+                char buf[17];
+                uitoa_hex(val, buf);
+                for (size_t j = 0; buf[j] != '\0'; j++) {
+                    console_putchar(buf[j], VGA_DEFAULT_COLOR);
+                }
+            } else {
+                console_putchar(fmt[i], VGA_DEFAULT_COLOR);
+            }
+        } else if (fmt[i] == '%') {
+            should_format = true;
+        } else {
+            console_putchar(fmt[i], VGA_DEFAULT_COLOR);
+        }
+    }
+
+    va_end(args);
+}