3 files changed, 155 insertions, 0 deletions
diff --git a/src/kernel/compile_flags.txt b/src/kernel/compile_flags.txt
new file mode 100644
index 0000000..11ef7f9
--- /dev/null
+++ b/src/kernel/compile_flags.txt
@@ -0,0 +1 @@
+-I../include/
diff --git a/src/kernel/kernel.c b/src/kernel/kernel.c
new file mode 100644
index 0000000..50da3c6
--- /dev/null
+++ b/src/kernel/kernel.c
@@ -0,0 +1,21 @@
+#include "print.h"
+
+// Check if the compiler thinks we are targeting the wrong OS
+#if defined(__linux__)
+#error "Not using cross compiler!"
+#endif
+
+// Only works for 32 bit ix86 target
+#if !defined(__i386__)
+#error "Must use ix86-elf compiler"
+#endif
+
+// Color Constants
+
+void kernel_main(void) {
+  print_clear();
+  print_set_color(PRINT_COLOR_YELLOW, PRINT_COLOR_BLACK);
+  printf("printf\n\tint: %d\n\tstring: %s\n\tchar: %c\n\tpercent: "
+         "%%\n\tnothing: %n",
+         1287, "World! ", 't');
+}
diff --git a/src/kernel/print.c b/src/kernel/print.c
new file mode 100644
index 0000000..35533cd
--- /dev/null
+++ b/src/kernel/print.c
@@ -0,0 +1,133 @@
+#include "print.h"
+#include "str.h"
+#include <stdarg.h>
+// Constants
+static const size_t NUM_COLS = 80;
+static const size_t NUM_ROWS = 25;
+
+// Char struct
+struct Char {
+  uint8_t character;
+  uint8_t color;
+};
+
+// Set video mem buffer
+struct Char *buffer = (struct Char *)0xb8000;
+// Set current row and col
+size_t col = 0;
+size_t row = 0;
+
+// Default colors
+uint8_t color = PRINT_COLOR_WHITE | PRINT_COLOR_BLACK << 4;
+
+// clear row
+void clear_row(size_t row) {
+  // Define empty character
+  struct Char empty = (struct Char){
+    character : ' ',
+    color : color,
+  };
+
+  // For every col in row, set vmem to empty
+  for (size_t col = 0; col < NUM_COLS; col++) {
+    buffer[col + NUM_COLS * row] = empty;
+  }
+}
+
+// Call clear_row for every row
+void print_clear() {
+  for (size_t i = 0; i < NUM_ROWS; i++) {
+    clear_row(i);
+  }
+}
+
+// newline
+void print_newline() {
+  // Reset col and iterate row if not at bottom of screen
+  col = 0;
+  if (row < NUM_ROWS - 1) {
+    row++;
+    return;
+  }
+
+  // If at bottom of screen, move all the text up one row
+  for (size_t row = 1; row < NUM_ROWS; row++) {
+    for (size_t col = 0; col < NUM_COLS; col++) {
+      struct Char character = buffer[col + NUM_COLS * row];
+      buffer[col + NUM_COLS * (row - 1)] = character;
+    }
+  }
+
+  // Clear
+  clear_row(NUM_ROWS - 1);
+}
+
+// printchar
+void print_char(char character) {
+  // If \n, call newline
+  if (character == '\n') {
+    print_newline();
+    return;
+  }
+
+  if (character == '\t') {
+    print_str("    \0");
+    return;
+  }
+
+  // if cols is too large, overflow
+  if (col > NUM_COLS) {
+    print_newline();
+  }
+
+  // set video memeory to requested character
+  buffer[col + NUM_COLS * row] = (struct Char){
+    character : (uint8_t)character,
+    color : color,
+  };
+
+  // iterate col
+  col++;
+}
+
+// print_str
+void print_str(char *str) {
+  // while character != '\0' print char
+  for (size_t i = 0; str[i] != '\0'; ++i)
+    print_char(str[i]);
+}
+
+// Set color byte to requested colors using color enum from print.h
+void print_set_color(uint8_t foreground, uint8_t background) {
+  color = foreground + (background << 4);
+}
+
+void printf(const char *str, ...) {
+  va_list args;
+  va_start(args, str);
+  char temp_str[256];
+
+  for (size_t i = 0; str[i] != '\0'; ++i) {
+    if (str[i] == '%') {
+      switch (str[++i]) {
+      case 'i':
+      case 'd':
+        print_str(itoa(va_arg(args, int), temp_str));
+        break;
+      case 's':
+        print_str(va_arg(args, char *));
+        break;
+      case 'c':
+        print_char(va_arg(args, int));
+        break;
+      case '%':
+        print_char('%');
+      case 'n':
+        break;
+      }
+      continue;
+    }
+    print_char(str[i]);
+  }
+  va_end(args);
+}