New version, License & new implementations

Author: bobrossrtx

kernel/kernel.c

@@ -1,5 +1,29 @@
+/**
+ * @file kernel.c
+ * @author Owen Boreham (owenkadeboreham@gmail.com)
+ * @version 0.1.3
+ * @date 2021-07-06
+ * 
+ * @copyright Copyright (c) 2021 TinyKernel
+ * This file is part of TinyKernel which is released
+ * under Apache License 2.0.  See file LICENSE or go
+ * to https://www.apache.org/licenses/LICENSE-2.0 for
+ * full license details.
+ */
+
+
 #include "kernel.h"
 
+// Index for video buffer array
+uint32 vga_index;
+// Counter to store new lines
+static uint32 next_line_index = 1;
+// Fore & Back color values
+uint8 g_fore_color = WHITE, g_back_color = BLUE;
+// digit ascii code for printing integers
+int digit_ascii_codes[10] = {0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37, 0x38, 0x39};
+
+
 /*
  * 16 bit video buffer elements(register ax)
  * 8 bits(ah) higher :
@@ -8,7 +32,7 @@
  * 8 bits(al) lower :
  *      8 bits : ASCII character to print
  * */
-uint16 vga_entry(unsigned char ch, uint8 fore_color, uint8 back_color) 
+uint16 vga_entry(unsigned char ch, uint8 fore_color, uint8 back_color)
 {
   uint16 ax = 0;
   uint8 ah = 0, al = 0;
@@ -28,33 +52,131 @@ uint16 vga_entry(unsigned char ch, uint8 fore_color, uint8 back_color)
 void clear_vga_buffer(uint16 **buffer, uint8 fore_color, uint8 back_color)
 {
     uint32 i;
-    for(i = 0; i < BUFSIZE; i++) {
+    for(i = 0; i < BUFSIZE; i++)
+    {
         (*buffer)[i] = vga_entry(NULL, fore_color, back_color);
     }
+    next_line_index = 1;
+    vga_index = 0;
 }
 
 // Initialize vga buffer
 void init_vga(uint8 fore_color, uint8 back_color)
 {
   vga_buffer = (uint16*)VGA_ADDRESS; // Point vga_buffer pointer to VGA_ADDRESS
   clear_vga_buffer(&vga_buffer, fore_color, back_color);
+  g_fore_color = fore_color;
+  g_back_color = back_color;
+}
+
+void default_colors()
+{
+  g_fore_color = WHITE;
+  g_back_color = BLACK;
+}
+
+/*
+Increase vga_index by width of row(80)
+*/
+void print_new_line()
+{
+  if (next_line_index >= 55) 
+  {
+    next_line_index = 0;
+    clear_vga_buffer(&vga_buffer, g_fore_color, g_back_color);
+  }
+  vga_index = 80 * next_line_index;
+  next_line_index++;
+}
+
+// Assign ascii character to video buffer
+void print_char(char ch)
+{
+  vga_buffer[vga_index] = vga_entry(ch, g_fore_color, g_back_color);
+  vga_index++;
+}
+
+uint32 strlen(const char* str)
+{
+  uint32 length = 0;
+  while (str[length])
+    length++;
+  return length;
+}
+
+uint32 digit_count(int num)
+{
+  uint32 count = 0;
+  if (num == 0)
+    return 1;
+  while(num > 0) 
+  {
+    count++;
+    num = num/10;
+  }
+  return count;
+}
+
+void itoa(int num, char *number)
+{
+  int dgcount = digit_count(num);
+  int index = dgcount - 1;
+  char x;
+  if (num == 0 && dgcount == 1)
+  {
+    number[0] = '0';
+    number[1] = '\0';
+  }
+  else
+  {
+    while (num != 0)
+    {
+      x = num % 10;
+      number[index] = x + '0';
+      index--;
+      num = num / 10;
+    }
+    number[dgcount] = '\0';
+  }
+}
+
+// Print string is calling print_char
+void print_string(char *str)
+{
+  uint32 index = 0;
+  while (str[index])
+  {
+    print_char(str[index]);
+    index++;
+  }
+}
+
+// Print int by converting it into string
+// then print string
+void print_int(int num)
+{
+  char str_num[digit_count(num)+1];
+  itoa(num, str_num);
+  print_string(str_num);
 }
 
 void kernel_entry()
 {
   // First init vga with fore & back colors
   init_vga(WHITE, BLACK);
 
-  // Assign each ASCII character to video buffer
-  vga_buffer[0] = vga_entry('H', WHITE, BLACK);
-  vga_buffer[1] = vga_entry('e', WHITE, BLACK);
-  vga_buffer[2] = vga_entry('l', WHITE, BLACK);
-  vga_buffer[3] = vga_entry('l', WHITE, BLACK);
-  vga_buffer[4] = vga_entry('o', WHITE, BLACK);
-  vga_buffer[5] = vga_entry(' ', WHITE, BLACK);
-  vga_buffer[6] = vga_entry('W', WHITE, BLACK);
-  vga_buffer[7] = vga_entry('o', WHITE, BLACK);
-  vga_buffer[8] = vga_entry('r', WHITE, BLACK);
-  vga_buffer[9] = vga_entry('l', WHITE, BLACK);
-  vga_buffer[10] = vga_entry('d', WHITE, BLACK);
+  /**
+   * @brief Printing "Hello World!\n", "1234456789\n", "Goodbye World!"
+   * Call the above function to print something
+   * here to change the fore & back color,
+   * assign g_fore_color & g_back_color to color values
+   *  g_fore_color = BRIGHT_RED;
+   */
+  print_string("Hello World!");
+  print_new_line();
+  g_fore_color = BRIGHT_GREEN;
+  print_int(123456789);
+  default_colors();
+  print_new_line();
+  print_string("Goodbye World!");
 }