From a4d167972377776f189bfd073dba60a8f69eba39 Mon Sep 17 00:00:00 2001
From: Xnoe <xnoe@xnoe.moe>
Date: Thu, 2 Sep 2021 15:09:21 +0100
Subject: [PATCH] Added primitive printf implementation, can print decimal
 ints, hex ints and strings

---
 kernel32.c | 123 ++++++++++++++++++++++++++++++++++++++++++++---------
 1 file changed, 104 insertions(+), 19 deletions(-)

diff --git a/kernel32.c b/kernel32.c
index 5cad07c..8ad01c5 100644
--- a/kernel32.c
+++ b/kernel32.c
@@ -1,6 +1,7 @@
+#include <stdarg.h>
 #include "types.h"
 
-uint8_t* VMEM_ADDR = (uint8_t*)0xb8000;
+uint16_t* VMEM_ADDR = (uint16_t*)0xb8000;
 const int TERM_WIDTH = 80;
 const int TERM_HEIGHT = 25;
 
@@ -16,7 +17,7 @@ uint8_t inb(uint16_t portnumber) {
   return result;
 }
 
-uint16_t get_cursor_position() {
+uint16_t get_curpos() {
   uint16_t cursor_position = 0;
   uint8_t* cursor_position_split = (uint8_t*)&cursor_position;
   outb(0x3D4, 0x0F);
@@ -27,7 +28,7 @@ uint16_t get_cursor_position() {
 }
 
 void init_term() {
-  uint16_t cursor_position = get_cursor_position();
+  uint16_t cursor_position = get_curpos();
 
   cursor_y = cursor_position / TERM_WIDTH;
   cursor_x = cursor_position % TERM_WIDTH;
@@ -35,43 +36,127 @@ void init_term() {
 
 void clear_screen()  {
   for (int i=0; i<TERM_WIDTH*TERM_HEIGHT; i++) {
-    VMEM_ADDR[i*2] = 0x20;
-    VMEM_ADDR[i*2 + 1] = 0x07;
+    VMEM_ADDR[i] = 0x0720;
   }
 }
 
+void clear_line(int line) {
+  for (int x=0; x<TERM_WIDTH; x++) {
+    VMEM_ADDR[TERM_WIDTH*line + x] = 0x0720;
+  }
+}
+
+void set_curpos_raw(int curpos) {
+  uint8_t* cursor_position_split = (uint8_t*)&curpos;
+  outb(0x3D4, 0x0F);
+  outb(0x3D5, cursor_position_split[0]);
+  outb(0x3D4, 0x0E);
+  outb(0x3D5, cursor_position_split[1]);
+}
+
 void set_curpos(int x, int y) {
+  set_curpos_raw(y * TERM_WIDTH + x);
+  
   cursor_x = x;
   cursor_y = y;
 }
 
-void print(const char* string) {
+int int_to_decimal(unsigned int number, char* string_buffer) {
+  for (int i=0; i<11; i++)
+    string_buffer[i] = 0;
+  
+  int index = 9;
+  unsigned int acc = number;
+  while (acc != 0) {
+    string_buffer[index--] = 0x30+(acc%10);
+    acc /= 10;
+  }
+  return (index+1);
+}
+
+char dec_to_hex[16] = {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'};
+
+int int_to_hex(unsigned int number, char* string_buffer) { 
+  for (int i=0; i<9; i++)
+    string_buffer[i] = 0;
+  
+  int index = 7;
+  unsigned int acc = number;
+  while (acc != 0) {
+    string_buffer[index--] = dec_to_hex[acc%0x10];
+    acc /= 0x10;
+  }
+  return (index+1);
+}
+
+void printf(const char* string, ...) {
+  va_list ptr;
+  va_start(ptr, string);
+
   int index = 0;
+  int count = 0;
   char current;
   while (current=string[index++]) {
+    count++;
     if (current == '\n') {
-      set_curpos(0, cursor_y+1);
-      continue;
-    }
-
-    int mem_pos = cursor_y * TERM_WIDTH + cursor_x++;
-    VMEM_ADDR[mem_pos*2] = current;
-    VMEM_ADDR[mem_pos*2 + 1] = 0x07;
-
-    if (index == TERM_WIDTH) {
       cursor_x = 0;
       cursor_y++;
     }
-  }
-}
 
+    if (cursor_x == TERM_WIDTH) {
+      cursor_x = 0;
+      cursor_y++;
+    }
+
+    if (cursor_y == TERM_HEIGHT) {
+      for (int i=1; i<TERM_HEIGHT; i++) {
+        for (int x=0; x<TERM_WIDTH; x++) {
+          int from = i * TERM_WIDTH + x;
+          int to = (i-1) * TERM_WIDTH + x;
+          VMEM_ADDR[to] = VMEM_ADDR[from];
+        }
+      }
+      clear_line(24);
+      cursor_y--;
+    }
+
+    if (current == '%') {
+      int type = string[index++];
+      int offset;
+      switch (type) {
+        case 'd':
+          char decimal_buffer[11];
+          offset = int_to_decimal(va_arg(ptr, int), decimal_buffer);
+          printf(decimal_buffer + offset);
+          break;
+        case 'x':
+          char hex_buffer[8];
+          offset = int_to_hex(va_arg(ptr, int), hex_buffer);
+          printf(hex_buffer + offset);
+          break;
+        case 's':
+          printf(va_arg(ptr, const char*));
+      }
+      continue;
+    }
+
+    if (current != '\n') {
+      int mem_pos = cursor_y * TERM_WIDTH + cursor_x++;
+      VMEM_ADDR[mem_pos] = current + (0x07<<8);
+    }
+  }
+
+  set_curpos(cursor_x, cursor_y);
+
+  va_end(ptr);
+}
 
 int main() {
   init_term();
 
-  print("KERNEL32 OK!\n\n");
+  printf("KERNEL32 OK!\n");
 
-  print("Hello, World!\n\nWe are running XnoeOS Code in C now, Protected Mode has been achieved and everything is working super nicely!\n\nHow wonderful!\n\nNow I just need to hope my print function works properly too~~");
+  printf("Hello, World!\n\nWe are running XnoeOS Code in C now, Protected Mode has been achieved and everything is working super nicely!\n\nHow wonderful!\n\nNow I just need to hope my print function works properly too~~\n");
 
   while (1) {}
 }
\ No newline at end of file