keyboard - How to make a scanf() type function in a 32bit os in c? -

i trying make os in c , assembly in 32-bits protected mode. trying create scanf() type function gets keyboard input until enter button pressed. have basic keyboard irq handler setup prints typed , want implement scanf() function have problems return value keyboard handler main kernel.

heres code keyboard handler.

unsigned int shift_key = 0;  unsigned int caps_key = 0;   int counter = 0;  char *sbuf;  int scan = 1;  void keyboard_handler(registers_t regs) {   // monitor_write("handler called");  unsigned char scancode;  scancode = get_scancode(); if(scancode == 0x2a )      {        shift_key = 1;//shift key pressed      //monitor_write("shift + ");  }        else if(scancode == 0xaa)     {          shift_key= 0;//shift key not pressed      //  monitor_write("unshift");  }      else if(scancode == 0x3a && caps_key == 1)      {         caps_key = 0;//caps key pressed  //  monitor_write("shift + ");  }       else if(scancode == 0x3a && caps_key == 0)       {         caps_key = 1;//caps key pressed  //  monitor_write("shift + ");  }    //left arrow      else if(scancode == 0x4b)  {      move_cursor_lr(1,0);  }  //right arrow  else if(scancode == 0x4d)  {      move_cursor_lr(0,1);  }  else      {                if (shift_key == 1 && caps_key == 0)          {             // int shiftaltctrl = 1;//put see special keys      pressed          monitor_put(kkbdus[scancode]);                if (scan == 1 && kkbdus[scancode] != '\n')          {          sbuf[counter] = kkbdus[scancode];                 counter++ ;          }      }             if (caps_key == 1 && shift_key == 0)          {             // int shiftaltctrl = 1;//put see special keys pressed          monitor_put(kkbdus[scancode]);                if (scan == 1 && kkbdus[scancode] != '\n')          {          sbuf[counter] = kkbdus[scancode] ;                counter++ ;          }      }              if(shift_key == 0 && caps_key == 0)      {              monitor_put(kbdus[scancode]); //prints character pressed                   if (scan == 1 && kbdus[scancode] != '\n')          {          sbuf[counter] = kbdus[scancode];                  counter++ ;          }      }         if( caps_key == 1 && shift_key == 1)      {          monitor_put(kbdus[scancode]);          if (scan == 1 && kbdus[scancode] != '\n')          {              sbuf[counter] = kbdus[scancode];                      counter++ ;          }      }      if(scan == 1 && kbdus[scancode] == '\n')       {            scan = 0;          sbuf[0] = '\0';      }      if(kbdus[scancode] == '\t')      {          monitor_write(sbuf);      }       }  } 

i using scan variable bool put chars in array when irq called. cant way return main file call it.

i thought of , tried piece of code worked. did made function in keyboard driver keep last char typed. , when want char call getch(); return char. , made main scanf(); in main file collect chars , first set them 0 same char not repeated , goes through while loop verify enter key pressed. , add char char* if not = 0 , if buffch variable set 1 if set 0 not print it.that theory.

here code:

in keyboard driver: added getch , getchter wich char , set 0 respectively.

char getch() {     char buf = sbuf; // clone buffer     getchter();      // set sbuf 0 same char not repeated     return buf;      // return buff. }  void getchter() {     sbuf = 0;       // setting sbuf 0 } 

and here scanf() function goes in main kernel file.

char* scanf() //scanf() called {     char* buff;      //make buffer     char key = '/0'; // make single char buffer     int = 0;       //counter     int n = 100;     // counter number limit of chars input     int buffch = 1;     while(i < n)  //until max char limit reached     {         buffch = 1;  // buffch used bool buffer or not buffer char          key = getch(); // last char typed         if(key == '\n') // if enter pressed stop         {             break;         }                if(key == '\b') if key backspace          {             //! dont buffer char             buffch = 0;              if (i > 0)  // if count more 0             {                 //! go 1 char in buffer                 i--;             }           }         //! add char if buffered         if (buffch == 1)         {             if (key != 0) // insure not 0 ie if repeated = 0              {                 buff[i++] = key; // add char buffer             }         }      }     buff[i] = '/0'; in last set string null terminated     return buff; // return buff } 

i hope helps other people :)