lib/libsys/kputc.c

   1 /* A server must occasionally print some message.  It uses a simple version of
   2  * printf() found in the system lib that calls kputc() to output characters.
   3  * Printing is done with a call to the kernel, and not by going through FS.
   4  *
   5  * This routine can only be used by servers and device drivers.  The kernel
   6  * must define its own kputc(). Note that the log driver also defines its own
   7  * kputc() to directly call the TTY instead of going through this library.
   8  */
   9
  10 #include "sysutil.h"
  11
  12 static char print_buf[DIAG_BUFSIZE];    /* output is buffered here */
  13
  14 /*===========================================================================*
  15  *                              kputc                                        *
  16  *===========================================================================*/
  17 void kputc(int c)
  18 {
  19 /* Accumulate another character.  If 0 or buffer full, print it. */
  20   static int buf_count;         /* # characters in the buffer */
  21
  22   if ((c == 0 && buf_count > 0) || buf_count == sizeof(print_buf)) {
  23         sys_sysctl(SYSCTL_CODE_DIAG, print_buf, buf_count);
  24         buf_count = 0;
  25   }
  26   if (c != 0) {
  27
  28         /* Append a single character to the output buffer. */
  29         print_buf[buf_count] = c;
  30         buf_count++;
  31   }
  32 }