display_uint16_t.c

#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <stdbool.h>

extern void lcddata(unsigned char n);

static inline uint16_t
display_uint16_t_digit(
  uint16_t n, uint16_t div,
  bool *leading_zero)
{
  char digit = 0;
  int shift = (div >= 10000) ? 2 : 3; // prevent overflow
  char add = 1 << shift;
  div <<= shift;
  while (add) {
    if (n >= div) {
      n -= div;
      digit += add;
    }
    div >>= 1;
    add >>= 1;
  }
  if (digit || *leading_zero) {
    lcddata(digit + '0');
    *leading_zero = true;
  }
  return n;
}

void display_uint16_t(uint16_t n)
{
  bool zero = false;
  n = display_uint16_t_digit(n, 10000, &zero);
  n = display_uint16_t_digit(n,  1000, &zero);
  n = display_uint16_t_digit(n,   100, &zero);
  n = display_uint16_t_digit(n,    10, &zero);
  lcddata(n + '0');
}