divmod10() : a fast replacement for /10 and %10 (unsigned)

Development Libraries
58

for long numbers:

original = 1408/24 = ~59us / digit to print
"tom" = 480/24 = ~20 us/digit to print (33%)
"paul" = 224/24 = ~ 9.5uS /digit to print (16%)

A quick arbitrary float test (same prog as above, slightly different printnumber)

  Serial.println(10737.41824, 4);
  Serial.println(1.01819584, 4);
  Serial.println(107.37, 2);

original printnumber
testing
10737.4179
1.0182
107.37
Time=2144
done

divmod10 printnumber
testing
10737.4179
1.0182
107.37
Time=1472
done

so for floats there is also serious gain ~30% gain

(note this gain is only due to the integral part, the remainder part is a loop using a float mul per digit

  // Extract digits from the remainder one at a time
  while (digits-- > 0)
  {
    remainder *= 10.0;
    int toPrint = int(remainder);
    n += print(toPrint);
    remainder -= toPrint; 
  }

this can be optimized to something like:

  // Extract digits from the remainder one at a time
  long t = 1;
  while (digits-- > 0) t *= 10;
  remainder *= t;
  n += print(long(remainder));

a quick test exposes the flaw in the proposed code but also indicates there is room for improvement.

testing
10737.4179
1.182 <<<<<< FAIL !!!
107.37
Time=1152 <<< (another 25%)
done