Code fix / improvements

[ledvinap]

Apply some changes to existing code. Split into separate commits with comments

[codecov-io]

Codecov Report

Merging #60 into master will decrease coverage by 1.37%. The diff coverage is 93.82%.

@@            Coverage Diff             @@
##           master      #60      +/-   ##
==========================================
- Coverage     100%   98.62%   -1.38%     
==========================================
  Files           1        1              
  Lines         359      363       +4     
==========================================
- Hits          359      358       -1     
- Misses          0        5       +5

Impacted Files	Coverage Δ
printf.c	98.62% <93.82%> (-1.38%)	:arrow_down:

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[axiomlegend]

Calling *out for each character is costly. Consider sprintf functionality. you call *out for every character only to do: if (a < b) a[i] = c; Lot of overhead for a few instructions. Definitely need to put most options to ntoa_format, etc. into a struct vs stack.

[ledvinap]

@axiomlegend : Yes, out is quite expensive, but also generic. In a lot of embedded applications output to serial port is (or SWO) desired, and using sprintf will complicate things a lot. One improvement is to use write semantics for output. Number of calls will be reduced, 1 write between %, 1 call for value output and one (or few chunks) for padding. Another optimization in my list is to move buffer limit test out of out function, slightly improving performance.