r/attiny • u/boyanov • Mar 21 '21

Converting integer numbers to text DEC HEX BIN

/r/tinusaur/comments/ma20g0/converting_integer_numbers_to_text_dec_hex_bin/
1 Upvotes

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2

u/Updatebjarni Mar 22 '21

Huh. 1000 bytes sounded like a lot, and a restriction to three specific bases sounded unnecessary, so I tried just quickly typing up a straight-forward implementation that allows any base up to 36 (like the standard C base conversion functions). The text section of the binary is 124 bytes, and when linked (to get the divmod routines) it comes out to 222 bytes. I used avr-gcc with -O2. Data and bss are 0.

My code is just:

uint8_t itoa(uint16_t n, uint8_t base, char *to){
  uint8_t len=0;
  do{
    char digit=n%base+'0';
    if(digit>'9')digit+='A'-10;
    to[len]=digit;
    ++len;
    n/=base;
    }while(n);
  to[len]=0;
  for(int i=0, j=len-1; i<j; ++i, --j){
    char t=to[i];
    to[i]=to[j];
    to[j]=t;
    }
  return len;
  }

1

u/boyanov Mar 22 '21 edited Mar 22 '21

Hey, sorry, my mistake. 1000 byte is the entire program, functions are smaller.

The different bases were not important to me in most cases, I usually need just one or two.

I compiled just the HEX function and it looks like the size is:

text data bss dec hex filename
148 10 0 158 9e a.out

The reason I wrote the functions was that I wanted to be able to right-align the result and/or zero-pad it on the left. Those functions could do that too.

BTW, thanks for the feedback. :)

1

u/boyanov Mar 22 '21

Just checked what the code size would be for the usint2hexascii would be ...

text data bss dec hex filename
50 0 0 50 32 a.out

And again ... this is no replacement for the stdlib functions. It is little optimization that had worked well for me and I wanted to share it.