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dbotkin
Joined: 08 Sep 2003
Posts: 197
Location: Omaha NE USA
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| Printing a variable number of leading zeros? |
 Posted: Thu Feb 16, 2006 9:36 pm |
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Hi,
I have a very simple statement:
| Code: | | printf("%03lu",data); |
Works great. I would like to let the user decide at run time how many leading zeros to print, say from 0 to 3. Or maybe 0 to 5. I've confirmed by experimentation that, as I suspected, printf() won't take a variable for the digit or digits in the printf() format. That would be far too easy.
Needless to say, I don't have enough program space left to do a switch/case or some other means to select one of several printf statements. Do you gurus have any suggestions, or does someone know some trick with printf() that I don't? |
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ak6dn
Joined: 08 Jan 2006
Posts: 23
Location: Saratoga, CA USA
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| Re: Printing a variable number of leading zeros? |
| Posted: Fri Feb 17, 2006 1:40 am |
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| dbotkin wrote: | Hi,
I have a very simple statement:
| Code: | | printf("%03lu",data); |
Works great. I would like to let the user decide at run time how many leading zeros to print, say from 0 to 3. Or maybe 0 to 5. I've confirmed by experimentation that, as I suspected, printf() won't take a variable for the digit or digits in the printf() format. That would be far too easy.
Needless to say, I don't have enough program space left to do a switch/case or some other means to select one of several printf statements. Do you gurus have any suggestions, or does someone know some trick with printf() that I don't? |
Well, you might think this would work, but it does not:
| Code: | char format[8];
sprintf(format, "%%0%dd\r\n", 6);
printf(format, 12);
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It just prints the format statement ('%06d\r\n'). I believe that CCS C actually parses the printf format at compile time and constructs a custom print format routine for each instance (rather than having a full blown generic printf routine always added to your code).
The smallest routine I could construct is:
| Code: | char number[9];
sprintf(number, "%08d", 12);
printf(&number[8-n]);
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where 'n' is the width of the output string you want to have (eg, 1-8). You should be able to optimize usage of this construct by embedding it in a subroutine, called with the number you want to print and the field width. |
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dbotkin
Joined: 08 Sep 2003
Posts: 197
Location: Omaha NE USA
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| Re: Printing a variable number of leading zeros? |
| Posted: Fri Feb 17, 2006 4:45 pm |
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| Quote: | The smallest routine I could construct is:
| Code: | char number[9];
sprintf(number, "%08d", 12);
printf(&number[8-n]);
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where 'n' is the width of the output string you want to have (eg, 1-8). You should be able to optimize usage of this construct by embedding it in a subroutine, called with the number you want to print and the field width. |
By George, I knew someone would have a good idea. I'll have to see if I can squeeze in another printf. I actually simplified the code in my first post; it's actually an sprintf, which puts ASCII charcters into an array that is then used to send the output in a different format. I may be able to just follow the sprintf with an fprintf. If that won't fit, I can always resort to a block of #ASM or something to do what I need.
Thanks! |
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