Mail Archives: djgpp/1998/05/10/18:16:36
Bruno Barberi Gnecco wrote:
>
> What is this _doprnt? Is there anything to do to improve it?
> Another questions... Why fprintf and putc, if I use just the first one?
> Would it be better to output char by char using putc (because the output is made
> of string, generated a char a time) instead of fprintf("%s")? Or would be fast way
> bufferize it? Is there a faster assembler function to substitute fprintf?
_doprnt() is an internal libc function that is called by all the
formatted print functions--printf(), fprintf(), sprintf(),
vsprintf()--to actually format and store the output. There is a
companion function _doscan() for the scanf() family of functions.
_doprnt() is fairly complex, as you can see if you examine the library
source code, so programs which use lots of formatted output can expect
to spend a fair portion of time there. One other thing to remember is
that the stdio output functions have to send their output through the
DOS file stream mechanism, which requires a protected mode to real mode
switch.
In all, the printf() mechanism is not very fast or efficient. If you
just want to output text, and don't need to use formatted output, it can
be substantially faster to use puts(), etc. You can also reduce the
size of your executable a great deal if you don't use any formatted
output or input commands; the associated functionality is fairly large.
As for why putc() is there, it's because _doprnt() calls putc()
internally.
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