c-将char *数组转换为int和float的最有效方法是什么？

Question

Sorry if it was already asked before, but I really couldn't find a clear answer to this question. Please, tell me, what is the fastest way of converting:

char * array to int
char * array to float

char * array stores a number, for example:

"12345"
"1234,56789"

If the fastest ways for x86 and x64 systems are different, please tell both of them.

EDIT: By "fastest", I mean "the most efficient", not "the most simple to use".

Answer 1

Start with atoi() and atof(), measure the speed, decide if it's a problem - then look for a solution

edit - it's almost certain that the I/O will dominate any time spent doing the conversion. If the conversion time does matter (after you profile) then if you know the format ie. ints are always 4digits, floats always have 5 decimal places, you might be able to write a hand tuned routine that does better than the standard lib

Answer 2

You can just use

atoi()

for ints and

atof()

for floats.

Answer 3

For int , the obvious loop is probably the fastest.

For float , it's much more complicated. If you don't care if the result is right, a similarly trivial loop is also fine. If you need the exact result, you'll want to use strtod or atof or similar since rolling your own is extremely difficult.