Would it be a sin to use memcpy() and leave things like input validation to a separate function? I'm nervous any time somebody takes a function with purpose X and uses it for purpose Y.
Uh, isn't using `memcpy()` to copy strings doing exactly that?
The problem is that `memcpy()` doesn't know about (of course) string terminators, so you have to do a separate call to `strlen()` to figure out the length, thus visiting every character twice which of course makes no sense at all (spoken like a C programmer I guess ... since I am one).
If you already know the length due to other means, then of course it's fine to use `memcpy()` as long as you remember to include the terminator. :)
The reason you would want to use memcpy would be if 1) you already know what the length is, 2) if you need a custom validator for your input, 3) you don't want to validate your input (however snprintf() is doing that), 4) if the string may include nulls or there is no null terminator.
But the fifth reason may be that depending on snprintf as your "custom-validator-and-encoder-plus-null-terminator" may introduce subtle bugs in your program if you don't know exactly what snprintf is doing under the hood and what its limitations are. By using memcpy and a custom validator, you can be more explicit about how data is handled in your program and avoid uncertainty.
(by "validate" I mean handle the data as your program expects. this could be differentiating between ASCII/UTF-8/UTF-16/UTF-32, adding/preserving/removing a byte-order mark, eliminating non-printable characters, length requirements, custom terminators, or some other requirement of whatever is going to be using the new copy of the data)
