A pure bytes version of strstr?

Question

Is there a version of strstr that works over a fixed length of memory that may include null characters?

I could phrase my question like this: strncpy is to memcpy as strstr is to ?

Corvette

Better you can write a new c program to have such functionality. i dont think it would be a complex thing. – Nitroso

Answer 1

memmem, unfortunately it's GNU-specific rather than standard C. However, it's open-source so you can copy the code (if the license is amenable to you).

Cystocarp

Answer 2

Not in the standard library (which is not that large, so take a look). However writing your own is trivial, either directly byte by byte or using memchr() followed by memcmp() iteratively.

Pattison

+1, I like the idea to use memchr and memcpy. You can take a strstr implementation verbatim and replace all the str-functions with their mem-counterparts. – Dania

Good implementations of strstr are not trivial at all -- they use sophisticated algorithms to work much, much faster than a trivial algorithm can. For example here's the core of the implementation in GNU libc: bazaar.launchpad.net/~vcs-imports/glibc/master/view/head:/… – Pardner

@GregPrice : I am sot suggesting that the standard library strstr() is necessarily trivial; simply that the functionality that the OP requires can be trivially implemented, even if a generally optimal solution is less so. Standard library implementations must be highly optimised because their application is not known in advance. When writing code specific to an application, it only need be fast (or small) enough to meet he application needs. In this specific case an implementation similar to your example may be unwarranted. – Pattison

While the implementation of strstr() is surprisingly complex, the GNU implementation of memmem() is short and simple. If this function is not available on your platform, it's only a few lines long (and even shorter if you can do without all the pointer casting). – Bedizen

Answer 3

In the standard library, no. However, a quick google search for "safe c string library" turns up several potentially useful results. Without knowing more about the task you are trying to perform, I cannot recommend any particular third-party implementation.

If this is the only "safe" function that you need beyond the standard functions, then it may be best to roll your own rather than expend the effort of integrating a third-party library, provided you are confident that you can do so without introducing additional bugs.

Feasible

I don't see the word "safe" in the question. – Vladamar

You are correct that I took a slightly different interpretation of the question. A broad reading of "may include nulls" could lead on to believe that it also may not include nulls. As lack of null termination is a major issue that leads people to consider strncpy() (and, indeed, strlcpy()), it seemed appropriate to address my answer from that direction, since other answers had already covered other approaches. I attempted to note this by stating "Without knowing more about the task ... I cannot recommend any particular third-party implementation." Perhaps I could have been more clear. – Feasible