thodg/libgit2/src

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  • Hash : 83e8a6b3
    Author : Patrick Steinhardt
    Date : 2018-10-18T16:08:46

    util: provide `git__memmem` function Unfortunately, neither the `memmem` nor the `strnstr` functions are part of any C standard but are merely extensions of C that are implemented by e.g. glibc. Thus, there is no standardized way to search for a string in a block of memory with a limited size, and using `strstr` is to be considered unsafe in case where the buffer has not been sanitized. In fact, there are some uses of `strstr` in exactly that unsafe way in our codebase. Provide a new function `git__memmem` that implements the `memmem` semantics. That is in a given haystack of `n` bytes, search for the occurrence of a byte sequence of `m` bytes and return a pointer to the first occurrence. The implementation chosen is the "Not So Naive" algorithm from [1]. It was chosen as the implementation is comparably simple while still being reasonably efficient in most cases. Preprocessing happens in constant time and space, searching has a time complexity of O(n*m) with a slightly sub-linear average case. [1]: http://www-igm.univ-mlv.fr/~lecroq/string/

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