bulat.ziganshin:
Hello Donald,
Friday, July 14, 2006, 8:11:22 AM, you wrote:
afaik, CStringLen don't require zero byte at the end of string. So the following implementation will be much faster and still correct (not tested, it's just sketch):
Well spotted! I've applied this patch, with a tiny tweak (you missed a withForeignPtr in useAsCStringLen).
thanks. after writing this letter i spotted unsafeUseAsCStringLen and used it. now i'm curious about having these 4 functions:
useAsCString useAsCStringLen unsafeUseAsCString unsafeUseAsCStringLen
and differences between their behavior. may be, it will be better to keep only first two functions, with semantics already implemented (with my patch) - `useAsCString` add zero byte while useAsCStringLen doesn't ?
Ok, the story is: We'd like to be able to efficiently pass ByteStrings to C. However, * CString has to be null terminated * ByteStrings aren't null terminated. So, we have: useAsCString, which copies a ByteString, and adds a \0 byte, O(n) unafeUseAsCString, zero-copy version, assumes there's already a null byte, O(1) Now, on the other hand, we have the CStringLen type, which doesn't need a null byte. The CString type is isomorphic to a ByteString, so: useAsCStringLen, which is just a cast. O(1) unsafeUseAsCStringLen is a synonym for useAsCStringLen. I've clarified the documentation for the CString functions to make this clear. Cheers, Don