passing a byte array from go to cgo

Question

I have the following C code

uint32_t cHash32(const char *s, size_t len) { return util::Hash32(s, len); }

I am calling it from a go project as follows

func Hash32(s []byte) uint32 {
    return uint32(C.cHash32((*C.char)(unsafe.Pointer(&s)),   C.size_t(len(s))))
}

Somehow the result is broken.

When passing "hi" the expected result should be 4063302914 according to the python bindings to the same library (farmhash by google).

I guess that assuming s can be translated to a *C.char is a bit naive isn't it!

How do I pass the content of s as a *C.char?

Try replacing `unsafe.Pointer(&s)` with `unsafe.Pointer(&s[0])`. FWIW, A [Go binding for farmhash](https://godoc.org/github.com/dgryski/go-farmhash) already exists. — , Jul 11 '15 at 13:15
Those bindings are broken afaict. I can get it to segfault! also it reports way different stuff than the other bindings from other languages (python-farmhash); — Seif Lotfy, Jul 11 '15 at 14:16
[RTM](https://github.com/golang/go/wiki/cgo), also [this](http://blog.golang.org/go-slices-usage-and-internals). — thwd, Jul 11 '15 at 14:24
the code in which `::` is used for namespace qualification doesn't quite look like C. — The Paramagnetic Croissant, Jul 11 '15 at 14:55

score 3 · Answer 1 · answered Jul 23 '15 at 04:00

Yes, you can create *C.char in Go via C.CString. cgo is not allowed on google playground, so you will need to download this link and run it locally to use it.

http://play.golang.org/p/inthA1i0C2

Convert the byte slice to a string, then to *char C.CString(string([]byte("bytes"))).

passing a byte array from go to cgo

1 Answers1