I saw in some libraries and used the following technique to interop with C
code. For example
// sum.c
long long sum(long long* xs, unsigned int len){
long long s = 0;
for(int i=0; i<len; i++) s += xs[i];
return s;
}
Run
# sum.nim
{.compile: "sum.c" .}
proc sum(buf: ptr clonglong, len: csize_t): clonglong {.importc.}
proc sum_seq_wrapper(xs: seq[int]): int =
if xs.len == 0: return 0
let n = sum(cast[ptr clonglong](xs[0].unsafeAddr), xs.len.uint)
result = n.int
when isMainModule:
let xs = @[1,2,3]
echo sum_seq_wrapper(xs)
Run
I am 100% sure, but it doesn't seem to me `xs` would be freed during `sum`. I
also see people apply the same technique to string.
