I just want call C function
static inline uint64_t wyhash(const void* key, uint64_t len, uint64_t seed)
from Swift like that
func hash<T: Any>(key: T, seed: UInt64) -> UInt64 { wyhash(...) }
Is it possible? And how?
To compute the size, use MemoryLayout:
func hash<T>(key: T, seed: UInt64) -> UInt64 {
let len = UInt64(MemoryLayout.size(ofValue: key))
return withUnsafePointer(to: key) { myhash($0, len, seed) }
}
Keep in mind that structural types may have internal padding, and I don't believe Swift promises that to be initialized. So you may wind up hashing random values if you're not careful what you pass here. And of course types may have non-obvious internal state that can cause "equal" values to hash differently or vice versa. Given the likelihood of difficult-to-diagnose bugs, I would typically suggest writing specific overloads for types you know are acceptable to this function rather than trying to hash over Any. At a minimum, I'd constrain T to some protocol (with no syntactic requirements) that expresses "I've checked that this type is myhash-able."