mirror of
https://github.com/matrix-construct/construct
synced 2024-05-19 11:23:45 +02:00
53 lines
1.8 KiB
C++
53 lines
1.8 KiB
C++
// Matrix Construct
|
|
//
|
|
// Copyright (C) Matrix Construct Developers, Authors & Contributors
|
|
// Copyright (C) 2016-2018 Jason Volk <jason@zemos.net>
|
|
//
|
|
// Permission to use, copy, modify, and/or distribute this software for any
|
|
// purpose with or without fee is hereby granted, provided that the above
|
|
// copyright notice and this permission notice is present in all copies. The
|
|
// full license for this software is available in the LICENSE file.
|
|
|
|
#pragma once
|
|
#define HAVE_IRCD_UTIL_HASH_H
|
|
|
|
namespace ircd::util
|
|
{
|
|
// constexpr bernstein string hasher suite; these functions will hash the
|
|
// string at compile time leaving an integer residue at runtime. Decent
|
|
// primes are at least 7681 and 5381.
|
|
template<size_t PRIME = 7681> constexpr size_t hash(const char16_t *const str, const size_t i = 0);
|
|
template<size_t PRIME = 7681> constexpr size_t hash(const string_view str, const size_t i = 0);
|
|
|
|
// Note that at runtime this hash uses multiplication on every character
|
|
// which can consume many cycles...
|
|
template<size_t PRIME = 7681> size_t hash(const std::u16string &str, const size_t i = 0);
|
|
}
|
|
|
|
/// Runtime hashing of a std::u16string (for js). Non-cryptographic.
|
|
template<size_t PRIME>
|
|
size_t
|
|
ircd::util::hash(const std::u16string &str,
|
|
const size_t i)
|
|
{
|
|
return i >= str.size()? PRIME : (hash(str, i+1) * 33ULL) ^ str.at(i);
|
|
}
|
|
|
|
/// Runtime hashing of a string_view. Non-cryptographic.
|
|
template<size_t PRIME>
|
|
constexpr size_t
|
|
ircd::util::hash(const string_view str,
|
|
const size_t i)
|
|
{
|
|
return i >= str.size()? PRIME : (hash(str, i+1) * 33ULL) ^ str.at(i);
|
|
}
|
|
|
|
/// Compile-time hashing of a wider string literal (for js). Non-cryptographic.
|
|
template<size_t PRIME>
|
|
constexpr size_t
|
|
ircd::util::hash(const char16_t *const str,
|
|
const size_t i)
|
|
{
|
|
return !str[i]? PRIME : (hash(str, i+1) * 33ULL) ^ str[i];
|
|
}
|