hash.h

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/*
 Copyright (c) 2026 - SD-Innovation S.A.S. - FRANCE
*/
 
/*
ver: 2.x.x - build: 2026-04-28
*/
 
/*
The zlib License

Copyright (c) 2026 SD-Innovation S.A.S. 

This software is provided ‘as-is’, without any express or implied
warranty. In no event will the authors be held liable for any damages
arising from the use of this software.

Permission is granted to anyone to use this software for any purpose,
including commercial applications, and to alter it and redistribute it
freely, subject to the following restrictions:

1. The origin of this software must not be misrepresented; you must not
claim that you wrote the original software. If you use this software
in a product, an acknowledgment in the product documentation would be
appreciated but is not required.

2. Altered source versions must be plainly marked as such, and must not be
misrepresented as being the original software.

3. This notice may not be removed or altered from any source
distribution.

*/
 
#pragma once
 
#include <cstdint>
#include <span>
#include <string_view>
 
namespace sdi_toolBox::common::utils::hash
{
//--------------------------------------------------------------
constexpr std::uint32_t fnv1a(std::span<const std::byte> data) noexcept;
 
constexpr std::uint32_t fnv1a(std::string_view sv) noexcept;
 
template<typename T>
  requires std::is_trivially_copyable_v<T>
constexpr std::uint32_t fnv1a(const T &value) noexcept;
 
constexpr std::uint64_t fnv1a_64(std::span<const std::byte> data) noexcept;
 
constexpr std::uint64_t fnv1a_64(std::string_view sv) noexcept;
 
template<typename T>
  requires std::is_trivially_copyable_v<T>
constexpr std::uint64_t fnv1a_64(const T &value) noexcept;
//--------------------------------------------------------------
 
//--------------------------------------------------------------
/* Compute the FNV-1a 32-bit hash for a span of bytes */
inline constexpr std::uint32_t fnv1a(const std::span<const std::byte> data) noexcept
{
  constexpr std::uint32_t FNV_OFFSET_BASIS = 2166136261u;
  constexpr std::uint32_t FNV_PRIME        = 16777619u;
 
  std::uint32_t hash = FNV_OFFSET_BASIS;
  for (const auto b : data)
  {
    hash ^= static_cast<std::uint32_t>(std::to_integer<std::uint8_t>(b));
    hash *= FNV_PRIME;
  }
  return hash;
}
//--------------------------------------------------------------
/* Compute the FNV-1a 32-bit hash for a std::string_view */
inline constexpr std::uint32_t fnv1a(const std::string_view sv) noexcept
{
  return fnv1a({ reinterpret_cast<const std::byte *>(sv.data()), sv.size() });
}
//--------------------------------------------------------------
/* Compute the FNV-1a 32-bit hash for a trivially copyable POD object */
template<typename T>
  requires std::is_trivially_copyable_v<T>
inline constexpr std::uint32_t fnv1a(const T &value) noexcept
{
  return fnv1a({ reinterpret_cast<const std::byte *>(std::addressof(value)), sizeof(T) });
}
//--------------------------------------------------------------
/* Compute the FNV-1a 64-bit hash for a span of bytes */
inline constexpr std::uint64_t fnv1a_64(const std::span<const std::byte> data) noexcept
{
  constexpr std::uint64_t FNV_OFFSET_BASIS = 14695981039346656037ull;
  constexpr std::uint64_t FNV_PRIME        = 1099511628211ull;
 
  std::uint64_t hash = FNV_OFFSET_BASIS;
  for (const auto b : data)
  {
    hash ^= static_cast<std::uint64_t>(std::to_integer<std::uint8_t>(b));
    hash *= FNV_PRIME;
  }
  return hash;
}
//--------------------------------------------------------------
/* Compute the FNV-1a 64-bit hash for a std::string_view */
inline constexpr std::uint64_t fnv1a_64(const std::string_view sv) noexcept
{
  return fnv1a_64({ reinterpret_cast<const std::byte *>(sv.data()), sv.size() });
}
//--------------------------------------------------------------
/* Compute the FNV-1a 64-bit hash for a trivially copyable POD object */
template<typename T>
  requires std::is_trivially_copyable_v<T>
inline constexpr std::uint64_t fnv1a_64(const T &value) noexcept
{
  return fnv1a_64(std::span<const std::byte>{ reinterpret_cast<const std::byte *>(std::addressof(value)), sizeof(T) });
}
//--------------------------------------------------------------
}     // namespace sdi_toolBox::common::utils::hash