ladybird/AK/Traits.h
Lenny Maiorani 4333a9a8d6 AK: Find a value in any container offering iterators
Problem:
- `find` is implemented inside of each container. This coupling
  requires that each container needs to individually provide `find`.

Solution:
- Decouple the `find` functionality from the container. This allows
  provides a `find` algorithm which can work with all
  containers. Containers can still provide their own `find` in the
  case where it can be optimized.
- This also allows for searching sub-ranges of a container rather than
  the entire container as some of the container-specific member
  functions enforced.

Note:
- @davidstone's talk from 2015 C++Now conference entitled "Functions
  Want to be Free" encourages this style:
  (https://www.youtube.com/watch?v=_lVlC0xzXDc), but it does come at
  the cost of composability.
- A logical follow-on to this is to provide a mechanism to use a
  short-hand function which automatically searches the entire
  container. This could automatically use the container-provided
  version if available so that functions which provide their own
  optimized version get the benefit.
2021-01-11 19:45:05 +01:00

107 lines
3.4 KiB
C++

/*
* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice, this
* list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#pragma once
#include <AK/Forward.h>
#include <AK/HashFunctions.h>
namespace AK {
template<typename T>
struct GenericTraits {
using PeekType = T;
static constexpr bool is_trivial() { return false; }
static constexpr bool equals(const T& a, const T& b) { return a == b; }
};
template<typename T>
struct Traits : public GenericTraits<T> {
};
template<>
struct Traits<int> : public GenericTraits<int> {
static constexpr bool is_trivial() { return true; }
static unsigned hash(int i) { return int_hash(i); }
};
template<>
struct Traits<char> : public GenericTraits<char> {
static constexpr bool is_trivial() { return true; }
static unsigned hash(char c) { return int_hash(c); }
};
template<>
struct Traits<i16> : public GenericTraits<i16> {
static constexpr bool is_trivial() { return true; }
static unsigned hash(i16 i) { return int_hash(i); }
};
template<>
struct Traits<i64> : public GenericTraits<i64> {
static constexpr bool is_trivial() { return true; }
static unsigned hash(i64 i) { return u64_hash(i); }
};
template<>
struct Traits<unsigned> : public GenericTraits<unsigned> {
static constexpr bool is_trivial() { return true; }
static unsigned hash(unsigned u) { return int_hash(u); }
};
template<>
struct Traits<u8> : public GenericTraits<u8> {
static constexpr bool is_trivial() { return true; }
static unsigned hash(u8 u) { return int_hash(u); }
};
template<>
struct Traits<u16> : public GenericTraits<u16> {
static constexpr bool is_trivial() { return true; }
static unsigned hash(u16 u) { return int_hash(u); }
};
template<>
struct Traits<u64> : public GenericTraits<u64> {
static constexpr bool is_trivial() { return true; }
static unsigned hash(u64 u) { return u64_hash(u); }
};
template<typename T>
struct Traits<T*> : public GenericTraits<T*> {
static unsigned hash(const T* p)
{
return int_hash((unsigned)(__PTRDIFF_TYPE__)p);
}
static constexpr bool is_trivial() { return true; }
static bool equals(const T* a, const T* b) { return a == b; }
};
}
using AK::GenericTraits;
using AK::Traits;