Constexpr hash

Author: qpyq

August undefined, 2024

Web请注意主要区别-无法使用 std::hash ，因为我们无法控制 std::hash 的算法，因此必须将其重新实现为 constexpr 以便在编译时对其进行评估。此外，在 std 中没有"透明"哈希，因此您不能(不创建 std::string)哈希原始字符缓冲区作为 std::string 。 http://c.biancheng.net/view/7781.html

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Webunsigned constexpr const_hash(char const *input) { return *input ? static_cast(*input) + 33 * const_hash(input + 1) : 5381; } … http://www.duoduokou.com/c/27121849420694307082.html hydration backpack outdoor products

C++11 constexpr：验证是否为常量表达式（长篇神文）

WebMar 15, 2024 · inline constexpr uint64_t hash_64_fnv1a_const (const char* const str, const uint64_t value = val_64_const) noexcept { return (str [0] == '\0') ? value : hash_64_fnv1a_const (&str [1], (value ^ uint64_t (str [0])) * prime_64_const); } WebJun 21, 2024 · At the base of all this lies compile-time string hashing. This is done to get a unique (ideally) hash for every type name so that we can create a lookup table. By … http://duoduokou.com/cplusplus/36739602131562177108.htmlhydration backpack big 5

Exploring Compile Time Hashing « The blog at the bottom of the sea

entt/hashed_string.hpp at master · skypjack/entt · GitHub

WebIf I am not mistaken, Java has switch-case statements that support strings. Such a thing is not possible with plain c++ but there is a workaround if we use a constexp hash function for converting a string to a size_t value. constexpr size_t hash (const char* str) { const long long p = 131; const long long m = 4294967291; // 2^32 - 5, largest 32 ... WebComputes a constexpr (minimal) perfect hash function generator. There are times when one wishes there was a fast simple way to do things like this: There are options: std::unordered_map (map of function pointers), a bunch of if / else, a switch () of hashed strings, gperf (GNU's perfect hash function generator), etc. hydration bdaWebThis repository contains a header-only library allowing compile-time only ( consteval) calculation of SHA-1, SHA-224, SHA-256, SHA-384, SHA-512, SHA-512/224, and SHA-512/256 digests as defined in FIPS 180-4. This library is restricted to compile-time only because there are much more efficient libraries to provide runtime hash calculations. massage gun with heated tip

"WebApr 2, 2014 · 这个函数只有短短的一行，利用递归得到了与上面hash_函数得到的同样值，由于用constexpr声明了函数，因此编译器可以在编译期得出一个字符串的hash值，而这正是关键，既然是编译器就可以得到的整型常量，自然可以放到switch的case标签处了。" - Constexpr hash

Constexpr hash

WebApr 8, 2024 · 第一种解决方案：加上constexpr，具体后面阐述。 C++17 引入 if constexpr 支持在编译期执行, 可以将之应用于泛型编程中的条件判断, if constexpr (hasSerialize::value) 第二种解决方案：就是不用if语句了，而是将这个函数分成两个函数，每个函数对应一个分支。如何分？ WebSep 23, 2016 · constexpr unsigned int hash = crc32("Hello1"); // 1) Debug: Run Time 00007FF71F7A1ABE xor edx,edx 00007FF71F7A1AC0 lea rcx,[string "Hello1" (07FF71F7AB124h)] 00007FF71F7A1AC7 call crc32 (07FF71F7A10C3h) 00007FF71F7A1ACC mov dword ptr [hash],eax constexpr unsigned int hashTestHello2 …

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Webconstexpr 关键字的功能是使指定的常量表达式获得在程序编译阶段计算出结果的能力，而不必等到程序运行阶段。. C++ 11 标准中，constexpr 可用于修饰普通变量、函数（包括模板函数）以及类的构造函数。. 注意，获得在编译阶段计算出结果的能力，并不代表 ... WebGaming meets modern C++ - a fast and reliable entity component system (ECS) and much more - entt/hashed_string.hpp at master · skypjack/entt

WebOct 27, 2024 · mapbox::eternal::map() is a factory function that produces a constexpr map from the std::pairs passed to it. Alternatively, use … Webconstexpr hash. 分类: 小技巧. 自从有了constexpr函数后, 感觉可以用在非常多的地方, 用在hash计算上是一个很不错的方案. 如果遇到很多字符串的话, 很多地方会采用hash的方式处理. 最大的原因就是如果hash值不同, 原字符串肯定不同.

WebThis repository contains a header-only library allowing compile-time only ( consteval) calculation of SHA-1, SHA-224, SHA-256, SHA-384, SHA-512, SHA-512/224, and SHA-512/256 digests as defined in FIPS 180-4. This … WebMar 8, 2024 · 위 예제의 컴파일 오류를 해결할 수 있는 열쇠가 바로 constexpr 함수라는 것을요. HashCode 함수를 constexpr 함수로 만든다면 컴파일 시점에 상수화되어 case 표현식에도 사용할 수 있게 될겁니다. 이제 HashCode 함수를 constexpr 버전으로 다시 작성해보겠습니다.

WebNov 16, 2016 · constexpr syntax to pre-calculate the hash value and sometimes with the help of template recursion in compile time. Example A Java string's hashCode () is one of the simplest hash function which uses Horner's method: h =s[0]∗31(n−1) +s[1]∗31(n−2)+...+s[n−1] h = s [ 0] ∗ 31 ( n − 1) + s [ 1] ∗ 31 ( n − 2) +... + s [ n − 1]

WebMar 10, 2024 · static constexpr auto get_index_and_bucket (K key) { constexpr std:: size_t hash_value = hash (key); constexpr std:: size_t ix = hash_value % sizeof ... (Bs); using …hydration bearWebMar 15, 2024 · hash_fnv1a_constexpr.h This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the …hydration bathWebOct 27, 2024 · mapbox::eternal::map() is a factory function that produces a constexpr map from the std::pairs passed to it. Alternatively, use mapbox::eternal::hash_map() to construct a hash map. The key needs a specialization of std::hash.; Use mapbox::eternal::string for constexpr strings.; If you …hydration backpacks for cycling