問(wèn)題描述

我開(kāi)發(fā)了一個(gè)具有許多內(nèi)置函數(shù)的腳本引擎，所以要調(diào)用任何函數(shù)，我的代碼只是進(jìn)入了一個(gè) if .. else if .. else if 墻檢查名稱(chēng)，但我想開(kāi)發(fā)一個(gè)更有效的解決方案.

I developed a scripting engine that has many built-in functions, so to call any function, my code just went into an if .. else if .. else if wall checking the name but I would like to develop a more efficient solution.

我應(yīng)該使用 hashmap 以字符串作為鍵和指針作為值嗎?我怎么能通過(guò)使用 STL 映射來(lái)做到這一點(diǎn)?

Should I use a hashmap with strings as keys and pointers as values? How could I do it by using an STL map?

編輯:我想到的另一點(diǎn)是:當(dāng)然使用映射會(huì)迫使編譯器不內(nèi)聯(lián)函數(shù)，但我的低效方法沒(méi)有因函數(shù)調(diào)用的必要性而產(chǎn)生的任何開(kāi)銷(xiāo)，它只是執(zhí)行代碼.

EDIT: Another point that came into my mind: of course using a map will force the compiler not to inline functions, but my inefficient approach didn't have any overhead generated by the necessity of function calls, it just executes code.

所以我想知道函數(shù)調(diào)用產(chǎn)生的開(kāi)銷(xiāo)是否會(huì)比使用 if..else 鏈更好..否則我可以通過(guò)在運(yùn)行時(shí)檢查一個(gè)字符來(lái)最小化比較次數(shù)(會(huì)更長(zhǎng)但更快).

So I wonder if the overhead generated by the function call will be any better than having an if..else chain.. otherwise I could minimize the number of comparisons by checking a character at runtime (will be longer but faster).

推薦答案

無(wú)論你的函數(shù)簽名是什么:

Whatever your function signatures are:

typedef void (*ScriptFunction)(void); // function pointer type
typedef std::unordered_map<std::string, ScriptFunction> script_map;

// ...

void some_function()
{
}

// ...

script_map m;
m.emplace("blah", &some_function);

// ...

void call_script(const std::string& pFunction)
{
    auto iter = m.find(pFunction);
    if (iter == m.end())
    {
        // not found
    }

    (*iter->second)();
}

注意 ScriptFunction 類(lèi)型可以泛化為 std::function</*whatever*/> 這樣你就可以支持任何可調(diào)用的東西，而不僅僅是函數(shù)指針.

Note that the ScriptFunction type could be generalized to std::function</* whatever*/> so you can support any callable thing, not just exactly function pointers.

這篇關(guān)于使用函數(shù)指針的 STL 映射的文章就介紹到這了，希望我們推薦的答案對(duì)大家有所幫助，也希望大家多多支持html5模板網(wǎng)！