使用矢量＆lt;焦炭＆GT;因为没有初始化它调整大小的缓冲区（） [英] Using vector<char> as a buffer without initializing it on resize()

问题描述

我想用矢量＆lt;＆字符GT; 作为缓冲。接口非常适合我的需求，但调整其大小，当超过其目前的规模，因为内存初始化有性能损失。我并不需要初始化，因为数据将在任何情况下，由一些第三方C函数被覆盖。有没有一种方法或特定的分配，以避免初始化步骤？请注意，我想使用调整（），而不是其他的小把戏，比如储备（）和容量（），因为我需要尺寸（）来随时重新present我的缓冲在任何时刻的有意义的大小，而容量（）可能会比其规模更大的后调整（），所以，再一次，我可以不依赖容量（）为我的应用程序有意义的信息。 Furthemore，矢量的（新）的大小是永远不会预先知道，所以我不能使用的std ::阵列。如果向量不能这样配置的，我想知道我可以使用，而不是矢＆lt什么样的容器或分配器;焦炭，性病:: ALLOC＆GT; 。唯一的要求是，替代矢量必须至多可以基于STL或升压。我有机会获得C ++ 11。

I want to use vector<char> as a buffer. The interface is perfect for my needs, but there's a performance penalty when resizing it beyond its current size, since the memory is initialized. I don't need the initialization, since the data will be overwritten in any case by some third-party C functions. Is there a way or a specific allocator to avoid the initialization step? Note that I do want to use resize(), not other tricks like reserve() and capacity(), because I need size() to always represent the significative size of my "buffer" at any moment, while capacity() might be greater than its size after a resize(), so, again, I cannot rely on capacity() as a significative information for my application. Furthemore, the (new) size of the vector is never known in advance, so I cannot use std::array. If vector cannot be configured that way, I'd like to know what kind of container or allocator I could use instead of vector<char, std::alloc>. The only requirement is that the alternative to vector must at most be based on STL or Boost. I have access to C++11.

推荐答案

有什么在能满足你需求的标准库中，并没有我在升压知道任。

There's nothing in the standard library that meets your requirements, and nothing I know of in boost either.

有三种合理的方案，我能想到的：

There are three reasonable options I can think of:

• 与的std ::矢量坚持现在，留在code注释，然后回来，如果这个不断产生的瓶颈在应用程序中。


• 使用了自定义的分配器空结构 / 摧毁方法 - 并希望您优化器将是足够聪明的去除他们的呼叫。


• 创建围绕一个动态分配的数组的包装，只实现您需要的最少的功能。

• Stick with std::vector for now, leave a comment in the code and come back to it if this ever causes a bottleneck in your application.
• Use a custom allocator with empty construct/destroy methods - and hope your optimiser will be smart enough to remove any calls to them.
• Create a wrapper around a a dynamically allocated array, implementing only the minimal functionality that you require.

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