C ++文件不写入磁盘 [英] C++ FILE without writing to disk

问题描述

我正在使用一个函数库，它有很多函数可以写入 FILE ，但是没有一个函数可以方便地将相同的数据转储到内存中的对象。有没有办法创建一个 FILE 对象（或覆盖它），而不是写入磁盘的数据存储在内存中 - 我想避免性能击中

更新：每个Rob的建议，尝试stringstream：

  ss.put（c）; 
 
 std :: string myval = ss.str（）; 
 $ b printf（Value：％s \\\
写完之后：％i length％lu \\\
，myval.c_str（），c，myval.length（））; 
  

但是，现在试图从stringstream中获取数据我已经添加了二进制数据吗？

解决方案

除了已经提到的GNU的 fmemopen ），这在POSIX中被称为 open_memstream ，类似的解决方案可以结合 mmap（）（使用MAP_ANONYMOUS）或任何其他操作系统特定的函数，返回一个文件描述符到一块内存，编辑：这是错误的，mmap不会创建一个文件描述符。

I'm using a library that has quite a few functions that write to a FILE but none that seem to conveniently dump the same data to an object in memory. Is there any way to create a FILE object (or override it) that stores the data in memory instead of writing to disk -- I'd like to avoid the performance hit of opening/writing/reading from files over and over again.

UPDATE: per Rob's suggestion, trying stringstream:

ss.put(c);

std::string myval = ss.str();

printf("Value: %s\n after writing: %i length %lu\n",myval.c_str(),c, myval.length());

But, now trying to get the data (binary) out of the stringstream has me stuck -- how do I grab the binary data I've been adding?

解决方案

Beside the already mentioned GNU's fmemopen(), which is known in POSIX as open_memstream, similar solution can be obtained combining mmap() (using MAP_ANONYMOUS) or any other OS-specific function that returns a file descriptor to a block of memory, and fdopen().

EDIT: that was wrong, mmap doesn't create a file descriptor.

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