通过JNA传递的InputStream C code作为一个文件指针 [英] Pass InputStream through JNA to C code as a File Pointer

问题描述

我有写在C（即我不能编辑）一个DLL，它有一定的函数原型看起来像

I've got a DLL written in C (that I can't edit) that has some function prototype that looks like

#include <stdio.h>
void foo(FILE *bar);

我想创建一个JNA接口DLL，它是不清楚我需要通过为FILE *酒吧的说法。我想我需要传递一个InputStream（这是我的preference），但JNA文学似乎关于这个问题的很少。

I'd like to create a JNA interface to the DLL and it's unclear what I need to pass for the FILE *bar argument. I assume I need to pass an InputStream (which is my preference), but the JNA literature seems sparse on the subject.

将在Java接口是什么样的？什么才是我真正需要传递到foo？

What would the Java interface look like? and what do I really need to pass to foo?

编辑：富假定酒吧是FOPEN的结果，并要求操作，如的fscanf

foo assumes bar is the result of an fopen and calls operations like fscanf.

编辑2：最终，我在Java中的字符串，我需要用C阅读就好像它是一个文件，（这可能是一个不同的问题完全）。理想情况下，我想，以避免写文件，这就是为什么一个InputStream转换为C文件指针是那么理想（看样子相当困难）。

Edit 2: Ultimately, I have a string in Java that I need to read in C as if it were a file, (which might be a different question altogether). Ideally I'd like to avoid writing the file, which is why converting an InputStream to a C file pointer is so desirable (and evidently quite difficult).

推荐答案

我不相信你可以做到这一点 - 你有没有简单的方法来访问的的内部的InputStream 实例，甚至是的FileInputStream 将最有可能不是一个stdio FILE之上实现*。要查看您的Java接口应该是什么样的，你需要发布更多有关富功能 - 它做什么以及如何使用它

I don't believe you can do this - you have no easy way to access the internals of of an InputStream instance, and even a FileInputStream will most likely not be implemented on top of a stdio FILE *. To see what your Java interface should be like, you'll need to post more about the foo function - what it does and how you use it.

如果你不关心什么<​​code> FILE * 实际上做，您可以使用JNA调用 code高达FOPEN ，传递文件名和开模，并通过对富，如结果传递作为一个不透明的价值（伪code）：

If you don't care about what the FILE * actually does, you can code up using JNA to call fopen, passing in the file name and open mode, and pass the result as an opaque value through to foo, e.g. (pseudocode):

path = "MyFile.txt";
bar = Libc.fopen(path, "r");
Libfoo.foo(bar);

更新：如果您需要有一个包含，如果它是在一个文件，你需要处理的数据的字符串，我觉得你的运气了。不幸的是，标准C库不是建立在流抽象，这意味着你不太可能能够达到你想要什么，除非你可以打开什么看起来像一个文件名，但会导致你的字符串数据之上;然而，这将是非常非常容易硬着头皮和字符串保存到一个临时文件，然后打开与的fopen ： - （

Update: If you need to have a string which contains data which you need treated as if it were in a file, I think you are out of luck. Unfortunately, the standard C library is not built on top of a stream abstraction, which means that you are unlikely to be able to achieve what you want unless you can open what looks like a filename but leads to your string data; however, it's going to be much, much easier to bite the bullet and save the string to a temporary file, then open that with fopen :-(

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