問題描述
我聽說過一些關(guān)于用 Java 編寫設(shè)備驅(qū)動(dòng)程序的消息(聽說是用我的耳朵"而不是從互聯(lián)網(wǎng)上聽到的)并且想知道......我一直認(rèn)為設(shè)備驅(qū)動(dòng)程序是在操作系統(tǒng)級(jí)別上運(yùn)行的，因此必須用與操作系統(tǒng)相同的語言(因此主要是 CI 假設(shè))
I heard something about writing device drivers in Java (heard as in "with my ears", not from the internet) and was wondering... I always thought device drivers operated on an operating system level and thus must be written in the same language as the OS (thus mostly C I suppose)
- 我一般是錯(cuò)的嗎假設(shè)?(好像是這樣)
- 外星人"中的司機(jī)如何操作系統(tǒng)中使用的語言?
- 有什么要求(來自編程語言的觀點(diǎn))無論如何都需要設(shè)備驅(qū)動(dòng)程序?
感謝閱讀
推薦答案
有幾種方法可以做到這一點(diǎn).
There are a couple of ways this can be done.
首先，在操作系統(tǒng)級(jí)別"運(yùn)行的代碼不需要使用與操作系統(tǒng)相同的語言編寫.它只需要能夠與操作系統(tǒng)代碼鏈接在一起.幾乎所有語言都可以與 C 互操作，而這正是我們所需要的.
First, code running at "OS level" does not need to be written in the same language as the OS. It merely has to be able to be linked together with OS code. Virtually all languages can interoperate with C, which is really all that's needed.
所以語言方面，技術(shù)上沒有問題.Java函數(shù)可以調(diào)用C函數(shù)，C函數(shù)可以調(diào)用Java函數(shù).如果操作系統(tǒng)不是用 C 編寫的(比如說，為了論證它是用 C++ 編寫的)，那么操作系統(tǒng) C++ 代碼可以調(diào)用一些中間 C 代碼，這些代碼會(huì)轉(zhuǎn)發(fā)給你的 Java，反之亦然.C 幾乎是編程的一種通用語言.
So language-wise, there is technically no problem. Java functions can call C functions, and C functions can call Java functions. And if the OS isn't written in C (let's say, for the sake of argument that it's written in C++), then the OS C++ code can call into some intermediate C code, which forwards to your Java, and vice versa. C is pretty much a lingua franca of programming.
程序一旦被編譯(編譯為本機(jī)代碼)，其源語言就不再相關(guān).無論源代碼在編譯之前是用哪種語言編寫的，匯編程序看起來都差不多.只要你使用與操作系統(tǒng)相同的調(diào)用約定，就沒有問題.
Once a program has been compiled (to native code), its source language is no longer relevant. Assembler looks much the same regardless of which language the source code was written in before compilation. As long as you use the same calling convention as the OS, it's no problem.
更大的問題是運(yùn)行時(shí)支持.操作系統(tǒng)中沒有很多軟件服務(wù)可用.例如，通常沒有 Java 虛擬機(jī).(從技術(shù)上講，沒有理由不存在，但通常，但通常可以安全地假設(shè)它不存在).
A bigger problem is runtime support. Not a lot of software services are available in the OS. There usually is no Java virtual machine, for example. (There is no reason why there technically couldn't be, but usually, but usually, it's safe to assume that it's not present).
不幸的是，在其默認(rèn)"表示中，作為 Java 字節(jié)碼，Java 程序需要很多基礎(chǔ)設(shè)施.它需要Java VM來解釋和JIT字節(jié)碼，它需要類庫等等.
Unfortunately, in its "default" representation, as Java bytecode, a Java program requires a lot of infrastructure. It needs the Java VM to interpret and JIT the bytecode, and it needs the class library and so on.
但是有兩種方法可以解決這個(gè)問題:
But there are two ways around this:
- 在內(nèi)核中支持 Java.這將是一個(gè)不尋常的步驟，但可以做到.
- 或者將您的 Java 源代碼編譯為本機(jī)格式.Java 程序不必編譯為 Java 字節(jié)碼.您可以將其編譯為 x86 匯編程序.這同樣適用于您使用的任何類庫.這些也可以一直編譯到匯編程序.當(dāng)然，部分 Java 類庫需要某些不可用的操作系統(tǒng)功能，但可以避免使用這些類.
所以是的，這是可以做到的.但這并不簡單，也不清楚你會(huì)得到什么.
So yes, it can be done. But it's not straightforward, and it's unclear what you'd gain.
當(dāng)然，另一個(gè)問題可能是 Java 不允許您訪問任意內(nèi)存位置，這會(huì)使很多硬件通信變得非常棘手.但這也可以解決，也許可以通過調(diào)用非常簡單的 C 函數(shù)來簡單地將相關(guān)的內(nèi)存區(qū)域作為數(shù)組返回，供 Java 處理.
Of course another problem may be that Java won't let you access arbitrary memory locations, which would make a lot of hardware communication pretty tricky. But that could be worked around too, perhaps by calling into very simple C functions which simply return the relevant memory areas as arrays for Java to work on.
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