DOSBox Direct

DOS Direct is an emulation backend based on DOSBox, you can create it with the following command:

const ci = await emulators.dosboxDirect(bundle);

Direct version is universal, it can work in Node.js environment. But it has a strong disadvantage: it's working on the main browser thread. So it can easily the app froze a browser for some amount of time, and not be very responsive.

Accessing file system

In direct mode you can easily access emscripten module:

const ci = await emulators.dosboxDirect(bundle);
ci.transport.module // <-- emscripten module

Emscripten module provide lowlevel api to change file system:

const ci = await emulators.dosboxDirect(bundle);
ci.transport.module.FS // <-- emscripten FS api

You can also rescan DOS devices:

const ci = await emulators.dosboxDirect(bundle);
ci.transport.module._rescanFilesystem();

Accessing memory

In direct mode you can dump whole memory of dos:

const ci = await emulators.dosboxDirect(bundle);
ci.transport.module._dumpMemory(copyDosMemory);
ci.transport.module.memoryContents // <-- now you can access contents using this var

If you need to copy the entire memory, pass true as argument. The memoryContents contains the following:

{
        "memBase": ...,
        "ip": ...,
        "flags": ...,
        "registers": {
            "ax": ...,
            "cx": ...,
            "dx": ...,
            "sp": ...,
            "bp": ...,
            "si": ...,
            "di": ...
        },
        "segments_values": {
            "es": ...,
            "cs": ...,
            "ss": ...,
            "ds": ...,
            "fs": ...,
            "gs": ...
        },
        "segments_physical": {
            "es": ...,
            "cs": ...,
            "ss": ...,
            "ds": ...,
            "fs": ...,
            "gs": ...
        },
        "numPages": ...,
        "memoryCopy": ...
}

Pausing execution

In direct mode, you can pause the Dosbox execution loop without pausing the emscripten loop. This lets you pause and inspect the current memory, for instance.

const ci = await emulators.dosboxDirect(bundle);
ci.transport.module._pauseExecution(true);

The _pauseExecution function takes as its argument whether it should be paused or should resume. To resume once you have completed:

ci.transport.module._pauseExecution(false);

Last modified: 11 июля 2024