Handle file descriptors as usize

[saza-ku]

File descriptors are handled as i32 in WASI functions arguments, like this.

pub export fn fd_close(fd: i32) callconv(.C) WasiError

We pass them around as i32. But indices must be usize in Zig, so we must cast them every time we index the file descriptor table.

    pub fn get(self: *Self, fd: i32) ?*Stream {
        const streams = self.streams.acquire();
        defer self.streams.release();
        const s = &streams.*[@as(usize, @intCast(fd))];
        if (s.* == null) {
            return null;
        }

        return @as(*Stream, @ptrCast(s));
    }

To avoid it, we want to cast fd to usize in WASI functions, and handle it as usize in stream module.

[dierbei]

@saza-ku I'd like to try to fix that.

[saza-ku]

Sure!

[dierbei]

@saza-ku I'd like to wait for those two pull requests to merge before making changes.

Eventually they can be tested together.

[saza-ku]

Now they are merged!

[dierbei]

@saza-ku I have a problem now.

The previous i32 was 4 bytes, the usize needs 8 bytes to be aligned, something needs to be changed if I switch to usize.

usize, on 64-bit platforms, has an alignment of 8, This was also my first exposure to the concept.

But at the moment I don't know what will happen.

// old code
const fd1 = @as(*usize, @ptrFromInt(4 + linear_memory_offset));

// new code
const fd1 = @as(*usize, @ptrFromInt(8 + linear_memory_offset));

I'll have to keep testing it.

[saza-ku]

Is this code in the integration tests?
If so we could just rearrange memory address.

Are there any other codes which need some fixes about alignment?

[dierbei]

@saza-ku Yes, there are many areas that need to be modified.

But now I have a problem, the test functions（testClientSocket、testServerSocket） seem to be running at the same time, because their logs seem to be printing at the same time:

mewz/src/wasi.zig

Lines 644 to 650 in 0c6724f

	if (!testClientSocket()) {
	return;
	}
	if (!testServerSocket()) {
	return;
	}

Is this normal? I don't quite understand this test now.

My thought is that if they are running at the same time, will this cause the data to be overwritten.

[saza-ku]

@dierbei Sorry for being late! I had a paper due.

But now I have a problem, the test functions（testClientSocket、testServerSocket） seem to be running at the same time, because their logs seem to be printing at the same time:

Mewz is single thread, so it should be impossible.

You debug it on Codespaces, right? I think #65 would be related. I'll investigate the issue first.

[dierbei]

Sorry for being late! I had a paper due.

It's okay, I'm always on.