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@igrep
Created December 28, 2023 03:35
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import { WASI, OpenFile, wasi } from "@bjorn3/browser_wasi_shim";
// Workaround for https://github.com/bjorn3/browser_wasi_shim/issues/14
export function patchWasi(self: WASI): void {
self.wasiImport.poll_oneoff = ((
inPtr: number,
outPtr: number,
nsubscriptions: number,
sizeOutPtr: number,
): number => {
if (nsubscriptions < 0) {
return wasi.ERRNO_INVAL;
}
const size_subscription = 48;
const subscriptions = new DataView(
self.inst.exports.memory.buffer,
inPtr,
nsubscriptions * size_subscription,
);
const size_event = 32;
const events = new DataView(
self.inst.exports.memory.buffer,
outPtr,
nsubscriptions * size_event,
);
for (let i = 0; i < nsubscriptions; ++i) {
const subscription_userdata_offset = 0;
const userdata = subscriptions.getBigUint64(
i * size_subscription + subscription_userdata_offset,
true,
);
const subscription_u_offset = 8;
const subscription_u_tag = subscriptions.getUint8(
i * size_subscription + subscription_u_offset,
);
const subscription_u_tag_size = 1;
const event_userdata_offset = 0;
const event_error_offset = 8;
const event_type_offset = 10;
const event_fd_readwrite_nbytes_offset = 16;
const event_fd_readwrite_flags_offset = 16 + 8;
events.setBigUint64(
i * size_event + event_userdata_offset,
userdata,
true,
);
events.setUint32(
i * size_event + event_error_offset,
wasi.ERRNO_SUCCESS,
true,
);
function assertOpenFileAvailable(): OpenFile {
const fd = subscriptions.getUint32(
i * size_subscription +
subscription_u_offset +
subscription_u_tag_size,
true,
);
const openFile = self.fds[fd];
if (!(openFile instanceof OpenFile)) {
throw new Error(`FD#${fd} cannot be polled!`);
}
return openFile;
}
function setEventFdReadWrite(size: bigint): void {
events.setUint16(
i * size_event + event_type_offset,
wasi.EVENTTYPE_FD_READ,
true,
);
events.setBigUint64(
i * size_event + event_fd_readwrite_nbytes_offset,
size,
true,
);
events.setUint16(
i * size_event + event_fd_readwrite_flags_offset,
0,
true,
);
}
switch (subscription_u_tag) {
case wasi.EVENTTYPE_CLOCK:
events.setUint16(
i * size_event + event_type_offset,
wasi.EVENTTYPE_CLOCK,
true,
);
break;
case wasi.EVENTTYPE_FD_READ:
const fileR = assertOpenFileAvailable();
setEventFdReadWrite(fileR.file.size);
break;
case wasi.EVENTTYPE_FD_WRITE:
// I'm not sure why, but an unavailable (already closed) FD is referenced here. So don't call assertOpenFileAvailable.
setEventFdReadWrite(1n << 31n);
break;
default:
throw new Error(`Unknown event type: ${subscription_u_tag}`);
}
}
const size_size = 4;
const outNSize = new DataView(
self.inst.exports.memory.buffer,
sizeOutPtr,
size_size,
);
outNSize.setUint32(0, nsubscriptions, true);
return wasi.ERRNO_SUCCESS;
}) as (...args: unknown[]) => unknown;
}
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