threadman_thread.js

/* global WebAssembly */

export default function thread(self) {
    const MAXMEM = 32767;
    let instance;
    let memory;

    if (self) {
        self.onmessage = function(e) {
            let data;
            if (e.data) {
                data = e.data;
            } else {
                data = e;
            }

            if (data[0].cmd == "INIT") {
                init(data[0]).then(function() {
                    self.postMessage(data.result);
                });
            } else if (data[0].cmd == "TERMINATE") {
                process.exit();
            } else {
                const res = runTask(data);
                self.postMessage(res);
            }
        };
    }

    async function init(data) {
        const code = new Uint8Array(data.code);
        const wasmModule = await WebAssembly.compile(code);
        memory = new WebAssembly.Memory({initial:data.init, maximum: MAXMEM});

        instance = await WebAssembly.instantiate(wasmModule, {
            env: {
                "memory": memory
            }
        });
    }



    function alloc(length) {
        const u32 = new Uint32Array(memory.buffer, 0, 1);
        while (u32[0] & 3) u32[0]++;  // Return always aligned pointers
        const res = u32[0];
        u32[0] += length;
        if (u32[0] + length > memory.buffer.byteLength) {
            const currentPages = memory.buffer.byteLength / 0x10000;
            let requiredPages = Math.floor((u32[0] + length) / 0x10000)+1;
            if (requiredPages>MAXMEM) requiredPages=MAXMEM;
            memory.grow(requiredPages-currentPages);
        }
        return res;
    }

    function allocBuffer(buffer) {
        const p = alloc(buffer.byteLength);
        setBuffer(p, buffer);
        return p;
    }

    function getBuffer(pointer, length) {
        const u8 = new Uint8Array(memory.buffer);
        return new Uint8Array(u8.buffer, u8.byteOffset + pointer, length);
    }

    function setBuffer(pointer, buffer) {
        const u8 = new Uint8Array(memory.buffer);
        u8.set(new Uint8Array(buffer), pointer);
    }

    function runTask(task) {
        if (task[0].cmd == "INIT") {
            return init(task[0]);
        }
        const ctx = {
            vars: [],
            out: []
        };
        const u32a = new Uint32Array(memory.buffer, 0, 1);
        const oldAlloc = u32a[0];
        for (let i=0; i<task.length; i++) {
            switch (task[i].cmd) {
            case "ALLOCSET":
                ctx.vars[task[i].var] = allocBuffer(task[i].buff);
                break;
            case "ALLOC":
                ctx.vars[task[i].var] = alloc(task[i].len);
                break;
            case "SET":
                setBuffer(ctx.vars[task[i].var], task[i].buff);
                break;
            case "CALL": {
                const params = [];
                for (let j=0; j<task[i].params.length; j++) {
                    const p = task[i].params[j];
                    if (typeof p.var !== "undefined") {
                        params.push(ctx.vars[p.var] + (p.offset || 0));
                    } else if (typeof p.val != "undefined") {
                        params.push(p.val);
                    }
                }
                instance.exports[task[i].fnName](...params);
                break;
            }
            case "GET":
                ctx.out[task[i].out] = getBuffer(ctx.vars[task[i].var], task[i].len).slice();
                break;
            default:
                throw new Error("Invalid cmd");
            }
        }
        const u32b = new Uint32Array(memory.buffer, 0, 1);
        u32b[0] = oldAlloc;
        return ctx.out;
    }


    return runTask;
}