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wasi: improve JavaScript API #4

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Sep 11, 2019
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wasi: improve JavaScript API #4

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118fb4f
wasi: improve JavaScript API
cjihrig Sep 9, 2019
2b0131c
wasi: support SharedArrayBuffers as memory
cjihrig Sep 10, 2019
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41 changes: 34 additions & 7 deletions lib/wasi.js
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Original file line number Diff line number Diff line change
@@ -1,9 +1,11 @@
// TODO(cjihrig): Put WASI behind a flag.
// TODO(cjihrig): Provide a mechanism to bind to WASM modules.
'use strict';
/* global WebAssembly */
const { Array, ArrayPrototype } = primordials;
const { ERR_INVALID_ARG_TYPE } = require('internal/errors').codes;
const { WASI: _WASI } = internalBinding('wasi');
const { isAnyArrayBuffer } = require('internal/util/types');


class WASI {
Expand All @@ -12,7 +14,7 @@ class WASI {
throw new ERR_INVALID_ARG_TYPE('options', 'object', options);

// eslint-disable-next-line prefer-const
let { args, env, preopens } = options;
let { args, env, preopens, memory } = options;

if (Array.isArray(args))
args = ArrayPrototype.map(args, (arg) => { return String(arg); });
Expand Down Expand Up @@ -43,12 +45,37 @@ class WASI {

// TODO(cjihrig): Validate preopen object schema.

// TODO(cjihrig): Temporarily expose these for development.
// eslint-disable-next-line no-undef
const memory = Buffer.alloc(200000);
this._memory = memory;
this._view = new DataView(memory.buffer);
this._wasi = new _WASI(args, envPairs, preopens, memory);
if (memory instanceof WebAssembly.Memory) {
memory = memory.buffer;
} else if (!isAnyArrayBuffer(memory)) {
throw new ERR_INVALID_ARG_TYPE(
'options.memory', 'WebAssembly.Memory', memory);
}

const wrap = new _WASI(args, envPairs, preopens, memory);

for (const prop in wrap) {
wrap[prop] = wrap[prop].bind(wrap);
}

this.wasiImport = wrap;
}

static start(instance) {
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What happens if instance.memory !== options.memory passed to new WASI? Should this be considered an API hazard?

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Since start() is a static method, I don't think that should matter, right?

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Right I see, but then should there be some memory binding in this method instead?

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So, I'm assuming that WASI.start() is not the same thing as the API being discussed in #3. I'm thinking of WASI.start() as more of a building block API, and #3 as a higher level API.

With that assumption, consider the following example:

'use strict';
const fs = require('fs');
const { WASI } = require('wasi');
const pathname = '/path/to/something.wasm';
const buffer = fs.readFileSync(pathname);
const memory = new WebAssembly.Memory({ initial: 1 });
const wasi = new WASI({ args: [], env: process.env, memory });

(async () => {
  const compiled = await WebAssembly.compile(buffer);
  const importObject = { wasi_unstable: wasi.wasiImport };
  const instance = await WebAssembly.instantiate(compiled, importObject);

  WASI.start(instance);
})();

In this case, WASI.start() just attempts to call the _start() or __wasi_unstable_reactor_start() export if one exists. By this point, instance should have everything bound properly, or WebAssembly.instantiate() will fail.

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I see. For commands that export their memories, a memory injection API would still likely be needed though.

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Agreed. I plan to have a WASI.prototype.setMemory() (or something along those lines) eventually.

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If setMemory can take a SharedArrayBuffer that could be awesome (although I am not sure if that is allowed)

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I just pushed up 2b0131c to this PR. It allows the memory passed to the WASI constructor to be a SharedArrayBuffer (or any other ArrayBuffer). Once setMemory() is added, it will also support SABs.

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This is really cool and useful thanks :]

if (!(instance instanceof WebAssembly.Instance)) {
throw new ERR_INVALID_ARG_TYPE(
'instance', 'WebAssembly.Instance', instance);
}

const exports = instance.exports;

if (exports === null || typeof exports !== 'object')
throw new ERR_INVALID_ARG_TYPE('instance.exports', 'Object', exports);

if (exports._start)
exports._start();
else if (exports.__wasi_unstable_reactor_start)
exports.__wasi_unstable_reactor_start();
}
}

Expand Down
43 changes: 18 additions & 25 deletions src/node_wasi.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -9,7 +9,7 @@ namespace node {
namespace wasi {

using v8::Array;
using v8::ArrayBufferView;
using v8::ArrayBuffer;
using v8::Context;
using v8::FunctionCallbackInfo;
using v8::FunctionTemplate;
Expand All @@ -26,10 +26,7 @@ WASI::WASI(Environment* env,
uvwasi_options_t* options) : BaseObject(env, object) {
/* uvwasi_errno_t err = */ uvwasi_init(&uvw_, options);

if (memory->IsNull())
memory_.Reset();
else
memory_.Reset(env->isolate(), memory.As<ArrayBufferView>());
memory_.Reset(env->isolate(), memory.As<ArrayBuffer>());
}


Expand All @@ -44,7 +41,7 @@ void WASI::New(const FunctionCallbackInfo<Value>& args) {
CHECK(args[0]->IsArray());
CHECK(args[1]->IsArray());
// CHECK(args[2]->IsArray());
CHECK(args[3]->IsArrayBufferView() || args[3]->IsNull());
CHECK(args[3]->IsArrayBuffer() || args[3]->IsSharedArrayBuffer());

Environment* env = Environment::GetCurrent(args);
Local<Context> context = env->context();
Expand Down Expand Up @@ -106,17 +103,14 @@ void WASI::ArgsGet(const FunctionCallbackInfo<Value>& args) {
CHECK(args[1]->IsUint32());
ASSIGN_OR_RETURN_UNWRAP(&wasi, args.This());
Environment* env = wasi->env();
Local<ArrayBufferView> abv = PersistentToLocal::Default(env->isolate(),
wasi->memory_);
// if (!abv->HasBuffer())
// return UVWASI_ENOBUFS;
CHECK(abv->HasBuffer());
Local<ArrayBuffer> ab = PersistentToLocal::Default(env->isolate(),
wasi->memory_);

// TODO(cjihrig): Check for buffer overflows.

uint32_t argv_offset = args[0].As<Uint32>()->Value();
uint32_t argv_buf_offset = args[1].As<Uint32>()->Value();
char* buf = static_cast<char*>(abv->Buffer()->GetContents().Data());
char* buf = static_cast<char*>(ab->GetContents().Data());
char** argv = new char*[wasi->uvw_.argc];
char* argv_buf = &buf[argv_buf_offset];
uvwasi_errno_t err = uvwasi_args_get(&wasi->uvw_, argv, argv_buf);
Expand Down Expand Up @@ -171,17 +165,14 @@ void WASI::EnvironGet(const FunctionCallbackInfo<Value>& args) {
CHECK(args[1]->IsUint32());
ASSIGN_OR_RETURN_UNWRAP(&wasi, args.This());
Environment* env = wasi->env();
Local<ArrayBufferView> abv = PersistentToLocal::Default(env->isolate(),
wasi->memory_);
// if (!abv->HasBuffer())
// return UVWASI_ENOBUFS;
CHECK(abv->HasBuffer());
Local<ArrayBuffer> ab = PersistentToLocal::Default(env->isolate(),
wasi->memory_);

// TODO(cjihrig): Check for buffer overflows.

uint32_t environ_offset = args[0].As<Uint32>()->Value();
uint32_t environ_buf_offset = args[1].As<Uint32>()->Value();
char* buf = static_cast<char*>(abv->Buffer()->GetContents().Data());
char* buf = static_cast<char*>(ab->GetContents().Data());
char** environ = new char*[wasi->uvw_.envc];
char* environ_buf = &buf[environ_buf_offset];
uvwasi_errno_t err = uvwasi_environ_get(&wasi->uvw_, environ, environ_buf);
Expand Down Expand Up @@ -380,7 +371,12 @@ void WASI::PollOneoff(const FunctionCallbackInfo<Value>& args) {


void WASI::ProcExit(const FunctionCallbackInfo<Value>& args) {
args.GetReturnValue().Set(UVWASI_ENOTSUP);
WASI* wasi;
CHECK_EQ(args.Length(), 1);
CHECK(args[0]->IsUint32());
ASSIGN_OR_RETURN_UNWRAP(&wasi, args.This());
uint32_t code = args[0].As<Uint32>()->Value();
args.GetReturnValue().Set(uvwasi_proc_exit(&wasi->uvw_, code));
}


Expand Down Expand Up @@ -416,12 +412,9 @@ void WASI::SockShutdown(const FunctionCallbackInfo<Value>& args) {

inline uvwasi_errno_t WASI::writeUInt32(uint32_t value, uint32_t offset) {
Environment* env = this->env();
Local<ArrayBufferView> abv = PersistentToLocal::Default(env->isolate(),
this->memory_);
if (!abv->HasBuffer())
return UVWASI_ENOBUFS;

uint8_t* buf = static_cast<uint8_t*>(abv->Buffer()->GetContents().Data());
Local<ArrayBuffer> ab = PersistentToLocal::Default(env->isolate(),
this->memory_);
uint8_t* buf = static_cast<uint8_t*>(ab->GetContents().Data());
// Bounds check. UVWASI_EOVERFLOW

buf[offset++] = value & 0xFF;
Expand Down
2 changes: 1 addition & 1 deletion src/node_wasi.h
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Original file line number Diff line number Diff line change
Expand Up @@ -77,7 +77,7 @@ class WASI : public BaseObject {
~WASI() override;
inline uvwasi_errno_t writeUInt32(uint32_t value, uint32_t offset);
uvwasi_t uvw_;
v8::Persistent<v8::ArrayBufferView> memory_;
v8::Persistent<v8::ArrayBuffer> memory_;
};


Expand Down