wasi: make preopen directories configurable

lib/wasi.js

@@ -2,7 +2,7 @@
 // TODO(cjihrig): Provide a mechanism to bind to WASM modules.
 'use strict';
 /* global WebAssembly */
-const { Array, ArrayPrototype } = primordials;
+const { Array, ArrayPrototype, Object } = primordials;
 const { ERR_INVALID_ARG_TYPE } = require('internal/errors').codes;
 const { WASI: _WASI } = internalBinding('wasi');
 const kSetMemory = Symbol('setMemory');
@@ -35,17 +35,18 @@ class WASI {
       throw new ERR_INVALID_ARG_TYPE('options.env', 'Object', env);
     }
 
-    if (preopens == null) {
-      preopens = null;
-    } else if (typeof preopens !== 'object') {
+    const preopenArray = [];
+
+    if (typeof preopens === 'object' && preopens !== null) {
+      Object.keys(preopens).forEach((key) => {
+        preopenArray.push(String(key));
+        preopenArray.push(String(preopens[key]));
+      });
+    } else if (preopens !== undefined) {
       throw new ERR_INVALID_ARG_TYPE('options.preopens', 'Object', preopens);
-    } else {
-      //
     }
 
-    // TODO(cjihrig): Validate preopen object schema.
-
-    const wrap = new _WASI(args, envPairs, preopens);
+    const wrap = new _WASI(args, envPairs, preopenArray);
 
     for (const prop in wrap) {
       wrap[prop] = wrap[prop].bind(wrap);

src/node_wasi.cc

@@ -81,7 +81,7 @@ void WASI::New(const FunctionCallbackInfo<Value>& args) {
   CHECK_EQ(args.Length(), 3);
   CHECK(args[0]->IsArray());
   CHECK(args[1]->IsArray());
-  // CHECK(args[2]->IsArray());
+  CHECK(args[2]->IsArray());
 
   Environment* env = Environment::GetCurrent(args);
   Local<Context> context = env->context();
@@ -113,12 +113,23 @@ void WASI::New(const FunctionCallbackInfo<Value>& args) {
   }
   options.envp[envc] = nullptr;
 
-  // TODO(cjihrig): Process the preopens for real.
-  options.preopenc = 1;
-  options.preopens =
-    static_cast<uvwasi_preopen_t*>(calloc(1, sizeof(uvwasi_preopen_t)));
-  options.preopens[0].mapped_path = "/sandbox";
-  options.preopens[0].real_path = ".";
+  Local<Array> preopens = args[2].As<Array>();
+  CHECK_EQ(preopens->Length() % 2, 0);
+  options.preopenc = preopens->Length() / 2;
+  options.preopens = static_cast<uvwasi_preopen_t*>(
+    calloc(options.preopenc, sizeof(uvwasi_preopen_t)));
+  int index = 0;
+  for (uint32_t i = 0; i < preopens->Length(); i += 2) {
+    auto mapped = preopens->Get(context, i).ToLocalChecked();
+    auto real = preopens->Get(context, i + 1).ToLocalChecked();
+    CHECK(mapped->IsString());
+    CHECK(real->IsString());
+    node::Utf8Value mapped_path(env->isolate(), mapped);
+    node::Utf8Value real_path(env->isolate(), real);
+    options.preopens[index].mapped_path = strdup(*mapped_path);
+    options.preopens[index].real_path = strdup(*real_path);
+    index++;
+  }
 
   new WASI(env, args.This(), &options);
 

test/wasi/c/read_file.c

@@ -7,7 +7,8 @@ int main() {
 
   char c = fgetc(file);
   while (c != EOF) {
-    assert(fputc(c, stdout) != EOF);
+    int wrote = fputc(c, stdout);
+    assert(wrote != EOF);
     c = fgetc(file);
   }
 }

test/wasi/test-wasi.js

@@ -2,11 +2,18 @@
 require('../common');
 
 if (process.argv[2] === 'wasi-child') {
+  const fixtures = require('../common/fixtures');
   const fs = require('fs');
   const path = require('path');
   const { WASI } = require('wasi');
   const wasmDir = path.join(__dirname, 'wasm');
-  const wasi = new WASI({ args: [], env: process.env });
+  const wasi = new WASI({
+    args: [],
+    env: process.env,
+    preopens: {
+      '/sandbox': fixtures.path('wasi')
+    }
+  });
   const importObject = { wasi_unstable: wasi.wasiImport };
   const modulePath = path.join(wasmDir, `${process.argv[3]}.wasm`);
   const buffer = fs.readFileSync(modulePath);