contextify: use offset/length from Uint8Array

Do not blindly take data from underlying `ArrayBuffer`, use `ByteOffset`/`ByteLength` of `Uint8Array` itself. Additionally, fix tests that weren't actually properly running because of V8's internal code cache. The code should be different, otherwise the cached data won't be used at all. Fix: #4939 PR-URL: #4947 Reviewed-By: Ben Noordhuis <[email protected]>

Author: indutny

src/node_contextify.cc

@@ -518,10 +518,11 @@ class ContextifyScript : public BaseObject{
 
  ScriptCompiler::CachedData* cached_data = nullptr;
 if (!cached_data_buf.IsEmpty()){
-ArrayBuffer::Contents contents =
- cached_data_buf.ToLocalChecked()->Buffer()->GetContents();
+Local<Uint8Array> ui8 = cached_data_buf.ToLocalChecked();
+ArrayBuffer::Contents contents = ui8->Buffer()->GetContents();
  cached_data = newScriptCompiler::CachedData(
-static_cast<uint8_t*>(contents.Data()), contents.ByteLength());
+static_cast<uint8_t*>(contents.Data()) + ui8->ByteOffset(),
+ ui8->ByteLength());
  }
 
  ScriptOrigin origin(filename, lineOffset, columnOffset);

test/parallel/test-vm-cached-data.js

@@ -4,30 +4,58 @@ const assert = require('assert');
 constvm=require('vm');
 constBuffer=require('buffer').Buffer;
 
-constoriginalSource='(function bcd(){return \'original\'})';
+functiongetSource(tag){
+return`(function ${tag}(){return \'${tag}\'})`;
+}
 
-// It should produce code cache
-constoriginal=newvm.Script(originalSource,{
-produceCachedData: true
-});
-assert(original.cachedDatainstanceofBuffer);
+functionproduce(source){
+constscript=newvm.Script(source,{
+produceCachedData: true
+});
+assert(script.cachedDatainstanceofBuffer);
 
-assert.equal(original.runInThisContext()(),'original');
+returnscript.cachedData;
+}
 
-// It should consume code cache
-constsuccess=newvm.Script(originalSource,{
-cachedData: original.cachedData
-});
-assert(!success.cachedDataRejected);
+functiontestProduceConsume(){
+constsource=getSource('original');
 
-assert.equal(success.runInThisContext()(),'original');
+constdata=produce(source);
 
-// It should reject invalid code cache
-constreject=newvm.Script('(function abc(){return \'invalid\'})',{
-cachedData: original.cachedData
-});
-assert(reject.cachedDataRejected);
-assert.equal(reject.runInThisContext()(),'invalid');
+// It should consume code cache
+constscript=newvm.Script(source,{
+cachedData: data
+});
+assert(!script.cachedDataRejected);
+assert.equal(script.runInThisContext()(),'original');
+}
+testProduceConsume();
+
+functiontestRejectInvalid(){
+constsource=getSource('invalid');
+
+constdata=produce(source);
+
+// It should reject invalid code cache
+constscript=newvm.Script(getSource('invalid_1'),{
+cachedData: data
+});
+assert(script.cachedDataRejected);
+assert.equal(script.runInThisContext()(),'invalid_1');
+}
+testRejectInvalid();
+
+functiontestRejectSlice(){
+constsource=getSource('slice');
+
+constdata=produce(source).slice(4);
+
+constscript=newvm.Script(source,{
+cachedData: data
+});
+assert(script.cachedDataRejected);
+}
+testRejectSlice();
 
 // It should throw on non-Buffer cachedData
 assert.throws(()=>{