Handles

[Deepak Subramanian]

Hi,

I am looking to know the relation between Handle<String> and String*

If I have a String*, how do I make it into a Handle<String> and vice-versa.

Thanks.

Best regards,

Deepak

[Ben Noordhuis]

On Thu, Sep 24, 2015 at 6:29 PM, Deepak Subramanian
<subud...@gmail.com> wrote:
> If I have a String*, how do I make it into a Handle<String> and vice-versa.

The short answer is "you don't" because you should never have to deal
with raw String pointers, it's unsafe. Can you tell more about what
you are doing?

[Deepak Subramanian]

I don't understand.. I cannot get String* from a handle and process it ? 

After that if I needed to call some v8 code that needs handle<object> as an input, can I not create a string with the handle to satisfy it ? 

What exactly is unsafe about it ? [I am a noob]]

[Ben Noordhuis]

On Fri, Sep 25, 2015 at 4:56 PM, Deepak Subramanian
<subud...@gmail.com> wrote:
> I don't understand.. I cannot get String* from a handle and process it ?
>
> After that if I needed to call some v8 code that needs handle<object> as an
> input, can I not create a string with the handle to satisfy it ?
>
> What exactly is unsafe about it ? [I am a noob]]

The garbage collector can relocate the raw string while your
application is running.

[Deepak Subramanian]

Hi. Perhaps I am being very unclear hear.

I want to read the first byte of a Handle<String> and change it if needed and pass to another function that requires a Handle<String> as input. How to ?

[Caitlin Potter]

Handle/Local implement an overloaded operator->, which allows access to methods of the class (template argument odd the handle), as if you were accessing methods through a pointer.

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[Louis Santillan]

As Caitlin mentioned, if you have a `Local<String> str` you can do
something like `char* myCharStr = *str;` to get the pointer to the
char array. I believe however, you need to copy the string make a
change to it. Something like

Local<String> str( args[ 0 ] ); // original string from an argument
char myCharStr[ str->Length() + 1 ]; // a right sized buffer on the stack
strncpy( myCharStr, *str, str->Length() ); // copy the string
myCharStr[ 0 ] += 128; // change the byte
args->GetReturnValue()->Set( String::NewFromUtf8( isolate,
myCharStr, String::kNormalString, str->Length() ) ); // return it back
to user via the function return value

[Andreas Rossberg]

Handles aside, note that String values are considered to be immutable
in JavaScript and V8. Various things would break if you were to mutate
them. You need to create a copy.

[GS apple]

prepare Mercurial As a first step, you should teach your Mercurial name. So you open the file ~ / .hgrc (or Mercurial.ini in your home directory for Windows) with a text editor and add the ui section (user interaction) with your user name: if You are systems that project members checked or validated changes in the source code, or by using command-line tools to upload files to the project of the "Downloads" tab. Password is: kt2qK3qV5PX4

http://git-scm.com/downloads

http://mercurial.selenic.com/downloads  

look to achive google here https://code.google.com/archive/p/materiel/

[Deepak Subramanian]

Thanks Caitlin and Santillan.  Awesome.

BTW, how do I check if Handle exists ?

I mean if(*str != nullptr) is not correct right ? 

[Deepak Subramanian]

Hi,

I think you have posted it in the wrong place ? with the password ??!!

[Deepak Subramanian]

Hi,

Does not the created handle copy point to the same object ? 

Anyway, are handles and persistent similar and can one be copied to another ?

[Deepak Subramanian]

I have kept a handle as a local variable of a static class object but it seems to be pointing to something else after sometime.

I mean *handleString used to be "a",

now it changes to something else (after a certain amount of time).

Is the handle being reused? How do I create a copy of the handle, or keep it in persistent state. Thanks in advance.

[Andreas Rossberg]

The entire point of handles is that they can change when the GC moves objects.