> First, how big is the data member of the object ?
As I said before. Capacity is the size of the memory allocated that data
points at.
> Is it as big as the actual array buffer length which I declare on
JavaScript
It will be either as big, or bigger. It can grow.
bytes_used will be the size that matches javascript.
> which I can build on top of it a typedarray ?
This is a slightly different question, (and needs clarifying)
When you create a typedarray in C++, it needs an array buffer.
When you create a typedarray in javascript, it will have an array buffer
behind it. (which you may or may not have created in javascript or c++,
there are several ways of approaching this)
> So, when a typedarray is build on top of an areaybuffer instance, how do
I get to call the arraybufferbuilder::append ?
Aha! a more specific question!
Are you trying to call arraybufferbuilder::append in javascript, or c++?
Why? are you trying to make a typedarray bigger? (in javascript or c++?)
I believe once created they're a fixed size in javascript.
I have a feeling on the c++ side, you can't change the size once created
(but I may be wrong, you have direct access to the buffer's buffercontents
via the bufferview...)
Can you make your question a lot more specific? post some code?
On Monday, 10 September 2018 22:38:16 UTC+1, dan Med wrote:
>
> First, how big is the data member of the object ? Is it as big as the
> actual array buffer length which I declare on JavaScript and which I can
> build on top of it a typedarray ?
>
> No, I’m just trying to understand how v8 works, I know it is a big thing
> but at least how it moves then I might read the code and understand, extra
> parts.
>
> So, when a typedarray is build on top of an areaybuffer instance, how do I
> get to call the arraybufferbuilder::append ?
>
>
>
>
>
> On Mon, 10 Sep 2018 at 23:30, @soylentgraham <gra...@grahamreeves.com
> <javascript:>> wrote:
>
>> I'm guessing you may be a bit new to unmanaged-memory languages/systems.
>>
>> buffer is an object, (it's structure/layout will look a bit like it's
>> class declaration, but it's a little more complex than that) that was
>> allocated somewhere sometime, (you can figure out where, but really you
>> don't need to, for this purpose it's just an object)
>> data is a member of that object, that points to some memory (somewhere
>> else, maybe allocated by a different system, in a different place)
>> you have no idea (and you shouldn't need to know, or use the information)
>> the "offset" from the buffer-object to the data. They are not necessarily
>> related, or share the same memory space. (and in most cases, they're not
>> even real memory addresses, they're more like identifiers)
>>
>> Simple Javascript scripts can look like C sometimes (a few variables here
>> and there, a few array creations), but underneath it's doing a lot more
>> moving things around.
>> function x()
>> {
>> var a = new array(10);
>> var b = new array(100);
>> }
>> This may look like it allocates 2 arrays, but more than likely it's doing
>> something radically different with actual memory.
>>
>>
>> > so how can i see the memory management ?
>> As I said, you can't see the javascript side so easily (other than using
>> the v8 debugging/inspector tools)
>> But if you want to see the C-side memory (which MAY be where the data
>> that buffer points at came from) you can make your own allocator that v8
>> can use.
>> If you then breakpoint each call, you'll know when V8 is allocating some
>> memory to use (which may or may not be a direct object in javascript, an
>> array or typed array in javascript may not directly allocate here)
>>
>>
>> class TV8Allocator : public v8::ArrayBuffer::Allocator
>>
>> {
>>
>> public:
>>
>> virtual void* Allocate(size_t length) override;
>>
>> virtual void* AllocateUninitialized(size_t length) override;
>>
>> virtual void Free(void* data, size_t length) override;
>>
>> };
>>
>>
>> void* TV8Allocator::Allocate(size_t length)
>>
>> {
>>
>> auto* Bytes = new uint8_t[length];
>>
>> for ( auto i=0; i<length; i++ )
>>
>> Bytes[i] = 0;
>>
>> return Bytes;
>>
>> }
>>
>>
>> void* TV8Allocator::AllocateUninitialized(size_t length)
>>
>> {
>>
>> auto* Bytes = new uint8_t[length];
>>
>> return Bytes;
>>
>> }
>>
>>
>> void TV8Allocator::Free(void* data, size_t length)
>>
>> {
>>
>> auto* data8 = reinterpret_cast<uint8_t*>(data);
>>
>> delete[] data8;
>>
>> }
>>
>> v8::Isolate::CreateParams create_params;
>>
>> create_params.array_buffer_allocator = &mAllocator;
>>
>>
>>
>> > Cause i saw the code but didn't find how it handles all the possible
>> javascript i might write into a script file....
>>
>>
>> Your computer most likely has more memory than you'll ever write in a
>> script :)
>>
>> If you're trying to work out where your script goes... arraybuffer isn't
>> the right place.
>>
>>
>> Do you NEED to know? What exactly are you trying to achieve? (take a
>> step back from the code and describe what you're trying to do;
>>
>> are you trying to make an app? learn how memory works in c++? learn how
>> memory is used in javascript? Why your app uses 1gb of memory?
>>
>>
>>
>>
>> On Monday, 10 September 2018 22:10:54 UTC+1, dan Med wrote:
>>>
>>> How big is the offset from buffer to data ?
>>> const void* Data
>>> <https://cs.chromium.org/chromium/src/third_party/blink/renderer/platform/wtf/typed_arrays/array_buffer_builder.h?l=80&gs=kythe%253A%252F%252Fchromium%253Flang%253Dc%25252B%25252B%253Fpath%253Dsrc%252Fthird_party%252Fblink%252Frenderer%252Fplatform%252Fwtf%252Ftyped_arrays%252Farray_buffer_builder.h%2523b8F1aEDx%25252F6En%25252FkOKh2zVkvONjtDNg9gr5KG7gT9XeJk%25253D&gsn=Data&ct=xref_usages>()
>>>
>>> const { return buffer_
>>> <https://cs.chromium.org/chromium/src/third_party/blink/renderer/platform/wtf/typed_arrays/array_buffer_builder.h?l=94&ct=xref_jump_to_def&gsn=buffer_>
>>> ->
>>> <https://cs.chromium.org/chromium/src/base/memory/scoped_refptr.h?l=218&ct=xref_jump_to_def&gsn=-%3E>
>>> Data
>>> <https://cs.chromium.org/chromium/src/third_party/blink/renderer/platform/wtf/typed_arrays/array_buffer.h?l=225&ct=xref_jump_to_def&gsn=Data>();
>>>
>>> }
>>>
>>> sorry for spamming emails, i will try to condensate more
>>>
>>> Il giorno lun 10 set 2018 alle ore 23:07 dan Med <litoki...@gmail.com>
>>> ha scritto:
>>>
>>>> Cause i saw the code but didn't find how it handles all the possible
>>>> javascript i might write into a script file....
>>>>
>>>> Il giorno lun 10 set 2018 alle ore 23:06 dan Med <litoki...@gmail.com>
>>>> ha scritto:
>>>>
>>>>> But after using it for a little while, I have found v8 in general is
>>>>> pretty simple. It provides an interface to C functions and memory. This
>>>>> is
>>>>> kinda what it's for.
>>>>>
>>>>> so how can i see the memory management ?
>>>>>
>>>>>
>>>>> Il giorno lun 10 set 2018 alle ore 23:06 dan Med <litoki...@gmail.com>
>>>>> ha scritto:
>>>>>
>>>>>> So, the hole length of this raw memory is set to be Data ? And to use
>>>>>> it i should create a view on top of it like with typedarrays?
>>>>>>
>>>>>>
>>>>>> So to call arraybuffer::append i should first, try to make the typed
>>>>>> array bigger that action will call the arraybuffer::append ? i didn't
>>>>>> ask
>>>>>> how memcpy work, i didn't get the Data() thing, in the class that's all.
>>>>>>
>>>>>> Il giorno lun 10 set 2018 alle ore 22:55 @soylentgraham <
>>>>>> gra...@grahamreeves.com> ha scritto:
>>>>>>
>>>>>>> > How can i understand the structure in memory of an arraybuffer and
>>>>>>> > how big is the data field which is pointed by this void pointerIt has
>>>>>>> > no structure. It is just a series of linear bytes, raw memory,
>>>>>>> > allocated by the memory allocator. (If you implement your own memory
>>>>>>> > allocator you can catch when this happens)It's just the data(buffer)
>>>>>>> > for an array.
>>>>>>> > How are they represented in memory....It IS memory. It's nothing more
>>>>>>> > (it's an array of bytes)
>>>>>>> > How big is the data field ?If by "field", you mean, the data
>>>>>>> > buffer... it's Capacity
>>>>>>> > <https://cs.chromium.org/chromium/src/third_party/blink/renderer/platform/wtf/typed_arrays/array_buffer_builder.h?l=76&gs=kythe%253A%252F%252Fchromium%253Flang%253Dc%25252B%25252B%253Fpath%253Dsrc%252Fthird_party%252Fblink%252Frenderer%252Fplatform%252Fwtf%252Ftyped_arrays%252Farray_buffer_builder.h%2523kB%25252BJ1WxDvoDqf1c8Tz5Ol3yne4lD03cRpevK2LHMUZk%25253D&gsn=Capacity&ct=xref_usages>
>>>>>>> > (capacity is how much it can fit) in length. But not how much is
>>>>>>> > being used. (bytes_used)
>>>>>>> If you're curious about when memory grows, reallocates, is written to,
>>>>>>> accessed... it might be worth setting up your environment so you can
>>>>>>> debug it by stepping through the code as it executes. You can watch
>>>>>>> memory, (this would show what memcpy changes) see the values passed
>>>>>>> around, track when memory gets allocated etc.
>>>>>>> Your questions are a mix of very broad, ("How does v8 work") and very
>>>>>>> specific programming questions (what is memcpy() doing)Broad questions
>>>>>>> are very hard to answer in general. ("How does a car work")
>>>>>>>
>>>>>>> I agree, simply browsing the code doesn't give a good overview of say,
>>>>>>> how the javascript compiler works, or how memory is utilised. (How it
>>>>>>> is allocated is very simple, on the C/++ side it doesn't implement any
>>>>>>> memory management, and the array buffer/view is a view of the C-side
>>>>>>> memory)But after using it for a little while, I have found v8 in
>>>>>>> general is pretty simple. It provides an interface to C functions and
>>>>>>> memory. This is kinda what it's for.
>>>>>>> But the point of v8 is that it does a lot of that for you. I don't
>>>>>>> REALLY need to know how the memory is tracked on the javascript side,
>>>>>>> it just works (if I'm using the API correctly)Then again, if you NEED
>>>>>>> to know how it works for a specific purpose (very restricted memory,
>>>>>>> fixing a bug), we can help you a lot more easily by answering a very
>>>>>>> specific question. ("My car's low-oil light is blinking, where do I
>>>>>>> fill it up")
>>>>>>> If you're just curious as to how the entire v8 engine works... that's a
>>>>>>> massive ask. A lot of people work on it, and there is a lot of work and
>>>>>>> topics involved.Your best bet is reading the (limited) documentation on
>>>>>>> the wiki, and read the blog posts https://v8project.blogspot.com/ which
>>>>>>> go into quite a lot of detail on each post topic.I've not seen any real
>>>>>>> general overview (the wiki itself says it's out of date) so, stepping
>>>>>>> through all the code as it executes is probably your best bet.
>>>>>>>
>>>>>>>
>>>>>>> On Monday, 10 September 2018 21:25:37 UTC+1, dan Med wrote:
>>>>>>>>
>>>>>>>> in this snippet for example
>>>>>>>>
>>>>>>>> namespace WTF
>>>>>>>> <https://cs.chromium.org/chromium/src/third_party/blink/renderer/platform/wtf/typed_arrays/array_buffer_builder.h?l=40&gs=kythe%253A%252F%252Fchromium%253Flang%253Dc%25252B%25252B%2523WTF%252523n%252523namespace&gsn=WTF&ct=xref_usages>
>>>>>>>> {// A utility class to build an ArrayBuffer instance. Validity must
>>>>>>>> be checked// by isValid() before using an instance.class WTF_EXPORT
>>>>>>>> <https://cs.chromium.org/chromium/src/third_party/blink/renderer/platform/wtf/wtf_export.h?l=46&ct=xref_jump_to_def&gsn=WTF_EXPORT>
>>>>>>>> ArrayBufferBuilder
>>>>>>>> <https://cs.chromium.org/chromium/src/third_party/blink/renderer/platform/wtf/typed_arrays/array_buffer_builder.h?l=44&gs=kythe%253A%252F%252Fchromium%253Flang%253Dc%25252B%25252B%253Fpath%253Dsrc%252Fthird_party%252Fblink%252Frenderer%252Fplatform%252Fwtf%252Ftyped_arrays%252Farray_buffer_builder.h%2523ArrayBufferBuilder%25253AWTF%252523c%252523hTnYOn1mFcU%2Bkythe%253A%252F%252Fchromium%253Flang%253Dc%25252B%25252B%253Fpath%253Dsrc%252Fthird_party%252Fblink%252Frenderer%252Fplatform%252Fwtf%252Ftyped_arrays%252Farray_buffer_builder.h%2523NyhHD05MjDx8XOe1m%25252BLqXBLvqdjWPsLmDrRvvmR2Ywk%25253D&gsn=ArrayBufferBuilder&ct=xref_usages>
>>>>>>>> final { // Disallow copying since it's expensive and we don't want
>>>>>>>> code to do it by // accident. USING_FAST_MALLOC
>>>>>>>> <https://cs.chromium.org/chromium/src/third_party/blink/renderer/platform/wtf/allocator.h?l=146&ct=xref_jump_to_def&gsn=USING_FAST_MALLOC>(ArrayBufferBuilder
>>>>>>>>
>>>>>>>> <https://cs.chromium.org/chromium/src/third_party/blink/renderer/platform/wtf/typed_arrays/array_buffer_builder.h?l=44&ct=xref_jump_to_def&gsn=ArrayBufferBuilder>);
>>>>>>>> public: // Creates an ArrayBufferBuilder using the default capacity.
>>>>>>>> ArrayBufferBuilder
>>>>>>>> <https://cs.chromium.org/chromium/src/third_party/blink/renderer/platform/wtf/typed_arrays/array_buffer_builder.h?l=51&gs=kythe%253A%252F%252Fchromium%253Flang%253Dc%25252B%25252B%253Fpath%253Dsrc%252Fthird_party%252Fblink%252Frenderer%252Fplatform%252Fwtf%252Ftyped_arrays%252Farray_buffer_builder.h%2523me5JBk4wDIaIJCK86MiUpy%25252BnGYRZwEr0AvVg3KaU0pw%25253D&gsn=ArrayBufferBuilder&ct=xref_usages>();
>>>>>>>> ArrayBufferBuilder
>>>>>>>> <https://cs.chromium.org/chromium/src/third_party/blink/renderer/platform/wtf/typed_arrays/array_buffer_builder.h?l=53&gs=kythe%253A%252F%252Fchromium%253Flang%253Dc%25252B%25252B%253Fpath%253Dsrc%252Fthird_party%252Fblink%252Frenderer%252Fplatform%252Fwtf%252Ftyped_arrays%252Farray_buffer_builder.h%2523VW0P45Tk9IGjtOqM%25252B9dHdJ64so3WDAfcY1jNBLt0GNY%25253D&gsn=ArrayBufferBuilder&ct=xref_usages>(unsigned
>>>>>>>> capacity
>>>>>>>> <https://cs.chromium.org/chromium/src/third_party/blink/renderer/platform/wtf/typed_arrays/array_buffer_builder.h?l=53&gs=kythe%253A%252F%252Fchromium%253Flang%253Dc%25252B%25252B%253Fpath%253Dsrc%252Fthird_party%252Fblink%252Frenderer%252Fplatform%252Fwtf%252Ftyped_arrays%252Farray_buffer_builder.h%2523trfcCH7BPCRWiubGq1QF9bypkCRNYtWGHb2AzglMces%25253D&gsn=capacity&ct=xref_usages>)
>>>>>>>> : bytes_used_
>>>>>>>> <https://cs.chromium.org/chromium/src/third_party/blink/renderer/platform/wtf/typed_arrays/array_buffer_builder.h?l=92&ct=xref_jump_to_def&gsn=bytes_used_>(0),
>>>>>>>> variable_capacity_
>>>>>>>> <https://cs.chromium.org/chromium/src/third_party/blink/renderer/platform/wtf/typed_arrays/array_buffer_builder.h?l=93&ct=xref_jump_to_def&gsn=variable_capacity_>(true)
>>>>>>>> { buffer_
>>>>>>>> <https://cs.chromium.org/chromium/src/third_party/blink/renderer/platform/wtf/typed_arrays/array_buffer_builder.h?l=94&ct=xref_jump_to_def&gsn=buffer_>
>>>>>>>> =
>>>>>>>> <https://cs.chromium.org/chromium/src/base/memory/scoped_refptr.h?l=226&ct=xref_jump_to_def&gsn=%3D>
>>>>>>>> ArrayBuffer
>>>>>>>> <https://cs.chromium.org/chromium/src/third_party/blink/renderer/platform/wtf/typed_arrays/array_buffer.h?l=42&ct=xref_jump_to_def&gsn=ArrayBuffer>::Create
>>>>>>>>
>>>>>>>> <https://cs.chromium.org/chromium/src/third_party/blink/renderer/platform/wtf/typed_arrays/array_buffer.h?l=125&ct=xref_jump_to_def&gsn=Create>(capacity
>>>>>>>>
>>>>>>>> <https://cs.chromium.org/chromium/src/third_party/blink/renderer/platform/wtf/typed_arrays/array_buffer_builder.h?l=53&ct=xref_jump_to_def&gsn=capacity>,
>>>>>>>> 1); } bool IsValid
>>>>>>>> <https://cs.chromium.org/chromium/src/third_party/blink/renderer/platform/wtf/typed_arrays/array_buffer_builder.h?l=58&gs=kythe%253A%252F%252Fchromium%253Flang%253Dc%25252B%25252B%253Fpath%253Dsrc%252Fthird_party%252Fblink%252Frenderer%252Fplatform%252Fwtf%252Ftyped_arrays%252Farray_buffer_builder.h%2523Bx72YH%25252BiA4nF5ZIPsFhA9MQpdVCDOCRHSZa0Ksg6Wp4%25253D&gsn=IsValid&ct=xref_usages>()
>>>>>>>> const { return buffer_
>>>>>>>> <https://cs.chromium.org/chromium/src/third_party/blink/renderer/platform/wtf/typed_arrays/array_buffer_builder.h?l=94&ct=xref_jump_to_def&gsn=buffer_>.get
>>>>>>>>
>>>>>>>> <https://cs.chromium.org/chromium/src/base/memory/scoped_refptr.h?l=211&ct=xref_jump_to_def&gsn=get>();
>>>>>>>> } // Appending empty data is not allowed. unsigned Append
>>>>>>>> <https://cs.chromium.org/chromium/src/third_party/blink/renderer/platform/wtf/typed_arrays/array_buffer_builder.h?l=61&gs=kythe%253A%252F%252Fchromium%253Flang%253Dc%25252B%25252B%253Fpath%253Dsrc%252Fthird_party%252Fblink%252Frenderer%252Fplatform%252Fwtf%252Ftyped_arrays%252Farray_buffer_builder.h%2523BHKR8BlIFhr03faCJF5mu7RDXZ%25252FPtZDAlnACyKmv1XM%25253D&gsn=Append&ct=xref_usages>(const
>>>>>>>> char* data
>>>>>>>> <https://cs.chromium.org/chromium/src/third_party/blink/renderer/platform/wtf/typed_arrays/array_buffer_builder.h?l=61&gs=kythe%253A%252F%252Fchromium%253Flang%253Dc%25252B%25252B%253Fpath%253Dsrc%252Fthird_party%252Fblink%252Frenderer%252Fplatform%252Fwtf%252Ftyped_arrays%252Farray_buffer_builder.h%25233VvJP%25252BUI3abzouA4%25252FYSBHt09pw3AiNI9e9QAJGooqYI%25253D&gsn=data&ct=xref_usages>,
>>>>>>>> unsigned length
>>>>>>>> <https://cs.chromium.org/chromium/src/third_party/blink/renderer/platform/wtf/typed_arrays/array_buffer_builder.h?l=61&gs=kythe%253A%252F%252Fchromium%253Flang%253Dc%25252B%25252B%253Fpath%253Dsrc%252Fthird_party%252Fblink%252Frenderer%252Fplatform%252Fwtf%252Ftyped_arrays%252Farray_buffer_builder.h%2523xOZXOK9mCrzsbUtqCxdbDuLg939IJhl7gbf0EykKwnY%25253D&gsn=length&ct=xref_usages>);
>>>>>>>> // Returns the accumulated data as an ArrayBuffer instance. If
>>>>>>>> needed, // creates a new ArrayBuffer instance and copies contents
>>>>>>>> from the internal // buffer to it. Otherwise, returns a RefPtr
>>>>>>>> pointing to the internal // buffer. scoped_refptr
>>>>>>>> <https://cs.chromium.org/chromium/src/base/memory/scoped_refptr.h?l=167&ct=xref_jump_to_def&gsn=scoped_refptr><ArrayBuffer
>>>>>>>>
>>>>>>>> <https://cs.chromium.org/chromium/src/third_party/blink/renderer/platform/wtf/typed_arrays/array_buffer.h?l=42&ct=xref_jump_to_def&gsn=ArrayBuffer>>
>>>>>>>> ToArrayBuffer
>>>>>>>> <https://cs.chromium.org/chromium/src/third_party/blink/renderer/platform/wtf/typed_arrays/array_buffer_builder.h?l=67&gs=kythe%253A%252F%252Fchromium%253Flang%253Dc%25252B%25252B%253Fpath%253Dsrc%252Fthird_party%252Fblink%252Frenderer%252Fplatform%252Fwtf%252Ftyped_arrays%252Farray_buffer_builder.h%2523JX559OA9Zt0rALNU4DOTOkzcmtws4U5V42xhN0rrbow%25253D&gsn=ToArrayBuffer&ct=xref_usages>();
>>>>>>>> // Converts the accumulated data into a String using the default
>>>>>>>> encoding. String
>>>>>>>> <https://cs.chromium.org/chromium/src/third_party/blink/renderer/platform/wtf/text/wtf_string.h?l=64&ct=xref_jump_to_def&gsn=String>
>>>>>>>> ToString
>>>>>>>> <https://cs.chromium.org/chromium/src/third_party/blink/renderer/platform/wtf/typed_arrays/array_buffer_builder.h?l=70&gs=kythe%253A%252F%252Fchromium%253Flang%253Dc%25252B%25252B%253Fpath%253Dsrc%252Fthird_party%252Fblink%252Frenderer%252Fplatform%252Fwtf%252Ftyped_arrays%252Farray_buffer_builder.h%2523VMCyw7t%25252FF0UIo65pz8LTbfX5k5G4pIXrUNQbDNKDjaE%25253D&gsn=ToString&ct=xref_usages>();
>>>>>>>> // Number of bytes currently accumulated. unsigned ByteLength
>>>>>>>> <https://cs.chromium.org/chromium/src/third_party/blink/renderer/platform/wtf/typed_arrays/array_buffer_builder.h?l=73&gs=kythe%253A%252F%252Fchromium%253Flang%253Dc%25252B%25252B%253Fpath%253Dsrc%252Fthird_party%252Fblink%252Frenderer%252Fplatform%252Fwtf%252Ftyped_arrays%252Farray_buffer_builder.h%2523P5Klo%25252BJeJiug%25252FrSAfsaHI8wAnW8h5UBg2%25252BoJByO85kA%25253D&gsn=ByteLength&ct=xref_usages>()
>>>>>>>> const { return bytes_used_
>>>>>>>> <https://cs.chromium.org/chromium/src/third_party/blink/renderer/platform/wtf/typed_arrays/array_buffer_builder.h?l=92&ct=xref_jump_to_def&gsn=bytes_used_>;
>>>>>>>> } // Number of bytes allocated. unsigned Capacity
>>>>>>>> <https://cs.chromium.org/chromium/src/third_party/blink/renderer/platform/wtf/typed_arrays/array_buffer_builder.h?l=76&gs=kythe%253A%252F%252Fchromium%253Flang%253Dc%25252B%25252B%253Fpath%253Dsrc%252Fthird_party%252Fblink%252Frenderer%252Fplatform%252Fwtf%252Ftyped_arrays%252Farray_buffer_builder.h%2523kB%25252BJ1WxDvoDqf1c8Tz5Ol3yne4lD03cRpevK2LHMUZk%25253D&gsn=Capacity&ct=xref_usages>()
>>>>>>>> const { return buffer_
>>>>>>>> <https://cs.chromium.org/chromium/src/third_party/blink/renderer/platform/wtf/typed_arrays/array_buffer_builder.h?l=94&ct=xref_jump_to_def&gsn=buffer_>->
>>>>>>>>
>>>>>>>> <https://cs.chromium.org/chromium/src/base/memory/scoped_refptr.h?l=218&ct=xref_jump_to_def&gsn=-%3E>ByteLength
>>>>>>>>
>>>>>>>> <https://cs.chromium.org/chromium/src/third_party/blink/renderer/platform/wtf/typed_arrays/array_buffer.h?l=249&ct=xref_jump_to_def&gsn=ByteLength>();
>>>>>>>> } void ShrinkToFit
>>>>>>>> <https://cs.chromium.org/chromium/src/third_party/blink/renderer/platform/wtf/typed_arrays/array_buffer_builder.h?l=78&gs=kythe%253A%252F%252Fchromium%253Flang%253Dc%25252B%25252B%253Fpath%253Dsrc%252Fthird_party%252Fblink%252Frenderer%252Fplatform%252Fwtf%252Ftyped_arrays%252Farray_buffer_builder.h%2523WBvAUuWtgva6ffSXIiEGEkt%25252FFFbeCcQcsCz5E%25252FHCKOo%25253D&gsn=ShrinkToFit&ct=xref_usages>();
>>>>>>>> const void* Data
>>>>>>>> <https://cs.chromium.org/chromium/src/third_party/blink/renderer/platform/wtf/typed_arrays/array_buffer_builder.h?l=80&gs=kythe%253A%252F%252Fchromium%253Flang%253Dc%25252B%25252B%253Fpath%253Dsrc%252Fthird_party%252Fblink%252Frenderer%252Fplatform%252Fwtf%252Ftyped_arrays%252Farray_buffer_builder.h%2523b8F1aEDx%25252F6En%25252FkOKh2zVkvONjtDNg9gr5KG7gT9XeJk%25253D&gsn=Data&ct=xref_usages>()
>>>>>>>> const { return buffer_
>>>>>>>> <https://cs.chromium.org/chromium/src/third_party/blink/renderer/platform/wtf/typed_arrays/array_buffer_builder.h?l=94&ct=xref_jump_to_def&gsn=buffer_>->
>>>>>>>>
>>>>>>>> <https://cs.chromium.org/chromium/src/base/memory/scoped_refptr.h?l=218&ct=xref_jump_to_def&gsn=-%3E>Data
>>>>>>>>
>>>>>>>> <https://cs.chromium.org/chromium/src/third_party/blink/renderer/platform/wtf/typed_arrays/array_buffer.h?l=225&ct=xref_jump_to_def&gsn=Data>();
>>>>>>>> } // If set to false, the capacity won't be expanded and when
>>>>>>>> appended data // overflows, the overflowed part will be dropped.
>>>>>>>> void SetVariableCapacity
>>>>>>>> <https://cs.chromium.org/chromium/src/third_party/blink/renderer/platform/wtf/typed_arrays/array_buffer_builder.h?l=84&gs=kythe%253A%252F%252Fchromium%253Flang%253Dc%25252B%25252B%253Fpath%253Dsrc%252Fthird_party%252Fblink%252Frenderer%252Fplatform%252Fwtf%252Ftyped_arrays%252Farray_buffer_builder.h%25232ib6USbezkKcLs8hjPaCz4GUGrUHdD%25252BeN%25252FKenERnRLA%25253D&gsn=SetVariableCapacity&ct=xref_usages>(bool
>>>>>>>> value
>>>>>>>> <https://cs.chromium.org/chromium/src/third_party/blink/renderer/platform/wtf/typed_arrays/array_buffer_builder.h?l=84&gs=kythe%253A%252F%252Fchromium%253Flang%253Dc%25252B%25252B%253Fpath%253Dsrc%252Fthird_party%252Fblink%252Frenderer%252Fplatform%252Fwtf%252Ftyped_arrays%252Farray_buffer_builder.h%2523vUjrriXMW5FurGjU87jcAlZRQs3b8JSgA4Tt1xrSq7I%25253D&gsn=value&ct=xref_usages>)
>>>>>>>> { variable_capacity_
>>>>>>>> <https://cs.chromium.org/chromium/src/third_party/blink/renderer/platform/wtf/typed_arrays/array_buffer_builder.h?l=93&ct=xref_jump_to_def&gsn=variable_capacity_>
>>>>>>>> = value
>>>>>>>> <https://cs.chromium.org/chromium/src/third_party/blink/renderer/platform/wtf/typed_arrays/array_buffer_builder.h?l=84&ct=xref_jump_to_def&gsn=value>;
>>>>>>>> } private: // Expands the size of m_buffer to size + m_bytesUsed
>>>>>>>> bytes. Returns true // iff successful. If reallocation is needed,
>>>>>>>> copies only data in // [0, m_bytesUsed) range. bool ExpandCapacity
>>>>>>>> <https://cs.chromium.org/chromium/src/third_party/blink/renderer/platform/wtf/typed_arrays/array_buffer_builder.h?l=90&gs=kythe%253A%252F%252Fchromium%253Flang%253Dc%25252B%25252B%253Fpath%253Dsrc%252Fthird_party%252Fblink%252Frenderer%252Fplatform%252Fwtf%252Ftyped_arrays%252Farray_buffer_builder.h%2523szv9AYLlP3J7qhn%25252Fm%25252BJqzPmSgWf45%25252BRVwVxvXDk3WYQ%25253D&gsn=ExpandCapacity&ct=xref_usages>(unsigned
>>>>>>>> size
>>>>>>>> <https://cs.chromium.org/chromium/src/third_party/blink/renderer/platform/wtf/typed_arrays/array_buffer_builder.h?l=90&gs=kythe%253A%252F%252Fchromium%253Flang%253Dc%25252B%25252B%253Fpath%253Dsrc%252Fthird_party%252Fblink%252Frenderer%252Fplatform%252Fwtf%252Ftyped_arrays%252Farray_buffer_builder.h%2523mXwymG5xtblCCeS4C9QcnmOwJxql8nYDr2HLqNZVJ8I%25253D&gsn=size&ct=xref_usages>);
>>>>>>>> unsigned bytes_used_
>>>>>>>> <https://cs.chromium.org/chromium/src/third_party/blink/renderer/platform/wtf/typed_arrays/array_buffer_builder.h?l=92&gs=kythe%253A%252F%252Fchromium%253Flang%253Dc%25252B%25252B%253Fpath%253Dsrc%252Fthird_party%252Fblink%252Frenderer%252Fplatform%252Fwtf%252Ftyped_arrays%252Farray_buffer_builder.h%2523x95FyaH%25252BSeW1SF4BFhX9oIq7qgtHy3xzXCMmc37LcL8%25253D&gsn=bytes_used_&ct=xref_usages>;
>>>>>>>> bool variable_capacity_
>>>>>>>> <https://cs.chromium.org/chromium/src/third_party/blink/renderer/platform/wtf/typed_arrays/array_buffer_builder.h?l=93&gs=kythe%253A%252F%252Fchromium%253Flang%253Dc%25252B%25252B%253Fpath%253Dsrc%252Fthird_party%252Fblink%252Frenderer%252Fplatform%252Fwtf%252Ftyped_arrays%252Farray_buffer_builder.h%2523FKWGJXbcZ%25252BRuy6YD7uxQ765XV8Mhciv4FM%25252FF5B3bNvU%25253D&gsn=variable_capacity_&ct=xref_usages>;
>>>>>>>> scoped_refptr
>>>>>>>> <https://cs.chromium.org/chromium/src/base/memory/scoped_refptr.h?l=167&ct=xref_jump_to_def&gsn=scoped_refptr><ArrayBuffer
>>>>>>>>
>>>>>>>> <https://cs.chromium.org/chromium/src/third_party/blink/renderer/platform/wtf/typed_arrays/array_buffer.h?l=42&ct=xref_jump_to_def&gsn=ArrayBuffer>>
>>>>>>>> buffer_
>>>>>>>> <https://cs.chromium.org/chromium/src/third_party/blink/renderer/platform/wtf/typed_arrays/array_buffer_builder.h?l=94&gs=kythe%253A%252F%252Fchromium%253Flang%253Dc%25252B%25252B%253Fpath%253Dsrc%252Fthird_party%252Fblink%252Frenderer%252Fplatform%252Fwtf%252Ftyped_arrays%252Farray_buffer_builder.h%2523aFDjYtlmS2tmLXL2XyJ158HoigBmsAdzguhOSb6XQIw%25253D&gsn=buffer_&ct=xref_usages>;
>>>>>>>> DISALLOW_COPY_AND_ASSIGN
>>>>>>>> <https://cs.chromium.org/chromium/src/base/macros.h?l=33&ct=xref_jump_to_def&gsn=DISALLOW_COPY_AND_ASSIGN>(ArrayBufferBuilder
>>>>>>>>
>>>>>>>> <https://cs.chromium.org/chromium/src/third_party/blink/renderer/platform/wtf/typed_arrays/array_buffer_builder.h?l=96&gs=kythe%253A%252F%252Fchromium%253Flang%253Dc%25252B%25252B%253Fpath%253Dsrc%252Fthird_party%252Fblink%252Frenderer%252Fplatform%252Fwtf%252Ftyped_arrays%252Farray_buffer_builder.h%2523E6nSXqAY3ipexrHDKPfjzHqWqWIsAlT3EH3KVhT57GQ%25253D&gsn=ArrayBufferBuilder&ct=xref_usages>);};}
>>>>>>>> // namespace WTF
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> How can i understand the structure in memory of an arraybuffer and how
>>>>>>>> big is the data field which is pointed by this void pointerHow are
>>>>>>>> they represented in memory....How big is the data field ?
>>>>>>>>
>>>>>>>>
>>>>>>>> Il giorno lun 10 set 2018 alle ore 22:19 dan Med <
>>>>>>>> litoki...@gmail.com> ha scritto:
>>>>>>>>
>>>>>>>>> i already did that and btw it is under the WTF/webkit .
>>>>>>>>> I'm interested how v8 handles javascript into every detail if u
>>>>>>>>> can guide me...
>>>>>>>>> Tell me which repository are being used by v8 on the related topic
>>>>>>>>> that would help me really much.
>>>>>>>>>
>>>>>>>>> By when it is called i mean, which javascript code will enable me
>>>>>>>>> to call that funciton cause if u click u can't go any further than
>>>>>>>>> that,
>>>>>>>>>
>>>>>>>>> Il giorno lun 10 set 2018 alle ore 21:53 Jakob Kummerow <
>>>>>>>>> jkum...@chromium.org> ha scritto:
>>>>>>>>>
>>>>>>>>>> On Mon, Sep 10, 2018 at 12:22 PM dan Med <litoki...@gmail.com>
>>>>>>>>>> wrote:
>>>>>>>>>>
>>>>>>>>>>> I don't quite see if this google group is useful or not,
>>>>>>>>>>> everybody keeps answering me with superficial things,
>>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> You said you wanted to read the compiler's source but couldn't
>>>>>>>>>> find it, so I told you that it's in src/compiler/. If that was not
>>>>>>>>>> the
>>>>>>>>>> answer you wanted, then try asking a different question?
>>>>>>>>>>
>>>>>>>>>> Please also keep in mind that people's time is limited. The
>>>>>>>>>> easier/quicker it is to answer your question, the more likely you
>>>>>>>>>> are to
>>>>>>>>>> get an answer.
>>>>>>>>>>
>>>>>>>>>> i don't care about the trminology like tell me which allocator it
>>>>>>>>>>> uses when and why or at least if there's something i can read to
>>>>>>>>>>> understand.....
>>>>>>>>>>> I'm surprised u don't know what a JIT page is, basically if you
>>>>>>>>>>> call a function foo() let's say 100 times then v8,had enough time
>>>>>>>>>>> to
>>>>>>>>>>> understand the parameters given to that specific function and how
>>>>>>>>>>> to
>>>>>>>>>>> optimize it efficently based on it's prediction/observation.
>>>>>>>>>>>
>>>>>>>>>>> I'm not interested in the terminology of things, (that's just a
>>>>>>>>>>> matter of reading the source code ) i'm more in reading how it
>>>>>>>>>>> works when
>>>>>>>>>>> and why..
>>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> It's great that you want to understand how things work.
>>>>>>>>>> Terminology is an important aspect of that though, because it
>>>>>>>>>> enables
>>>>>>>>>> communication. If we use different words for the same thing, we
>>>>>>>>>> won't
>>>>>>>>>> understand each other.
>>>>>>>>>> Based on your explanation, I'm guessing that by "JIT page" you
>>>>>>>>>> mean "the strategy V8 uses to select functions for optimization".
>>>>>>>>>> The core
>>>>>>>>>> of that logic is in MarkCandidatesForOptimization in
>>>>>>>>>> src/runtime-profiler.cc.
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>> For example when is ArrayBufferBuilder::Append called ??
>>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> I don't know; it's not part of V8. But you can use Code Search to
>>>>>>>>>> find out where anything is called, just click the function in
>>>>>>>>>> question to
>>>>>>>>>> get a list of call sites:
>>>>>>>>>> https://cs.chromium.org/chromium/src/third_party/blink/renderer/platform/wtf/typed_arrays/array_buffer_builder.h?q=ArrayBufferBuilder&sq=package:chromium&g=0&l=61
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>> And i thing i've looked at the entire v8 source code but didn't
>>>>>>>>>>> find much, apart from the array.js file which describes some
>>>>>>>>>>> javascript
>>>>>>>>>>> function, i don't understand where's the rest....
>>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> Il giorno lun 10 set 2018 alle ore 20:45 Jakob Kummerow <
>>>>>>>>>>> jkum...@chromium.org> ha scritto:
>>>>>>>>>>>
>>>>>>>>>>>> On Sun, Sep 9, 2018 at 8:54 AM dan Med <litoki...@gmail.com>
>>>>>>>>>>>> wrote:
>>>>>>>>>>>>
>>>>>>>>>>>>> Oh and one more thing, i've surfed perhaps the entire source
>>>>>>>>>>>>> code of v8 at least the interesting parts, but what i came across
>>>>>>>>>>>>> was just
>>>>>>>>>>>>> very short code execpt for some builtins written in javascript i
>>>>>>>>>>>>> believe,
>>>>>>>>>>>>> can't find all of the things i've found on the documentation such
>>>>>>>>>>>>> as the
>>>>>>>>>>>>> interpreter
>>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>>> src/interpreter/
>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>>>> and the JIT compilers,
>>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>>> src/compiler/
>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>>>> one more thing i'd like to understand how the memory is
>>>>>>>>>>>>> handeled like how can i read about the JIT pages,
>>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>>> What's a JIT page?
>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>>>> or which memory allocator does v8 use
>>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>>> It uses several allocation techniques for different purposes.
>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>>>> and it's garbage collector
>>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>>> src/heap/
>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>>> Thank you !
>>>>>>>>>>>>>
>>>>>>>>>>>>> Il giorno dom 9 set 2018 alle ore 17:51 dan Med <
>>>>>>>>>>>>> litoki...@gmail.com> ha scritto:
>>>>>>>>>>>>>
>>>>>>>>>>>>>> I don't have understood this part, let me explain it to you.
>>>>>>>>>>>>>> This is how i get it tell me if i'm wrong at any part.
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> I need to understand how is the structure in memory of the
>>>>>>>>>>>>>> arraybuffer how is it represented and if the data of the array
>>>>>>>>>>>>>> are directly
>>>>>>>>>>>>>> stored at an offset accessed by buffer_ -> data().
>>>>>>>>>>>>>>
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> before the call to expand capacity it does create an array
>>>>>>>>>>>>>>
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> the arraybuffer in src
>>>>>>>>>>>>>> <https://cs.chromium.org/chromium/src/>/third_party
>>>>>>>>>>>>>> <https://cs.chromium.org/chromium/src/third_party/>/blink
>>>>>>>>>>>>>> <https://cs.chromium.org/chromium/src/third_party/blink/>/
>>>>>>>>>>>>>> renderer
>>>>>>>>>>>>>> <https://cs.chromium.org/chromium/src/third_party/blink/renderer/>
>>>>>>>>>>>>>> /platform
>>>>>>>>>>>>>> <https://cs.chromium.org/chromium/src/third_party/blink/renderer/platform/>
>>>>>>>>>>>>>> /wtf
>>>>>>>>>>>>>> <https://cs.chromium.org/chromium/src/third_party/blink/renderer/platform/wtf/>
>>>>>>>>>>>>>> /typed_arrays
>>>>>>>>>>>>>> <https://cs.chromium.org/chromium/src/third_party/blink/renderer/platform/wtf/typed_arrays/>
>>>>>>>>>>>>>> /array_buffer_builder.cc
>>>>>>>>>>>>>> <https://cs.chromium.org/chromium/src/third_party/blink/renderer/platform/wtf/typed_arrays/array_buffer_builder.cc>
>>>>>>>>>>>>>> is
>>>>>>>>>>>>>> called whenever the renderer (has to execute some javascript
>>>>>>>>>>>>>> which defines
>>>>>>>>>>>>>> arraybuffers)
>>>>>>>>>>>>>> First when is arraybuffer::append called, cause i know that
>>>>>>>>>>>>>> if someone need to reallocate a bigger arraybuffer then a new
>>>>>>>>>>>>>> instance will
>>>>>>>>>>>>>> be created and filled with the old values if the length in the
>>>>>>>>>>>>>> original
>>>>>>>>>>>>>> array isn't has much as the user reqeusted ?
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> One more thing is, when this class is called, the arraybuffer
>>>>>>>>>>>>>> is always set to the initial length of static const int
>>>>>>>>>>>>>> kDefaultBufferCapacity
>>>>>>>>>>>>>> <https://cs.chromium.org/chromium/src/third_party/blink/renderer/platform/wtf/typed_arrays/array_buffer_builder.cc?l=38&gs=kythe%253A%252F%252Fchromium%253Flang%253Dc%25252B%25252B%253Fpath%253Dsrc%252Fthird_party%252Fblink%252Frenderer%252Fplatform%252Fwtf%252Ftyped_arrays%252Farray_buffer_builder.cc%2523YXDT7WTpXCAcuhdyTlkuCzsfCzI%25252BoHLRFAlkbCrkx4g%25253D&gsn=kDefaultBufferCapacity&ct=xref_usages>
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> = 32768; if in the javascript i declare an arraybuffer of
>>>>>>>>>>>>>> 20bytes will it allocate of
>>>>>>>>>>>>>> 32768bytes anyway =?
>>>>>>>>>>>>>>
>>>>>>>>>>>>>>
>>>>>>>>>>>>>>
>>>>>>>>>>>>>>
>>>>>>>>>>>>>>
>>>>>>>>>>>>>>
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> Il giorno mar 4 set 2018 alle ore 12:14 Graham Reeves <
>>>>>>>>>>>>>> gra...@grahamreeves.com> ha scritto:
>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> > is std::numeric_limits
>>>>>>>>>>>>>>> <https://cs.chromium.org/chromium/src/buildtools/third_party/libc%2B%2B/trunk/include/limits?l=442&ct=xref_jump_to_def&gsn=numeric_limits>
>>>>>>>>>>>>>>> <unsigned>::max
>>>>>>>>>>>>>>> <https://cs.chromium.org/chromium/src/buildtools/third_party/libc%2B%2B/trunk/include/limits?l=450&ct=xref_jump_to_def&gsn=max>();
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> referring to the max unsigned int value ? cause the source code
>>>>>>>>>>>>>>> won't find
>>>>>>>>>>>>>>> it
>>>>>>>>>>>>>>> Yes, that's the maximum value unsigned (an unsigned int) can
>>>>>>>>>>>>>>> be, but what do you mean by, the source won't find it?
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> On Monday, 3 September 2018 19:55:48 UTC+1, dan Med wrote:
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> Can someone help me out?
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> Il giorno sab 1 set 2018 alle ore 15:30 <
>>>>>>>>>>>>>>>> litoki...@gmail.com> ha scritto:
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> array_buffer_builder.cc in src
>>>>>>>>>>>>>>>>> <https://cs.chromium.org/chromium/src/>/third_party
>>>>>>>>>>>>>>>>> <https://cs.chromium.org/chromium/src/third_party/>/blink
>>>>>>>>>>>>>>>>> <https://cs.chromium.org/chromium/src/third_party/blink/>/
>>>>>>>>>>>>>>>>> renderer
>>>>>>>>>>>>>>>>> <https://cs.chromium.org/chromium/src/third_party/blink/renderer/>
>>>>>>>>>>>>>>>>> /platform
>>>>>>>>>>>>>>>>> <https://cs.chromium.org/chromium/src/third_party/blink/renderer/platform/>
>>>>>>>>>>>>>>>>> /wtf
>>>>>>>>>>>>>>>>> <https://cs.chromium.org/chromium/src/third_party/blink/renderer/platform/wtf/>
>>>>>>>>>>>>>>>>> /
>>>>>>>>>>>>>>>>> <https://cs.chromium.org/chromium/src/third_party/blink/renderer/platform/wtf/typed_arrays/>
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>
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