[squeak-dev] FFI Inbox: FFI-Kernel-nice.119.mcz

Marcel Taeumel marcel.taeumel at hpi.de
Mon Jun 22 08:31:47 UTC 2020


> throw that code away, and have a look at  in VMMakerInbox, you will understand better...

Not so sure ... because I think we do not agree on the status quo yet. We should do that first. Understand the compiledSpec as is. Then move forward.

> So hopefully, we shall throw away the FFIFlagStructure and make your life easier at image side :)

Not so sure. See above. 

Best,
Marcel
Am 22.06.2020 10:28:12 schrieb Nicolas Cellier <nicolas.cellier.aka.nice at gmail.com>:
No, no,
throw that code away, and have a look at  in VMMakerInbox, you will understand better...

In fact, if you read my proposals, I'd like to get rid of FFIFlagStructure altogether...
Either a type is atomic or composite, it's not both nor neither...
So we ain't gonna need 2 flags FFIFlagAtomic and FFIFlagStructure.

So hopefully, we shall throw away the FFIFlagStructure and make your life easier at image side :)


Le lun. 22 juin 2020 à 10:19, Marcel Taeumel <marcel.taeumel at hpi.de [mailto:marcel.taeumel at hpi.de]> a écrit :

Hi Nicolas,

sure, there might be a difference. But you have all the information you need directly in the plugin already:



Let me catch up on this later this week.

Best,
Marcel
Am 22.06.2020 09:56:05 schrieb Nicolas Cellier <nicolas.cellier.aka.nice at gmail.com [mailto:nicolas.cellier.aka.nice at gmail.com]>:
Hi Marcel,
So you mean that I don't really need to distinguish pointer to struct and pointer to atomic type alias?
Maybe...

There is currently a difference:
- an atomic type alias has an immediate value as handle
  it thus cannot be passed as parameter by reference
  (well, for aliases to pointers, I don't really know...)

- a struct has a memory zone as value (ExternalAddress or direct ByteArray)
 it thus can be passed as parameter by reference without having to resort to an ExternalData.
See ffiPassStructureArgumentByReference: oop Class: oopClass expectedClass: argClass In: calloutState
vs ffiPassAtomicArgumentByReference: oop Class: oopClass expectedClass: argClass In: calloutState


Le lun. 22 juin 2020 à 09:18, Marcel Taeumel <marcel.taeumel at hpi.de [mailto:marcel.taeumel at hpi.de]> a écrit :

Hi Nicolas,

thanks! :-) I will take a look at it during this week, I hope. 

Here is a first thought:

I don't think that the pointer types for external structs should have the FFIFlagStructure."referentClass" should be more than enough for the FFI plugin side for both coercing and return-value packaging.

So, -1 for now but maybe I overlooked a use case. Raising this FFIFlagStructure here for such pointer types really messes up a lot of my current conceptual model about the relationship of ExternalStructure and ExternalType/ExternalStructureType. :-)

Why is "referentClass" not enough for the plugin side? Just check for ifNil, if not, instantiate and put instVar 0 to the return value. Done. ;-) For coercing, just compare argument class with "referentClass" in the argType; then check for the pointer flag. Maybe discriminate between ByteArray and ExternalAddress. 

...please don't raise FFIFlagStructure for pointer types for external structures... pretty please ^__^

Best,
Marcel

Am 21.06.2020 22:34:09 schrieb commits at source.squeak.org [mailto:commits at source.squeak.org] <commits at source.squeak.org [mailto:commits at source.squeak.org]>:
Nicolas Cellier uploaded a new version of FFI-Kernel to project FFI Inbox:
http://source.squeak.org/FFIinbox/FFI-Kernel-nice.119.mcz [http://source.squeak.org/FFIinbox/FFI-Kernel-nice.119.mcz]

==================== Summary ====================

Name: FFI-Kernel-nice.119
Author: nice
Time: 21 June 2020, 10:34:00.334284 pm
UUID: 3f2eca9d-8f55-476c-a0b0-c5ed6368a6b4
Ancestors: FFI-Kernel-nice.118

Make the compiledSpecs of struct pointers conform to the experimental FFI branch (thru #adjustPointerType)

See https://github.com/OpenSmalltalk/opensmalltalk-vm/tree/experimental_FFI [https://github.com/OpenSmalltalk/opensmalltalk-vm/tree/experimental_FFI]

Simplify a bit ExternalData access (at: / at:put:).
The assumption that ExternalDataType is the type of the contents and not the type of the reference helps simplifying IMO.

We might want to make it more complete once we deal with pointer arity.
It's not the case yet.

=============== Diff against FFI-Kernel-nice.118 ===============

Item was changed:
----- Method: ExternalData>>at: (in category 'accessing') -----
at: index

- self
- assert: [index = 1 or: [type isAtomic]]
- description: 'Should not read non-atomic pointer as array'.
-
((1 > index) or: [size notNil and: [index > size]])
ifTrue: [^ self errorSubscriptBounds: index].

+ ^ type
- ^ type asNonPointerType
handle: handle
+ at: ((index-1) * type byteSize) + 1!
- at: ((index-1) * type asNonPointerType byteSize) + 1!

Item was changed:
----- Method: ExternalData>>at:put: (in category 'accessing') -----
at: index put: value

- self
- assert: [index = 1 or: [type isAtomic]]
- description: 'Should not read non-atomic pointer as array'.
-
((1 > index) or: [size notNil and: [index > size]])
ifTrue: [^ self errorSubscriptBounds: index].

+ ^ type
- ^ type asNonPointerType
handle: handle
+ at: ((index-1) * type byteSize) + 1
- at: ((index-1) * type asNonPointerType byteSize) + 1
put: value!

Item was changed:
----- Method: ExternalStructure class>>compileAllFields (in category 'system startup') -----
compileAllFields
"
ExternalStructure compileAllFields
"
+ | priorAuthorInitials |
- | priorAuthorInitials fieldSpec |
priorAuthorInitials := Utilities authorInitialsPerSe.
[Utilities setAuthorInitials: 'FFI'.

self allStructuresInCompilationOrder do: [:structClass |
+ | fieldSpec |
fieldSpec := structClass fields.
self flag: #discuss. "mt: Why do we need that extra layout check? Performance gain is minimal..."
(structClass hasFieldLayoutChanged: fieldSpec)
ifTrue: [structClass compileFieldsSilently: fieldSpec].
structClass externalType "asNonPointerType"
compiledSpec: structClass compiledSpec;
+ byteAlignment: structClass byteAlignment;
+ adjustPointerType.
- byteAlignment: structClass byteAlignment.
structClass organization removeEmptyCategories].
"Compilation of fields only needs external types temporarily. Non-weak references to external types are only in methods with FFI calls."
ExternalType cleanupUnusedTypes.

] ensure: [Utilities setAuthorInitials: priorAuthorInitials]!

Item was added:
+ ----- Method: ExternalStructureType>>adjustPointerType (in category 'private') -----
+ adjustPointerType
+ self isPointerType
+ ifFalse: [self asPointerType
+ compiledSpec: (WordArray with: ((self compiledSpec first
+ bitAnd: FFIFlagAtomic + FFIFlagStructure)
+ bitOr: self class pointerSpec));
+ byteAlignment: self class pointerAlignment]!

Item was changed:
----- Method: ExternalType class>>initializeStructureTypes (in category 'class initialization') -----
initializeStructureTypes
"Reset all non-pointer struct types to zero and their pointer companions to the appropriate pointer size."

StructTypes ifNil: [
StructTypes := WeakValueDictionary new].

self cleanupUnusedTypes.

StructTypes valuesDo:[:structType |
structType "asNonPointerType"
compiledSpec: (WordArray with: self structureSpec);
byteAlignment: nil.
structType asPointerType
+ compiledSpec: (WordArray with: self pointerSpec + self structureSpec);
- compiledSpec: (WordArray with: self pointerSpec);
byteAlignment: nil].!

Item was changed:
----- Method: ExternalType>>handle:at: (in category 'external data') -----
handle: handle at: byteOffset
"Read the receiver's external type using the given handle and the byteOffset. This is the dynamic version of #readFieldAt:."

+ | address value |
- | result |
- self checkType.
-
self isPointerType
+ ifTrue:
+ [address := handle pointerAt: byteOffset length: self byteSize.
+ ^ExternalData
+ fromHandle: address
+ type: self asNonPointerType].
+ self isAtomic
+ ifTrue:
+ ["Answer atomic value"
+ value := handle
- ifFalse: [
- "Answer atomic value"
- ^ handle
perform: (AtomicSelectors at: self atomicType)
+ with: byteOffset.
+ ^referentClass ifNil: [value] ifNotNil: [referentClass fromHandle: value]].
+
+ referentClass isNil
+ ifTrue: [self error: 'unknown type'].
+ self isEmpty ifTrue: [self error: 'Empty structure'].
+
+ ^referentClass fromHandle: (handle structAt: byteOffset length: self byteSize)!
- with: byteOffset]
- ifTrue: [
- ^ referentClass
- ifNotNil: [
- "Answer structure, union, or type alias"
- referentClass fromHandle: (handle pointerAt: byteOffset length: self byteSize)]
- ifNil: [
- "Answer wrapper that points to external data"
- result := ExternalData
- fromHandle: (handle pointerAt: byteOffset length: self byteSize)
- type: self.
- self = ExternalType string
- ifTrue: [result fromCString]
- ifFalse: [result]]]!

Item was changed:
----- Method: ExternalType>>handle:at:put: (in category 'external data') -----
handle: handle at: byteOffset put: value
"Write a value using the receiver's external type at the given handle and byteOffset. This is the dynamic version of #writeFieldAt:with:."

- self checkType.
-
self isPointerType
- ifFalse: [ "set atomic value"
- self flag: #addTypeCheck. "mt: Note that there is currently no mapping from objects that represent valid atomics to atomic types."
- handle
- perform: ((AtomicSelectors at: self atomicType), 'put:') asSymbol
- with: byteOffset
- with: value]
ifTrue: [ "set pointer to struct/union/alias"
+ self assert: [value externalType == self asNonPointerType].
- self assert: [value externalType == self].
handle
pointerAt: byteOffset
put: value getHandle
+ length: self byteSize.
+ ^value].
+
+ self isAtomic
+ ifTrue:
+ [ "set atomic value"
+ self flag: #addTypeCheck. "mt: Note that there is currently no mapping from objects that represent valid atomics to atomic types."
+ handle
+ perform: ((AtomicSelectors at: self atomicType), 'put:') asSymbol
+ with: byteOffset
+ with: value.
+ ^value].
+
+ referentClass isNil
+ ifTrue: [self error: 'unknown type'].
+ self isEmpty ifTrue: [self error: 'Empty structure'].
+
+ self assert: [value externalType == self].
+ handle structAt: byteOffset put: value getHandle length: self byteSize.
+ ^value
+ !
- length: self byteSize].!




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