FFI: FFI-Kernel-mt.155.mcz

Marcel Taeumel uploaded a new version of FFI-Kernel to project FFI:
http://source.squeak.org/FFI/FFI-Kernel-mt.155.mcz

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

Name: FFI-Kernel-mt.155
Author: mt
Time: 17 May 2021, 8:45:06.479407 am
UUID: bf403e45-81e8-cf42-8cbf-1cbede10602d
Ancestors: FFI-Kernel-mt.154

Adds endianness to platform description.

=============== Diff against FFI-Kernel-mt.154 ===============

Item was changed:
  Object subclass: #FFIPlatformDescription
+ instanceVariableNames: 'name osVersion subtype wordSize endianness'
- instanceVariableNames: 'name osVersion subtype wordSize'
  classVariableNames: 'LastPlatform'
  poolDictionaries: ''
  category: 'FFI-Kernel-Support'!
 
  !FFIPlatformDescription commentStamp: 'mt 6/2/2020 15:18' prior: 0!
  This class stores the information about the current (host) platform. It supports testing instances for platform compatibility and specificity. The entire FFI machinery should go through here, when making platform-specific decisions such as when figuring out the #wordSize for pointers to external memory (i.e., ExternalAddress class >> #new) or when looking up compatible definitions for external pools (i.e., ExternalPool class >> #compatibleResolvedDefinitions).
 
 
  1. DETECT PLATFORM CHANGE ON STARTUP
 
  This class is registered for system startup. It then checks whether the current platform is different from the last one. In that case, a selection of FFI classes gets notified such as ExternalObject and ExternalType.
 
 
  2. PLATFORM SPECIFICITY
 
  Platform descriptions may be unspecific, that is, some of their values may be undefined. For example, (FFIPlatformDescription name: 'unix') creates a valid description but is not specific about #osVersion or #wordSize. When comparing such descriptions, precedence of the platform values are:
 
  platform name > osVersion > subtype > wordSize
 
  So, if one description has a #name and the other does not, the first one is more specific. If both have #name but only the second one has #osVersion, the second one is more specific. If one has only #wordSize and another one has only #subtype, the second one is more specific because #subtype has a higher precedence than #wordSize.
 
 
  3. PLATFORM COMPATIBILITY
 
  Platform descriptions implement a notion of compatibility, which is coupled to its notion of specificity as mentioned before. Using the same rules of precedence, compatibility is checked by comparing the description's values. If not specificed, compatibility is assumed. If specified, values must match via #= to be regarded compatible.
 
  Here is an interesting edge case of two compatible platform descriptions:
 
  | p1 p2 |
  p1 := FFIPlatformDescription name: 'Win32' osVersion: '' subtype: 'IX86' wordSize: nil.
  p2 := FFIPlatformDescription name: '' osVersion: 'linux-gnu' subtype: '' wordSize: 8.
  p1 isCompatibleWith: p2.
 
  Consequently, the developer has to be careful with unspecific platform descriptions, which are used, for example, in the definitions of external pools.
 
 
  4. FURTHER READING
 
  - all references to FFIPlatformDescription
  - all senders of #wordSize
  - class comments of ExternalAddress, ExternalType, ExternalPool, ExternalObject
  !

Item was added:
+ ----- Method: FFIPlatformDescription class>>currentEndianness (in category 'accessing') -----
+ currentEndianness
+ "self currentEndianness"
+
+ ^ Smalltalk os endianness!

Item was added:
+ ----- Method: FFIPlatformDescription>>endianness (in category 'accessing') -----
+ endianness
+
+ ^ endianness ifNil: [endianness := self class currentEndianness]!

Item was added:
+ ----- Method: FFIPlatformDescription>>endianness: (in category 'accessing') -----
+ endianness: aSymbol
+
+ endianness := aSymbol.!