泛型（Vector）如何在AVM内部工作？ [英] How do generics (Vector) work inside the AVM?

问题描述

支持泛型（目前只有 Vector。< *> ，并被Adobe称为后缀类型参数）被添加到Flash Player 10中，但唯一的

具体来说，我注意到一个新的操作码（0x53）和一个新的多重类型（0x1D）这似乎是相关的，但他们的用法没有记录。

注意：这个问题的答案已经知道，因为它更容易在这里找到比我的博客或Adobe Bug DB。

解决方案

泛型类型，尽管很有可能。

对声明（无参数）泛型（Vector）的引用是通过一个常量（Vector，< int>，而不是Vector。<>）的引用是由一个类型化的泛型类型引用的一个新的多类型（0x1D），我称之为GenericName。 GenericName的格式如下：

  [Kind] [TypeDefinition] [ParamCount] [Param1] [Param2] [ParamN] 
 
 
 
 
  
 
 $ ul 
 
 [TypeDefinition]是U30中的一个多元表
 
  [ParamCount]是多少个类型参数的U8（U30？）
 
 [ParamX]是一个U30的多表。
 
  
 
 
显然泛型一般不支持，所以ParamCount将始终为1对于Vector。< *>）。
 
 
 
另一个有趣的事情是如何创建类的实例。在Flash 10（0x53）中添加了一个新的操作码，我将其称为MakeGenericType。 MakeGenericType用下面的堆栈声明：
 $ b $ pre $  TypeDefinition，ParameterType1，ParameterTypeN  - > GenericType 
  

它也有一个参数，U8（U30？）指定堆栈中有多少个参数。您一般会看到MakeGenericType是这样使用的：



  GetLex [TypeDefinitionMultiname] 
 GetLex [ParameterTypeMultiname] 
 MakeGeneric [ParamCount] 
 Coerce [GenericNameMultiname] 
 Construct [ConstructorParamCount] 
  

如果你有以下...

$ pre $ code $ GetLex __AS3 __。vec :: Vector
GetLex int
MakeGeneric 1
Coerce __AS3 __。vec :: Vector。< int>
构造0


现在您将拥有一个Vector实例。< int> p>

Support for generics (currently only Vector.<*>, and called 'postfix type parameters' by Adobe) was added in Flash Player 10, but the only AVM2 documentation does not describe how these objects are accessed.

Specifically, I noticed a new opcode (0x53) and a new multiname kind (0x1D) that seem relevant, but their usage is not documented.

NB: This question was created with the answer already known as it is more easily found here than on my blog or the Adobe Bug DB.

解决方案

The reverse engineering work I did on this did not include declaring your own generic types, though it's very likely possible.

References to the declaring (parameterless) generic type (Vector) are made through a regular qualified name (though any multiname should do).

References to a typed generic type (Vector.<int> as opposed to Vector.<>) are made by a new multiname kind (0x1D), which I call GenericName. GenericName has a format like so:

[Kind] [TypeDefinition] [ParamCount] [Param1] [Param2] [ParamN]

Where:

• [TypeDefinition] is a U30 into the multiname table
• [ParamCount] is a U8 (U30?) of how many type parameters there are
• [ParamX] is a U30 into the multiname table.

Obviously generics are not generally supported yet, so ParamCount will always be 1 (for Vector.<*>).

The other interesting thing is how instances of the class are created. A new opcode was added in Flash 10 (0x53), which I will call MakeGenericType. MakeGenericType is declared with the following stack:

TypeDefinition, ParameterType1, ParameterTypeN -> GenericType

It also has one parameter, a U8 (U30?) specifying how many parameters are on the stack. You will generally see MakeGenericType being used like this:

GetLex [TypeDefinitionMultiname]
GetLex [ParameterTypeMultiname]
MakeGeneric [ParamCount]
Coerce [GenericNameMultiname]
Construct [ConstructorParamCount]

So if you had the following...

GetLex __AS3__.vec::Vector
GetLex int
MakeGeneric 1
Coerce __AS3__.vec::Vector.<int>
Construct 0

You would now have an instance of Vector.<int>

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