ASIS Architecture

ASIS package architecture

package ASIS - Package ASIS, together with its children, provides the interface between an Ada environment (as defined by ISO/IEC 8652:1995) and any tool requiring information fromit. Valuable semantic and syntactic information is made available via queries through child packages of package ASIS.Package Asis contains commontypes and subtypes used for the ASIS interface and its child packages. Important common types include:

• Type Context helps identify the compilation units considered to be analyzable as part of the Ada compilation environment.
• Type Element is an abstraction of entities within a logical Ada syntax tree.
• Element Kinds are a set of enumeration types providing a mapping to the Ada syntax.
• Type Compilation_Unit is an abstraction for Ada compilation units.
• Unit Kinds are a set of enumeration types describing the various kinds of compilation units.
• Type Traverse_Control provides a mechanism to control iterative traversals of a logical syntax tree.
• Type Program_Text provides an abstraction for the program text for a program's source code.

Package Asis also encapsulates implementor-specific declarations, which are made available to ASIS and its client applications in an implementor-independent manner. Package ASIS is the root of the ASIS interface. All other packages are child packages of package Asis. These packages are:

• Asis.Ada_Environments - This child package encapsulates a set of queriesthat map physical Ada compilation and program execution environments to logical ASIS environments. An ASIS Context is associated with some set ofAda compilation units maintained by an underlying Ada implementation. After this association has been made, this set of units is considered to bepart of the compile-time Ada environment, which forms the outermost context of any compilation, as specified in section 10.1.4 of the Ada Reference manual. This same environment context provides the implicit outermost anonymous task during program execution. If an Ada implementation supports the notion of a program library or "library" as specified in section 10(2) of the Ada Reference Manual, then an ASIS Context value can be mappedonto one or more implementor libraries represented by Containers. More than one context may be manipulated at a time. Important interfaces include: Associate, Dissociate, Open, and Close. The type Container and its supporting functions are provided in the child package Asis.Ada_Environments.Containers.

• Asis.Implementation - This child package provides operations to initialize and finalize the ASIS interface. It also provides queries for the error status of the ASIS implementation. Its child package Asis.Implementation.Permissions provides queries to determine options usedby an implementation.

• Asis.Compilation_Units - This child package encapsulates a set of queries that implement the ASIS Compilation_Unit abstraction. It defines queries that deal with Compilation_Units and the gateway queries between Compilation_Units, Elements, and Ada_Environments. More than one compilation unit may be manipulated at one time. The child package Asis.Compilation_Units.Times encapsulates the time related functions used within ASIS. A second child package, Asis.Compilation_Units.Relations encapsulates the semantic relationship concepts used in ASIS. Relation queries provide references to compilation units that are related,in some specific fashion, to one or more given compilation units.

• Asis.Iterator - This child package encapsulates the Traverse_Element mechanism to perform an iterative traversal of a logical syntax tree. Duringthe traversal, ASIS can analyze the various elements present and provideapplication processing via generic procedures instantiated by the application using queries to decompose ASIS elements into the logical semantic tree of the Ada program. This key mechanism is the heart of most ASIS tools.

• Asis.Elements - This child package encapsulates a set of queries that operate on all elements and some queries specific to A_Pragma elements. Element_Kinds, defined in package Asis are defined as enumeration types describing the various kinds of elements. ASIS offers a hierarchical classification of elements. At the highest level, the Element_Kinds type providesliterals that define "kinds" or classes into which all non-nil elements are grouped. Element_Kinds are: Not_An_Element, A_Pragma, A_Defining_Name, A_Declaration, A_Definition, An_Expression, An_Association, A_Statement, A_Path, A_Clause, and An_Exception_Handler. Elements in each of the Element_Kinds classes, with the exception of An_Exception_Handler, can be further classified by a subordinate kind at the next level in the hierarchy.

• Asis.Clauses - This child package encapsulates a set of queries that operate on the A_Clause element.

• Asis.Declarations - This child package encapsulates a set of queries that operate on A_Defining_Name and A_Declaration elements.

• Asis.Definitions - This child package encapsulates a set of queries thatoperate on A_Definition elements.

• Asis.Expressions - This child package encapsulates a set of queries thatoperate on An_Expression and An_Association elements.

• Asis.Statements - This child package encapsulates a set of queries that operate on A_Statement, A_Path, and An_Exception_Handler elements.

• Asis.Text - This child package encapsulates a set of operations to access the text of ASIS Elements. This text is represented as logical lines from the source code of the external representation of a compilation unit. Type Line is defined to support program text operations. It assumes no knowledge of the existence, location, or form of the program text.

• Asis.Errors - This child package provides an enumeration type identifying the error kinds used for the ASIS interface.

• Asis.Exceptions - This child package identifies all defined ASIS exceptions.

• Asis.Ids - This child package encapsulates a set of operations and queries that implement the ASIS Id abstraction. An Id is a way to identify a particular element (i.e., a unique reference to an Element) which is efficient and persistent as long as the environment is not recompiled.

• Asis.Data_Decomposition - This optional child package encapsulates a setof operations to decompose data values using the ASIS type information and a portable data stream, representing a data value of that type. Its child package Asis.Data_Decomposition.Portable_Transfer provides support for logging and delogging of application data using ASIS. Internal packages of Asis.Data_Decomposition.Portable_Transfer include: Portable_Constrained_Subtype, Portable_Unconstrained_Record_Type, Portable_Array_Type_1 (for one dimensional arrays), Portable_Array_Type_2 (for two dimensional arrays), and Portable_Array_Type_3 (for three dimensional arrays).