Applications and Geodes: 1.1 Geodes: Geode Components and Structures

GEOS SDK TechDocs

1 Geodes

1.2 Launching an Application

A geode is simply a special type of GEOS file. It has a special file header that gets loaded in as the geode's core block. This file header contains the geode's type, attributes, release and protocol levels, and many other pieces of information necessary for GEOS to work with the geode. You never will have to know the exact structure of this header as the kernel provides routines necessary to access important portions of it.

Several important items contained in the header are listed below.

• Core Block Handle
  The core block contains its own memory handle, filled in when the geode is loaded into memory.
• Geode Attributes
  Each geode has a record of type GeodeAttrs . The geode attributes are described below in Geode Attributes .
• Release and Protocol Levels
  Each geode can have release and protocol levels associated with it to ensure compatibility between different versions. Release and protocol levels are discussed in Protocol Numbers .
• Geode Name
  Each geode has a geode name and extension specified in the geode parameters ( .gp ) file.
• Geode Token
  Every geode has a token associated with it in the token database. The token describes the geode's icon and is a structure of type GeodeToken . Tokens and icons are discussed in Creating Icons .
• Geode Reference Count
  The geode's reference count is stored in the core block. See above for a discussion of the reference count and how it's managed.
• Geode File Handle
  The file handle of the geode identifies the open GEO file so the kernel can locate, load, and access its various resources.
• Geode Process Handle
  Each geode that has a parent process will have the handle of the process in its core block. This is the handle of the parent process' core block. (The parent process is the owner of the thread that loaded the geode. It is notified when the geode exits, if the exiting geode is a process.)
• Handle of the Next Geode
  Because geode core blocks are stored in a linked list, each core block must contain a reference to the next geode in the list.
• Handle of Private Data Space
  Each geode that is not the kernel can have a "private data space." This private data space is discussed in Temporary Geode Memory .
• Resource, Library, and Driver Information
  Each geode that imports or exports library or driver information must keep the import and export specifics available. Additionally, each geode must keep track of the resources it owns. All this information is stored in tables referenced from within the core block.

Geode Attributes

Each geode has in its core block a record of type GeodeAttrs . This record defines several things about the geode, including which aspects it uses and which of its aspects have been initialized. The GeodeAttrs record contains one bit for each of the following attributes.

GA_PROCESS

This geode has a process aspect and therefore an initial event-driven thread.

GA_LIBRARY

This geode has a library aspect and therefore exports routines (and possibly object classes).

GA_DRIVER

This geode has a driver aspect and therefore has a driver table, in which the strategy routine is specified.

GA_KEEP_FILE_OPEN

This geode must have its .GEO file kept open because its resources may be discardable or are initially discarded.

GA_SYSTEM

This geode is a privileged geode and is almost certainly a system-used driver. These geodes have special exit requirements.

GA_MULTI_LAUNCHABLE

This geode may be loaded more than once and therefore may have more than one instance of its core block in memory.

GA_APPLICATION

This geode is a user-launchable application.

GA_DRIVER_INITIALIZED

This flag is set if the geode has had its driver aspect initialized (if the driver's strategy routine has been initialized). This flag will be set dynamically by the kernel.

GA_LIBRARY_INITIALIZED

This flag is set if the geode has had its library aspect initialized (if the library's entry routine has been called). This flag will be set dynamically by the kernel.

GA_GEODE_INITIALIZED

This flag is set if all aspects of the geode have been initialized.

GA_USES_COPROC

This geode uses a math coprocessor if one is available.

GA_REQUIRES_COPROC

This geode requires the presence of a math coprocessor or a coprocessor emulator.

GA_HAS_GENERAL_CONSUMER_MODE

This geode may be run in the General Consumer (appliance) Mode.

GA_ENTRY_POINTS_IN_C

This geode has its library entry routine in C rather than assembly language.

Geode Token

As stated above, every geode is associated with a token in the token database. This token is defined by the use of a GeodeToken structure. This structure and its uses are discussed in Creating Icons .

GEOS SDK TechDocs

1 Geodes

1.2 Launching an Application