GEOS SDK TechDocs
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1 Design Philosophy
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1.2 Transport Driver Overview
The Mailbox library implements an Inbox/Outbox system. This lets the user select an appropriate device through which to transport the information; it also lets the user select a delivery time (though most applications will always designate messages for immediate delivery, so it is possible that the first release of the Inbox/Outbox system will not support applications setting an early-bound for delivery time). (Most applications will do this by including the Mailbox Library's MailboxSendControl device, which the user can use to create an outgoing message.)
The application must, when requested, package up information in a format acceptable to a transport driver being used. (Most applications will only need to support one or a few different data formats, such as GStrings or raw text in a VM Chain.) It then registers this message with the Mailbox library.
The Mailbox library stores messages that have not yet been transmitted in its outbox . Messages are held in the outbox until the hardware connection necessary for transmission is available. For example, if the transport driver needed a direct serial link, the message would stay in the outbox until that link was available. An application can also specify that a message not be delivered until a specific time. In this case, the message will automatically remain in the outbox until that time. While a message is in the outbox, the device's user can examine information about the message, and (if he or she chooses) delay or cancel its delivery.
When the time comes to send the message, the Mailbox library activates the appropriate data and transport drivers. This activation is transparent to an application developer. It is helpful to understand how a transport driver operates, however.
GEOS SDK TechDocs
|
| 1 Design Philosophy
| 1.2 Transport Driver Overview