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Inside Macintosh: Networking /

Chapter 11 - Ethernet, Token Ring, and Fiber Distributed Data Interface / Ethernet, Token Ring, and FDDI Reference

Data Structures

The Write-Data Structure

To send data directly from the Ethernet, token ring, or FDDI driver, you must provide a write-data structure and pass the EWrite function a pointer to it. A write-data structure contains a series of pairs of length words and pointers. Each pair indicates the length and location of a portion of the data that constitutes the packet to be sent over the network. The interface files for the driver do not include a type declaration for the write-data structure. Here is an example type declaration that you can include in your application.

TYPE  WDSElement = 
RECORD
   entryLength:   Integer;
   entryPtr:      Ptr;
END;

Field Description

entryLength

The length of the data pointer to by entryPtr.

entryPtr

A pointer to the data that is part of the packet to be sent using the EWrite function.

For more information about the write-data structure, see "Using a Write-Data Structure to Transmit Ethernet Data" beginning on page 11-10.