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<concept id="GUID-D1C5BB01-6780-41D6-B47B-43D4C983B0B6" xml:lang="en"><title>API Export</title><shortdesc>This document discusses how to export a device driver API.</shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>

<p>A driver can export its API to be used by other Kernel code by

using IMPORT_C in the declaration and EXPORT_C in the definition.

When the driver is built, these functions are exported to a <filepath>.def</filepath> file. The <filepath>.def</filepath> file is specific

to the platform to which the driver is built. </p>

<codeblock id="GUID-3E732A29-D285-5A51-AF25-9B4B06049632" xml:space="preserve">// Kernel extension internal API

class DExController: public DBase

    {

    …

    void MyExAPI();

    …

    };

// Client interface API

class TExClientInterface

    {

    …

    // static function being exported, this API will go into def file 

    // generated while building

    IMPORT_C static void MyExAPI();

    …

    };

// Global instance of the object

DExController *ExController = NULL; 

// Implementation of the kernel extension's exported function

EXPORT_C void TExClientInterface::MyExAPI()

    {

    …

    ExController->MyExAPI();

    …

    }</codeblock>

<p>Kernel extensions can also provide information to user programs

by setting attributes that can be read through the system HAL (Hardware

Abstration Layer) API. See<xref href="GUID-124AC7EE-E227-5358-A755-628FFE257250.dita"> Handler Implementation</xref> for more information on this. </p>