Apple Network Setup manual OSStatus err AssertdbRef = nil Assertentity

C H A P T E R 2

Using Network Setup

Note

The sample shown in Listing 2-7, which opens and closes the entity before reading each preference, is implemented in an inefficient manner for the sake of clarity. If you are reading multiple preferences, it is more efficient to open the entity once. Then read the preferences by calling OTCfgGetPrefs or OTCfgSetPrefs multiple times and close the entity when you’re done. ◆

A noteworthy point about reading preferences is that the OTCfgOpenPrefs function does not take an area parameter. This is because the CfgEntityRef itself implicitly includes the area. The significant of this point is demonstrated in the section “Working with Sets” (page 42).

You can use the MyReadFixedSizePref routine shown in Listing 2-7 to read specific preferences within an entity. For example, Listing 2-8 shows how to read the DHCP lease information from a TCP/IP network connection entity. The routine calls MyReadFixedSizePref, passing it the appropriate preference type (kOTCfgTCPDHCPLeaseInfoPref), a pointer to the corresponding C structure, and the size of the structure.

Listing 2-8Reading the DHCP lease info preference in a TCP/IP network connection entity

static OSStatus MyReadDHCPLeaseInfo(CfgDatabaseRef dbRef, const CfgEntityRef *entity, OTCfgTCPDHCPLeaseInfo *dhcpInfo)

{

OSStatus err;
assert(dbRef	!= nil);
assert(entity	!=	nil);
assert(dhcpInfo !=		nil);

err = MyReadFixedSizePref(dbRef, entity, kOTCfgTCPDHCPLeaseInfoPref, dhcpInfo, sizeof(*dhcpInfo));

return err;

}

36Reading and Writing Preferences