GET_MESSAGE_PTR

GET_MESSAGE_PTR MsgIdentifier, Reg

Returns the address of the given message. The macro carries out no other processing.

• Return the message address in the given register.

MsgIdentifier

Message identifier of the message to retrieve.

Reg

Name of register that recieves the message address.

A register name can also be given for the MsgIdentifier parameter. If a register name is given, the register value is checked at runtime to determine which table to look in for the message. Because this requires additional code to support, this register-based version of the macro should be avoided.

The overhead of the register-based version can be avoided by an alternate form of the GET_MESSAGE_PTR macro:

Get_Message_Ptr MsgIdentifier, Reg1, Reg2

This alternative form places into Reg1 a pointer to the message string whose identifier is MsgIdentifier + Reg2. No range checking is performed; the value MsgIdentifier + Reg2 must be of the same message type as MsgIdentifier. For example, if you have a series of three messages, declared contiguously:

VxD_MESSAGE_SEG
DECLARE_MESSAGE MsgFirst, <"First message">
DECLARE_MESSAGE MsgSecond, <"Second Message">
DECLARE_MESSAGE MsgThird, <"Third message">
VxD_MESSAGE_ENDS

then the line:

GET_MESSAGE_PTR MsgFirst, eax, esi

would load into the EAX register a pointer to MsgFirst, if ESI = 0, a pointer to MsgSecond if ESI = 1, and a pointer to MsgThird if ESI = 2. Any other value for ESI is an error and will load garbage or possibly even page fault.