Call of PB dynamic Connection Library and external Function

External functions: functions written in other languages stored in the dynamic link library.

1. External Functions

Steps for describing external functions:

1) first open the object to describe the external function;

2) In the script window, select declare from the first drop-down list box and Global External funnal or local external funnal from the second drop-down list box;

3) in the script window, enter the statements that describe the external functions;

4) Save the object;

Syntax of external functions:

{Access} function returndatatype name ({ref} datatype1 arg1 ,..., {Ref} datatypen argn}) Library "libname"

Alias for "extname"

Describes the syntax of the external process:

{Access} subroutine name ({ref} datatype1 arg1 ,..., {Ref} datatypen argn}) Library "libname"

Alias for "extname"

2. External function call example

1. Get the username information:

1.1 button Clicked:

Long ll_RTN

String ls_UserName

Long ll_BufferLen

Ll_BufferLen = MAX_LENGTH

Ls_UserName = Space (MAX_LENGTH)

// Obtain the name of the current system user

Ll_RTN = GetUserName (ls_UserName, ll_BufferLen)

If ll_RTN <> 0 Then

MessageBox ("prompt message", "the current system user name is:" + Trim (ls_UserName ))

Else

MessageBox ("prompt message", "function call failed! ")

End If

1.2 instance variable: CONSTANT Long MAX_LENGTH = 256

1.3 external functions:

FUNCTION Long GetUserName (REF String lpBuffer, REF Long nSize) LIBRARY "advapi32.dll" alias for "GetUserNameA"

2. Obtain the computer name:

2.1 button Clicked:

// Obtain the computer name

Long ll_RTN

String ls_ComputerName

Long ll_BufferLen

Ll_BufferLen = MAX_COMPUTERNAME_LENGTH + 225

Ls_ComputerName = Space (MAX_COMPUTERNAME_LENGTH + 225)

Ll_RTN = GetComputerName (ls_ComputerName, ll_BufferLen)

If ll_RTN <> 0 Then

MessageBox ("prompt message", "computer name:" + Trim (ls_ComputerName ))

Else

MessageBox ("prompt message", "function call failed! ")

End If

2.2 instance variable: CONSTANT Long MAX_COMPUTERNAME_LENGTH = 31

2.3 external functions:

FUNCTION Long GetComputerName (REF String lpBuffer, REF Long nSize) LIBRARY "kernel32" alias for "GetComputerNameA"