Passing strings – PB Docs 125

Passing strings

PowerBuilder assumes all string arguments and returned values
use Unicode encoding. If a function uses strings with ANSI encoding,
you need to add an ALIAS FOR clause to the function declaration
and add a semicolon followed by the ansi keyword.
For example:

The same statement in C would point to a buffer containing
the String:

Since the String is passed by value,
the C function can change the contents of its local copy of CODE,
but the original variable in PowerBuilder is not affected.

When you pass a string to an external function, either by
value or by reference, PowerBuilder passes a pointer to the string.
If you pass by value, any changes the function makes to the string
are not accessible to PowerBuilder. If you pass by reference, they
are.

The following statement declares the external C function NAME2 in PowerBuilder.
This function returns a String and expects
a String argument to be passed by reference:

In C, the statement would be the same as when the argument
is passed by value, shown above:

The String argument is passed by reference,
and the C function can change the contents of the argument and the
original variable in PowerBuilder. For example, Strcpy(CODE,STUMP) would
change the contents of CODE to STUMP and
change the variable in the calling PowerBuilder script to the contents
of variable STUMP.

If the function NAME2 in the preceding
example takes a user ID and replaces it with the user’s
name, the PowerScript string variable CODE must
be long enough to hold the returned value. To ensure that this is
true, declare the String and then use the Space function
to fill the String with blanks equal to the maximum
number of characters you expect the function to return.

If the maximum number of characters allowed for a user’s
name is 40 and the ID is always five characters, you would fill
the String CODE with 35
blanks before calling the external function:

For information about the Space function,
see the PowerScript Reference.

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