Varchar2 "Width" during code execution

Question

Release 10g2 --
Is it possible to in some way determine the defined "width" of a char variable (esp. varchar2) during code execution?
For example, given:
=================================
strng VARCHAR2(<width>)
BEGIN
strng := function(sizeof(strng))
=================================
Is there any reasonably straightforward manner to create that "sizeof" function which can return the max width of strng to the function? I'd like to make sure, without writing exception logic, that I don't overflow the boundary of the strng variable. This is fairly easy to do in c but I don't see anything readily analogous in Oracle. Assume that strng is not tied to a table column, in particular, although that, too (i.e., created using %TYPE in the definition) would probably be useful to be determinable as well.
Any suggestions as to how one might accomplish this without some absurd "fill until the exception occurs" loop would be appreciated.

Answer 1

Thanks, I searched for something like that but didn't find it.
There is a function called VSIZE in Oracle 9i, but it returns the memory length of the ACTUAL string, not the theoretical maximum. The only way I see for you is to select the string length from the data dictionary, look at ALL_TAB_COLUMNS. Or write a loop with an exception section, trying to add one character after another until the exception is raised. This is correct, VSIZE does not do what I'm after. The specific link above deals more with the special case of %TYPE. I'm more interested in the general case of a defined variable -- Where in the Data Dictionary would I look for information about a variable? (I don't necessarily need instructions, but a pointer to something to read that should cover what I'm after would be helpful-- even a book reference would be of use, since it's hard to tell what books cover what topics well -- I don't mind becoming more knowledgeable about the DD, that seems like widely useful info anyway).
Any suggestions, links, pointers, would be greatly appreciated, thanks.