Firebird 2.1 Language Reference Update

Notes:
External functions (UDFs)
For more information about passing NULLs to UDFs, see the note at the end of this book.
• Depending on how you declare it (see CSTRING note), this function can accept and return strings of up to
32767 characters.
• When calling this function, make sure endlength does not exceed the declared result length.
• If endlength is less than str's length, str is truncated to endlength. If endlength is negative, the
result is NULL.
• A NULL endlength is treated as if it were 0.
• If padchar is empty, or if padchar is NULL and the function has been declared without the NULL keyword
after the last argument, str is returned unchanged (or truncated to endlength).
• Before Firebird 2.0, the result type was CHAR(n).
• A bug that caused an endless loop if padchar was empty or NULL has been fixed in 2.0.
• In Firebird 1.5.1 and below, the default declaration used CSTRING(80) instead of CSTRING(255).
Library: ib_udf
Changed in: 1.5, 1.5.2, 2.0
Better alternative: Internal function TRIM()
rtrim
Description: Returns the input string with any trailing space characters removed. In new code, you are advised
to use the internal function TRIM instead, as it is both more powerful and more versatile.
Result type: VARCHAR(n)
Syntax (unchanged):
rtrim (str)
Declaration:
DECLARE EXTERNAL FUNCTION rtrim
CSTRING(255) NULL
RETURNS CSTRING(255) FREE_IT
ENTRY_POINT 'IB_UDF_rtrim' MODULE_NAME 'ib_udf'
The above declaration is from the file ib_udf2.sql. The NULL after the argument is an optional
addition that became available in Firebird 2. If the argument is declared with the NULL keyword,
the engine will pass a NULL argument value unchanged to the function. This leads to a NULL result,
which is correct. Without the NULL keyword (your only option in pre-2.0 versions), NULL is passed
to the function as an empty string and the result is an empty string as well.
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