The RCSString interface provides an abstract interface to the text strings associated with RCS files. Behind the abstract interface are hidden a number of different implementations, each appropriate for a different situation. The goal of this approach is efficiency.

For example, most strings that were present in the original RCS file are implemented as pointers into the memory-mapped image of the file itself. Thus, those strings can contain huge numbers of characters without consuming any memory resources.

INTERFACE RCSString;

CONST Brand = "RCSString";

TYPE
  T = OBJECT METHODS
    toText(): TEXT := NIL;
    numLines(): CARDINAL := NIL;
    iterate(): Iterator := NIL;
  END;

  Iterator = OBJECT METHODS
    next(VAR line: T): BOOLEAN := NIL;
  END;

The numLines method returns the number of lines in the string. If the last line does not have a terminating newline character, it still counts as a line.

The iterate method constructs an iterator that accesses the individual lines of the string in sequence. Each call to the Iterator's next method sets the VAR parameter to the next line of the string, and returns TRUE. If there are no more lines, next returns FALSE.

Each returned line includes its terminating newline, if any. The last line won't necessarily end with a newline.

PROCEDURE FromText(text: TEXT): T;

Construct an RCSString.T from the given TEXT.

END RCSString.