'''Cheney's Copying Collector'''

The Fenichel-Yochelson collector given in the [wiki:CopyingGarbageCollector]
page has the disadvantage of using a recursive copying algorithm.  Since
Cheney's discovery of an efficient iterative technique for its implementation
copying collection has proved popular with implementors.  Although garbage
collection technology has moved beyond simple stop-and-copy collection, this
technique remains the most widely adopted basis for more sophisticated
techniques, such as generational and incremental collectors.


Cheney's algorithm:
{{{
flip() =
    Fromspace, Tospace = Tospace, Fromspace
    top_of_space = Tospace + space_size
    scan = free = Tospace

    for R in roots
        R = copy(R)

    while scan < free
        for P in Children(scan)
            *P = copy(*P)
        scan = scan + size (scan)

copy(P) =
    if forwarded(P)
        return forwarding_address(P)
    else
        addr = free
        move(P,free)
        free = free + size(P)
        forwarding_address(P) = addr
        return addr

}}}


extracted from:[[BR]]
Garbage Collection: Algorithms for Automatic Dynamic Memory Management[[BR]]
by Richard Jones and Rafael Sims[[BR]]
[http://www.cs.kent.ac.uk/people/staff/rej/gc.html]