source: libcfa/src/bits/sequence.hfa @ 221c542e

//
// Cforall Version 1.0.0 Copyright (C) 2021 University of Waterloo
//
// The contents of this file are covered under the licence agreement in the
// file "LICENCE" distributed with Cforall.
//
// bits/sequence.hfa -- PUBLIC
// Intrusive doubly-linked list
//
// Author           : Colby Alexander Parsons & Peter A. Buhr
// Created On       : Thu Jan 21 19:46:50 2021
// Last Modified By :
// Last Modified On :
// Update Count     :
//

#pragma once

#include "bits/collection.hfa"
#include "bits/defs.hfa"

struct Seqable {
        __cfa_anonymous_object(Colable);
        // pointer to previous node in the list
        struct Seqable * back;
};

#ifdef __cforall
static inline {
        // PUBLIC

        void ?{}( Seqable & sq ) {
                ((Colable &)sq){};
                sq.back = 0p;
        } // post: ! listed()

        Seqable & getBack( Seqable & sq ) with( sq ) {
                return *back;
        }

        // PRIVATE

        Seqable *& Back( Seqable * sq ) {
                return sq->back;
        }
} // distribution


// A Sequence(T) is a Collection(T) defining the ordering of a uStack and uQueue, and to insert and remove elements
// anywhere in the sequence. T must be a public descendant of uSeqable.

// The implementation is a typical doubly-linked list, except the next field of the last node points at the first node
// and the back field of the last node points at the first node (circular).

forall( T & ) {
        struct Sequence {
                // Plan 9 inheritance
                inline Collection;
        };

        static inline {
                void ?{}( Sequence(T) &, const Sequence(T) & ) = void; // no copy
                Sequence(T) & ?=?( const Sequence(T) & ) = void; // no assignment

                void ?{}( Sequence(T) & s ) with( s ) {
                        ((Collection &)s){};
                }       // post: isEmpty()
        }

        static inline forall(| { T *& Back ( T * ); T *& Next ( T * ); }) {
                // wrappers to make Collection have T
                T & head( Sequence(T) & s ) with( s ) {
                        return *(T *)head( (Collection &)s );
                } // post: empty() & head() == 0 | !empty() & head() in *s

                // Return a pointer to the last sequence element, without removing it.
                T & tail( Sequence(T) & s ) with( s ) {
                        return root ? (T &)*Back( &head( s ) ) : *0p;
                }       // post: empty() & tail() == 0 | !empty() & tail() in *s

                // Return a pointer to the element after *n, or 0p if list empty.
                T * succ( Sequence(T) & s, T * n ) with( s ) {  // pre: *n in *s
                        #ifdef __CFA_DEBUG__
                        if ( ! listed( n ) ) abort( "(Sequence &)%p.succ( %p ) : Node is not on a list.", &s, n );
                        #endif // __CFA_DEBUG__
                        return Next( n ) == &head( s ) ? 0p : Next( n );
                } // post: n == tail() & succ(n) == 0 | n != tail() & *succ(n) in *s

                // Return a pointer to the element before *n, or 0p if list empty.
                T * pred( Sequence(T) & s, T * n ) with( s ) {  // pre: *n in *s
                        #ifdef __CFA_DEBUG__
                        if ( ! listed( n ) ) abort( "(Sequence &)%p.pred( %p ) : Node is not on a list.", &s, n );
                        #endif // __CFA_DEBUG__
                        return n == &head( s ) ? 0p : Back( n );
                } // post: n == head() & head(n) == 0 | n != head() & *pred(n) in *s


                // Insert *n into the sequence before *bef, or at the end if bef == 0p.
                T & insertBef( Sequence(T) & s, T & n, T & bef ) with( s ) { // pre: !n->listed() & *bef in *s
                        #ifdef __CFA_DEBUG__
                        if ( listed( &n ) ) abort( "(Sequence &)%p.insertBef( %p, %p ) : Node is already on another list.", &s, n, &bef );
                        #endif // __CFA_DEBUG__
                        if ( &bef == &head( s ) ) {                                     // must change root
                                if ( root ) {
                                        Next( &n ) = &head( s );
                                        Back( &n ) = Back( &head( s ) );
                                        // inserted node must be consistent before it is seen
                                        asm( "" : : : "memory" );                       // prevent code movement across barrier
                                        Back( &head( s ) ) = &n;
                                        Next( Back( &n ) ) = &n;
                                } else {
                                        Next( &n ) = &n;
                                        Back( &n ) = &n;
                                } // if
                                // inserted node must be consistent before it is seen
                                asm( "" : : : "memory" );                               // prevent code movement across barrier
                                root = &n;
                        } else {
                                if ( ! &bef ) &bef = &head( s );
                                Next( &n ) = &bef;
                                Back( &n ) = Back( &bef );
                                // inserted node must be consistent before it is seen
                                asm( "" : : : "memory" );                               // prevent code movement across barrier
                                Back( &bef ) = &n;
                                Next( Back( &n ) ) = &n;
                        } // if
                        return n;
                }       // post: n->listed() & *n in *s & succ(n) == bef


                // Insert *n into the sequence after *aft, or at the beginning if aft == 0.
                T & insertAft( Sequence(T) & s, T & aft, T & n ) with( s ) {    // pre: !n->listed() & *aft in *s
                        #ifdef __CFA_DEBUG__
                        if ( listed( &n ) ) abort( "(Sequence &)%p.insertAft( %p, %p ) : Node is already on another list.", &s, &aft, &n );
                        #endif // __CFA_DEBUG__
                        if ( ! &aft ) {                                                         // must change root
                                if ( root ) {
                                        Next( &n ) = &head( s );
                                        Back( &n ) = Back( &head( s ) );
                                        // inserted node must be consistent before it is seen
                                        asm( "" : : : "memory" );                       // prevent code movement across barrier
                                        Back( &head( s ) ) = &n;
                                        Next( Back( &n ) ) = &n;
                                } else {
                                        Next( &n ) = &n;
                                        Back( &n ) = &n;
                                } // if
                                asm( "" : : : "memory" );                               // prevent code movement across barrier
                                root = &n;
                        } else {
                                Next( &n ) = Next( &aft );
                                Back( &n ) = &aft;
                                // inserted node must be consistent before it is seen
                                asm( "" : : : "memory" );                               // prevent code movement across barrier
                                Back( Next( &n ) ) = &n;
                                Next( &aft ) = &n;
                        } // if
                        return n;
                } // post: n->listed() & *n in *s & succ(n) == bef

                // pre: n->listed() & *n in *s
                T & remove( Sequence(T) & s, T & n ) with( s ) { // O(1)
                        #ifdef __CFA_DEBUG__
                        if ( ! listed( &n ) ) abort( "(Sequence &)%p.remove( %p ) : Node is not on a list.", &s, &n );
                        #endif // __CFA_DEBUG__
                        if ( &n == &head( s ) ) {
                                if ( Next( &head( s ) ) == &head( s ) ) root = 0p;
                                else root = Next( &head( s ) );
                        } // if
                        Back( Next( &n ) ) = Back( &n );
                        Next( Back( &n ) ) = Next( &n );
                        Next( &n ) = Back( &n ) = 0p;
                        return n;
                } // post: !n->listed()

                // Add an element to the head of the sequence.
                T & addHead( Sequence(T) & s, T & n ) {                 // pre: !n->listed(); post: n->listed() & head() == n
                        return insertAft( s, *0p, n );
                }

                // Add an element to the tail of the sequence.
                T & addTail( Sequence(T) & s, T & n ) {                 // pre: !n->listed(); post: n->listed() & head() == n
                        return insertBef( s, n, *0p );
                }

                // Add an element to the tail of the sequence.
                T & add( Sequence(T) & s, T & n ) {                             // pre: !n->listed(); post: n->listed() & head() == n
                        return addTail( s, n );
                }

                // Remove and return the head element in the sequence.
                T & dropHead( Sequence(T) & s ) {
                        T & n = head( s );
                        return &n ? remove( s, n ), n : *0p;
                }

                // Remove and return the head element in the sequence.
                T & drop( Sequence(T) & s ) {
                        return dropHead( s );
                }

                // Remove and return the tail element in the sequence.
                T & dropTail( Sequence(T) & s ) {
                        T & n = tail( s );
                        return &n ? remove( s, n ), n : *0p;
                }

                // Transfer the "from" list to the end of s sequence; the "from" list is empty after the transfer.
                void transfer( Sequence(T) & s, Sequence(T) & from ) with( s ) {
                        if ( empty( from ) ) return;                            // "from" list empty ?
                        if ( empty( s ) ) {                                                     // "to" list empty ?
                                root = from.root;
                        } else {                                                                        // "to" list not empty
                                T * toEnd = Back( &head( s ) );
                                T * fromEnd = Back( &head( from ) );
                                Back( (T *)root ) = fromEnd;
                                Next( fromEnd ) = &head( s );
                                Back( (T *)from.root ) = toEnd;
                                Next( toEnd ) = &head( from );
                        } // if
                        from.root = 0p;                                                         // mark "from" list empty
                }

                // Transfer the "from" list up to node "n" to the end of s list; the "from" list becomes the sequence after node "n".
                // Node "n" must be in the "from" list.
                void split( Sequence(T) & s, Sequence(T) & from, T & n ) with( s ) {
                        #ifdef __CFA_DEBUG__
                        if ( ! listed( &n ) ) abort( "(Sequence &)%p.split( %p ) : Node is not on a list.", &s, &n );
                        #endif // __CFA_DEBUG__
                        Sequence(T) to;
                        to.root = from.root;                                            // start of "to" list
                        from.root = Next( &n );                                         // start of "from" list
                        if ( to.root == from.root ) {                           // last node in list ?
                                from.root = 0p;                                                 // mark "from" list empty
                        } else {
                                Back( &head( from ) ) = Back( &head( to ) ); // fix "from" list
                                Next( Back( &head( to ) ) ) = &head( from );
                                Next( &n ) = &head( to );                               // fix "to" list
                                Back( &head( to ) ) = &n;
                        } // if
                        transfer( s, to );
                }
        } // distribution
} // distribution

forall( T & | { T *& Back ( T * ); T *& Next ( T * ); } ) {
        // SeqIter(T) is used to iterate over a Sequence(T) in head-to-tail order.
        struct SeqIter {
                inline ColIter;
                // The Sequence must be passed to pred and succ to check for the end of the Sequence and return 0p. Without
                // passing the sequence, traversing would require its length. Thus the iterator needs a pointer to the sequence
                // to pass to succ/pred. Both stack and queue just encounter 0p since the lists are not circular.
                Sequence(T) * seq;                                                              // FIX ME: cannot be reference
        };

        static inline {
                void ?{}( SeqIter(T) & si ) with( si ) {
                        ((ColIter &)si){};
                        seq = 0p;
                } // post: elts = null

                // Create a iterator active in sequence s.
                void ?{}( SeqIter(T) & si, Sequence(T) & s ) with( si ) {
                        ((ColIter &)si){};
                        seq = &s;
                        curr = &head( s );
                } // post: elts = null

                void ?{}( SeqIter(T) & si, Sequence(T) & s, T & start ) with( si ) {
                        ((ColIter &)si){};
                        seq = &s;
                        curr = &start;
                } // post: elts = null

                // Make the iterator active in sequence s.
                void over( SeqIter(T) & si, Sequence(T) & s ) with( si ) {
                        seq = &s;
                        curr = &head( s );
                } // post: elts = {e in s}

                bool ?|?( SeqIter(T) & si, T && tp ) with( si ) {
                        if ( curr ) {
                                &tp = Curr( si );
                                T * n = succ( *seq, Curr( si ) );
                                curr = n == &head( *seq ) ? 0p : n;
                        } else &tp = 0p;
                        return &tp != 0p;
                }
        } // distribution


        // A SeqIterRev(T) is used to iterate over a Sequence(T) in tail-to-head order.
        struct SeqIterRev {
                inline ColIter;
                // See above for explanation.
                Sequence(T) * seq;                                                              // FIX ME: cannot be reference
        };

        static inline {
                void ?{}( SeqIterRev(T) & si ) with( si ) {
                        ((ColIter &)si){};
                        seq = 0p;
                } // post: elts = null

                // Create a iterator active in sequence s.
                void ?{}( SeqIterRev(T) & si, Sequence(T) & s ) with( si ) {
                        ((ColIter &)si){};
                        seq = &s;
                        curr = &tail( s );
                } // post: elts = null

                void ?{}( SeqIterRev(T) & si, Sequence(T) & s, T & start ) with( si ) {
                        ((ColIter &)si){};
                        seq = &s;
                        curr = &start;
                } // post: elts = null

                // Make the iterator active in sequence s.
                void over( SeqIterRev(T) & si, Sequence(T) & s ) with( si ) {
                        seq = &s;
                        curr = &tail( s );
                } // post: elts = {e in s}

                bool ?|?( SeqIterRev(T) & si, T && tp ) with( si ) {
                        if ( curr ) {
                                &tp = Curr( si );
                                T * n = pred( *seq, Curr( si ) );
                                curr = n == &tail( *seq ) ? 0p : n;
                        } else &tp = 0p;
                        return &tp != 0p;
                }
        } // distribution
} // distribution

#endif