/*
 * CXSPARSE: a Concise Sparse Matrix package - Extended.
 * Copyright (c) 2006-2009, Timothy A. Davis.
 * http://www.cise.ufl.edu/research/sparse/CXSparse
 * 
 * CXSparse is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 * 
 * CXSparse is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * Lesser General Public License for more details.
 * 
 * You should have received a copy of the GNU Lesser General Public
 * License along with this Module; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
 */

#include "cs.h"
/* drop entries for which fkeep(A(i,j)) is false; return nz if OK, else -1 */
CS_INT cs_fkeep (cs *A, CS_INT (*fkeep) (CS_INT, CS_INT, CS_ENTRY, void *), void *other)
{
    CS_INT j, p, nz = 0, n, *Ap, *Ai ;
    CS_ENTRY *Ax ;
    if (!CS_CSC (A) || !fkeep) return (-1) ;    /* check inputs */
    n = A->n ; Ap = A->p ; Ai = A->i ; Ax = A->x ;
    for (j = 0 ; j < n ; j++)
    {
        p = Ap [j] ;                        /* get current location of col j */
        Ap [j] = nz ;                       /* record new location of col j */
        for ( ; p < Ap [j+1] ; p++)
        {
            if (fkeep (Ai [p], j, Ax ? Ax [p] : 1, other))
            {
                if (Ax) Ax [nz] = Ax [p] ;  /* keep A(i,j) */
                Ai [nz++] = Ai [p] ;
            }
        }
    }
    Ap [n] = nz ;                           /* finalize A */
    cs_sprealloc (A, 0) ;                   /* remove extra space from A */
    return (nz) ;
}