/* lnkan.f -- translated by f2c (version 19980913).
   You must link the resulting object file with the libraries:
	-lf2c -lm   (in that order)
*/

#include "f2c.h"

/* $Procedure      LNKAN  ( LNK, allocate node ) */
/* Subroutine */ int lnkan_(integer *pool, integer *new__)
{
    extern /* Subroutine */ int chkin_(char *, ftnlen), sigerr_(char *, 
	    ftnlen), chkout_(char *, ftnlen), setmsg_(char *, ftnlen);

/* $ Abstract */

/*     Allocate a node in a doubly linked list pool. */

/* $ Disclaimer */

/*     THIS SOFTWARE AND ANY RELATED MATERIALS WERE CREATED BY THE */
/*     CALIFORNIA INSTITUTE OF TECHNOLOGY (CALTECH) UNDER A U.S. */
/*     GOVERNMENT CONTRACT WITH THE NATIONAL AERONAUTICS AND SPACE */
/*     ADMINISTRATION (NASA). THE SOFTWARE IS TECHNOLOGY AND SOFTWARE */
/*     PUBLICLY AVAILABLE UNDER U.S. EXPORT LAWS AND IS PROVIDED "AS-IS" */
/*     TO THE RECIPIENT WITHOUT WARRANTY OF ANY KIND, INCLUDING ANY */
/*     WARRANTIES OF PERFORMANCE OR MERCHANTABILITY OR FITNESS FOR A */
/*     PARTICULAR USE OR PURPOSE (AS SET FORTH IN UNITED STATES UCC */
/*     SECTIONS 2312-2313) OR FOR ANY PURPOSE WHATSOEVER, FOR THE */
/*     SOFTWARE AND RELATED MATERIALS, HOWEVER USED. */

/*     IN NO EVENT SHALL CALTECH, ITS JET PROPULSION LABORATORY, OR NASA */
/*     BE LIABLE FOR ANY DAMAGES AND/OR COSTS, INCLUDING, BUT NOT */
/*     LIMITED TO, INCIDENTAL OR CONSEQUENTIAL DAMAGES OF ANY KIND, */
/*     INCLUDING ECONOMIC DAMAGE OR INJURY TO PROPERTY AND LOST PROFITS, */
/*     REGARDLESS OF WHETHER CALTECH, JPL, OR NASA BE ADVISED, HAVE */
/*     REASON TO KNOW, OR, IN FACT, SHALL KNOW OF THE POSSIBILITY. */

/*     RECIPIENT BEARS ALL RISK RELATING TO QUALITY AND PERFORMANCE OF */
/*     THE SOFTWARE AND ANY RELATED MATERIALS, AND AGREES TO INDEMNIFY */
/*     CALTECH AND NASA FOR ALL THIRD-PARTY CLAIMS RESULTING FROM THE */
/*     ACTIONS OF RECIPIENT IN THE USE OF THE SOFTWARE. */

/* $ Required_Reading */

/*     LNK */

/* $ Keywords */

/*     LIST */

/* $ Declarations */
/* $ Brief_I/O */

/*     Variable  I/O  Description */
/*     --------  ---  -------------------------------------------------- */
/*     POOL      I-O  A doubly linked list pool. */
/*     NEW        O   Number of new node that was allocated. */
/*     LBPOOL     P   Lower bound of pool column indices. */

/* $ Detailed_Input */

/*     POOL           is a doubly linked list pool. */

/* $ Detailed_Output */

/*     POOL           is the input pool, with the following */
/*                    modifications: */

/*                       -- NEW is an allocated node:  both the forward */
/*                          and backward pointers of NEW are -NEW. */

/*                       -- The node that was the successor of NEW on */
/*                          input is the head of the free list on output. */


/*     NEW            is the number of the newly allocated node. */

/* $ Parameters */

/*     LBPOOL        is the lower bound of the column indices of the POOL */
/*                   array.  The columns indexed LBPOOL to 0 are reserved */
/*                   as a control area for the pool. */

/* $ Exceptions */

/*     1)  If no free nodes are available for allocation, the error */
/*         SPICE(NOFREENODES) is signalled. */

/* $ Files */

/*     None. */

/* $ Particulars */

/*     In a doubly linked list pool, an `allocated node' is one that has */
/*     been removed from the free list.  An allocated node may be linked */
/*     to other nodes or may be unlinked; in the latter case, both the */
/*     forward and backward pointers of the node will be the negative of */
/*     the node number. */

/*     A node must be allocated before it can be linked to another */
/*     node. */

/* $ Examples */

/*     1)  Let POOL be a doubly linked list pool.  To build a new list */
/*         of ten nodes, the code fragment below can be used: */

/*            C */
/*            C     We'll use LNKILA ( LNK, insert list after */
/*            C     a specified node ) to add nodes to the tail of the */
/*            C     list. */
/*            C */
/*                  PREV = 0 */

/*                  DO I = 1, 10 */

/*                     CALL LNKAN  ( POOL, NODE       ) */
/*                     CALL LNKILA ( PREV, NODE, POOL ) */
/*                     PREV = NODE */

/*                  END DO */


/*     2)  In this version of example (1), we check that a sufficient */
/*         number of free nodes are available before building the list: */

/*            C */
/*            C     Make sure we have 10 free nodes available. */
/*            C     Signal an error if not.  Use LNKNFN to obtain */
/*            C     the number of free nodes. */
/*            C */
/*                  IF ( LNKNFN(POOL) .LT. 10 ) THEN */

/*                     CALL SETMSG ( 'Only # free nodes are available '// */
/*                 .                 'but 10 are required.'            ) */
/*                     CALL ERRINT ( '#', LNKNFN(POOL)                 ) */
/*                     CALL SIGERR ( 'POOL_TOO_SMALL'                  ) */
/*                     RETURN */

/*                  END IF */

/*                     [ Build list ] */
/*                           . */
/*                           . */
/*                           . */

/* $ Restrictions */

/*     Linked list pools must be initialized via the routine */
/*     LNKINI.  Failure to initialize a linked list pool */
/*     will almost certainly lead to confusing results. */

/* $ Literature_References */

/*     None. */

/* $ Author_and_Institution */

/*     N.J. Bachman   (JPL) */
/*     W.L. Taber     (JPL) */

/* $ Version */

/* -    SPICELIB Version 1.0.0, 19-DEC-1995 (NJB) (WLT) */

/* -& */
/* $ Index_Entries */

/*     allocate node from linked list pool */

/* -& */

/*     Local parameters */


/*     The control area contains 3 elements.  They are: */

/*        The "size" of the pool, that is, the number */
/*        of nodes in the pool. */

/*        The number of free nodes in the pool. */

/*        The "free pointer," which is the column index of the first free */
/*        node. */

/*     Parameters defining the row and column indices of these control */
/*     elements are given below. */


/*     Each assigned node consists of a backward pointer and a forward */
/*     pointer. */

/*        +-------------+       +-------------+       +-------------+ */
/*        |  forward--> |       |  forward--> |       |  forward--> | */
/*        +-------------+  ...  +-------------+  ...  +-------------+ */
/*        | <--backward |       | <--backward |       | <--backward | */
/*        +-------------+       +-------------+       +-------------+ */

/*            node 1                 node I              node SIZE */




/*     Free nodes say that that's what they are.  The way they say it */
/*     is by containing the value FREE in their backward pointers. */
/*     Needless to say, FREE is a value that cannot be a valid pointer. */


/*     Discovery check-in is used in place of standard SPICE error */
/*     handling. */

    if (pool[11] == 0) {
	chkin_("LNKAN", (ftnlen)5);
	setmsg_("There are no free nodes left for allocating in the supplied"
		" linked list pool. ", (ftnlen)78);
	sigerr_("SPICE(NOFREENODES)", (ftnlen)18);
	chkout_("LNKAN", (ftnlen)5);
	return 0;
    }

/*     The caller gets the first free node.  The forward pointer of */
/*     this node indicates the next free node.  After this, there's one */
/*     less free node. */

    *new__ = pool[8];
    pool[8] = pool[(*new__ << 1) + 10];
    --pool[11];

/*     The forward and backward pointers of the allocated node become */
/*     the negatives of the node numbers of the head and tail nodes */
/*     of the list containing NEW.  Since this is a singleton list, */
/*     both pointers are -NEW. */

    pool[(*new__ << 1) + 10] = -(*new__);
    pool[(*new__ << 1) + 11] = -(*new__);
    return 0;
} /* lnkan_ */

