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Annotation of src/usr.bin/sudo/list.c, Revision 1.2

1.1       millert     1: /*
                      2:  * Copyright (c) 2007-2008 Todd C. Miller <Todd.Miller@courtesan.com>
                      3:  *
                      4:  * Permission to use, copy, modify, and distribute this software for any
                      5:  * purpose with or without fee is hereby granted, provided that the above
                      6:  * copyright notice and this permission notice appear in all copies.
                      7:  *
                      8:  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
                      9:  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
                     10:  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
                     11:  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
                     12:  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
                     13:  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
                     14:  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
                     15:  * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
                     16:  * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
                     17:  */
                     18:
                     19: #include <config.h>
                     20:
                     21: #include <sys/types.h>
                     22: #include <stdio.h>
                     23: #ifdef STDC_HEADERS
                     24: # include <stdlib.h>
                     25: # include <stddef.h>
                     26: #else
                     27: # ifdef HAVE_STDLIB_H
                     28: #  include <stdlib.h>
                     29: # endif
                     30: #endif /* STDC_HEADERS */
                     31:
                     32: #include "sudo.h"
                     33:
                     34: struct list_proto {
                     35:     struct list_proto *prev;
                     36:     struct list_proto *next;
                     37: };
                     38:
                     39: struct list_head_proto {
                     40:     struct list_proto *first;
                     41:     struct list_proto *last;
                     42: };
                     43:
                     44: /*
                     45:  * Pop the last element off the end of vh.
                     46:  * Returns the popped element.
                     47:  */
                     48: void *
                     49: tq_pop(vh)
                     50:     void *vh;
                     51: {
                     52:     struct list_head_proto *h = (struct list_head_proto *)vh;
                     53:     void *last = NULL;
                     54:
                     55:     if (!tq_empty(h)) {
                     56:        last = (void *)h->last;
                     57:        if (h->first == h->last) {
                     58:            h->first = NULL;
                     59:            h->last = NULL;
                     60:        } else {
                     61:            h->last = h->last->prev;
                     62:            h->last->next = NULL;
                     63:        }
                     64:     }
                     65:     return (last);
                     66: }
                     67:
                     68: /*
                     69:  * Convert from a semi-circle queue to normal doubly-linked list
                     70:  * with a head node.
                     71:  */
                     72: void
                     73: list2tq(vh, vl)
                     74:     void *vh;
                     75:     void *vl;
                     76: {
                     77:     struct list_head_proto *h = (struct list_head_proto *)vh;
                     78:     struct list_proto *l = (struct list_proto *)vl;
                     79:
                     80:     if (l != NULL) {
                     81: #ifdef DEBUG
                     82:        if (l->prev == NULL) {
                     83:            warningx("list2tq called with non-semicircular list");
                     84:            abort();
                     85:        }
                     86: #endif
                     87:        h->first = l;
                     88:        h->last = l->prev;      /* l->prev points to the last member of l */
                     89:        l->prev = NULL;         /* zero last ptr now that we have a head */
                     90:     } else {
                     91:        h->first = NULL;
                     92:        h->last = NULL;
                     93:     }
                     94: }
                     95:
                     96: /*
                     97:  * Append one queue (or single entry) to another using the
                     98:  * circular properties of the prev pointer to simplify the logic.
                     99:  */
                    100: void
                    101: list_append(vl1, vl2)
                    102:     void *vl1;
                    103:     void *vl2;
                    104: {
                    105:     struct list_proto *l1 = (struct list_proto *)vl1;
                    106:     struct list_proto *l2 = (struct list_proto *)vl2;
                    107:     void *tail = l2->prev;
                    108:
                    109:     l1->prev->next = l2;
                    110:     l2->prev = l1->prev;
                    111:     l1->prev = tail;
                    112: }
                    113:
                    114: /*
                    115:  * Append the list of entries to the head node and convert
                    116:  * e from a semi-circle queue to normal doubly-linked list.
                    117:  */
                    118: void
                    119: tq_append(vh, vl)
                    120:     void *vh;
                    121:     void *vl;
                    122: {
                    123:     struct list_head_proto *h = (struct list_head_proto *)vh;
                    124:     struct list_proto *l = (struct list_proto *)vl;
                    125:     void *tail = l->prev;
                    126:
                    127:     if (h->first == NULL)
                    128:        h->first = l;
                    129:     else
                    130:        h->last->next = l;
                    131:     l->prev = h->last;
                    132:     h->last = tail;
                    133: }