1 // Copyright Joyent, Inc. and other Node contributors.
3 // Permission is hereby granted, free of charge, to any person obtaining a
4 // copy of this software and associated documentation files (the
5 // "Software"), to deal in the Software without restriction, including
6 // without limitation the rights to use, copy, modify, merge, publish,
7 // distribute, sublicense, and/or sell copies of the Software, and to permit
8 // persons to whom the Software is furnished to do so, subject to the
9 // following conditions:
11 // The above copyright notice and this permission notice shall be included
12 // in all copies or substantial portions of the Software.
14 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
15 // OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
16 // MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
17 // NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
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20 // USE OR OTHER DEALINGS IN THE SOFTWARE.
23 list._idleNext = list;
24 list._idlePrev = list;
29 // show the most idle item
31 if (list._idlePrev == list) return null;
32 return list._idlePrev;
37 // remove the most idle item from the list
38 function shift(list) {
39 var first = list._idlePrev;
43 exports.shift = shift;
46 // remove a item from its list
47 function remove(item) {
49 item._idleNext._idlePrev = item._idlePrev;
53 item._idlePrev._idleNext = item._idleNext;
56 item._idleNext = null;
57 item._idlePrev = null;
59 exports.remove = remove;
62 // remove a item from its list and place at the end.
63 function append(list, item) {
65 item._idleNext = list._idleNext;
66 list._idleNext._idlePrev = item;
67 item._idlePrev = list;
68 list._idleNext = item;
70 exports.append = append;
73 function isEmpty(list) {
74 return list._idleNext === list;
76 exports.isEmpty = isEmpty;