root / Ganeti / HTools / PeerMap.hs @ c9926b22
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1 | e4f08c46 | Iustin Pop | {-| |
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2 | e4f08c46 | Iustin Pop | Module abstracting the peer map implementation. |
3 | e4f08c46 | Iustin Pop | |
4 | e4f08c46 | Iustin Pop | This is abstracted separately since the speed of peermap updates can |
5 | e4f08c46 | Iustin Pop | be a significant part of the total runtime, and as such changing the |
6 | e4f08c46 | Iustin Pop | implementation should be easy in case it's needed. |
7 | e4f08c46 | Iustin Pop | |
8 | e4f08c46 | Iustin Pop | -} |
9 | e4f08c46 | Iustin Pop | |
10 | e2fa2baf | Iustin Pop | {- |
11 | e2fa2baf | Iustin Pop | |
12 | e2fa2baf | Iustin Pop | Copyright (C) 2009 Google Inc. |
13 | e2fa2baf | Iustin Pop | |
14 | e2fa2baf | Iustin Pop | This program is free software; you can redistribute it and/or modify |
15 | e2fa2baf | Iustin Pop | it under the terms of the GNU General Public License as published by |
16 | e2fa2baf | Iustin Pop | the Free Software Foundation; either version 2 of the License, or |
17 | e2fa2baf | Iustin Pop | (at your option) any later version. |
18 | e2fa2baf | Iustin Pop | |
19 | e2fa2baf | Iustin Pop | This program is distributed in the hope that it will be useful, but |
20 | e2fa2baf | Iustin Pop | WITHOUT ANY WARRANTY; without even the implied warranty of |
21 | e2fa2baf | Iustin Pop | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
22 | e2fa2baf | Iustin Pop | General Public License for more details. |
23 | e2fa2baf | Iustin Pop | |
24 | e2fa2baf | Iustin Pop | You should have received a copy of the GNU General Public License |
25 | e2fa2baf | Iustin Pop | along with this program; if not, write to the Free Software |
26 | e2fa2baf | Iustin Pop | Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA |
27 | e2fa2baf | Iustin Pop | 02110-1301, USA. |
28 | e2fa2baf | Iustin Pop | |
29 | e2fa2baf | Iustin Pop | -} |
30 | e2fa2baf | Iustin Pop | |
31 | 669d7e3d | Iustin Pop | module Ganeti.HTools.PeerMap |
32 | 71e13e48 | Iustin Pop | ( PeerMap |
33 | 71e13e48 | Iustin Pop | , Key |
34 | 71e13e48 | Iustin Pop | , Elem |
35 | 71e13e48 | Iustin Pop | , empty |
36 | 71e13e48 | Iustin Pop | , accumArray |
37 | 71e13e48 | Iustin Pop | , Ganeti.HTools.PeerMap.find |
38 | 71e13e48 | Iustin Pop | , add |
39 | 71e13e48 | Iustin Pop | , remove |
40 | 71e13e48 | Iustin Pop | , maxElem |
41 | 669d7e3d | Iustin Pop | ) where |
42 | e4f08c46 | Iustin Pop | |
43 | e4f08c46 | Iustin Pop | import Data.Maybe (fromMaybe) |
44 | e4f08c46 | Iustin Pop | import Data.List |
45 | e4f08c46 | Iustin Pop | import Data.Function |
46 | e4f08c46 | Iustin Pop | import Data.Ord |
47 | e4f08c46 | Iustin Pop | |
48 | 608efcce | Iustin Pop | import Ganeti.HTools.Types |
49 | 608efcce | Iustin Pop | |
50 | 608efcce | Iustin Pop | type Key = Ndx |
51 | e4f08c46 | Iustin Pop | type Elem = Int |
52 | e4f08c46 | Iustin Pop | type PeerMap = [(Key, Elem)] |
53 | e4f08c46 | Iustin Pop | |
54 | 9188aeef | Iustin Pop | -- * Initialization functions |
55 | 9188aeef | Iustin Pop | |
56 | 9188aeef | Iustin Pop | -- | Create a new empty map. |
57 | e4f08c46 | Iustin Pop | empty :: PeerMap |
58 | e4f08c46 | Iustin Pop | empty = [] |
59 | e4f08c46 | Iustin Pop | |
60 | 9188aeef | Iustin Pop | -- | Our reverse-compare function. |
61 | e4f08c46 | Iustin Pop | pmCompare :: (Key, Elem) -> (Key, Elem) -> Ordering |
62 | e4f08c46 | Iustin Pop | pmCompare a b = (compare `on` snd) b a |
63 | e4f08c46 | Iustin Pop | |
64 | 9188aeef | Iustin Pop | -- | Add or update (via a custom function) an element. |
65 | e4f08c46 | Iustin Pop | addWith :: (Elem -> Elem -> Elem) -> Key -> Elem -> PeerMap -> PeerMap |
66 | e4f08c46 | Iustin Pop | addWith fn k v lst = |
67 | e4f08c46 | Iustin Pop | let r = lookup k lst |
68 | e4f08c46 | Iustin Pop | in |
69 | e4f08c46 | Iustin Pop | case r of |
70 | e4f08c46 | Iustin Pop | Nothing -> insertBy pmCompare (k, v) lst |
71 | e4f08c46 | Iustin Pop | Just o -> insertBy pmCompare (k, fn o v) (remove k lst) |
72 | e4f08c46 | Iustin Pop | |
73 | 17c59f4b | Iustin Pop | -- | Create a PeerMap from an association list, with possible duplicates |
74 | 17c59f4b | Iustin Pop | accumArray :: (Elem -> Elem -> Elem) -- ^ function used to merge the elements |
75 | 17c59f4b | Iustin Pop | -> [(Key, Elem)] -- ^ source data |
76 | 17c59f4b | Iustin Pop | -> PeerMap -- ^ results |
77 | 17c59f4b | Iustin Pop | accumArray fn lst = |
78 | e4f08c46 | Iustin Pop | case lst of |
79 | e4f08c46 | Iustin Pop | [] -> empty |
80 | 17c59f4b | Iustin Pop | (k, v):xs -> addWith fn k v $ accumArray fn xs |
81 | e4f08c46 | Iustin Pop | |
82 | 9188aeef | Iustin Pop | -- * Basic operations |
83 | 9188aeef | Iustin Pop | |
84 | 9188aeef | Iustin Pop | -- | Returns either the value for a key or zero if not found |
85 | e4f08c46 | Iustin Pop | find :: Key -> PeerMap -> Elem |
86 | 9f6dcdea | Iustin Pop | find k = fromMaybe 0 . lookup k |
87 | e4f08c46 | Iustin Pop | |
88 | 9188aeef | Iustin Pop | -- | Add an element to a peermap, overwriting the previous value |
89 | e4f08c46 | Iustin Pop | add :: Key -> Elem -> PeerMap -> PeerMap |
90 | 9f6dcdea | Iustin Pop | add = addWith (flip const) |
91 | e4f08c46 | Iustin Pop | |
92 | 9188aeef | Iustin Pop | -- | Remove an element from a peermap |
93 | e4f08c46 | Iustin Pop | remove :: Key -> PeerMap -> PeerMap |
94 | e4f08c46 | Iustin Pop | remove k c = case c of |
95 | e4f08c46 | Iustin Pop | [] -> [] |
96 | e4f08c46 | Iustin Pop | (x@(x', _)):xs -> if k == x' then xs |
97 | 9f6dcdea | Iustin Pop | else x:remove k xs |
98 | e4f08c46 | Iustin Pop | |
99 | 9188aeef | Iustin Pop | -- | Find the maximum element. |
100 | 9188aeef | Iustin Pop | -- |
101 | 9188aeef | Iustin Pop | -- Since this is a sorted list, we just get the value at the head of |
102 | 9188aeef | Iustin Pop | -- the list, or zero for a null list |
103 | e4f08c46 | Iustin Pop | maxElem :: PeerMap -> Elem |
104 | 71e13e48 | Iustin Pop | maxElem c = if null c then 0 else snd . head $ c |