root / Ganeti / HTools / Utils.hs @ a334d536
History | View | Annotate | Download (7 kB)
1 |
{-| Utility functions -} |
---|---|
2 |
|
3 |
{- |
4 |
|
5 |
Copyright (C) 2009, 2010 Google Inc. |
6 |
|
7 |
This program is free software; you can redistribute it and/or modify |
8 |
it under the terms of the GNU General Public License as published by |
9 |
the Free Software Foundation; either version 2 of the License, or |
10 |
(at your option) any later version. |
11 |
|
12 |
This program is distributed in the hope that it will be useful, but |
13 |
WITHOUT ANY WARRANTY; without even the implied warranty of |
14 |
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
15 |
General Public License for more details. |
16 |
|
17 |
You should have received a copy of the GNU General Public License |
18 |
along with this program; if not, write to the Free Software |
19 |
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA |
20 |
02110-1301, USA. |
21 |
|
22 |
-} |
23 |
|
24 |
module Ganeti.HTools.Utils |
25 |
( |
26 |
debug |
27 |
, debugFn |
28 |
, debugXy |
29 |
, sepSplit |
30 |
, varianceCoeff |
31 |
, commaJoin |
32 |
, readEitherString |
33 |
, loadJSArray |
34 |
, fromObj |
35 |
, maybeFromObj |
36 |
, tryFromObj |
37 |
, fromJVal |
38 |
, asJSObject |
39 |
, asObjectList |
40 |
, fromJResult |
41 |
, tryRead |
42 |
, formatTable |
43 |
, annotateResult |
44 |
, defaultGroupID |
45 |
) where |
46 |
|
47 |
import Control.Monad (liftM) |
48 |
import Data.List |
49 |
import qualified Text.JSON as J |
50 |
import Text.Printf (printf) |
51 |
|
52 |
import Debug.Trace |
53 |
|
54 |
import Ganeti.HTools.Types |
55 |
|
56 |
-- * Debug functions |
57 |
|
58 |
-- | To be used only for debugging, breaks referential integrity. |
59 |
debug :: Show a => a -> a |
60 |
debug x = trace (show x) x |
61 |
|
62 |
-- | Displays a modified form of the second parameter before returning it |
63 |
debugFn :: Show b => (a -> b) -> a -> a |
64 |
debugFn fn x = debug (fn x) `seq` x |
65 |
|
66 |
-- | Show the first parameter before returning the second one |
67 |
debugXy :: Show a => a -> b -> b |
68 |
debugXy a b = debug a `seq` b |
69 |
|
70 |
-- * Miscelaneous |
71 |
|
72 |
-- | Comma-join a string list. |
73 |
commaJoin :: [String] -> String |
74 |
commaJoin = intercalate "," |
75 |
|
76 |
-- | Split a string on a separator and return an array. |
77 |
sepSplit :: Char -> String -> [String] |
78 |
sepSplit sep s |
79 |
| x == "" && xs == [] = [] |
80 |
| xs == [] = [x] |
81 |
| ys == [] = [x,""] |
82 |
| otherwise = x:sepSplit sep ys |
83 |
where (x, xs) = break (== sep) s |
84 |
ys = drop 1 xs |
85 |
|
86 |
-- * Mathematical functions |
87 |
|
88 |
-- Simple and slow statistical functions, please replace with better |
89 |
-- versions |
90 |
|
91 |
-- | Our modified standard deviation function (not, it's not the variance) |
92 |
varianceCoeff :: [Double] -> Double |
93 |
varianceCoeff lst = |
94 |
-- first, calculate the list length and sum lst in a single step, |
95 |
-- for performance reasons |
96 |
let (ll', sx) = foldl' (\(rl, rs) e -> |
97 |
let rl' = rl + 1 |
98 |
rs' = rs + e |
99 |
in rl' `seq` rs' `seq` (rl', rs')) (0::Int, 0) lst |
100 |
ll = fromIntegral ll'::Double |
101 |
mv = sx / ll |
102 |
av = foldl' (\accu em -> let d = em - mv in accu + d * d) 0.0 lst |
103 |
bv = sqrt (av / ll) -- stddev |
104 |
cv = bv / ll -- standard deviation divided by list length |
105 |
in cv |
106 |
|
107 |
-- * JSON-related functions |
108 |
|
109 |
-- | Converts a JSON Result into a monadic value. |
110 |
fromJResult :: Monad m => String -> J.Result a -> m a |
111 |
fromJResult s (J.Error x) = fail (s ++ ": " ++ x) |
112 |
fromJResult _ (J.Ok x) = return x |
113 |
|
114 |
-- | Tries to read a string from a JSON value. |
115 |
-- |
116 |
-- In case the value was not a string, we fail the read (in the |
117 |
-- context of the current monad. |
118 |
readEitherString :: (Monad m) => J.JSValue -> m String |
119 |
readEitherString v = |
120 |
case v of |
121 |
J.JSString s -> return $ J.fromJSString s |
122 |
_ -> fail "Wrong JSON type" |
123 |
|
124 |
-- | Converts a JSON message into an array of JSON objects. |
125 |
loadJSArray :: (Monad m) |
126 |
=> String -- ^ Operation description (for error reporting) |
127 |
-> String -- ^ Input message |
128 |
-> m [J.JSObject J.JSValue] |
129 |
loadJSArray s = fromJResult s . J.decodeStrict |
130 |
|
131 |
-- | Reads the value of a key in a JSON object. |
132 |
fromObj :: (J.JSON a, Monad m) => String -> [(String, J.JSValue)] -> m a |
133 |
fromObj k o = |
134 |
case lookup k o of |
135 |
Nothing -> fail $ printf "key '%s' not found in %s" k (show o) |
136 |
Just val -> fromKeyValue k val |
137 |
|
138 |
-- | Reads the value of an optional key in a JSON object. |
139 |
maybeFromObj :: (J.JSON a, Monad m) => String -> [(String, J.JSValue)] |
140 |
-> m (Maybe a) |
141 |
maybeFromObj k o = |
142 |
case lookup k o of |
143 |
Nothing -> return Nothing |
144 |
Just val -> liftM Just (fromKeyValue k val) |
145 |
|
146 |
-- | Reads a JValue, that originated from an object key |
147 |
fromKeyValue :: (J.JSON a, Monad m) |
148 |
=> String -- ^ The key name |
149 |
-> J.JSValue -- ^ The value to read |
150 |
-> m a |
151 |
fromKeyValue k val = |
152 |
fromJResult (printf "key '%s', value '%s'" k (show val)) (J.readJSON val) |
153 |
|
154 |
-- | Annotate a Result with an ownership information |
155 |
annotateResult :: String -> Result a -> Result a |
156 |
annotateResult owner (Bad s) = Bad $ owner ++ ": " ++ s |
157 |
annotateResult _ v = v |
158 |
|
159 |
-- | Try to extract a key from a object with better error reporting |
160 |
-- than fromObj |
161 |
tryFromObj :: (J.JSON a) => |
162 |
String -> [(String, J.JSValue)] -> String -> Result a |
163 |
tryFromObj t o k = annotateResult t (fromObj k o) |
164 |
|
165 |
-- | Small wrapper over readJSON. |
166 |
fromJVal :: (Monad m, J.JSON a) => J.JSValue -> m a |
167 |
fromJVal v = |
168 |
case J.readJSON v of |
169 |
J.Error s -> fail ("Cannot convert value " ++ show v ++ ", error: " ++ s) |
170 |
J.Ok x -> return x |
171 |
|
172 |
-- | Converts a JSON value into a JSON object. |
173 |
asJSObject :: (Monad m) => J.JSValue -> m (J.JSObject J.JSValue) |
174 |
asJSObject (J.JSObject a) = return a |
175 |
asJSObject _ = fail "not an object" |
176 |
|
177 |
-- | Coneverts a list of JSON values into a list of JSON objects. |
178 |
asObjectList :: (Monad m) => [J.JSValue] -> m [J.JSObject J.JSValue] |
179 |
asObjectList = mapM asJSObject |
180 |
|
181 |
-- * Parsing utility functions |
182 |
|
183 |
-- | Parse results from readsPrec |
184 |
parseChoices :: (Monad m, Read a) => String -> String -> [(a, String)] -> m a |
185 |
parseChoices _ _ ((v, ""):[]) = return v |
186 |
parseChoices name s ((_, e):[]) = |
187 |
fail $ name ++ ": leftover characters when parsing '" |
188 |
++ s ++ "': '" ++ e ++ "'" |
189 |
parseChoices name s _ = fail $ name ++ ": cannot parse string '" ++ s ++ "'" |
190 |
|
191 |
-- | Safe 'read' function returning data encapsulated in a Result. |
192 |
tryRead :: (Monad m, Read a) => String -> String -> m a |
193 |
tryRead name s = parseChoices name s $ reads s |
194 |
|
195 |
-- | Format a table of strings to maintain consistent length |
196 |
formatTable :: [[String]] -> [Bool] -> [[String]] |
197 |
formatTable vals numpos = |
198 |
let vtrans = transpose vals -- transpose, so that we work on rows |
199 |
-- rather than columns |
200 |
mlens = map (maximum . map length) vtrans |
201 |
expnd = map (\(flds, isnum, ml) -> |
202 |
map (\val -> |
203 |
let delta = ml - length val |
204 |
filler = replicate delta ' ' |
205 |
in if delta > 0 |
206 |
then if isnum |
207 |
then filler ++ val |
208 |
else val ++ filler |
209 |
else val |
210 |
) flds |
211 |
) (zip3 vtrans numpos mlens) |
212 |
in transpose expnd |
213 |
|
214 |
-- | Default group UUID (just a string, not a real UUID) |
215 |
defaultGroupID :: GroupID |
216 |
defaultGroupID = "00000000-0000-0000-0000-000000000000" |