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1--
2-- KEEPER.LUA
3--
4-- Keeper state logic
5--
6-- This code is read in for each "keeper state", which are the hidden, inter-
7-- mediate data stores used by Lanes inter-state communication objects.
8--
9-- Author: Asko Kauppi <akauppi@gmail.com>
10--
11--[[
12===============================================================================
13
14Copyright (C) 2008 Asko Kauppi <akauppi@gmail.com>
15
16Permission is hereby granted, free of charge, to any person obtaining a copy
17of this software and associated documentation files (the "Software"), to deal
18in the Software without restriction, including without limitation the rights
19to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
20copies of the Software, and to permit persons to whom the Software is
21furnished to do so, subject to the following conditions:
22
23The above copyright notice and this permission notice shall be included in
24all copies or substantial portions of the Software.
25
26THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
27IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
28FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
29AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
30LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
31OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
32THE SOFTWARE.
33
34===============================================================================
35]]--
36
37-- unique key instead of 'nil' in queues
38--
39assert( nil_sentinel )
40
41-- We only need to have base and table libraries (and io for debugging)
42--
43local table_remove= assert( table.remove )
44local table_concat= assert( table.concat )
45
46local function WR(...)
47 if io then
48 io.stderr:write( table_concat({...},'\t').."\n" )
49 end
50end
51
52-----
53-- Actual data store
54--
55-- { [linda_deep_ud]= { key= val [, ...] }
56-- ...
57-- }
58--
59local _data= {}
60
61-----
62-- Entries queued for use when the existing 'data[ud][key]' entry is consumed.
63--
64-- { [linda_deep_ud]= { key= { val [, ... } [, ...] }
65-- ...
66-- }
67--
68local _incoming= {}
69
70-----
71-- Length limits (if any) for queues
72--
73-- 0: don't queue values at all; ':send()' waits if the slot is not vacant
74-- N: allow N values to be queued (slot itself + N-1); wait if full
75-- nil: no limits, '_incoming' may grow endlessly
76--
77local _limits= {}
78
79-----
80-- data_tbl, incoming_tbl, limits_tbl = tables( linda_deep_ud )
81--
82-- Gives appropriate tables for a certain Linda (creates them if needed)
83--
84local function tables( ud )
85 -- tables are created either all or nothing
86 --
87 if not _data[ud] then
88 _data[ud]= {}
89 _incoming[ud]= {}
90 _limits[ud]= {}
91 end
92 return _data[ud], _incoming[ud], _limits[ud]
93end
94
95
96local function DEBUG(title,ud,key)
97 assert( title and ud and key )
98
99 local data,incoming,_= tables(ud)
100
101 local s= tostring(data[key])
102 for _,v in ipairs( incoming[key] or {} ) do
103 s= s..", "..tostring(v)
104 end
105 WR( "*** "..title.." ("..tostring(key).."): ", s )
106end
107
108
109-----
110-- bool= send( linda_deep_ud, key, ... )
111--
112-- Send new data (1..N) to 'key' slot. This send is atomic; all the values
113-- end up one after each other (this is why having possibility for sending
114-- multiple values in one call is deemed important).
115--
116-- If the queue has a limit, values are sent only if all of them fit in.
117--
118-- Returns: 'true' if all the values were placed
119-- 'false' if sending would exceed the queue limit (wait & retry)
120--
121function send( ud, key, ... )
122
123 local data,incoming,limits= tables(ud)
124
125 local n= select('#',...)
126 if n==0 then return true end -- nothing to send
127
128 -- Initialize queue for all keys that have been used with ':send()'
129 --
130 if incoming[key]==nil then
131 incoming[key]= {}
132 end
133
134 local len= data[key] and 1+#incoming[key] or 0
135 local m= limits[key]
136
137 if m and len+n > m then
138 return false -- would exceed the limit; try again later
139 end
140
141 for i=1,n do
142 local val= select(i,...)
143
144 -- 'nil' in the data replaced by sentinel
145 if val==nil then
146 val= nil_sentinel
147 end
148
149 if len==0 then
150 data[key]= val
151 len= 1
152 else
153 incoming[key][len]= val
154 len= len+1
155 end
156 end
157 return true
158end
159
160
161-----
162-- [val, key]= receive( linda_deep_ud, key [, ...] )
163--
164-- Read any of the given keys, consuming the data found. Keys are read in
165-- order.
166--
167function receive( ud, ... )
168
169 local data,incoming,_= tables(ud)
170
171 for i=1,select('#',...) do
172 local key= select(i,...)
173 local val= data[key]
174
175 if val~=nil then
176 if incoming[key] and incoming[key][1]~=nil then
177 -- pop [1] from 'incoming[key]' into the actual slot
178 data[key]= table_remove( incoming[key], 1 )
179 else
180 data[key]= nil -- empty the slot
181 end
182 if val==nil_sentinel then
183 val= nil
184 end
185 return val, key
186 end
187 end
188 --return nil
189end
190
191
192-----
193-- = limit( linda_deep_ud, key, uint )
194--
195function limit( ud, key, n )
196
197 local _,_,limits= tables(ud)
198
199 limits[key]= n
200end
201
202
203-----
204-- void= set( linda_deep_ud, key, [val] )
205--
206function set( ud, key, val )
207
208 local data,incoming,_= tables(ud)
209
210 -- Setting a key to 'nil' really clears it; only queing uses sentinels.
211 --
212 data[key]= val
213 incoming[key]= nil
214end
215
216
217-----
218-- [val]= get( linda_deep_ud, key )
219--
220function get( ud, key )
221
222 local data,_,_= tables(ud)
223
224 local val= data[key]
225 if val==nil_sentinel then
226 val= nil
227 end
228 return val
229end
230
231
232-----
233-- void= clear( linda_deep_ud )
234--
235-- Clear the data structures used for a Linda (at its destructor)
236--
237function clear( ud )
238
239 _data[ud]= nil
240 _incoming[ud]= nil
241 _limits[ud]= nil
242end
243
244