1 | package com.hammurapi.extract; |
2 | |
3 | import java.util.HashMap; |
4 | import java.util.Map; |
5 | import java.util.concurrent.TimeUnit; |
6 | |
7 | import com.hammurapi.extract.ComparisonResult.Type; |
8 | |
9 | |
10 | /** |
11 | * Base class for extractors, implements value caching. |
12 | * @author Pavel Vlasov. |
13 | * |
14 | * @param <T> |
15 | * @param <V> |
16 | */ |
17 | public abstract class ExtractorBase<T, V, C> implements Extractor<T, V, C> { |
18 | |
19 | protected TimeUnit costUnit; |
20 | protected long invocations; |
21 | protected double totalCost; |
22 | protected boolean nanos; |
23 | protected double cost; |
24 | protected double initialCost; |
25 | |
26 | /** |
27 | * @param initialCost Initial cost. If positive, this value is added to the calculated cost. If costUnit is null, |
28 | * then cost is always equal to the initial cost. If negative and time unit is not null, then absolute value is used as first measurement of cost. |
29 | * @param costUnit If this argument is not null, then extractor cost is |
30 | * calculated as average time to execute extractInternal() method in specified time unit. |
31 | * If time unit is nanoseconds or microseconds, then System.nanoTime() method is used for |
32 | * measurement, otherwise Systsm.currentTimeMillis() is used. |
33 | */ |
34 | protected ExtractorBase(double initialCost, TimeUnit costUnit) { |
35 | this.costUnit = costUnit; |
36 | this.initialCost = initialCost; |
37 | if (initialCost<0 && costUnit!=null) { |
38 | invocations = 1; |
39 | totalCost = initialCost; |
40 | } else { |
41 | this.cost = initialCost; |
42 | } |
43 | nanos = costUnit!=null && TimeUnit.MILLISECONDS.compareTo(costUnit)>0; |
44 | } |
45 | |
46 | @SuppressWarnings("unchecked") |
47 | public V extract(C context, Map<C, Map<Extractor<T, ? super V, C>, ? super V>> cache, T... obj) { |
48 | long start = 0; |
49 | if (costUnit!=null) { |
50 | start = nanos ? System.nanoTime() : System.currentTimeMillis(); |
51 | } |
52 | try { |
53 | if (cache==null) { |
54 | return extractInternal(context, cache, obj); |
55 | } |
56 | |
57 | synchronized (cache) { |
58 | Map<Extractor<T, ? super V, C>, ? super V> ce = cache.get(context); |
59 | if (ce==null) { |
60 | ce = createCacheEntry(); |
61 | cache.put(context, ce); |
62 | } |
63 | |
64 | V ret = (V) ce.get(this); |
65 | if (ret==null) { |
66 | ret = extractInternal(context, cache, obj); |
67 | ce.put(this, ret); |
68 | } |
69 | return ret; |
70 | } |
71 | } finally { |
72 | if (costUnit!=null) { |
73 | long end = nanos ? System.nanoTime() : System.currentTimeMillis(); |
74 | totalCost += costUnit.convert(end-start, nanos ? TimeUnit.NANOSECONDS : TimeUnit.MICROSECONDS); |
75 | ++invocations; |
76 | } |
77 | } |
78 | } |
79 | |
80 | @Override |
81 | public double getCost() { |
82 | |
83 | if (invocations==0) { |
84 | return cost; |
85 | } |
86 | |
87 | return cost + totalCost/invocations; |
88 | } |
89 | |
90 | /** |
91 | * Basic comparisons with True and False. |
92 | * @param otherPredicate |
93 | * @return |
94 | */ |
95 | public ComparisonResult compareTo(Extractor<T, V, C> other) { |
96 | if (this==other) { |
97 | return ComparisonResult.EQUAL_NM; |
98 | } |
99 | |
100 | // True is less restrictive than anything but self. |
101 | if (other instanceof True) { |
102 | return ComparisonResult.MORE_RESTRICTIVE_NM; |
103 | } |
104 | |
105 | // False is more restrictive than anything but self. |
106 | if (other instanceof False) { |
107 | return ComparisonResult.LESS_RESTRICTIVE_NM; |
108 | } |
109 | |
110 | if (other instanceof FacadeExtractor && !(this instanceof FacadeExtractor)) { |
111 | ComparisonResult cr = other.compareTo(this); |
112 | if (cr==null) { |
113 | return cr; |
114 | } |
115 | switch (cr.getType()) { |
116 | case EQUAL: |
117 | case NOT_EQUAL: |
118 | case OPPOSITE: |
119 | return cr; |
120 | case LESS_RESTRICTIVE: |
121 | return new ComparisonResult(Type.MORE_RESTRICTIVE, ComparisonResult.inverse(cr.getIndexMap(), parameterIndices())); |
122 | case MORE_RESTRICTIVE: |
123 | return new ComparisonResult(Type.LESS_RESTRICTIVE, ComparisonResult.inverse(cr.getIndexMap(), parameterIndices())); |
124 | case OPPOSITE_LESS_RESTRICTIVE: |
125 | return new ComparisonResult(Type.OPPOSITE_LESS_RESTRICTIVE, ComparisonResult.inverse(cr.getIndexMap(), parameterIndices())); |
126 | case OPPOSITE_MORE_RESTRICTIVE: |
127 | return new ComparisonResult(Type.OPPOSITE_MORE_RESTRICTIVE, ComparisonResult.inverse(cr.getIndexMap(), parameterIndices())); |
128 | } |
129 | } |
130 | |
131 | return ComparisonResult.NOT_EQUAL_NM; |
132 | } |
133 | |
134 | |
135 | protected abstract V extractInternal(C context, Map<C, Map<Extractor<T, ? super V, C>, ? super V>> cache, T... obj); |
136 | |
137 | protected Map<Extractor<T, ? super V, C>, ? super V> createCacheEntry() { |
138 | return new HashMap<Extractor<T,? super V,C>, V>(); |
139 | } |
140 | |
141 | @Override |
142 | public boolean equals(Object obj) { |
143 | if (this == obj) { |
144 | return true; |
145 | } |
146 | if (obj instanceof Extractor) { |
147 | ComparisonResult cr = compareTo((Extractor) obj); |
148 | if (ComparisonResult.Type.EQUAL.equals(cr.getType()) && cr.isOneToOneMapping()) { |
149 | return true; |
150 | } |
151 | } |
152 | return false; |
153 | } |
154 | |
155 | } |