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+// Copyright (c) 2015, the Dart project authors. Please see the AUTHORS file |
+// for details. All rights reserved. Use of this source code is governed by a |
+// BSD-style license that can be found in the LICENSE file. |
+ |
+library dart_style.src.rule_set; |
+ |
+import 'rule/rule.dart'; |
+ |
+/// An optimized data structure for storing a set of values for some rules. |
+/// |
+/// This conceptually behaves roughly like a `Map<Rule, int>`, but is much |
+/// faster since it avoids hashing. Instead, it assumes the line splitter has |
+/// provided an ordered list of [Rule]s and that each rule's [index] field has |
+/// been set to point to the rule in the list. |
+/// |
+/// Internally, this then just stores the values in a sparse list whose indices |
+/// are the indices of the rules. |
+class RuleSet { |
+ List<int> _values; |
+ |
+ RuleSet(int numRules) : this._(new List(numRules)); |
+ |
+ RuleSet._(this._values); |
+ |
+ /// Returns `true` of [rule] is bound in this set. |
+ bool contains(Rule rule) => _values[rule.index] != null; |
+ |
+ /// Gets the bound value for [rule] or `0` if it is not bound. |
+ int getValue(Rule rule) { |
+ var value = _values[rule.index]; |
+ if (value != null) return value; |
+ |
+ return 0; |
+ } |
+ |
+ /// Invokes [callback] for each rule in [rules] with the rule's value, which |
+ /// will be `null` if it is not bound. |
+ void forEach(List<Rule> rules, callback(Rule rule, int value)) { |
+ var i = 0; |
+ for (var rule in rules) { |
+ var value = _values[i]; |
+ if (value != null) callback(rule, value); |
+ i++; |
+ } |
+ } |
+ |
+ /// Creates a new [RuleSet] with the same bound rule values as this one. |
+ RuleSet clone() => new RuleSet._(_values.toList(growable: false)); |
+ |
+ /// Binds [rule] to [value] then checks to see if that violates any |
+ /// constraints. |
+ /// |
+ /// Returns `true` if all constraints between the bound rules are valid. Even |
+ /// if not, this still modifies the [RuleSet]. |
+ /// |
+ /// If an unbound rule gets constrained to `-1` (meaning it must split, but |
+ /// can split any way it wants), invokes [onSplitRule] with it. |
+ bool tryBind(List<Rule> rules, Rule rule, int value, onSplitRule(Rule rule)) { |
+ _values[rule.index] = value; |
+ |
+ // Test this rule against the other rules being bound. |
+ for (var other in rules) { |
+ if (rule == other) continue; |
+ |
+ var otherValue = _values[other.index]; |
+ var constraint = rule.constrain(value, other); |
+ |
+ if (otherValue == null) { |
+ // The other rule is unbound, so see if we can constrain it eagerly to |
+ // a value now. |
+ if (constraint == -1) { |
+ // If we know the rule has to split and there's only one way it can, |
+ // just bind that. |
+ if (other.numValues == 2) { |
+ if (!tryBind(rules, other, 1, onSplitRule)) return false; |
+ } else { |
+ onSplitRule(other); |
+ } |
+ } else if (constraint != null) { |
+ // Bind the other rule to its value and recursively propagate its |
+ // constraints. |
+ if (!tryBind(rules, other, constraint, onSplitRule)) return false; |
+ } |
+ } else { |
+ // It's already bound, so see if the new rule's constraint disallows |
+ // that value. |
+ if (constraint == -1) { |
+ if (otherValue == 0) return false; |
+ } else if (constraint != null) { |
+ if (otherValue != constraint) return false; |
+ } |
+ |
+ // See if the other rule's constraint allows us to use this value. |
+ constraint = other.constrain(otherValue, rule); |
+ if (constraint == -1) { |
+ if (value == 0) return false; |
+ } else if (constraint != null) { |
+ if (value != constraint) return false; |
+ } |
+ } |
+ } |
+ |
+ return true; |
+ } |
+ |
+ String toString() => |
+ _values.map((value) => value == null ? "?" : value).join(" "); |
+} |
+ |
+/// For each chunk, this tracks if it has been split and, if so, what the |
+/// chosen column is for the following line. |
+/// |
+/// Internally, this uses a list where each element corresponds to the column |
+/// of the chunk at that index in the chunk list, or `null` if that chunk did |
+/// not split. This had about a 10% perf improvement over using a [Set] of |
+/// splits. |
+class SplitSet { |
+ List<int> _columns; |
+ |
+ /// The cost of the solution that led to these splits. |
+ int get cost => _cost; |
+ int _cost; |
+ |
+ /// Creates a new empty split set for a line with [numChunks]. |
+ SplitSet(int numChunks) : _columns = new List(numChunks - 1); |
+ |
+ /// Marks the line after chunk [index] as starting at [column]. |
+ void add(int index, int column) { |
+ _columns[index] = column; |
+ } |
+ |
+ /// Returns `true` if the chunk at [splitIndex] should be split. |
+ bool shouldSplitAt(int index) => |
+ index < _columns.length && _columns[index] != null; |
+ |
+ /// Gets the zero-based starting column for the chunk at [index]. |
+ int getColumn(int index) => _columns[index]; |
+ |
+ /// Sets the resulting [cost] for the splits. |
+ /// |
+ /// This can only be called once. |
+ void setCost(int cost) { |
+ assert(_cost == null); |
+ _cost = cost; |
+ } |
+ |
+ String toString() { |
+ var result = []; |
+ for (var i = 0; i < _columns.length; i++) { |
+ if (_columns[i] != null) { |
+ result.add("$i:${_columns[i]}"); |
+ } |
+ } |
+ |
+ return result.join(" "); |
+ } |
+} |