1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
|
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
* vim: set ts=8 sts=2 et sw=2 tw=80:
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#ifndef js_UbiNodePostOrder_h
#define js_UbiNodePostOrder_h
#include "mozilla/Attributes.h"
#include <utility>
#include "js/UbiNode.h"
#include "js/Vector.h"
namespace js {
class SystemAllocPolicy;
}
namespace JS {
class AutoCheckCannotGC;
namespace ubi {
/**
* A post-order depth-first traversal of `ubi::Node` graphs.
*
* No GC may occur while an instance of `PostOrder` is live.
*
* The `NodeVisitor` type provided to `PostOrder::traverse` must have the
* following member:
*
* bool operator()(Node& node)
*
* The node visitor method. This method is called once for each `node`
* reachable from the start set in post-order.
*
* This visitor function should return true on success, or false if an error
* occurs. A false return value terminates the traversal immediately, and
* causes `PostOrder::traverse` to return false.
*
* The `EdgeVisitor` type provided to `PostOrder::traverse` must have the
* following member:
*
* bool operator()(Node& origin, Edge& edge)
*
* The edge visitor method. This method is called once for each outgoing
* `edge` from `origin` that is reachable from the start set.
*
* NB: UNLIKE NODES, THERE IS NO GUARANTEED ORDER IN WHICH EDGES AND THEIR
* ORIGINS ARE VISITED!
*
* This visitor function should return true on success, or false if an error
* occurs. A false return value terminates the traversal immediately, and
* causes `PostOrder::traverse` to return false.
*/
struct PostOrder {
private:
struct OriginAndEdges {
Node origin;
EdgeVector edges;
OriginAndEdges(const Node& node, EdgeVector&& edges)
: origin(node), edges(std::move(edges)) {}
OriginAndEdges(const OriginAndEdges& rhs) = delete;
OriginAndEdges& operator=(const OriginAndEdges& rhs) = delete;
OriginAndEdges(OriginAndEdges&& rhs)
: origin(rhs.origin), edges(std::move(rhs.edges)) {
MOZ_ASSERT(&rhs != this, "self-move disallowed");
}
OriginAndEdges& operator=(OriginAndEdges&& rhs) {
this->~OriginAndEdges();
new (this) OriginAndEdges(std::move(rhs));
return *this;
}
};
using Stack = js::Vector<OriginAndEdges, 256, js::SystemAllocPolicy>;
using Set = js::HashSet<Node, js::DefaultHasher<Node>, js::SystemAllocPolicy>;
JSContext* cx;
Set seen;
Stack stack;
#ifdef DEBUG
bool traversed;
#endif
private:
[[nodiscard]] bool fillEdgesFromRange(EdgeVector& edges,
js::UniquePtr<EdgeRange>& range) {
MOZ_ASSERT(range);
for (; !range->empty(); range->popFront()) {
if (!edges.append(std::move(range->front()))) {
return false;
}
}
return true;
}
[[nodiscard]] bool pushForTraversing(const Node& node) {
EdgeVector edges;
auto range = node.edges(cx, /* wantNames */ false);
return range && fillEdgesFromRange(edges, range) &&
stack.append(OriginAndEdges(node, std::move(edges)));
}
public:
// Construct a post-order traversal object.
//
// The traversal asserts that no GC happens in its runtime during its
// lifetime via the `AutoCheckCannotGC&` parameter. We do nothing with it,
// other than require it to exist with a lifetime that encloses our own.
PostOrder(JSContext* cx, AutoCheckCannotGC&)
: cx(cx),
seen(),
stack()
#ifdef DEBUG
,
traversed(false)
#endif
{
}
// Add `node` as a starting point for the traversal. You may add
// as many starting points as you like. Returns false on OOM.
[[nodiscard]] bool addStart(const Node& node) {
if (!seen.put(node)) {
return false;
}
return pushForTraversing(node);
}
// Traverse the graph in post-order, starting with the set of nodes passed
// to `addStart` and applying `onNode::operator()` for each node in the
// graph and `onEdge::operator()` for each edge in the graph, as described
// above.
//
// This should be called only once per instance of this class.
//
// Return false on OOM or error return from `onNode::operator()` or
// `onEdge::operator()`.
template <typename NodeVisitor, typename EdgeVisitor>
[[nodiscard]] bool traverse(NodeVisitor onNode, EdgeVisitor onEdge) {
#ifdef DEBUG
MOZ_ASSERT(!traversed, "Can only traverse() once!");
traversed = true;
#endif
while (!stack.empty()) {
auto& origin = stack.back().origin;
auto& edges = stack.back().edges;
if (edges.empty()) {
if (!onNode(origin)) {
return false;
}
stack.popBack();
continue;
}
Edge edge = std::move(edges.back());
edges.popBack();
if (!onEdge(origin, edge)) {
return false;
}
auto ptr = seen.lookupForAdd(edge.referent);
// We've already seen this node, don't follow its edges.
if (ptr) {
continue;
}
// Mark the referent as seen and follow its edges.
if (!seen.add(ptr, edge.referent) || !pushForTraversing(edge.referent)) {
return false;
}
}
return true;
}
};
} // namespace ubi
} // namespace JS
#endif // js_UbiNodePostOrder_h
|
