1// Copyright 2012 the V8 project authors. All rights reserved.
2// Redistribution and use in source and binary forms, with or without
3// modification, are permitted provided that the following conditions are
4// met:
5//
6//     * Redistributions of source code must retain the above copyright
7//       notice, this list of conditions and the following disclaimer.
8//     * Redistributions in binary form must reproduce the above
9//       copyright notice, this list of conditions and the following
10//       disclaimer in the documentation and/or other materials provided
11//       with the distribution.
12//     * Neither the name of Google Inc. nor the names of its
13//       contributors may be used to endorse or promote products derived
14//       from this software without specific prior written permission.
15//
16// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
17// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
18// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
19// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
20// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
21// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
22// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
23// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
24// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
26// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27
28#ifndef V8_INTERFACE_H_
29#define V8_INTERFACE_H_
30
31#include "zone-inl.h"  // For operator new.
32
33namespace v8 {
34namespace internal {
35
36
37// This class implements the following abstract grammar of interfaces
38// (i.e. module types):
39//   interface ::= UNDETERMINED | VALUE | MODULE(exports)
40//   exports ::= {name : interface, ...}
41// A frozen module type is one that is fully determined. Unification does not
42// allow adding additional exports to frozen interfaces.
43// Otherwise, unifying modules merges their exports.
44// Undetermined types are unification variables that can be unified freely.
45
46class Interface : public ZoneObject {
47 public:
48  // ---------------------------------------------------------------------------
49  // Factory methods.
50
51  static Interface* NewValue() {
52    static Interface value_interface(VALUE + FROZEN);  // Cached.
53    return &value_interface;
54  }
55
56  static Interface* NewUnknown() {
57    return new Interface(NONE);
58  }
59
60  static Interface* NewModule() {
61    return new Interface(MODULE);
62  }
63
64  // ---------------------------------------------------------------------------
65  // Mutators.
66
67  // Add a name to the list of exports. If it already exists, unify with
68  // interface, otherwise insert unless this is closed.
69  void Add(Handle<String> name, Interface* interface, bool* ok) {
70    DoAdd(name.location(), name->Hash(), interface, ok);
71  }
72
73  // Unify with another interface. If successful, both interface objects will
74  // represent the same type, and changes to one are reflected in the other.
75  void Unify(Interface* that, bool* ok);
76
77  // Determine this interface to be a value interface.
78  void MakeValue(bool* ok) {
79    *ok = !IsModule();
80    if (*ok) Chase()->flags_ |= VALUE;
81  }
82
83  // Determine this interface to be a module interface.
84  void MakeModule(bool* ok) {
85    *ok = !IsValue();
86    if (*ok) Chase()->flags_ |= MODULE;
87  }
88
89  // Do not allow any further refinements, directly or through unification.
90  void Freeze(bool* ok) {
91    *ok = IsValue() || IsModule();
92    if (*ok) Chase()->flags_ |= FROZEN;
93  }
94
95  // ---------------------------------------------------------------------------
96  // Accessors.
97
98  // Look up an exported name. Returns NULL if not (yet) defined.
99  Interface* Lookup(Handle<String> name);
100
101  // Check whether this is still a fully undetermined type.
102  bool IsUnknown() { return Chase()->flags_ == NONE; }
103
104  // Check whether this is a value type.
105  bool IsValue() { return Chase()->flags_ & VALUE; }
106
107  // Check whether this is a module type.
108  bool IsModule() { return Chase()->flags_ & MODULE; }
109
110  // Check whether this is closed (i.e. fully determined).
111  bool IsFrozen() { return Chase()->flags_ & FROZEN; }
112
113  // ---------------------------------------------------------------------------
114  // Debugging.
115#ifdef DEBUG
116  void Print(int n = 0);  // n = indentation; n < 0 => don't print recursively
117#endif
118
119  // ---------------------------------------------------------------------------
120  // Implementation.
121 private:
122  enum Flags {    // All flags are monotonic
123    NONE = 0,
124    VALUE = 1,    // This type describes a value
125    MODULE = 2,   // This type describes a module
126    FROZEN = 4    // This type is fully determined
127  };
128
129  int flags_;
130  Interface* forward_;     // Unification link
131  ZoneHashMap* exports_;   // Module exports and their types (allocated lazily)
132
133  explicit Interface(int flags)
134    : flags_(flags),
135      forward_(NULL),
136      exports_(NULL) {
137#ifdef DEBUG
138    if (FLAG_print_interface_details)
139      PrintF("# Creating %p\n", static_cast<void*>(this));
140#endif
141  }
142
143  Interface* Chase() {
144    Interface* result = this;
145    while (result->forward_ != NULL) result = result->forward_;
146    if (result != this) forward_ = result;  // On-the-fly path compression.
147    return result;
148  }
149
150  void DoAdd(void* name, uint32_t hash, Interface* interface, bool* ok);
151  void DoUnify(Interface* that, bool* ok);
152};
153
154} }  // namespace v8::internal
155
156#endif  // V8_INTERFACE_H_
157