1/**
2 * Contains a registry for GC factories.
3 *
4 * Copyright: Copyright Digital Mars 2016.
5 * License:   $(WEB www.boost.org/LICENSE_1_0.txt, Boost License 1.0).
6 * Authors:   Martin Nowak
7 */
8module core.gc.registry;
9
10import core.gc.gcinterface : GC;
11
12/*@nogc nothrow:*/
13
14/**
15 * A factory function that instantiates an implementation of the GC interface.
16 * In case the instance was allocated on the C heap, it is supposed to
17 * free itself upon calling it's destructor.
18 *
19 * The factory should print an error and abort the program if it
20 * cannot successfully initialize the GC instance.
21 */
22alias GCFactory = GC function();
23
24/**
25 * Register a GC factory under the given `name`.  This function must be called
26 * from a C constructor before druntime is initialized.
27 *
28 * To use the registered GC, it's name must be specified gcopt runtime option,
29 * e.g. by passing $(TT, --DRT-gcopt=gc:my_gc_name) as application argument.
30 *
31 * Params:
32 *   name = name of the GC implementation; should be unique
33 *   factory = function to instantiate the implementation
34 * Note: The registry does not perform synchronization, as registration is
35 *   assumed to be executed serially, as is the case for C constructors.
36 * See_Also:
37 *   $(LINK2 https://dlang.org/spec/garbage.html#gc_config, Configuring the Garbage Collector)
38 */
39void registerGCFactory(string name, GCFactory factory) nothrow @nogc
40{
41    import core.stdc.stdlib : realloc;
42
43    auto ptr = cast(Entry*)realloc(entries.ptr, (entries.length + 1) * Entry.sizeof);
44    entries = ptr[0 .. entries.length + 1];
45    entries[$ - 1] = Entry(name, factory);
46}
47
48/**
49 * Called during runtime initialization to initialize a GC instance of given `name`.
50 *
51 * Params:
52 *   name = name of the GC to instantiate
53 * Returns:
54 *   The created GC instance or `null` if no factory for that name was registered
55 */
56GC createGCInstance(string name)
57{
58    import core.stdc.stdlib : free;
59
60    foreach (entry; entries)
61    {
62        if (entry.name != name)
63            continue;
64        auto instance = entry.factory();
65        // only one GC at a time for now, so free the registry to not leak
66        free(entries.ptr);
67        entries = null;
68        return instance;
69    }
70    return null;
71}
72
73// list of all registerd GCs
74const(Entry[]) registeredGCFactories(scope int dummy=0) nothrow @nogc
75{
76    return entries;
77}
78
79private:
80
81struct Entry
82{
83    string name;
84    GCFactory factory;
85}
86
87__gshared Entry[] entries;
88