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0db71e0f RS |
1 | #ifndef MERGESORT_H |
2 | #define MERGESORT_H | |
3 | ||
318051ea RS |
4 | /* Combine two sorted lists. Take from `list` on equality. */ |
5 | #define DEFINE_LIST_MERGE_INTERNAL(name, type) \ | |
6 | static type *name##__merge(type *list, type *other, \ | |
7 | int (*compare_fn)(const type *, const type *))\ | |
8 | { \ | |
9 | type *result = list, *tail; \ | |
10 | int prefer_list = compare_fn(list, other) <= 0; \ | |
11 | \ | |
12 | if (!prefer_list) { \ | |
13 | result = other; \ | |
14 | SWAP(list, other); \ | |
15 | } \ | |
16 | for (;;) { \ | |
17 | do { \ | |
18 | tail = list; \ | |
19 | list = name##__get_next(list); \ | |
20 | if (!list) { \ | |
21 | name##__set_next(tail, other); \ | |
22 | return result; \ | |
23 | } \ | |
24 | } while (compare_fn(list, other) < prefer_list); \ | |
25 | name##__set_next(tail, other); \ | |
26 | prefer_list ^= 1; \ | |
27 | SWAP(list, other); \ | |
28 | } \ | |
29 | } | |
30 | ||
31 | /* | |
32 | * Perform an iterative mergesort using an array of sublists. | |
33 | * | |
34 | * n is the number of items. | |
35 | * ranks[i] is undefined if n & 2^i == 0, and assumed empty. | |
36 | * ranks[i] contains a sublist of length 2^i otherwise. | |
37 | * | |
38 | * The number of bits in a void pointer limits the number of objects | |
39 | * that can be created, and thus the number of array elements necessary | |
40 | * to be able to sort any valid list. | |
41 | * | |
42 | * Adding an item to this array is like incrementing a binary number; | |
43 | * positional values for set bits correspond to sublist lengths. | |
44 | */ | |
45 | #define DEFINE_LIST_SORT_INTERNAL(scope, name, type) \ | |
46 | scope void name(type **listp, \ | |
47 | int (*compare_fn)(const type *, const type *)) \ | |
48 | { \ | |
49 | type *list = *listp; \ | |
50 | type *ranks[bitsizeof(type *)]; \ | |
51 | size_t n = 0; \ | |
52 | \ | |
53 | if (!list) \ | |
54 | return; \ | |
55 | \ | |
56 | for (;;) { \ | |
57 | int i; \ | |
58 | size_t m; \ | |
59 | type *next = name##__get_next(list); \ | |
60 | if (next) \ | |
61 | name##__set_next(list, NULL); \ | |
62 | for (i = 0, m = n;; i++, m >>= 1) { \ | |
63 | if (m & 1) { \ | |
64 | list = name##__merge(ranks[i], list, \ | |
65 | compare_fn); \ | |
66 | } else if (next) { \ | |
67 | break; \ | |
68 | } else if (!m) { \ | |
69 | *listp = list; \ | |
70 | return; \ | |
71 | } \ | |
72 | } \ | |
73 | n++; \ | |
74 | ranks[i] = list; \ | |
75 | list = next; \ | |
76 | } \ | |
77 | } | |
78 | ||
79 | #define DECLARE_LIST_SORT(scope, name, type) \ | |
80 | scope void name(type **listp, \ | |
81 | int (*compare_fn)(const type *, const type *)) | |
82 | ||
83 | #define DEFINE_LIST_SORT_DEBUG(scope, name, type, next_member, \ | |
84 | on_get_next, on_set_next) \ | |
85 | \ | |
86 | static inline type *name##__get_next(const type *elem) \ | |
87 | { \ | |
88 | on_get_next; \ | |
89 | return elem->next_member; \ | |
90 | } \ | |
91 | \ | |
92 | static inline void name##__set_next(type *elem, type *next) \ | |
93 | { \ | |
94 | on_set_next; \ | |
95 | elem->next_member = next; \ | |
96 | } \ | |
97 | \ | |
98 | DEFINE_LIST_MERGE_INTERNAL(name, type) \ | |
99 | DEFINE_LIST_SORT_INTERNAL(scope, name, type) \ | |
100 | DECLARE_LIST_SORT(scope, name, type) | |
101 | ||
102 | #define DEFINE_LIST_SORT(scope, name, type, next_member) \ | |
103 | DEFINE_LIST_SORT_DEBUG(scope, name, type, next_member, (void)0, (void)0) | |
104 | ||
0db71e0f | 105 | #endif |