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1 | #ifndef ITERATOR_H |
2 | #define ITERATOR_H | |
3 | ||
4 | /* | |
5 | * Generic constants related to iterators. | |
6 | */ | |
7 | ||
8 | /* | |
9 | * The attempt to advance the iterator was successful; the iterator | |
10 | * reflects the new current entry. | |
11 | */ | |
12 | #define ITER_OK 0 | |
13 | ||
14 | /* | |
15 | * The iterator is exhausted and has been freed. | |
16 | */ | |
17 | #define ITER_DONE -1 | |
18 | ||
19 | /* | |
20 | * The iterator experienced an error. The iteration has been aborted | |
21 | * and the iterator has been freed. | |
22 | */ | |
23 | #define ITER_ERROR -2 | |
24 | ||
25 | /* | |
26 | * Return values for selector functions for merge iterators. The | |
27 | * numerical values of these constants are important and must be | |
28 | * compatible with ITER_DONE and ITER_ERROR. | |
29 | */ | |
30 | enum iterator_selection { | |
31 | /* End the iteration without an error: */ | |
32 | ITER_SELECT_DONE = ITER_DONE, | |
33 | ||
34 | /* Report an error and abort the iteration: */ | |
35 | ITER_SELECT_ERROR = ITER_ERROR, | |
36 | ||
37 | /* | |
38 | * The next group of constants are masks that are useful | |
39 | * mainly internally. | |
40 | */ | |
41 | ||
42 | /* The LSB selects whether iter0/iter1 is the "current" iterator: */ | |
43 | ITER_CURRENT_SELECTION_MASK = 0x01, | |
44 | ||
45 | /* iter0 is the "current" iterator this round: */ | |
46 | ITER_CURRENT_SELECTION_0 = 0x00, | |
47 | ||
48 | /* iter1 is the "current" iterator this round: */ | |
49 | ITER_CURRENT_SELECTION_1 = 0x01, | |
50 | ||
51 | /* Yield the value from the current iterator? */ | |
52 | ITER_YIELD_CURRENT = 0x02, | |
53 | ||
54 | /* Discard the value from the secondary iterator? */ | |
55 | ITER_SKIP_SECONDARY = 0x04, | |
56 | ||
57 | /* | |
58 | * The constants that a selector function should usually | |
59 | * return. | |
60 | */ | |
61 | ||
62 | /* Yield the value from iter0: */ | |
63 | ITER_SELECT_0 = ITER_CURRENT_SELECTION_0 | ITER_YIELD_CURRENT, | |
64 | ||
65 | /* Yield the value from iter0 and discard the one from iter1: */ | |
66 | ITER_SELECT_0_SKIP_1 = ITER_SELECT_0 | ITER_SKIP_SECONDARY, | |
67 | ||
68 | /* Discard the value from iter0 without yielding anything this round: */ | |
69 | ITER_SKIP_0 = ITER_CURRENT_SELECTION_1 | ITER_SKIP_SECONDARY, | |
70 | ||
71 | /* Yield the value from iter1: */ | |
72 | ITER_SELECT_1 = ITER_CURRENT_SELECTION_1 | ITER_YIELD_CURRENT, | |
73 | ||
74 | /* Yield the value from iter1 and discard the one from iter0: */ | |
75 | ITER_SELECT_1_SKIP_0 = ITER_SELECT_1 | ITER_SKIP_SECONDARY, | |
76 | ||
77 | /* Discard the value from iter1 without yielding anything this round: */ | |
78 | ITER_SKIP_1 = ITER_CURRENT_SELECTION_0 | ITER_SKIP_SECONDARY | |
79 | }; | |
80 | ||
81 | #endif /* ITERATOR_H */ |