Merge branch 'bw/push-submodule-only'
[git] / iterator.h
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 */