| Michael Haggerty | 3bc581b | 2016-06-18 06:15:15 +0200 | [diff] [blame] | 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 */ |
