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| #ifndef ITERATOR_H | |
| #define ITERATOR_H | |
| /* | |
| * Generic constants related to iterators. | |
| */ | |
| /* | |
| * The attempt to advance the iterator was successful; the iterator | |
| * reflects the new current entry. | |
| */ | |
| #define ITER_OK 0 | |
| /* | |
| * The iterator is exhausted and has been freed. | |
| */ | |
| #define ITER_DONE -1 | |
| /* | |
| * The iterator experienced an error. The iteration has been aborted | |
| * and the iterator has been freed. | |
| */ | |
| #define ITER_ERROR -2 | |
| /* | |
| * Return values for selector functions for merge iterators. The | |
| * numerical values of these constants are important and must be | |
| * compatible with ITER_DONE and ITER_ERROR. | |
| */ | |
| enum iterator_selection { | |
| /* End the iteration without an error: */ | |
| ITER_SELECT_DONE = ITER_DONE, | |
| /* Report an error and abort the iteration: */ | |
| ITER_SELECT_ERROR = ITER_ERROR, | |
| /* | |
| * The next group of constants are masks that are useful | |
| * mainly internally. | |
| */ | |
| /* The LSB selects whether iter0/iter1 is the "current" iterator: */ | |
| ITER_CURRENT_SELECTION_MASK = 0x01, | |
| /* iter0 is the "current" iterator this round: */ | |
| ITER_CURRENT_SELECTION_0 = 0x00, | |
| /* iter1 is the "current" iterator this round: */ | |
| ITER_CURRENT_SELECTION_1 = 0x01, | |
| /* Yield the value from the current iterator? */ | |
| ITER_YIELD_CURRENT = 0x02, | |
| /* Discard the value from the secondary iterator? */ | |
| ITER_SKIP_SECONDARY = 0x04, | |
| /* | |
| * The constants that a selector function should usually | |
| * return. | |
| */ | |
| /* Yield the value from iter0: */ | |
| ITER_SELECT_0 = ITER_CURRENT_SELECTION_0 | ITER_YIELD_CURRENT, | |
| /* Yield the value from iter0 and discard the one from iter1: */ | |
| ITER_SELECT_0_SKIP_1 = ITER_SELECT_0 | ITER_SKIP_SECONDARY, | |
| /* Discard the value from iter0 without yielding anything this round: */ | |
| ITER_SKIP_0 = ITER_CURRENT_SELECTION_1 | ITER_SKIP_SECONDARY, | |
| /* Yield the value from iter1: */ | |
| ITER_SELECT_1 = ITER_CURRENT_SELECTION_1 | ITER_YIELD_CURRENT, | |
| /* Yield the value from iter1 and discard the one from iter0: */ | |
| ITER_SELECT_1_SKIP_0 = ITER_SELECT_1 | ITER_SKIP_SECONDARY, | |
| /* Discard the value from iter1 without yielding anything this round: */ | |
| ITER_SKIP_1 = ITER_CURRENT_SELECTION_0 | ITER_SKIP_SECONDARY | |
| }; | |
| #endif /* ITERATOR_H */ |