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