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82 строки
2.1 KiB
C
82 строки
2.1 KiB
C
#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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