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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 */