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0f1eb7d6e9
Now that all of its callers are gone, remove llist_mergesort(). Signed-off-by: René Scharfe <l.s.r@web.de> Signed-off-by: Junio C Hamano <gitster@pobox.com>
105 lines
2.9 KiB
C
105 lines
2.9 KiB
C
#ifndef MERGESORT_H
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#define MERGESORT_H
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/* Combine two sorted lists. Take from `list` on equality. */
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#define DEFINE_LIST_MERGE_INTERNAL(name, type) \
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static type *name##__merge(type *list, type *other, \
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int (*compare_fn)(const type *, const type *))\
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{ \
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type *result = list, *tail; \
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int prefer_list = compare_fn(list, other) <= 0; \
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\
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if (!prefer_list) { \
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result = other; \
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SWAP(list, other); \
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} \
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for (;;) { \
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do { \
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tail = list; \
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list = name##__get_next(list); \
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if (!list) { \
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name##__set_next(tail, other); \
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return result; \
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} \
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} while (compare_fn(list, other) < prefer_list); \
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name##__set_next(tail, other); \
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prefer_list ^= 1; \
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SWAP(list, other); \
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} \
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}
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/*
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* Perform an iterative mergesort using an array of sublists.
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*
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* n is the number of items.
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* ranks[i] is undefined if n & 2^i == 0, and assumed empty.
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* ranks[i] contains a sublist of length 2^i otherwise.
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*
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* The number of bits in a void pointer limits the number of objects
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* that can be created, and thus the number of array elements necessary
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* to be able to sort any valid list.
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*
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* Adding an item to this array is like incrementing a binary number;
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* positional values for set bits correspond to sublist lengths.
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*/
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#define DEFINE_LIST_SORT_INTERNAL(scope, name, type) \
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scope void name(type **listp, \
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int (*compare_fn)(const type *, const type *)) \
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{ \
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type *list = *listp; \
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type *ranks[bitsizeof(type *)]; \
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size_t n = 0; \
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\
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if (!list) \
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return; \
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\
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for (;;) { \
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int i; \
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size_t m; \
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type *next = name##__get_next(list); \
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if (next) \
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name##__set_next(list, NULL); \
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for (i = 0, m = n;; i++, m >>= 1) { \
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if (m & 1) { \
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list = name##__merge(ranks[i], list, \
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compare_fn); \
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} else if (next) { \
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break; \
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} else if (!m) { \
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*listp = list; \
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return; \
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} \
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} \
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n++; \
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ranks[i] = list; \
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list = next; \
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} \
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}
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#define DECLARE_LIST_SORT(scope, name, type) \
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scope void name(type **listp, \
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int (*compare_fn)(const type *, const type *))
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#define DEFINE_LIST_SORT_DEBUG(scope, name, type, next_member, \
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on_get_next, on_set_next) \
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\
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static inline type *name##__get_next(const type *elem) \
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{ \
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on_get_next; \
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return elem->next_member; \
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} \
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\
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static inline void name##__set_next(type *elem, type *next) \
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{ \
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on_set_next; \
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elem->next_member = next; \
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} \
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\
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DEFINE_LIST_MERGE_INTERNAL(name, type) \
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DEFINE_LIST_SORT_INTERNAL(scope, name, type) \
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DECLARE_LIST_SORT(scope, name, type)
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#define DEFINE_LIST_SORT(scope, name, type, next_member) \
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DEFINE_LIST_SORT_DEBUG(scope, name, type, next_member, (void)0, (void)0)
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#endif
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