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mergesort: remove llist_mergesort()
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>
authored by
René Scharfe
and committed by
Junio C Hamano
0f1eb7d6
9b9f5f62
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Makefile
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Makefile
-76
mergesort.c
-76
mergesort.c
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#include "cache.h"
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#include "mergesort.h"
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/* Combine two sorted lists. Take from `list` on equality. */
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static void *llist_merge(void *list, void *other,
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void *(*get_next_fn)(const void *),
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void (*set_next_fn)(void *, void *),
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int (*compare_fn)(const void *, const void *))
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{
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void *result = list, *tail;
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int prefer_list = compare_fn(list, other) <= 0;
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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 = get_next_fn(list);
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if (!list) {
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set_next_fn(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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set_next_fn(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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void *llist_mergesort(void *list,
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void *(*get_next_fn)(const void *),
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void (*set_next_fn)(void *, void *),
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int (*compare_fn)(const void *, const void *))
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{
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void *ranks[bitsizeof(void *)];
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size_t n = 0;
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if (!list)
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return NULL;
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for (;;) {
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int i;
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size_t m;
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void *next = get_next_fn(list);
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if (next)
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set_next_fn(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 = llist_merge(ranks[i], list, get_next_fn,
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set_next_fn, 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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return list;
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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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mergesort.h
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mergesort.h
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#ifndef MERGESORT_H
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#define MERGESORT_H
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/*
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* Sort linked list in place.
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* - get_next_fn() returns the next element given an element of a linked list.
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* - set_next_fn() takes two elements A and B, and makes B the "next" element
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* of A on the list.
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* - compare_fn() takes two elements A and B, and returns negative, 0, positive
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* as the same sign as "subtracting" B from A.
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*/
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void *llist_mergesort(void *list,
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void *(*get_next_fn)(const void *),
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void (*set_next_fn)(void *, void *),
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int (*compare_fn)(const void *, const void *));
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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, \