42c456ff81
Use size_t to match n when building the bitmask for checking whether a rank is occupied, instead of the default signed int. Signed-off-by: René Scharfe <l.s.r@web.de> Signed-off-by: Junio C Hamano <gitster@pobox.com>
85 lines
2.0 KiB
C
85 lines
2.0 KiB
C
#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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if (compare_fn(list, other) > 0) {
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result = other;
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goto 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) <= 0);
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set_next_fn(tail, other);
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other:
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do {
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tail = other;
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other = get_next_fn(other);
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if (!other) {
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set_next_fn(tail, list);
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return result;
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}
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} while (compare_fn(list, other) > 0);
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set_next_fn(tail, list);
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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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int i;
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while (list) {
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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; n & ((size_t)1 << i); i++)
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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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n++;
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ranks[i] = list;
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list = next;
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}
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for (i = 0; n; i++, n >>= 1) {
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if (!(n & 1))
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continue;
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if (list)
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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
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list = ranks[i];
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}
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return list;
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}
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