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git/mergesort.c
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#include "cache.h" | |
#include "mergesort.h" | |
struct mergesort_sublist { | |
void *ptr; | |
unsigned long len; | |
}; | |
static void *get_nth_next(void *list, unsigned long n, | |
void *(*get_next_fn)(const void *)) | |
{ | |
while (n-- && list) | |
list = get_next_fn(list); | |
return list; | |
} | |
static void *pop_item(struct mergesort_sublist *l, | |
void *(*get_next_fn)(const void *)) | |
{ | |
void *p = l->ptr; | |
l->ptr = get_next_fn(l->ptr); | |
l->len = l->ptr ? (l->len - 1) : 0; | |
return p; | |
} | |
void *llist_mergesort(void *list, | |
void *(*get_next_fn)(const void *), | |
void (*set_next_fn)(void *, void *), | |
int (*compare_fn)(const void *, const void *)) | |
{ | |
unsigned long l; | |
if (!list) | |
return NULL; | |
for (l = 1; ; l *= 2) { | |
void *curr; | |
struct mergesort_sublist p, q; | |
p.ptr = list; | |
q.ptr = get_nth_next(p.ptr, l, get_next_fn); | |
if (!q.ptr) | |
break; | |
p.len = q.len = l; | |
if (compare_fn(p.ptr, q.ptr) > 0) | |
list = curr = pop_item(&q, get_next_fn); | |
else | |
list = curr = pop_item(&p, get_next_fn); | |
while (p.ptr) { | |
while (p.len || q.len) { | |
void *prev = curr; | |
if (!p.len) | |
curr = pop_item(&q, get_next_fn); | |
else if (!q.len) | |
curr = pop_item(&p, get_next_fn); | |
else if (compare_fn(p.ptr, q.ptr) > 0) | |
curr = pop_item(&q, get_next_fn); | |
else | |
curr = pop_item(&p, get_next_fn); | |
set_next_fn(prev, curr); | |
} | |
p.ptr = q.ptr; | |
p.len = l; | |
q.ptr = get_nth_next(p.ptr, l, get_next_fn); | |
q.len = q.ptr ? l : 0; | |
} | |
set_next_fn(curr, NULL); | |
} | |
return list; | |
} |