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74 lines (63 sloc) 1.514 kb
#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;
}
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