mercurial/mpatch.h

convert: use a priority queue for sorting commits, to make sorting faster

To achieve this, we turn commit sorters into classes so they can
encapsulate state.

This reduces the sorting time from ~30s to ~10s on a 500k-commit
prefix of a repo I tried to convert. (and probably reduces the time
to sort the whole repo from many tens of minutes to minutes, but I
didn't try that again)

The date caching gets removed because priority queue already
caches the key.

#ifndef HG_MPATCH_H
#define HG_MPATCH_H

#define MPATCH_ERR_NO_MEM -3
#define MPATCH_ERR_CANNOT_BE_DECODED -2
#define MPATCH_ERR_INVALID_PATCH -1

struct mpatch_frag {
	int start, end, len;
	const char *data;
};

struct mpatch_flist {
	struct mpatch_frag *base, *head, *tail;
};

int mpatch_decode(const char *bin, ssize_t len, struct mpatch_flist **res);
ssize_t mpatch_calcsize(ssize_t len, struct mpatch_flist *l);
void mpatch_lfree(struct mpatch_flist *a);
int mpatch_apply(char *buf, const char *orig, ssize_t len,
                 struct mpatch_flist *l);
struct mpatch_flist *
mpatch_fold(void *bins, struct mpatch_flist *(*get_next_item)(void *, ssize_t),
            ssize_t start, ssize_t end);

#endif