view mercurial/bdiff.h @ 31209:dd2364f5180a

localrepo: handle rename with hardlinks properly

In "aftertrans", we rename "journal.*" to "undo.*". We expect "journal.*"
files to disappear after renaming.

However, if "journal.foo" and "undo.foo" refer to a same file (hardlink),
rename may be a no-op, leaving both files on disk, according to Linux
manpage [1]:

    If oldpath and newpath are existing hard links referring to the same
    file, then rename() does nothing, and returns  a  suc‐ cess status.

The POSIX specification [2] is not very clear about what to do.

To be safe, remove "undo.*" before the rename so "journal.*" cannot be left
on disk.

[1]: http://man7.org/linux/man-pages/man2/rename.2.html
[2]: http://pubs.opengroup.org/onlinepubs/9699919799/

#ifndef _HG_BDIFF_H_
#define _HG_BDIFF_H_

struct bdiff_line {
	int hash, n, e;
	ssize_t len;
	const char *l;
};

struct bdiff_hunk;
struct bdiff_hunk {
	int a1, a2, b1, b2;
	struct bdiff_hunk *next;
};

int bdiff_splitlines(const char *a, ssize_t len, struct bdiff_line **lr);
int bdiff_diff(struct bdiff_line *a, int an, struct bdiff_line *b, int bn,
	struct bdiff_hunk *base);
void bdiff_freehunks(struct bdiff_hunk *l);

#endif