root/replace_object.c

DEFINITIONS

1. replace_sha1_access
2. replace_object_pos
3. register_replace_object
4. register_replace_ref
5. prepare_replace_object
6. do_lookup_replace_object

#include "cache.h"
#include "sha1-lookup.h"
#include "refs.h"
#include "commit.h"

/*
 * An array of replacements.  The array is kept sorted by the original
 * sha1.
 */
static struct replace_object {
        unsigned char original[20];
        unsigned char replacement[20];
} **replace_object;

static int replace_object_alloc, replace_object_nr;

static const unsigned char *replace_sha1_access(size_t index, void *table)
{
        struct replace_object **replace = table;
        return replace[index]->original;
}

static int replace_object_pos(const unsigned char *sha1)
{
        return sha1_pos(sha1, replace_object, replace_object_nr,
                        replace_sha1_access);
}

static int register_replace_object(struct replace_object *replace,
                                   int ignore_dups)
{
        int pos = replace_object_pos(replace->original);

        if (0 <= pos) {
                if (ignore_dups)
                        free(replace);
                else {
                        free(replace_object[pos]);
                        replace_object[pos] = replace;
                }
                return 1;
        }
        pos = -pos - 1;
        ALLOC_GROW(replace_object, replace_object_nr + 1, replace_object_alloc);
        replace_object_nr++;
        if (pos < replace_object_nr)
                memmove(replace_object + pos + 1,
                        replace_object + pos,
                        (replace_object_nr - pos - 1) *
                        sizeof(*replace_object));
        replace_object[pos] = replace;
        return 0;
}

static int register_replace_ref(const char *refname,
                                const struct object_id *oid,
                                int flag, void *cb_data)
{
        /* Get sha1 from refname */
        const char *slash = strrchr(refname, '/');
        const char *hash = slash ? slash + 1 : refname;
        struct replace_object *repl_obj = xmalloc(sizeof(*repl_obj));

        if (strlen(hash) != 40 || get_sha1_hex(hash, repl_obj->original)) {
                free(repl_obj);
                warning("bad replace ref name: %s", refname);
                return 0;
        }

        /* Copy sha1 from the read ref */
        hashcpy(repl_obj->replacement, oid->hash);

        /* Register new object */
        if (register_replace_object(repl_obj, 1))
                die("duplicate replace ref: %s", refname);

        return 0;
}

static void prepare_replace_object(void)
{
        static int replace_object_prepared;

        if (replace_object_prepared)
                return;

        for_each_replace_ref(register_replace_ref, NULL);
        replace_object_prepared = 1;
        if (!replace_object_nr)
                check_replace_refs = 0;
}

/* We allow "recursive" replacement. Only within reason, though */
#define MAXREPLACEDEPTH 5

/*
 * If a replacement for object sha1 has been set up, return the
 * replacement object's name (replaced recursively, if necessary).
 * The return value is either sha1 or a pointer to a
 * permanently-allocated value.  This function always respects replace
 * references, regardless of the value of check_replace_refs.
 */
const unsigned char *do_lookup_replace_object(const unsigned char *sha1)
{
        int pos, depth = MAXREPLACEDEPTH;
        const unsigned char *cur = sha1;

        prepare_replace_object();

        /* Try to recursively replace the object */
        do {
                if (--depth < 0)
                        die("replace depth too high for object %s",
                            sha1_to_hex(sha1));

                pos = replace_object_pos(cur);
                if (0 <= pos)
                        cur = replace_object[pos]->replacement;
        } while (0 <= pos);

        return cur;
}