replace_object.c 2.92 KB
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#include "cache.h"
#include "sha1-lookup.h"
#include "refs.h"
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#include "commit.h"
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/*
 * An array of replacements.  The array is kept sorted by the original
 * sha1.
 */
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static struct replace_object {
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	struct object_id original;
	struct object_id replacement;
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} **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;
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	return replace[index]->original.hash;
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}

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)
{
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	int pos = replace_object_pos(replace->original.hash);
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	if (0 <= pos) {
		if (ignore_dups)
			free(replace);
		else {
			free(replace_object[pos]);
			replace_object[pos] = replace;
		}
		return 1;
	}
	pos = -pos - 1;
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	ALLOC_GROW(replace_object, replace_object_nr + 1, replace_object_alloc);
	replace_object_nr++;
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	if (pos < replace_object_nr)
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		MOVE_ARRAY(replace_object + pos + 1, replace_object + pos,
			   replace_object_nr - pos - 1);
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	replace_object[pos] = replace;
	return 0;
}

static int register_replace_ref(const char *refname,
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				const struct object_id *oid,
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				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));

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	if (get_oid_hex(hash, &repl_obj->original)) {
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		free(repl_obj);
		warning("bad replace ref name: %s", refname);
		return 0;
	}

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

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

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

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

	/* Try to recursively replace the object */
	do {
		if (--depth < 0)
			die("replace depth too high for object %s",
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			    oid_to_hex(oid));
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		pos = replace_object_pos(cur->hash);
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		if (0 <= pos)
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			cur = &replace_object[pos]->replacement;
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	} while (0 <= pos);

	return cur;
}