git/object-file-convert.c

#include "git-compat-util.h"
#include "gettext.h"
#include "strbuf.h"
#include "hex.h"
#include "repository.h"
#include "hash-ll.h"
#include "hash.h"
#include "object.h"
#include "loose.h"
#include "object-file-convert.h"

int repo_oid_to_algop(struct repository *repo, const struct object_id *src,
		      const struct git_hash_algo *to, struct object_id *dest)
{
	/*
	 * If the source algorithm is not set, then we're using the
	 * default hash algorithm for that object.
	 */
	const struct git_hash_algo *from =
		src->algo ? &hash_algos[src->algo] : repo->hash_algo;

	if (from == to) {
		if (src != dest)
			oidcpy(dest, src);
		return 0;
	}
	if (repo_loose_object_map_oid(repo, src, to, dest)) {
		/*
		 * We may have loaded the object map at repo initialization but
		 * another process (perhaps upstream of a pipe from us) may have
		 * written a new object into the map.  If the object is missing,
		 * let's reload the map to see if the object has appeared.
		 */
		repo_read_loose_object_map(repo);
		if (repo_loose_object_map_oid(repo, src, to, dest))
			return -1;
	}
	return 0;
}

static int decode_tree_entry_raw(struct object_id *oid, const char **path,
				 size_t *len, const struct git_hash_algo *algo,
				 const char *buf, unsigned long size)
{
	uint16_t mode;
	const unsigned hashsz = algo->rawsz;

	if (size < hashsz + 3 || buf[size - (hashsz + 1)]) {
		return -1;
	}

	*path = parse_mode(buf, &mode);
	if (!*path || !**path)
		return -1;
	*len = strlen(*path) + 1;

	oidread_algop(oid, (const unsigned char *)*path + *len, algo);
	return 0;
}

static int convert_tree_object(struct strbuf *out,
			       const struct git_hash_algo *from,
			       const struct git_hash_algo *to,
			       const char *buffer, size_t size)
{
	const char *p = buffer, *end = buffer + size;

	while (p < end) {
		struct object_id entry_oid, mapped_oid;
		const char *path = NULL;
		size_t pathlen;

		if (decode_tree_entry_raw(&entry_oid, &path, &pathlen, from, p,
					  end - p))
			return error(_("failed to decode tree entry"));
		if (repo_oid_to_algop(the_repository, &entry_oid, to, &mapped_oid))
			return error(_("failed to map tree entry for %s"), oid_to_hex(&entry_oid));
		strbuf_add(out, p, path - p);
		strbuf_add(out, path, pathlen);
		strbuf_add(out, mapped_oid.hash, to->rawsz);
		p = path + pathlen + from->rawsz;
	}
	return 0;
}

int convert_object_file(struct strbuf *outbuf,
			const struct git_hash_algo *from,
			const struct git_hash_algo *to,
			const void *buf, size_t len,
			enum object_type type,
			int gentle)
{
	int ret;

	/* Don't call this function when no conversion is necessary */
	if ((from == to) || (type == OBJ_BLOB))
		BUG("Refusing noop object file conversion");

	switch (type) {
	case OBJ_TREE:
		ret = convert_tree_object(outbuf, from, to, buf, len);
		break;
	case OBJ_COMMIT:
	case OBJ_TAG:
	default:
		/* Not implemented yet, so fail. */
		ret = -1;
		break;
	}
	if (!ret)
		return 0;
	if (gentle) {
		strbuf_release(outbuf);
		return ret;
	}
	die(_("Failed to convert object from %s to %s"),
		from->name, to->name);
}