path: root/refs/refs-internal.h

#ifndef REFS_REFS_INTERNAL_H
#define REFS_REFS_INTERNAL_H

/*
 * Data structures and functions for the internal use of the refs
 * module. Code outside of the refs module should use only the public
 * functions defined in "refs.h", and should *not* include this file.
 */

/*
 * The following flags can appear in `ref_update::flags`. Their
 * numerical values must not conflict with those of REF_NO_DEREF and
 * REF_FORCE_CREATE_REFLOG, which are also stored in
 * `ref_update::flags`.
 */

/*
 * The reference should be updated to new_oid.
 */
#define REF_HAVE_NEW (1 << 2)

/*
 * The current reference's value should be checked to make sure that
 * it agrees with old_oid.
 */
#define REF_HAVE_OLD (1 << 3)

/*
 * Return the length of time to retry acquiring a loose reference lock
 * before giving up, in milliseconds:
 */
long get_files_ref_lock_timeout_ms(void);

/*
 * Return true iff refname is minimally safe. "Safe" here means that
 * deleting a loose reference by this name will not do any damage, for
 * example by causing a file that is not a reference to be deleted.
 * This function does not check that the reference name is legal; for
 * that, use check_refname_format().
 *
 * A refname that starts with "refs/" is considered safe iff it
 * doesn't contain any "." or ".." components or consecutive '/'
 * characters, end with '/', or (on Windows) contain any '\'
 * characters. Names that do not start with "refs/" are considered
 * safe iff they consist entirely of upper case characters and '_'
 * (like "HEAD" and "MERGE_HEAD" but not "config" or "FOO/BAR").
 */
int refname_is_safe(const char *refname);

/*
 * Helper function: return true if refname, which has the specified
 * oid and flags, can be resolved to an object in the database. If the
 * referred-to object does not exist, emit a warning and return false.
 */
int ref_resolves_to_object(const char *refname,
			   const struct object_id *oid,
			   unsigned int flags);

enum peel_status {
	/* object was peeled successfully: */
	PEEL_PEELED = 0,

	/*
	 * object cannot be peeled because the named object (or an
	 * object referred to by a tag in the peel chain), does not
	 * exist.
	 */
	PEEL_INVALID = -1,

	/* object cannot be peeled because it is not a tag: */
	PEEL_NON_TAG = -2,

	/* ref_entry contains no peeled value because it is a symref: */
	PEEL_IS_SYMREF = -3,

	/*
	 * ref_entry cannot be peeled because it is broken (i.e., the
	 * symbolic reference cannot even be resolved to an object
	 * name):
	 */
	PEEL_BROKEN = -4
};

/*
 * Peel the named object; i.e., if the object is a tag, resolve the
 * tag recursively until a non-tag is found.  If successful, store the
 * result to oid and return PEEL_PEELED.  If the object is not a tag
 * or is not valid, return PEEL_NON_TAG or PEEL_INVALID, respectively,
 * and leave oid unchanged.
 */
enum peel_status peel_object(const struct object_id *name, struct object_id *oid);

/*
 * Copy the reflog message msg to buf, which has been allocated sufficiently
 * large, while cleaning up the whitespaces.  Especially, convert LF to space,
 * because reflog file is one line per entry.
 */
int copy_reflog_msg(char *buf, const char *msg);

/**
 * Information needed for a single ref update. Set new_oid to the new
 * value or to null_oid to delete the ref. To check the old value
 * while the ref is locked, set (flags & REF_HAVE_OLD) and set old_oid
 * to the old value, or to null_oid to ensure the ref does not exist
 * before update.
 */
struct ref_update {
	/*
	 * If (flags & REF_HAVE_NEW), set the reference to this value
	 * (or delete it, if `new_oid` is `null_oid`).
	 */
	struct object_id new_oid;

	/*
	 * If (flags & REF_HAVE_OLD), check that the reference
	 * previously had this value (or didn't previously exist, if
	 * `old_oid` is `null_oid`).
	 */
	struct object_id old_oid;

	/*
	 * One or more of REF_NO_DEREF, REF_FORCE_CREATE_REFLOG,
	 * REF_HAVE_NEW, REF_HAVE_OLD, or backend-specific flags.
	 */
	unsigned int flags;

	void *backend_data;
	unsigned int type;
	char *msg;

	/*
	 * If this ref_update was split off of a symref update via
	 * split_symref_update(), then this member points at that
	 * update. This is used for two purposes:
	 * 1. When reporting errors, we report the refname under which
	 *    the update was originally requested.
	 * 2. When we read the old value of this reference, we
	 *    propagate it back to its parent update for recording in
	 *    the latter's reflog.
	 */
	struct ref_update *parent_update;

	const char refname[FLEX_ARRAY];
};

int refs_read_raw_ref(struct ref_store *ref_store,
		      const char *refname, struct object_id *oid,
		      struct strbuf *referent, unsigned int *type);

/*
 * Write an error to `err` and return a nonzero value iff the same
 * refname appears multiple times in `refnames`. `refnames` must be
 * sorted on entry to this function.
 */
int ref_update_reject_duplicates(struct string_list *refnames,
				 struct strbuf *err);

/*
 * Add a ref_update with the specified properties to transaction, and
 * return a pointer to the new object. This function does not verify
 * that refname is well-formed. new_oid and old_oid are only
 * dereferenced if the REF_HAVE_NEW and REF_HAVE_OLD bits,
 * respectively, are set in flags.
 */
struct ref_update *ref_transaction_add_update(
		struct ref_transaction *transaction,
		const char *refname, unsigned int flags,
		const struct object_id *new_oid,
		const struct object_id *old_oid,
		const char *msg);

/*
 * Transaction states.
 *
 * OPEN:   The transaction is initialized and new updates can still be
 *         added to it. An OPEN transaction can be prepared,
 *         committed, freed, or aborted (freeing and aborting an open
 *         transaction are equivalent).
 *
 * PREPARED: ref_transaction_prepare(), which locks all of the
 *         references involved in the update and checks that the
 *         update has no errors, has been called successfully for the
 *         transaction. A PREPARED transaction can be committed or
 *         aborted.
 *
 * CLOSED: The transaction is no longer active. A transaction becomes
 *         CLOSED if there is a failure while building the transaction
 *         or if a transaction is committed or aborted. A CLOSED
 *         transaction can only be freed.
 */
enum ref_transaction_state {
	REF_TRANSACTION_OPEN     = 0,
	REF_TRANSACTION_PREPARED = 1,
	REF_TRANSACTION_CLOSED   = 2
};

/*
 * Data structure for holding a reference transaction, which can
 * consist of checks and updates to multiple references, carried out
 * as atomically as possible.  This structure is opaque to callers.
 */
struct ref_transaction {
	struct ref_store *ref_store;
	struct ref_update **updates;
	size_t alloc;
	size_t nr;
	enum ref_transaction_state state;
	void *backend_data;
};

/*
 * Check for entries in extras that are within the specified
 * directory, where dirname is a reference directory name including
 * the trailing slash (e.g., "refs/heads/foo/"). Ignore any
 * conflicting references that are found in skip. If there is a
 * conflicting reference, return its name.
 *
 * extras and skip must be sorted lists of reference names. Either one
 * can be NULL, signifying the empty list.
 */
const char *find_descendant_ref(const char *dirname,
				const struct string_list *extras,
				const struct string_list *skip);

/*
 * Check whether an attempt to rename old_refname to new_refname would
 * cause a D/F conflict with any existing reference (other than
 * possibly old_refname). If there would be a conflict, emit an error
 * message and return false; otherwise, return true.
 *
 * Note that this function is not safe against all races with other
 * processes (though rename_ref() catches some races that might get by
 * this check).
 */
int refs_rename_ref_available(struct ref_store *refs,
			      const char *old_refname,
			      const char *new_refname);

/* We allow "recursive" symbolic refs. Only within reason, though */
#define SYMREF_MAXDEPTH 5

/* Include broken references in a do_for_each_ref*() iteration: */
#define DO_FOR_EACH_INCLUDE_BROKEN 0x01

/*
 * Reference iterators
 *
 * A reference iterator encapsulates the state of an in-progress
 * iteration over references. Create an instance of `struct
 * ref_iterator` via one of the functions in this module.
 *
 * A freshly-created ref_iterator doesn't yet point at a reference. To
 * advance the iterator, call ref_iterator_advance(). If successful,
 * this sets the iterator's refname, oid, and flags fields to describe
 * the next reference and returns ITER_OK. The data pointed at by
 * refname and oid belong to the iterator; if you want to retain them
 * after calling ref_iterator_advance() again or calling
 * ref_iterator_abort(), you must make a copy. When the iteration has
 * been exhausted, ref_iterator_advance() releases any resources
 * assocated with the iteration, frees the ref_iterator object, and
 * returns ITER_DONE. If you want to abort the iteration early, call
 * ref_iterator_abort(), which also frees the ref_iterator object and
 * any associated resources. If there was an internal error advancing
 * to the next entry, ref_iterator_advance() aborts the iteration,
 * frees the ref_iterator, and returns ITER_ERROR.
 *
 * The reference currently being looked at can be peeled by calling
 * ref_iterator_peel(). This function is often faster than peel_ref(),
 * so it should be preferred when iterating over references.
 *
 * Putting it all together, a typical iteration looks like this:
 *
 *     int ok;
 *     struct ref_iterator *iter = ...;
 *
 *     while ((ok = ref_iterator_advance(iter)) == ITER_OK) {
 *             if (want_to_stop_iteration()) {
 *                     ok = ref_iterator_abort(iter);
 *                     break;
 *             }
 *
 *             // Access information about the current reference:
 *             if (!(iter->flags & REF_ISSYMREF))
 *                     printf("%s is %s\n", iter->refname, oid_to_hex(&iter->oid));
 *
 *             // If you need to peel the reference:
 *             ref_iterator_peel(iter, &oid);
 *     }
 *
 *     if (ok != ITER_DONE)
 *             handle_error();
 */
struct ref_iterator {
	struct ref_iterator_vtable *vtable;

	/*
	 * Does this `ref_iterator` iterate over references in order
	 * by refname?
	 */
	unsigned int ordered : 1;

	const char *refname;
	const struct object_id *oid;
	unsigned int flags;
};

/*
 * Advance the iterator to the first or next item and return ITER_OK.
 * If the iteration is exhausted, free the resources associated with
 * the ref_iterator and return ITER_DONE. On errors, free the iterator
 * resources and return ITER_ERROR. It is a bug to use ref_iterator or
 * call this function again after it has returned ITER_DONE or
 * ITER_ERROR.
 */
int ref_iterator_advance(struct ref_iterator *ref_iterator);

/*
 * If possible, peel the reference currently being viewed by the
 * iterator. Return 0 on success.
 */
int ref_iterator_peel(struct ref_iterator *ref_iterator,