summaryrefslogtreecommitdiff
path: root/refs/ref-cache.h
diff options
context:
space:
mode:
authorMichael Haggerty <mhagger@alum.mit.edu>2017-04-16 06:41:31 (GMT)
committerJunio C Hamano <gitster@pobox.com>2017-04-17 04:32:45 (GMT)
commit958f964691a250d9a7173f1c0a4c03fd9e71e2aa (patch)
treeb111a4b1ad558b60a61024b432061f63a99ad351 /refs/ref-cache.h
parent9fc3b06311f5a56b1933f046b06b3be22c17069b (diff)
downloadgit-958f964691a250d9a7173f1c0a4c03fd9e71e2aa.zip
git-958f964691a250d9a7173f1c0a4c03fd9e71e2aa.tar.gz
git-958f964691a250d9a7173f1c0a4c03fd9e71e2aa.tar.bz2
refs: split `ref_cache` code into separate files
The `ref_cache` code is currently too tightly coupled to `files-backend`, making the code harder to understand and making it awkward for new code to use `ref_cache` (as we indeed have planned). Start loosening that coupling by splitting `ref_cache` into a separate module. This commit moves code, adds declarations, and changes the visibility of some functions, but doesn't change any code. The modules are still too tightly coupled, but the situation will be improved in subsequent commits. Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>
Diffstat (limited to 'refs/ref-cache.h')
-rw-r--r--refs/ref-cache.h251
1 files changed, 251 insertions, 0 deletions
diff --git a/refs/ref-cache.h b/refs/ref-cache.h
new file mode 100644
index 0000000..2e7b1a3
--- /dev/null
+++ b/refs/ref-cache.h
@@ -0,0 +1,251 @@
+#ifndef REFS_REF_CACHE_H
+#define REFS_REF_CACHE_H
+
+/*
+ * Information used (along with the information in ref_entry) to
+ * describe a single cached reference. This data structure only
+ * occurs embedded in a union in struct ref_entry, and only when
+ * (ref_entry->flag & REF_DIR) is zero.
+ */
+struct ref_value {
+ /*
+ * The name of the object to which this reference resolves
+ * (which may be a tag object). If REF_ISBROKEN, this is
+ * null. If REF_ISSYMREF, then this is the name of the object
+ * referred to by the last reference in the symlink chain.
+ */
+ struct object_id oid;
+
+ /*
+ * If REF_KNOWS_PEELED, then this field holds the peeled value
+ * of this reference, or null if the reference is known not to
+ * be peelable. See the documentation for peel_ref() for an
+ * exact definition of "peelable".
+ */
+ struct object_id peeled;
+};
+
+/*
+ * Information used (along with the information in ref_entry) to
+ * describe a level in the hierarchy of references. This data
+ * structure only occurs embedded in a union in struct ref_entry, and
+ * only when (ref_entry.flag & REF_DIR) is set. In that case,
+ * (ref_entry.flag & REF_INCOMPLETE) determines whether the references
+ * in the directory have already been read:
+ *
+ * (ref_entry.flag & REF_INCOMPLETE) unset -- a directory of loose
+ * or packed references, already read.
+ *
+ * (ref_entry.flag & REF_INCOMPLETE) set -- a directory of loose
+ * references that hasn't been read yet (nor has any of its
+ * subdirectories).
+ *
+ * Entries within a directory are stored within a growable array of
+ * pointers to ref_entries (entries, nr, alloc). Entries 0 <= i <
+ * sorted are sorted by their component name in strcmp() order and the
+ * remaining entries are unsorted.
+ *
+ * Loose references are read lazily, one directory at a time. When a
+ * directory of loose references is read, then all of the references
+ * in that directory are stored, and REF_INCOMPLETE stubs are created
+ * for any subdirectories, but the subdirectories themselves are not
+ * read. The reading is triggered by get_ref_dir().
+ */
+struct ref_dir {
+ int nr, alloc;
+
+ /*
+ * Entries with index 0 <= i < sorted are sorted by name. New
+ * entries are appended to the list unsorted, and are sorted
+ * only when required; thus we avoid the need to sort the list
+ * after the addition of every reference.
+ */
+ int sorted;
+
+ /* A pointer to the files_ref_store that contains this ref_dir. */
+ struct files_ref_store *ref_store;
+
+ struct ref_entry **entries;
+};
+
+/*
+ * Bit values for ref_entry::flag. REF_ISSYMREF=0x01,
+ * REF_ISPACKED=0x02, REF_ISBROKEN=0x04 and REF_BAD_NAME=0x08 are
+ * public values; see refs.h.
+ */
+
+/*
+ * The field ref_entry->u.value.peeled of this value entry contains
+ * the correct peeled value for the reference, which might be
+ * null_sha1 if the reference is not a tag or if it is broken.
+ */
+#define REF_KNOWS_PEELED 0x10
+
+/* ref_entry represents a directory of references */
+#define REF_DIR 0x20
+
+/*
+ * Entry has not yet been read from disk (used only for REF_DIR
+ * entries representing loose references)
+ */
+#define REF_INCOMPLETE 0x40
+
+/*
+ * A ref_entry represents either a reference or a "subdirectory" of
+ * references.
+ *
+ * Each directory in the reference namespace is represented by a
+ * ref_entry with (flags & REF_DIR) set and containing a subdir member
+ * that holds the entries in that directory that have been read so
+ * far. If (flags & REF_INCOMPLETE) is set, then the directory and
+ * its subdirectories haven't been read yet. REF_INCOMPLETE is only
+ * used for loose reference directories.
+ *
+ * References are represented by a ref_entry with (flags & REF_DIR)
+ * unset and a value member that describes the reference's value. The
+ * flag member is at the ref_entry level, but it is also needed to
+ * interpret the contents of the value field (in other words, a
+ * ref_value object is not very much use without the enclosing
+ * ref_entry).
+ *
+ * Reference names cannot end with slash and directories' names are
+ * always stored with a trailing slash (except for the top-level
+ * directory, which is always denoted by ""). This has two nice
+ * consequences: (1) when the entries in each subdir are sorted
+ * lexicographically by name (as they usually are), the references in
+ * a whole tree can be generated in lexicographic order by traversing
+ * the tree in left-to-right, depth-first order; (2) the names of
+ * references and subdirectories cannot conflict, and therefore the
+ * presence of an empty subdirectory does not block the creation of a
+ * similarly-named reference. (The fact that reference names with the
+ * same leading components can conflict *with each other* is a
+ * separate issue that is regulated by refs_verify_refname_available().)
+ *
+ * Please note that the name field contains the fully-qualified
+ * reference (or subdirectory) name. Space could be saved by only
+ * storing the relative names. But that would require the full names
+ * to be generated on the fly when iterating in do_for_each_ref(), and
+ * would break callback functions, who have always been able to assume
+ * that the name strings that they are passed will not be freed during
+ * the iteration.
+ */
+struct ref_entry {
+ unsigned char flag; /* ISSYMREF? ISPACKED? */
+ union {
+ struct ref_value value; /* if not (flags&REF_DIR) */
+ struct ref_dir subdir; /* if (flags&REF_DIR) */
+ } u;
+ /*
+ * The full name of the reference (e.g., "refs/heads/master")
+ * or the full name of the directory with a trailing slash
+ * (e.g., "refs/heads/"):
+ */
+ char name[FLEX_ARRAY];
+};
+
+/*
+ * Return the index of the entry with the given refname from the
+ * ref_dir (non-recursively), sorting dir if necessary. Return -1 if
+ * no such entry is found. dir must already be complete.
+ */
+int search_ref_dir(struct ref_dir *dir, const char *refname, size_t len);
+
+struct ref_dir *get_ref_dir(struct ref_entry *entry);
+
+/*
+ * Create a struct ref_entry object for the specified dirname.
+ * dirname is the name of the directory with a trailing slash (e.g.,
+ * "refs/heads/") or "" for the top-level directory.
+ */
+struct ref_entry *create_dir_entry(struct files_ref_store *ref_store,
+ const char *dirname, size_t len,
+ int incomplete);
+
+struct ref_entry *create_ref_entry(const char *refname,
+ const unsigned char *sha1, int flag,
+ int check_name);
+
+void free_ref_entry(struct ref_entry *entry);
+
+/*
+ * Add a ref_entry to the end of dir (unsorted). Entry is always
+ * stored directly in dir; no recursion into subdirectories is
+ * done.
+ */
+void add_entry_to_dir(struct ref_dir *dir, struct ref_entry *entry);
+
+/*
+ * Remove the entry with the given name from dir, recursing into
+ * subdirectories as necessary. If refname is the name of a directory
+ * (i.e., ends with '/'), then remove the directory and its contents.
+ * If the removal was successful, return the number of entries
+ * remaining in the directory entry that contained the deleted entry.
+ * If the name was not found, return -1. Please note that this
+ * function only deletes the entry from the cache; it does not delete
+ * it from the filesystem or ensure that other cache entries (which
+ * might be symbolic references to the removed entry) are updated.
+ * Nor does it remove any containing dir entries that might be made
+ * empty by the removal. dir must represent the top-level directory
+ * and must already be complete.
+ */
+int remove_entry_from_dir(struct ref_dir *dir, const char *refname);
+
+/*
+ * Add a ref_entry to the ref_dir (unsorted), recursing into
+ * subdirectories as necessary. dir must represent the top-level
+ * directory. Return 0 on success.
+ */
+int add_ref_entry(struct ref_dir *dir, struct ref_entry *ref);
+
+/*
+ * If refname is a reference name, find the ref_dir within the dir
+ * tree that should hold refname. If refname is a directory name
+ * (i.e., it ends in '/'), then return that ref_dir itself. dir must
+ * represent the top-level directory and must already be complete.
+ * Sort ref_dirs and recurse into subdirectories as necessary. If
+ * mkdir is set, then create any missing directories; otherwise,
+ * return NULL if the desired directory cannot be found.
+ */
+struct ref_dir *find_containing_dir(struct ref_dir *dir,
+ const char *refname, int mkdir);
+
+/*
+ * Find the value entry with the given name in dir, sorting ref_dirs
+ * and recursing into subdirectories as necessary. If the name is not
+ * found or it corresponds to a directory entry, return NULL.
+ */
+struct ref_entry *find_ref_entry(struct ref_dir *dir, const char *refname);
+
+struct ref_iterator *cache_ref_iterator_begin(struct ref_dir *dir);
+
+typedef int each_ref_entry_fn(struct ref_entry *entry, void *cb_data);
+
+/*
+ * Call fn for each reference in dir that has index in the range
+ * offset <= index < dir->nr. Recurse into subdirectories that are in
+ * that index range, sorting them before iterating. This function
+ * does not sort dir itself; it should be sorted beforehand. fn is
+ * called for all references, including broken ones.
+ */
+int do_for_each_entry_in_dir(struct ref_dir *dir, int offset,
+ each_ref_entry_fn fn, void *cb_data);
+
+/*
+ * Peel the entry (if possible) and return its new peel_status. If
+ * repeel is true, re-peel the entry even if there is an old peeled
+ * value that is already stored in it.
+ *
+ * It is OK to call this function with a packed reference entry that
+ * might be stale and might even refer to an object that has since
+ * been garbage-collected. In such a case, if the entry has
+ * REF_KNOWS_PEELED then leave the status unchanged and return
+ * PEEL_PEELED or PEEL_NON_TAG; otherwise, return PEEL_INVALID.
+ */
+enum peel_status peel_entry(struct ref_entry *entry, int repeel);
+
+/*
+ * Load all of the refs from `dir` into our in-memory cache.
+ */
+void prime_ref_dir(struct ref_dir *dir);
+
+#endif /* REFS_REF_CACHE_H */