refs: store references hierarchically
Store references hierarchically in a tree that matches the pseudo-directory structure of the reference names. Add a new kind of ref_entry (with flag REF_DIR) to represent a whole subdirectory of references. Sort ref_dirs one subdirectory at a time. NOTE: the dirs can now be sorted as a side-effect of other function calls. Therefore, it would be problematic to do something from a each_ref_fn callback that could provoke the sorting of a directory that is currently being iterated over (i.e., the directory containing the entry that is being processed or any of its parents). This is a bit far-fetched, because a directory is always sorted just before being iterated over. Therefore, read-only accesses cannot trigger the sorting of a directory whose iteration has already started. But if a callback function would add a reference to a parent directory of the reference in the iteration, then try to resolve a reference under that directory, a re-sort could be triggered and cause the iteration to work incorrectly. Nevertheless...add a comment in refs.h warning against modifications during iteration. Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Michael Haggerty
Junio C Hamano
parent
81a79d8e27
commit
432ad41e60
276
refs.c
276
refs.c
@ -120,15 +120,54 @@ struct ref_dir {
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struct ref_entry **entries;
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};
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/* ISSYMREF=0x01, ISPACKED=0x02 and ISBROKEN=0x04 are public interfaces */
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#define REF_KNOWS_PEELED 0x10
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/* ISSYMREF=0x01, ISPACKED=0x02, and ISBROKEN=0x04 are public interfaces */
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#define REF_KNOWS_PEELED 0x08
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#define REF_DIR 0x10
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/*
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* A ref_entry represents either a reference or a "subdirectory" of
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* references. Each directory in the reference namespace is
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* represented by a ref_entry with (flags & REF_DIR) set and
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* containing a subdir member that holds the entries in that
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* directory. References are represented by a ref_entry with (flags &
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* REF_DIR) unset and a value member that describes the reference's
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* value. The flag member is at the ref_entry level, but it is also
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* needed to interpret the contents of the value field (in other
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* words, a ref_value object is not very much use without the
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* enclosing ref_entry).
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*
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* Reference names cannot end with slash and directories' names are
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* always stored with a trailing slash (except for the top-level
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* directory, which is always denoted by ""). This has two nice
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* consequences: (1) when the entries in each subdir are sorted
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* lexicographically by name (as they usually are), the references in
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* a whole tree can be generated in lexicographic order by traversing
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* the tree in left-to-right, depth-first order; (2) the names of
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* references and subdirectories cannot conflict, and therefore the
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* presence of an empty subdirectory does not block the creation of a
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* similarly-named reference. (The fact that reference names with the
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* same leading components can conflict *with each other* is a
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* separate issue that is regulated by is_refname_available().)
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*
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* Please note that the name field contains the fully-qualified
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* reference (or subdirectory) name. Space could be saved by only
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* storing the relative names. But that would require the full names
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* to be generated on the fly when iterating in do_for_each_ref(), and
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* would break callback functions, who have always been able to assume
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* that the name strings that they are passed will not be freed during
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* the iteration.
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*/
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struct ref_entry {
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unsigned char flag; /* ISSYMREF? ISPACKED? */
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union {
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struct ref_value value;
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struct ref_value value; /* if not (flags&REF_DIR) */
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struct ref_dir subdir; /* if (flags&REF_DIR) */
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} u;
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/* The full name of the reference (e.g., "refs/heads/master"): */
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/*
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* The full name of the reference (e.g., "refs/heads/master")
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* or the full name of the directory with a trailing slash
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* (e.g., "refs/heads/"):
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*/
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char name[FLEX_ARRAY];
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};
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@ -151,18 +190,29 @@ static struct ref_entry *create_ref_entry(const char *refname,
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return ref;
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}
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static void clear_ref_dir(struct ref_dir *dir);
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static void free_ref_entry(struct ref_entry *entry)
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{
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if (entry->flag & REF_DIR)
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clear_ref_dir(&entry->u.subdir);
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free(entry);
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}
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/* Add a ref_entry to the end of the ref_dir (unsorted). */
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static void add_ref(struct ref_dir *refs, struct ref_entry *ref)
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/*
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* Add a ref_entry to the end of dir (unsorted). Entry is always
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* stored directly in dir; no recursion into subdirectories is
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* done.
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*/
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static void add_entry_to_dir(struct ref_dir *dir, struct ref_entry *entry)
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{
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ALLOC_GROW(refs->entries, refs->nr + 1, refs->alloc);
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refs->entries[refs->nr++] = ref;
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ALLOC_GROW(dir->entries, dir->nr + 1, dir->alloc);
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dir->entries[dir->nr++] = entry;
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}
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/*
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* Clear and free all entries in dir, recursively.
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*/
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static void clear_ref_dir(struct ref_dir *dir)
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{
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int i;
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@ -173,6 +223,21 @@ static void clear_ref_dir(struct ref_dir *dir)
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dir->entries = NULL;
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}
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/*
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* Create a struct ref_entry object for the specified dirname.
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* dirname is the name of the directory with a trailing slash (e.g.,
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* "refs/heads/") or "" for the top-level directory.
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*/
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static struct ref_entry *create_dir_entry(const char *dirname)
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{
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struct ref_entry *direntry;
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int len = strlen(dirname);
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direntry = xcalloc(1, sizeof(struct ref_entry) + len + 1);
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memcpy(direntry->name, dirname, len + 1);
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direntry->flag = REF_DIR;
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return direntry;
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}
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static int ref_entry_cmp(const void *a, const void *b)
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{
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struct ref_entry *one = *(struct ref_entry **)a;
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@ -182,17 +247,21 @@ static int ref_entry_cmp(const void *a, const void *b)
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static void sort_ref_dir(struct ref_dir *dir);
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/*
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* Return the entry with the given refname from the ref_dir
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* (non-recursively), sorting dir if necessary. Return NULL if no
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* such entry is found.
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*/
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static struct ref_entry *search_ref_dir(struct ref_dir *dir, const char *refname)
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{
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struct ref_entry *e, **r;
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int len;
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if (refname == NULL)
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if (refname == NULL || !dir->nr)
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return NULL;
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if (!dir->nr)
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return NULL;
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sort_ref_dir(dir);
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len = strlen(refname) + 1;
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e = xmalloc(sizeof(struct ref_entry) + len);
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memcpy(e->name, refname, len);
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@ -207,6 +276,71 @@ static struct ref_entry *search_ref_dir(struct ref_dir *dir, const char *refname
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return *r;
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}
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/*
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* If refname is a reference name, find the ref_dir within the dir
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* tree that should hold refname. If refname is a directory name
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* (i.e., ends in '/'), then return that ref_dir itself. dir must
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* represent the top-level directory. Sort ref_dirs and recurse into
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* subdirectories as necessary. If mkdir is set, then create any
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* missing directories; otherwise, return NULL if the desired
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* directory cannot be found.
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*/
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static struct ref_dir *find_containing_dir(struct ref_dir *dir,
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const char *refname, int mkdir)
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{
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char *refname_copy = xstrdup(refname);
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char *slash;
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struct ref_entry *entry;
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for (slash = strchr(refname_copy, '/'); slash; slash = strchr(slash + 1, '/')) {
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char tmp = slash[1];
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slash[1] = '\0';
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entry = search_ref_dir(dir, refname_copy);
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if (!entry) {
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if (!mkdir) {
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dir = NULL;
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break;
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}
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entry = create_dir_entry(refname_copy);
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add_entry_to_dir(dir, entry);
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}
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slash[1] = tmp;
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assert(entry->flag & REF_DIR);
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dir = &entry->u.subdir;
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}
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free(refname_copy);
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return dir;
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}
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/*
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* Find the value entry with the given name in dir, sorting ref_dirs
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* and recursing into subdirectories as necessary. If the name is not
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* found or it corresponds to a directory entry, return NULL.
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*/
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static struct ref_entry *find_ref(struct ref_dir *dir, const char *refname)
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{
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struct ref_entry *entry;
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dir = find_containing_dir(dir, refname, 0);
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if (!dir)
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return NULL;
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entry = search_ref_dir(dir, refname);
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return (entry && !(entry->flag & REF_DIR)) ? entry : NULL;
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}
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/*
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* Add a ref_entry to the ref_dir (unsorted), recursing into
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* subdirectories as necessary. dir must represent the top-level
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* directory. Return 0 on success.
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*/
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static int add_ref(struct ref_dir *dir, struct ref_entry *ref)
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{
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dir = find_containing_dir(dir, ref->name, 1);
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if (!dir)
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return -1;
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add_entry_to_dir(dir, ref);
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return 0;
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}
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/*
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* Emit a warning and return true iff ref1 and ref2 have the same name
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* and the same sha1. Die if they have the same name but different
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@ -214,21 +348,25 @@ static struct ref_entry *search_ref_dir(struct ref_dir *dir, const char *refname
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*/
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static int is_dup_ref(const struct ref_entry *ref1, const struct ref_entry *ref2)
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{
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if (!strcmp(ref1->name, ref2->name)) {
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/* Duplicate name; make sure that the SHA1s match: */
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if (hashcmp(ref1->u.value.sha1, ref2->u.value.sha1))
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die("Duplicated ref, and SHA1s don't match: %s",
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ref1->name);
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warning("Duplicated ref: %s", ref1->name);
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return 1;
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} else {
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if (strcmp(ref1->name, ref2->name))
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return 0;
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}
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/* Duplicate name; make sure that they don't conflict: */
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if ((ref1->flag & REF_DIR) || (ref2->flag & REF_DIR))
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/* This is impossible by construction */
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die("Reference directory conflict: %s", ref1->name);
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if (hashcmp(ref1->u.value.sha1, ref2->u.value.sha1))
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die("Duplicated ref, and SHA1s don't match: %s", ref1->name);
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warning("Duplicated ref: %s", ref1->name);
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return 1;
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}
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/*
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* Sort the entries in dir (if they are not already sorted)
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* and remove any duplicate entries.
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* Sort the entries in dir non-recursively (if they are not already
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* sorted) and remove any duplicate entries.
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*/
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static void sort_ref_dir(struct ref_dir *dir)
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{
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@ -282,8 +420,9 @@ static int do_one_ref(const char *base, each_ref_fn fn, int trim,
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/*
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* Call fn for each reference in dir that has index in the range
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* offset <= index < dir->nr. This function does not sort the dir;
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* sorting should be done by the caller.
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* offset <= index < dir->nr. Recurse into subdirectories that are in
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* that index range, sorting them before iterating. This function
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* does not sort dir itself; it should be sorted beforehand.
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*/
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static int do_for_each_ref_in_dir(struct ref_dir *dir, int offset,
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const char *base,
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@ -292,7 +431,15 @@ static int do_for_each_ref_in_dir(struct ref_dir *dir, int offset,
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int i;
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assert(dir->sorted == dir->nr);
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for (i = offset; i < dir->nr; i++) {
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int retval = do_one_ref(base, fn, trim, flags, cb_data, dir->entries[i]);
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struct ref_entry *entry = dir->entries[i];
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int retval;
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if (entry->flag & REF_DIR) {
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sort_ref_dir(&entry->u.subdir);
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retval = do_for_each_ref_in_dir(&entry->u.subdir, 0,
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base, fn, trim, flags, cb_data);
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} else {
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retval = do_one_ref(base, fn, trim, flags, cb_data, entry);
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}
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if (retval)
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return retval;
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}
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@ -301,9 +448,10 @@ static int do_for_each_ref_in_dir(struct ref_dir *dir, int offset,
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/*
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* Call fn for each reference in the union of dir1 and dir2, in order
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* by refname. If an entry appears in both dir1 and dir2, then only
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* process the version that is in dir2. The input dirs must already
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* be sorted.
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* by refname. Recurse into subdirectories. If a value entry appears
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* in both dir1 and dir2, then only process the version that is in
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* dir2. The input dirs must already be sorted, but subdirs will be
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* sorted as needed.
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*/
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static int do_for_each_ref_in_dirs(struct ref_dir *dir1,
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struct ref_dir *dir2,
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@ -315,22 +463,55 @@ static int do_for_each_ref_in_dirs(struct ref_dir *dir1,
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assert(dir1->sorted == dir1->nr);
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assert(dir2->sorted == dir2->nr);
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while (i1 < dir1->nr && i2 < dir2->nr) {
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struct ref_entry *e1 = dir1->entries[i1];
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struct ref_entry *e2 = dir2->entries[i2];
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int cmp = strcmp(e1->name, e2->name);
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if (cmp < 0) {
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retval = do_one_ref(base, fn, trim, flags, cb_data, e1);
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i1++;
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} else {
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retval = do_one_ref(base, fn, trim, flags, cb_data, e2);
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i2++;
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if (cmp == 0) {
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/*
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* There was a ref in array1 with the
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* same name; ignore it.
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*/
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while (1) {
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struct ref_entry *e1, *e2;
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int cmp;
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if (i1 == dir1->nr) {
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return do_for_each_ref_in_dir(dir2, i2,
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base, fn, trim, flags, cb_data);
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}
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if (i2 == dir2->nr) {
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return do_for_each_ref_in_dir(dir1, i1,
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base, fn, trim, flags, cb_data);
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}
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e1 = dir1->entries[i1];
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e2 = dir2->entries[i2];
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cmp = strcmp(e1->name, e2->name);
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if (cmp == 0) {
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if ((e1->flag & REF_DIR) && (e2->flag & REF_DIR)) {
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/* Both are directories; descend them in parallel. */
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sort_ref_dir(&e1->u.subdir);
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sort_ref_dir(&e2->u.subdir);
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retval = do_for_each_ref_in_dirs(
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&e1->u.subdir, &e2->u.subdir,
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base, fn, trim, flags, cb_data);
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i1++;
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i2++;
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} else if (!(e1->flag & REF_DIR) && !(e2->flag & REF_DIR)) {
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/* Both are references; ignore the one from dir1. */
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retval = do_one_ref(base, fn, trim, flags, cb_data, e2);
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i1++;
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i2++;
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} else {
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die("conflict between reference and directory: %s",
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e1->name);
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}
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} else {
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struct ref_entry *e;
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if (cmp < 0) {
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e = e1;
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i1++;
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} else {
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e = e2;
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i2++;
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}
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if (e->flag & REF_DIR) {
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sort_ref_dir(&e->u.subdir);
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retval = do_for_each_ref_in_dir(
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&e->u.subdir, 0,
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base, fn, trim, flags, cb_data);
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} else {
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retval = do_one_ref(base, fn, trim, flags, cb_data, e);
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}
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}
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if (retval)
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@ -655,7 +836,7 @@ static int resolve_gitlink_packed_ref(struct ref_cache *refs,
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struct ref_entry *ref;
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struct ref_dir *dir = get_packed_refs(refs);
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ref = search_ref_dir(dir, refname);
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ref = find_ref(dir, refname);
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if (ref == NULL)
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return -1;
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@ -727,7 +908,7 @@ int resolve_gitlink_ref(const char *path, const char *refname, unsigned char *sh
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static int get_packed_ref(const char *refname, unsigned char *sha1)
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{
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struct ref_dir *packed = get_packed_refs(get_ref_cache(NULL));
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struct ref_entry *entry = search_ref_dir(packed, refname);
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struct ref_entry *entry = find_ref(packed, refname);
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if (entry) {
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hashcpy(sha1, entry->u.value.sha1);
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return 0;
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@ -904,7 +1085,7 @@ int peel_ref(const char *refname, unsigned char *sha1)
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if ((flag & REF_ISPACKED)) {
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struct ref_dir *dir = get_packed_refs(get_ref_cache(NULL));
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struct ref_entry *r = search_ref_dir(dir, refname);
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struct ref_entry *r = find_ref(dir, refname);
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if (r != NULL && r->flag & REF_KNOWS_PEELED) {
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hashcpy(sha1, r->u.value.peeled);
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@ -1404,8 +1585,7 @@ static int repack_without_ref(const char *refname)
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{
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struct repack_without_ref_sb data;
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struct ref_dir *packed = get_packed_refs(get_ref_cache(NULL));
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sort_ref_dir(packed);
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if (search_ref_dir(packed, refname) == NULL)
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if (find_ref(packed, refname) == NULL)
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return 0;
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data.refname = refname;
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data.fd = hold_lock_file_for_update(&packlock, git_path("packed-refs"), 0);
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7
refs.h
7
refs.h
@ -15,8 +15,11 @@ struct ref_lock {
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#define REF_ISBROKEN 0x04
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/*
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* Calls the specified function for each ref file until it returns nonzero,
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* and returns the value
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* Calls the specified function for each ref file until it returns
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* nonzero, and returns the value. Please note that it is not safe to
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* modify references while an iteration is in progress, unless the
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* same callback function invocation that modifies the reference also
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* returns a nonzero value to immediately stop the iteration.
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*/
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typedef int each_ref_fn(const char *refname, const unsigned char *sha1, int flags, void *cb_data);
|
||||
extern int head_ref(each_ref_fn, void *);
|
||||
|
||||
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Reference in New Issue
Block a user