From: Michael Haggerty <mhagger@xxxxxxxxxxxx>
Instead of reading the whole directory of loose references the first
time any are needed, only read them on demand, one directory at a
time.
Use a new ref_entry flag bit REF_INCOMPLETE to indicate that the entry
represents a REF_DIR that hasn't been read yet. Whenever any entries
from such a directory are needed, read all of the loose references
from that directory.
Signed-off-by: Michael Haggerty <mhagger@xxxxxxxxxxxx>
---
refs.c | 127 +++++++++++++++++++++++++++++++++++++++++++++++++---------------
1 file changed, 97 insertions(+), 30 deletions(-)
diff --git a/refs.c b/refs.c
index a0c687f..27ce968 100644
--- a/refs.c
+++ b/refs.c
@@ -101,6 +101,12 @@ int check_refname_format(const char *refname, int flags)
struct ref_entry;
+/*
+ * 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 {
unsigned char sha1[20];
unsigned char peeled[20];
@@ -108,6 +114,32 @@ struct ref_value {
struct ref_cache;
+/*
+ * 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;
@@ -127,19 +159,33 @@ struct ref_dir {
/* ISSYMREF=0x01, ISPACKED=0x02, and ISBROKEN=0x04 are public interfaces */
#define REF_KNOWS_PEELED 0x08
+
+/* ref_entry represents a directory of references */
#define REF_DIR 0x10
/*
+ * Entry has not yet been read from disk (used only for REF_DIR
+ * entries representing loose references)
+ */
+#define REF_INCOMPLETE 0x20
+
+/*
* 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. 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).
+ * 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
@@ -176,10 +222,18 @@ struct ref_entry {
char name[FLEX_ARRAY];
};
+static void read_loose_refs(const char *dirname, struct ref_dir *dir);
+
static struct ref_dir *get_ref_dir(struct ref_entry *entry)
{
+ struct ref_dir *dir;
assert(entry->flag & REF_DIR);
- return &entry->u.subdir;
+ dir = &entry->u.subdir;
+ if (entry->flag & REF_INCOMPLETE) {
+ read_loose_refs(entry->name, dir);
+ entry->flag &= ~REF_INCOMPLETE;
+ }
+ return dir;
}
static struct ref_entry *create_ref_entry(const char *refname,
@@ -237,17 +291,17 @@ static void clear_ref_dir(struct ref_dir *dir)
/*
* 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.
+ * "refs/heads/") or "" for the top-level directory.
*/
static struct ref_entry *create_dir_entry(struct ref_cache *ref_cache,
- const char *dirname)
+ const char *dirname, int incomplete)
{
struct ref_entry *direntry;
int len = strlen(dirname);
direntry = xcalloc(1, sizeof(struct ref_entry) + len + 1);
memcpy(direntry->name, dirname, len + 1);
direntry->u.subdir.ref_cache = ref_cache;
- direntry->flag = REF_DIR;
+ direntry->flag = REF_DIR | (incomplete ? REF_INCOMPLETE : 0);
return direntry;
}
@@ -263,7 +317,7 @@ static void sort_ref_dir(struct ref_dir *dir);
/*
* Return the entry with the given refname from the ref_dir
* (non-recursively), sorting dir if necessary. Return NULL if no
- * such entry is found.
+ * such entry is found. dir must already be complete.
*/
static struct ref_entry *search_ref_dir(struct ref_dir *dir, const char *refname)
{
@@ -294,7 +348,7 @@ static struct ref_entry *search_ref_dir(struct ref_dir *dir, const char *refname
* recursing). Sort dir if necessary. subdirname must be a directory
* name (i.e., end in '/'). If mkdir is set, then create the
* directory if it is missing; otherwise, return NULL if the desired
- * directory cannot be found.
+ * directory cannot be found. dir must already be complete.
*/
static struct ref_dir *search_for_subdir(struct ref_dir *dir,
const char *subdirname, int mkdir)
@@ -303,7 +357,13 @@ static struct ref_dir *search_for_subdir(struct ref_dir *dir,
if (!entry) {
if (!mkdir)
return NULL;
- entry = create_dir_entry(dir->ref_cache, subdirname);
+ /*
+ * Since dir is complete, the absence of a subdir
+ * means that the subdir really doesn't exist;
+ * therefore, create an empty record for it but mark
+ * the record complete.
+ */
+ entry = create_dir_entry(dir->ref_cache, subdirname, 0);
add_entry_to_dir(dir, entry);
}
return get_ref_dir(entry);
@@ -313,10 +373,10 @@ static struct ref_dir *search_for_subdir(struct ref_dir *dir,
* 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., ends in '/'), then return that ref_dir itself. dir must
- * represent the top-level directory. 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.
+ * 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.
*/
static struct ref_dir *find_containing_dir(struct ref_dir *dir,
const char *refname, int mkdir)
@@ -760,7 +820,7 @@ static struct ref_dir *get_packed_refs(struct ref_cache *refs)
const char *packed_refs_file;
FILE *f;
- refs->packed = create_dir_entry(refs, "");
+ refs->packed = create_dir_entry(refs, "", 0);
if (*refs->name)
packed_refs_file = git_path_submodule(refs->name, "packed-refs");
else
@@ -781,9 +841,9 @@ void add_packed_ref(const char *refname, const unsigned char *sha1)
}
/*
- * Read the loose references for refs from the namespace dirname.
- * dirname must end with '/'. dir must be the directory entry
- * corresponding to dirname.
+ * Read the loose references from the namespace dirname into dir
+ * (without recursing). dirname must end with '/'. dir must be the
+ * directory entry corresponding to dirname.
*/
static void read_loose_refs(const char *dirname, struct ref_dir *dir)
{
@@ -824,8 +884,8 @@ static void read_loose_refs(const char *dirname, struct ref_dir *dir)
/* Silently ignore. */
} else if (S_ISDIR(st.st_mode)) {
strbuf_addch(&refname, '/');
- read_loose_refs(refname.buf,
- search_for_subdir(dir, refname.buf, 1));
+ add_entry_to_dir(dir,
+ create_dir_entry(refs, refname.buf, 1));
} else {
if (*refs->name) {
hashclr(sha1);
@@ -850,10 +910,17 @@ static void read_loose_refs(const char *dirname, struct ref_dir *dir)
static struct ref_dir *get_loose_refs(struct ref_cache *refs)
{
if (!refs->loose) {
- refs->loose = create_dir_entry(refs, "");
- read_loose_refs("refs/",
- search_for_subdir(get_ref_dir(refs->loose),
- "refs/", 1));
+ /*
+ * Mark the top-level directory complete because we
+ * are about to read the only subdirectory that can
+ * hold references:
+ */
+ refs->loose = create_dir_entry(refs, "", 0);
+ /*
+ * Create an incomplete entry for "refs/":
+ */
+ add_entry_to_dir(get_ref_dir(refs->loose),
+ create_dir_entry(refs, "refs/", 1));
}
return get_ref_dir(refs->loose);
}
--
1.7.10
--
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