From e6ed3ca651fac702f9d9a9ef64a14c7efadf7365 Mon Sep 17 00:00:00 2001 From: Michael Haggerty Date: Tue, 17 Jan 2012 06:50:32 +0100 Subject: [PATCH] ref_array: keep track of whether references are sorted Keep track of how many entries at the beginning of a ref_array are already sorted. In sort_ref_array(), return early if the the array is already sorted (i.e., if no new references has been appended to the end of the list since the last call to sort_ref_array()). Sort ref_arrays only when needed, namely in search_ref_array() and in do_for_each_ref(). However, never call sort_ref_array() on the extra_refs, because extra_refs can contain multiple entries with the same name and because sort_ref_array() not only sorts, but de-dups its contents. This change is currently not useful, because entries are not added to ref_arrays after they are created. But in a moment they will be... Implementation note: we could store a binary "sorted" value instead of an integer, but storing the number of sorted entries leaves the way open for a couple of possible future optimizations: * In sort_ref_array(), sort *only* the unsorted entries, then merge them with the sorted entries. This should be faster if most of the entries are already sorted. * Teach search_ref_array() to do a binary search of any sorted entries, and if unsuccessful do a linear search of any unsorted entries. This would avoid the need to sort the list every time that search_ref_array() is called, and (given some intelligence about how often to sort) could significantly improve the speed in certain hypothetical usage patterns. Signed-off-by: Michael Haggerty Signed-off-by: Junio C Hamano --- refs.c | 33 ++++++++++++++++++++++++++------- 1 file changed, 26 insertions(+), 7 deletions(-) diff --git a/refs.c b/refs.c index 6f436f1cb..3785cc200 100644 --- a/refs.c +++ b/refs.c @@ -17,6 +17,15 @@ struct ref_entry { struct ref_array { 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; + struct ref_entry **refs; }; @@ -105,12 +114,18 @@ static int is_dup_ref(const struct ref_entry *ref1, const struct ref_entry *ref2 } } +/* + * Sort the entries in array (if they are not already sorted). + */ static void sort_ref_array(struct ref_array *array) { int i, j; - /* Nothing to sort unless there are at least two entries */ - if (array->nr < 2) + /* + * This check also prevents passing a zero-length array to qsort(), + * which is a problem on some platforms. + */ + if (array->sorted == array->nr) return; qsort(array->refs, array->nr, sizeof(*array->refs), ref_entry_cmp); @@ -124,7 +139,7 @@ static void sort_ref_array(struct ref_array *array) } array->refs[++i] = array->refs[j]; } - array->nr = i + 1; + array->sorted = array->nr = i + 1; } static struct ref_entry *search_ref_array(struct ref_array *array, const char *refname) @@ -137,7 +152,7 @@ static struct ref_entry *search_ref_array(struct ref_array *array, const char *r if (!array->nr) return NULL; - + sort_ref_array(array); len = strlen(refname) + 1; e = xmalloc(sizeof(struct ref_entry) + len); memcpy(e->name, refname, len); @@ -168,6 +183,10 @@ static struct ref_cache { static struct ref_entry *current_ref; +/* + * Never call sort_ref_array() on the extra_refs, because it is + * allowed to contain entries with duplicate names. + */ static struct ref_array extra_refs; static void clear_ref_array(struct ref_array *array) @@ -176,7 +195,7 @@ static void clear_ref_array(struct ref_array *array) for (i = 0; i < array->nr; i++) free(array->refs[i]); free(array->refs); - array->nr = array->alloc = 0; + array->sorted = array->nr = array->alloc = 0; array->refs = NULL; } @@ -268,7 +287,6 @@ static void read_packed_refs(FILE *f, struct ref_array *array) !get_sha1_hex(refline + 1, sha1)) hashcpy(last->peeled, sha1); } - sort_ref_array(array); } void add_extra_ref(const char *refname, const unsigned char *sha1, int flag) @@ -404,7 +422,6 @@ static struct ref_array *get_loose_refs(struct ref_cache *refs) { if (!refs->did_loose) { get_ref_dir(refs, "refs", &refs->loose); - sort_ref_array(&refs->loose); refs->did_loose = 1; } return &refs->loose; @@ -720,6 +737,8 @@ static int do_for_each_ref(const char *submodule, const char *base, each_ref_fn for (i = 0; i < extra->nr; i++) retval = do_one_ref(base, fn, trim, flags, cb_data, extra->refs[i]); + sort_ref_array(packed); + sort_ref_array(loose); while (p < packed->nr && l < loose->nr) { struct ref_entry *entry; int cmp = strcmp(packed->refs[p]->name, loose->refs[l]->name); -- 2.26.2