[PATCHv4 05/21] notes.h/c: Clarify the handling of notes objects that are == null_sha1
- From
Johan Herland <johan@herland.net>
- Date
- Oct 21, 2010, 02:08 UTC
- Message-ID
- <1287626936-32232-6-git-send-email-johan@herland.net>
- In-Reply-To
- <1287626936-32232-1-git-send-email-johan@herland.net>
Clearly specify how combine_notes functions are expected to handle null_sha1 in input. Also specify (and implement) that returning null_sha1 from a combine_notes function will cause the note in question to be removed.
Furthermore, document that passing note_sha1 == null_sha1 to add_note() is usually a no-op, except in cases where combining it with an existing note yields a new/changed result.
Signed-off-by: Johan Herland <johan@herland.net> --- notes.c | 12 +++++++++++- notes.h | 16 +++++++++++++++- 2 files changed, 26 insertions(+), 2 deletions(-)
diff --git a/notes.c b/notes.c index bfb3ea5..0c13a36 100644 --- a/notes.c +++ b/notes.c @@ -248,7 +248,10 @@ static void note_tree_insert(struct notes_tree *t, struct int_node *tree, switch (GET_PTR_TYPE(*p)) { case PTR_TYPE_NULL: assert(!*p); - *p = SET_PTR_TYPE(entry, type); + if (is_null_sha1(entry->val_sha1)) + free(entry); + else + *p = SET_PTR_TYPE(entry, type); return; case PTR_TYPE_NOTE: switch (type) { @@ -264,6 +267,9 @@ static void note_tree_insert(struct notes_tree *t, struct int_node *tree, sha1_to_hex(l->val_sha1), sha1_to_hex(entry->val_sha1), sha1_to_hex(l->key_sha1)); + + if (is_null_sha1(l->val_sha1)) + note_tree_remove(t, tree, n, entry); free(entry); return; } @@ -295,6 +301,10 @@ static void note_tree_insert(struct notes_tree *t, struct int_node *tree, /* non-matching leaf_node */ assert(GET_PTR_TYPE(*p) == PTR_TYPE_NOTE || GET_PTR_TYPE(*p) == PTR_TYPE_SUBTREE); + if (is_null_sha1(entry->val_sha1)) { /* skip insertion of empty note */ + free(entry); + return; + } new_node = (struct int_node *) xcalloc(sizeof(struct int_node), 1); note_tree_insert(t, new_node, n + 1, l, GET_PTR_TYPE(*p), combine_notes); diff --git a/notes.h b/notes.h index 20db42f..79ea797 100644 --- a/notes.h +++ b/notes.h @@ -12,7 +12,10 @@ * resulting SHA1 into the first SHA1 argument (cur_sha1). A non-zero return * value indicates failure. * - * The two given SHA1s must both be non-NULL and different from each other. + * The two given SHA1s shall both be non-NULL and different from each other. + * Either of them (but not both) may be == null_sha1, which indicates an + * empty/non-existent note. If the resulting SHA1 (cur_sha1) is == null_sha1, + * the note will be removed from the notes tree. * * The default combine_notes function (you get this when passing NULL) is * combine_notes_concatenate(), which appends the contents of the new note to @@ -90,6 +93,17 @@ void init_notes(struct notes_tree *t, const char *notes_ref, /* * Add the given note object to the given notes_tree structure * + * If there already exists a note for the given object_sha1, the given + * combine_notes function is invoked to break the tie. If not given (i.e. + * combine_notes == NULL), the default combine_notes function for the given + * notes_tree is used. + * + * Passing note_sha1 == null_sha1 indicates the addition of an + * empty/non-existent note. This is a (potentially expensive) no-op unless + * there already exists a note for the given object_sha1, AND combining that + * note with the empty note (using the given combine_notes function) results + * in a new/changed note. + * * IMPORTANT: The changes made by add_note() to the given notes_tree structure * are not persistent until a subsequent call to write_notes_tree() returns * zero.
-- 1.7.3.98.g5ad7d9