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authorJohan Herland <johan@herland.net>2010-02-13 22:28:19 +0100
committerJunio C Hamano <gitster@pobox.com>2010-02-13 19:36:13 -0800
commit73f464b5f3fe4dd5109b9fb9e58c1fe55393902d (patch)
tree02d1d26e0057bae465de2167ef76e6dfcff3eecc /notes.h
parentcd30539214bb09881b84c796a50d30e409dee3fa (diff)
downloadgit-73f464b5f3fe4dd5109b9fb9e58c1fe55393902d.tar.gz
Refactor notes concatenation into a flexible interface for combining notes
When adding a note to an object that already has an existing note, the current solution is to concatenate the contents of the two notes. However, the caller may instead wish to _overwrite_ the existing note with the new note, or maybe even _ignore_ the new note, and keep the existing one. There might also be other ways of combining notes that are only known to the caller. Therefore, instead of unconditionally concatenating notes, we let the caller specify how to combine notes, by passing in a pointer to a function for combining notes. The caller may choose to implement its own function for notes combining, but normally one of the following three conveniently supplied notes combination functions will be sufficient: - combine_notes_concatenate() combines the two notes by appending the contents of the new note to the contents of the existing note. - combine_notes_overwrite() replaces the existing note with the new note. - combine_notes_ignore() keeps the existing note, and ignores the new note. A combine_notes function can be passed to init_notes() to choose a default combine_notes function for that notes tree. If NULL is given, the notes tree falls back to combine_notes_concatenate() as the ultimate default. A combine_notes function can also be passed directly to add_note(), to control the notes combining behaviour for a note addition in particular. If NULL is passed, the combine_notes function registered for the given notes tree is used. Signed-off-by: Johan Herland <johan@herland.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
Diffstat (limited to 'notes.h')
-rw-r--r--notes.h34
1 files changed, 32 insertions, 2 deletions
diff --git a/notes.h b/notes.h
index 12acc38b08..20d6e171ff 100644
--- a/notes.h
+++ b/notes.h
@@ -2,6 +2,30 @@
#define NOTES_H
/*
+ * Function type for combining two notes annotating the same object.
+ *
+ * When adding a new note annotating the same object as an existing note, it is
+ * up to the caller to decide how to combine the two notes. The decision is
+ * made by passing in a function of the following form. The function accepts
+ * two SHA1s -- of the existing note and the new note, respectively. The
+ * function then combines the notes in whatever way it sees fit, and writes the
+ * 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 default combine_notes function (you get this when passing NULL) is
+ * combine_notes_concatenate(), which appends the contents of the new note to
+ * the contents of the existing note.
+ */
+typedef int combine_notes_fn(unsigned char *cur_sha1, const unsigned char *new_sha1);
+
+/* Common notes combinators */
+int combine_notes_concatenate(unsigned char *cur_sha1, const unsigned char *new_sha1);
+int combine_notes_overwrite(unsigned char *cur_sha1, const unsigned char *new_sha1);
+int combine_notes_ignore(unsigned char *cur_sha1, const unsigned char *new_sha1);
+
+/*
* Notes tree object
*
* Encapsulates the internal notes tree structure associated with a notes ref.
@@ -13,6 +37,7 @@
extern struct notes_tree {
struct int_node *root;
char *ref;
+ combine_notes_fn *combine_notes;
int initialized;
} default_notes_tree;
@@ -36,10 +61,15 @@ extern struct notes_tree {
*
* If you pass t == NULL, the default internal notes_tree will be initialized.
*
+ * The combine_notes function that is passed becomes the default combine_notes
+ * function for the given notes_tree. If NULL is passed, the default
+ * combine_notes function is combine_notes_concatenate().
+ *
* Precondition: The notes_tree structure is zeroed (this can be achieved with
* memset(t, 0, sizeof(struct notes_tree)))
*/
-void init_notes(struct notes_tree *t, const char *notes_ref, int flags);
+void init_notes(struct notes_tree *t, const char *notes_ref,
+ combine_notes_fn combine_notes, int flags);
/*
* Add the given note object to the given notes_tree structure
@@ -49,7 +79,7 @@ void init_notes(struct notes_tree *t, const char *notes_ref, int flags);
* zero.
*/
void add_note(struct notes_tree *t, const unsigned char *object_sha1,
- const unsigned char *note_sha1);
+ const unsigned char *note_sha1, combine_notes_fn combine_notes);
/*
* Remove the given note object from the given notes_tree structure