git/refs/iterator.c
Patrick Steinhardt 5e01d83841 refs: always treat iterators as ordered
In the preceding commit we have converted the reflog iterator of the
"files" backend to be ordered, which was the only remaining ref iterator
that wasn't ordered. Refactor the ref iterator infrastructure so that we
always assume iterators to be ordered, thus simplifying the code.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-02-21 09:58:06 -08:00

469 lines
12 KiB
C

/*
* Generic reference iterator infrastructure. See refs-internal.h for
* documentation about the design and use of reference iterators.
*/
#include "git-compat-util.h"
#include "refs.h"
#include "refs/refs-internal.h"
#include "iterator.h"
int ref_iterator_advance(struct ref_iterator *ref_iterator)
{
return ref_iterator->vtable->advance(ref_iterator);
}
int ref_iterator_peel(struct ref_iterator *ref_iterator,
struct object_id *peeled)
{
return ref_iterator->vtable->peel(ref_iterator, peeled);
}
int ref_iterator_abort(struct ref_iterator *ref_iterator)
{
return ref_iterator->vtable->abort(ref_iterator);
}
void base_ref_iterator_init(struct ref_iterator *iter,
struct ref_iterator_vtable *vtable)
{
iter->vtable = vtable;
iter->refname = NULL;
iter->oid = NULL;
iter->flags = 0;
}
void base_ref_iterator_free(struct ref_iterator *iter)
{
/* Help make use-after-free bugs fail quickly: */
iter->vtable = NULL;
free(iter);
}
struct empty_ref_iterator {
struct ref_iterator base;
};
static int empty_ref_iterator_advance(struct ref_iterator *ref_iterator)
{
return ref_iterator_abort(ref_iterator);
}
static int empty_ref_iterator_peel(struct ref_iterator *ref_iterator UNUSED,
struct object_id *peeled UNUSED)
{
BUG("peel called for empty iterator");
}
static int empty_ref_iterator_abort(struct ref_iterator *ref_iterator)
{
base_ref_iterator_free(ref_iterator);
return ITER_DONE;
}
static struct ref_iterator_vtable empty_ref_iterator_vtable = {
.advance = empty_ref_iterator_advance,
.peel = empty_ref_iterator_peel,
.abort = empty_ref_iterator_abort,
};
struct ref_iterator *empty_ref_iterator_begin(void)
{
struct empty_ref_iterator *iter = xcalloc(1, sizeof(*iter));
struct ref_iterator *ref_iterator = &iter->base;
base_ref_iterator_init(ref_iterator, &empty_ref_iterator_vtable);
return ref_iterator;
}
int is_empty_ref_iterator(struct ref_iterator *ref_iterator)
{
return ref_iterator->vtable == &empty_ref_iterator_vtable;
}
struct merge_ref_iterator {
struct ref_iterator base;
struct ref_iterator *iter0, *iter1;
ref_iterator_select_fn *select;
void *cb_data;
/*
* A pointer to iter0 or iter1 (whichever is supplying the
* current value), or NULL if advance has not yet been called.
*/
struct ref_iterator **current;
};
enum iterator_selection ref_iterator_select(struct ref_iterator *iter_worktree,
struct ref_iterator *iter_common,
void *cb_data UNUSED)
{
if (iter_worktree && !iter_common) {
/*
* Return the worktree ref if there are no more common refs.
*/
return ITER_SELECT_0;
} else if (iter_common) {
/*
* In case we have pending worktree and common refs we need to
* yield them based on their lexicographical order. Worktree
* refs that have the same name as common refs shadow the
* latter.
*/
if (iter_worktree) {
int cmp = strcmp(iter_worktree->refname,
iter_common->refname);
if (cmp < 0)
return ITER_SELECT_0;
else if (!cmp)
return ITER_SELECT_0_SKIP_1;
}
/*
* We now know that the lexicographically-next ref is a common
* ref. When the common ref is a shared one we return it.
*/
if (parse_worktree_ref(iter_common->refname, NULL, NULL,
NULL) == REF_WORKTREE_SHARED)
return ITER_SELECT_1;
/*
* Otherwise, if the common ref is a per-worktree ref we skip
* it because it would belong to the main worktree, not ours.
*/
return ITER_SKIP_1;
} else {
return ITER_DONE;
}
}
static int merge_ref_iterator_advance(struct ref_iterator *ref_iterator)
{
struct merge_ref_iterator *iter =
(struct merge_ref_iterator *)ref_iterator;
int ok;
if (!iter->current) {
/* Initialize: advance both iterators to their first entries */
if ((ok = ref_iterator_advance(iter->iter0)) != ITER_OK) {
iter->iter0 = NULL;
if (ok == ITER_ERROR)
goto error;
}
if ((ok = ref_iterator_advance(iter->iter1)) != ITER_OK) {
iter->iter1 = NULL;
if (ok == ITER_ERROR)
goto error;
}
} else {
/*
* Advance the current iterator past the just-used
* entry:
*/
if ((ok = ref_iterator_advance(*iter->current)) != ITER_OK) {
*iter->current = NULL;
if (ok == ITER_ERROR)
goto error;
}
}
/* Loop until we find an entry that we can yield. */
while (1) {
struct ref_iterator **secondary;
enum iterator_selection selection =
iter->select(iter->iter0, iter->iter1, iter->cb_data);
if (selection == ITER_SELECT_DONE) {
return ref_iterator_abort(ref_iterator);
} else if (selection == ITER_SELECT_ERROR) {
ref_iterator_abort(ref_iterator);
return ITER_ERROR;
}
if ((selection & ITER_CURRENT_SELECTION_MASK) == 0) {
iter->current = &iter->iter0;
secondary = &iter->iter1;
} else {
iter->current = &iter->iter1;
secondary = &iter->iter0;
}
if (selection & ITER_SKIP_SECONDARY) {
if ((ok = ref_iterator_advance(*secondary)) != ITER_OK) {
*secondary = NULL;
if (ok == ITER_ERROR)
goto error;
}
}
if (selection & ITER_YIELD_CURRENT) {
iter->base.refname = (*iter->current)->refname;
iter->base.oid = (*iter->current)->oid;
iter->base.flags = (*iter->current)->flags;
return ITER_OK;
}
}
error:
ref_iterator_abort(ref_iterator);
return ITER_ERROR;
}
static int merge_ref_iterator_peel(struct ref_iterator *ref_iterator,
struct object_id *peeled)
{
struct merge_ref_iterator *iter =
(struct merge_ref_iterator *)ref_iterator;
if (!iter->current) {
BUG("peel called before advance for merge iterator");
}
return ref_iterator_peel(*iter->current, peeled);
}
static int merge_ref_iterator_abort(struct ref_iterator *ref_iterator)
{
struct merge_ref_iterator *iter =
(struct merge_ref_iterator *)ref_iterator;
int ok = ITER_DONE;
if (iter->iter0) {
if (ref_iterator_abort(iter->iter0) != ITER_DONE)
ok = ITER_ERROR;
}
if (iter->iter1) {
if (ref_iterator_abort(iter->iter1) != ITER_DONE)
ok = ITER_ERROR;
}
base_ref_iterator_free(ref_iterator);
return ok;
}
static struct ref_iterator_vtable merge_ref_iterator_vtable = {
.advance = merge_ref_iterator_advance,
.peel = merge_ref_iterator_peel,
.abort = merge_ref_iterator_abort,
};
struct ref_iterator *merge_ref_iterator_begin(
struct ref_iterator *iter0, struct ref_iterator *iter1,
ref_iterator_select_fn *select, void *cb_data)
{
struct merge_ref_iterator *iter = xcalloc(1, sizeof(*iter));
struct ref_iterator *ref_iterator = &iter->base;
/*
* We can't do the same kind of is_empty_ref_iterator()-style
* optimization here as overlay_ref_iterator_begin() does,
* because we don't know the semantics of the select function.
* It might, for example, implement "intersect" by passing
* references through only if they exist in both iterators.
*/
base_ref_iterator_init(ref_iterator, &merge_ref_iterator_vtable);
iter->iter0 = iter0;
iter->iter1 = iter1;
iter->select = select;
iter->cb_data = cb_data;
iter->current = NULL;
return ref_iterator;
}
/*
* A ref_iterator_select_fn that overlays the items from front on top
* of those from back (like loose refs over packed refs). See
* overlay_ref_iterator_begin().
*/
static enum iterator_selection overlay_iterator_select(
struct ref_iterator *front, struct ref_iterator *back,
void *cb_data UNUSED)
{
int cmp;
if (!back)
return front ? ITER_SELECT_0 : ITER_SELECT_DONE;
else if (!front)
return ITER_SELECT_1;
cmp = strcmp(front->refname, back->refname);
if (cmp < 0)
return ITER_SELECT_0;
else if (cmp > 0)
return ITER_SELECT_1;
else
return ITER_SELECT_0_SKIP_1;
}
struct ref_iterator *overlay_ref_iterator_begin(
struct ref_iterator *front, struct ref_iterator *back)
{
/*
* Optimization: if one of the iterators is empty, return the
* other one rather than incurring the overhead of wrapping
* them.
*/
if (is_empty_ref_iterator(front)) {
ref_iterator_abort(front);
return back;
} else if (is_empty_ref_iterator(back)) {
ref_iterator_abort(back);
return front;
}
return merge_ref_iterator_begin(front, back, overlay_iterator_select, NULL);
}
struct prefix_ref_iterator {
struct ref_iterator base;
struct ref_iterator *iter0;
char *prefix;
int trim;
};
/* Return -1, 0, 1 if refname is before, inside, or after the prefix. */
static int compare_prefix(const char *refname, const char *prefix)
{
while (*prefix) {
if (*refname != *prefix)
return ((unsigned char)*refname < (unsigned char)*prefix) ? -1 : +1;
refname++;
prefix++;
}
return 0;
}
static int prefix_ref_iterator_advance(struct ref_iterator *ref_iterator)
{
struct prefix_ref_iterator *iter =
(struct prefix_ref_iterator *)ref_iterator;
int ok;
while ((ok = ref_iterator_advance(iter->iter0)) == ITER_OK) {
int cmp = compare_prefix(iter->iter0->refname, iter->prefix);
if (cmp < 0)
continue;
if (cmp > 0) {
/*
* As the source iterator is ordered, we
* can stop the iteration as soon as we see a
* refname that comes after the prefix:
*/
ok = ref_iterator_abort(iter->iter0);
break;
}
if (iter->trim) {
/*
* It is nonsense to trim off characters that
* you haven't already checked for via a
* prefix check, whether via this
* `prefix_ref_iterator` or upstream in
* `iter0`). So if there wouldn't be at least
* one character left in the refname after
* trimming, report it as a bug:
*/
if (strlen(iter->iter0->refname) <= iter->trim)
BUG("attempt to trim too many characters");
iter->base.refname = iter->iter0->refname + iter->trim;
} else {
iter->base.refname = iter->iter0->refname;
}
iter->base.oid = iter->iter0->oid;
iter->base.flags = iter->iter0->flags;
return ITER_OK;
}
iter->iter0 = NULL;
if (ref_iterator_abort(ref_iterator) != ITER_DONE)
return ITER_ERROR;
return ok;
}
static int prefix_ref_iterator_peel(struct ref_iterator *ref_iterator,
struct object_id *peeled)
{
struct prefix_ref_iterator *iter =
(struct prefix_ref_iterator *)ref_iterator;
return ref_iterator_peel(iter->iter0, peeled);
}
static int prefix_ref_iterator_abort(struct ref_iterator *ref_iterator)
{
struct prefix_ref_iterator *iter =
(struct prefix_ref_iterator *)ref_iterator;
int ok = ITER_DONE;
if (iter->iter0)
ok = ref_iterator_abort(iter->iter0);
free(iter->prefix);
base_ref_iterator_free(ref_iterator);
return ok;
}
static struct ref_iterator_vtable prefix_ref_iterator_vtable = {
.advance = prefix_ref_iterator_advance,
.peel = prefix_ref_iterator_peel,
.abort = prefix_ref_iterator_abort,
};
struct ref_iterator *prefix_ref_iterator_begin(struct ref_iterator *iter0,
const char *prefix,
int trim)
{
struct prefix_ref_iterator *iter;
struct ref_iterator *ref_iterator;
if (!*prefix && !trim)
return iter0; /* optimization: no need to wrap iterator */
CALLOC_ARRAY(iter, 1);
ref_iterator = &iter->base;
base_ref_iterator_init(ref_iterator, &prefix_ref_iterator_vtable);
iter->iter0 = iter0;
iter->prefix = xstrdup(prefix);
iter->trim = trim;
return ref_iterator;
}
struct ref_iterator *current_ref_iter = NULL;
int do_for_each_repo_ref_iterator(struct repository *r, struct ref_iterator *iter,
each_repo_ref_fn fn, void *cb_data)
{
int retval = 0, ok;
struct ref_iterator *old_ref_iter = current_ref_iter;
current_ref_iter = iter;
while ((ok = ref_iterator_advance(iter)) == ITER_OK) {
retval = fn(r, iter->refname, iter->oid, iter->flags, cb_data);
if (retval) {
/*
* If ref_iterator_abort() returns ITER_ERROR,
* we ignore that error in deference to the
* callback function's return value.
*/
ref_iterator_abort(iter);
goto out;
}
}
out:
current_ref_iter = old_ref_iter;
if (ok == ITER_ERROR)
return -1;
return retval;
}