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keyval: introduce keyval_merge

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This patch introduces a function that merges two keyval-produced
(or keyval-like) QDicts.  It can be used to emulate the behavior of
.merge_lists = true QemuOpts groups, merging -readconfig sections and
command-line options in a single QDict, and also to implement -set.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Paolo Bonzini 2020-11-12 08:40:11 -05:00
parent 3bb6944585
commit 9176e800db
3 changed files with 139 additions and 0 deletions
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1
include/qemu/option.h
View File

@ -149,5 +149,6 @@ QemuOptsList *qemu_opts_append(QemuOptsList *dst, QemuOptsList *list);
QDict *keyval_parse(const char *params, const char *implied_key,
bool *help, Error **errp);
void keyval_merge(QDict *old, const QDict *new, Error **errp);
#endif

58
tests/unit/test-keyval.c
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@ -747,6 +747,61 @@ static void test_keyval_visit_any(void)
visit_free(v);
}
static void test_keyval_merge_dict(void)
{
QDict *first = keyval_parse("opt1=abc,opt2.sub1=def,opt2.sub2=ghi,opt3=xyz",
NULL, NULL, &error_abort);
QDict *second = keyval_parse("opt1=ABC,opt2.sub2=GHI,opt2.sub3=JKL",
NULL, NULL, &error_abort);
QDict *combined = keyval_parse("opt1=ABC,opt2.sub1=def,opt2.sub2=GHI,opt2.sub3=JKL,opt3=xyz",
NULL, NULL, &error_abort);
Error *err = NULL;
keyval_merge(first, second, &err);
g_assert(!err);
g_assert(qobject_is_equal(QOBJECT(combined), QOBJECT(first)));
qobject_unref(first);
qobject_unref(second);
qobject_unref(combined);
}
static void test_keyval_merge_list(void)
{
QDict *first = keyval_parse("opt1.0=abc,opt2.0=xyz",
NULL, NULL, &error_abort);
QDict *second = keyval_parse("opt1.0=def",
NULL, NULL, &error_abort);
QDict *combined = keyval_parse("opt1.0=abc,opt1.1=def,opt2.0=xyz",
NULL, NULL, &error_abort);
Error *err = NULL;
keyval_merge(first, second, &err);
g_assert(!err);
g_assert(qobject_is_equal(QOBJECT(combined), QOBJECT(first)));
qobject_unref(first);
qobject_unref(second);
qobject_unref(combined);
}
static void test_keyval_merge_conflict(void)
{
QDict *first = keyval_parse("opt2=ABC",
NULL, NULL, &error_abort);
QDict *second = keyval_parse("opt2.sub1=def,opt2.sub2=ghi",
NULL, NULL, &error_abort);
QDict *third = qdict_clone_shallow(first);
Error *err = NULL;
keyval_merge(first, second, &err);
error_free_or_abort(&err);
keyval_merge(second, third, &err);
error_free_or_abort(&err);
qobject_unref(first);
qobject_unref(second);
qobject_unref(third);
}
int main(int argc, char *argv[])
{
g_test_init(&argc, &argv, NULL);
@ -760,6 +815,9 @@ int main(int argc, char *argv[])
g_test_add_func("/keyval/visit/optional", test_keyval_visit_optional);
g_test_add_func("/keyval/visit/alternate", test_keyval_visit_alternate);
g_test_add_func("/keyval/visit/any", test_keyval_visit_any);
g_test_add_func("/keyval/merge/dict", test_keyval_merge_dict);
g_test_add_func("/keyval/merge/list", test_keyval_merge_list);
g_test_add_func("/keyval/merge/conflict", test_keyval_merge_conflict);
g_test_run();
return 0;
}

80
util/keyval.c
View File

@ -310,6 +310,86 @@ static char *reassemble_key(GSList *key)
return g_string_free(s, FALSE);
}
/*
* Recursive worker for keyval_merge.
*
* @str is the path that led to the * current dictionary (to be used for
* error messages). It is modified internally but restored before the
* function returns.
*/
static void keyval_do_merge(QDict *dest, const QDict *merged, GString *str, Error **errp)
{
size_t save_len = str->len;
const QDictEntry *ent;
QObject *old_value;
for (ent = qdict_first(merged); ent; ent = qdict_next(merged, ent)) {
old_value = qdict_get(dest, ent->key);
if (old_value) {
if (qobject_type(old_value) != qobject_type(ent->value)) {
error_setg(errp, "Parameter '%s%s' used inconsistently",
str->str, ent->key);
return;
} else if (qobject_type(ent->value) == QTYPE_QDICT) {
/* Merge sub-dictionaries. */
g_string_append(str, ent->key);
g_string_append_c(str, '.');
keyval_do_merge(qobject_to(QDict, old_value),
qobject_to(QDict, ent->value),
str, errp);
g_string_truncate(str, save_len);
continue;
} else if (qobject_type(ent->value) == QTYPE_QLIST) {
/* Append to old list. */
QList *old = qobject_to(QList, old_value);
QList *new = qobject_to(QList, ent->value);
const QListEntry *item;
QLIST_FOREACH_ENTRY(new, item) {
qobject_ref(item->value);
qlist_append_obj(old, item->value);
}
continue;
} else {
assert(qobject_type(ent->value) == QTYPE_QSTRING);
}
}
qobject_ref(ent->value);
qdict_put_obj(dest, ent->key, ent->value);
}
}
/* Merge the @merged dictionary into @dest.
*
* The dictionaries are expected to be returned by the keyval parser, and
* therefore the only expected scalar type is the string. In case the same
* path is present in both @dest and @merged, the semantics are as follows:
*
* - lists are concatenated
*
* - dictionaries are merged recursively
*
* - for scalar values, @merged wins
*
* In case an error is reported, @dest may already have been modified.
*
* This function can be used to implement semantics analogous to QemuOpts's
* .merge_lists = true case, or to implement -set for options backed by QDicts.
*
* Note: while QemuOpts is commonly used so that repeated keys overwrite
* ("last one wins"), it can also be used so that repeated keys build up
* a list. keyval_merge() can only be used when the options' semantics are
* the former, not the latter.
*/
void keyval_merge(QDict *dest, const QDict *merged, Error **errp)
{
GString *str;
str = g_string_new("");
keyval_do_merge(dest, merged, str, errp);
g_string_free(str, TRUE);
}
/*
* Listify @cur recursively.
* Replace QDicts whose keys are all valid list indexes by QLists.