keyval: introduce keyval_parse_into

Allow parsing multiple keyval sequences into the same dictionary.
This will be used to simplify the parsing of the -M command line
option, which is currently a .merge_lists = true QemuOpts group.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

include/qemu/option.h

@@ -147,6 +147,8 @@ void qemu_opts_print_help(QemuOptsList *list, bool print_caption);
 void qemu_opts_free(QemuOptsList *list);
 QemuOptsList *qemu_opts_append(QemuOptsList *dst, QemuOptsList *list);
 
+QDict *keyval_parse_into(QDict *qdict, const char *params, const char *implied_key,
+                         bool *p_help, Error **errp);
 QDict *keyval_parse(const char *params, const char *implied_key,
                     bool *help, Error **errp);
 void keyval_merge(QDict *old, const QDict *new, Error **errp);

util/keyval.c

@@ -511,13 +511,14 @@ static QObject *keyval_listify(QDict *cur, GSList *key_of_cur, Error **errp)
  * If @p_help is not NULL, store whether help is requested there.
  * If @p_help is NULL and help is requested, fail.
  *
- * On success, return a dictionary of the parsed keys and values.
- * On failure, store an error through @errp and return NULL.
+ * On success, return @dict, now filled with the parsed keys and values.
+ *
+ * On failure, store an error through @errp and return NULL.  Any keys
+ * and values parsed so far will be in @dict nevertheless.
  */
-QDict *keyval_parse(const char *params, const char *implied_key,
-                    bool *p_help, Error **errp)
+QDict *keyval_parse_into(QDict *qdict, const char *params, const char *implied_key,
+                         bool *p_help, Error **errp)
 {
-    QDict *qdict = qdict_new();
     QObject *listified;
     const char *s;
     bool help = false;
@@ -526,7 +527,6 @@ QDict *keyval_parse(const char *params, const char *implied_key,
     while (*s) {
         s = keyval_parse_one(qdict, s, implied_key, &help, errp);
         if (!s) {
-            qobject_unref(qdict);
             return NULL;
         }
         implied_key = NULL;
@@ -536,15 +536,42 @@ QDict *keyval_parse(const char *params, const char *implied_key,
         *p_help = help;
     } else if (help) {
         error_setg(errp, "Help is not available for this option");
-        qobject_unref(qdict);
         return NULL;
     }
 
     listified = keyval_listify(qdict, NULL, errp);
     if (!listified) {
-        qobject_unref(qdict);
         return NULL;
     }
     assert(listified == QOBJECT(qdict));
     return qdict;
 }
+
+/*
+ * Parse @params in QEMU's traditional KEY=VALUE,... syntax.
+ *
+ * If @implied_key, the first KEY= can be omitted.  @implied_key is
+ * implied then, and VALUE can't be empty or contain ',' or '='.
+ *
+ * A parameter "help" or "?" without a value isn't added to the
+ * resulting dictionary, but instead is interpreted as help request.
+ * All other options are parsed and returned normally so that context
+ * specific help can be printed.
+ *
+ * If @p_help is not NULL, store whether help is requested there.
+ * If @p_help is NULL and help is requested, fail.
+ *
+ * On success, return a dictionary of the parsed keys and values.
+ * On failure, store an error through @errp and return NULL.
+ */
+QDict *keyval_parse(const char *params, const char *implied_key,
+                    bool *p_help, Error **errp)
+{
+    QDict *qdict = qdict_new();
+    QDict *ret = keyval_parse_into(qdict, params, implied_key, p_help, errp);
+
+    if (!ret) {
+        qobject_unref(qdict);
+    }
+    return ret;
+}