json: add const string dispatcher

This adds json_dispatch_const_string() which is similar to
json_dispatch_string() but doesn't store a strdup()'ed copy of the
string, but a pointer directly into the JSON record.

This should simplify cases where the json variant sticks around long
enough anyway.

diff --git a/src/shared/json.c b/src/shared/json.c
index 25e711964f016dd01b550f40c2f10f24133b6df6..2327cbcc9ce431590d712c3d6a0bf717ceeb3cca 100644 (file)
--- a/src/shared/json.c
+++ b/src/shared/json.c
@@ -3977,6 +3977,27 @@ int json_dispatch_string(const char *name, JsonVariant *variant, JsonDispatchFla
         return 0;
 }
 
+int json_dispatch_const_string(const char *name, JsonVariant *variant, JsonDispatchFlags flags, void *userdata) {
+        const char **s = userdata;
+
+        assert(variant);
+        assert(s);
+
+        if (json_variant_is_null(variant)) {
+                *s = NULL;
+                return 0;
+        }
+
+        if (!json_variant_is_string(variant))
+                return json_log(variant, flags, SYNTHETIC_ERRNO(EINVAL), "JSON field '%s' is not a string.", strna(name));
+
+        if ((flags & JSON_SAFE) && !string_is_safe(json_variant_string(variant)))
+                return json_log(variant, flags, SYNTHETIC_ERRNO(EINVAL), "JSON field '%s' contains unsafe characters, refusing.", strna(name));
+
+        *s = json_variant_string(variant);
+        return 0;
+}
+
 int json_dispatch_strv(const char *name, JsonVariant *variant, JsonDispatchFlags flags, void *userdata) {
         _cleanup_strv_free_ char **l = NULL;
         char ***s = userdata;

diff --git a/src/shared/json.h b/src/shared/json.h
index d1a6eb5eb91374d91e3060b0478a5f060483b535..a89381dc516880e0865b153ebabb9741b0d75717 100644 (file)
--- a/src/shared/json.h
+++ b/src/shared/json.h
@@ -273,6 +273,7 @@ typedef struct JsonDispatch {
 int json_dispatch(JsonVariant *v, const JsonDispatch table[], JsonDispatchCallback bad, JsonDispatchFlags flags, void *userdata);
 
 int json_dispatch_string(const char *name, JsonVariant *variant, JsonDispatchFlags flags, void *userdata);
+int json_dispatch_const_string(const char *name, JsonVariant *variant, JsonDispatchFlags flags, void *userdata);
 int json_dispatch_strv(const char *name, JsonVariant *variant, JsonDispatchFlags flags, void *userdata);
 int json_dispatch_boolean(const char *name, JsonVariant *variant, JsonDispatchFlags flags, void *userdata);
 int json_dispatch_tristate(const char *name, JsonVariant *variant, JsonDispatchFlags flags, void *userdata);