qapi-visit: Add visitor.type classification

We have three classes of QAPI visitors: input, output, and dealloc.
Currently, all implementations of these visitors have one thing in
common based on their visitor type: the implementation used for the
visit_type_enum() callback.  But since we plan to add more such
common behavior, in relation to documenting and further refining
the semantics, it makes more sense to have the visitor
implementations advertise which class they belong to, so the common
qapi-visit-core code can use that information in multiple places.

A later patch will better document the types of visitors directly
in visitor.h.

For this patch, knowing the class of a visitor implementation lets
us make input_type_enum() and output_type_enum() become static
functions, by replacing the callback function Visitor.type_enum()
with the simpler enum member Visitor.type.  Share a common
assertion in qapi-visit-core as part of the refactoring.

Move comments in opts-visitor.c to match the refactored layout.

Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <1461879932-9020-2-git-send-email-eblake@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>

diff --git a/include/qapi/visitor-impl.h b/include/qapi/visitor-impl.h
index 2bd8f292b2d53d48c9183e8514e8a50add2f3855..51c338a43d0d4c9c69ffb7cb8f9e80ac20794cf4 100644 (file)
--- a/include/qapi/visitor-impl.h
+++ b/include/qapi/visitor-impl.h
@@ -14,6 +14,17 @@
 
 #include "qapi/visitor.h"
 
+/*
+ * There are three classes of visitors; setting the class determines
+ * how QAPI enums are visited, as well as what additional restrictions
+ * can be asserted.
+ */
+typedef enum VisitorType {
+    VISITOR_INPUT,
+    VISITOR_OUTPUT,
+    VISITOR_DEALLOC,
+} VisitorType;
+
 struct Visitor
 {
     /* Must be set */
@@ -35,10 +46,6 @@ struct Visitor
     /* Optional, needed for dealloc visitor.  */
     void (*end_alternate)(Visitor *v);
 
-    /* Must be set. */
-    void (*type_enum)(Visitor *v, const char *name, int *obj,
-                      const char *const strings[], Error **errp);
-
     /* Must be set. */
     void (*type_int64)(Visitor *v, const char *name, int64_t *obj,
                        Error **errp);
@@ -58,11 +65,9 @@ struct Visitor
 
     /* May be NULL; most useful for input visitors. */
     void (*optional)(Visitor *v, const char *name, bool *present);
-};
 
-void input_type_enum(Visitor *v, const char *name, int *obj,
-                     const char *const strings[], Error **errp);
-void output_type_enum(Visitor *v, const char *name, int *obj,
-                      const char *const strings[], Error **errp);
+    /* Must be set */
+    VisitorType type;
+};
 
 #endif

diff --git a/include/qapi/visitor.h b/include/qapi/visitor.h
index 9a8d0105fbbcbe9ebe566753ad441d9c62e242de..690589f37dbc401df0e3eef9ab3789ac8b440a31 100644 (file)
--- a/include/qapi/visitor.h
+++ b/include/qapi/visitor.h
@@ -78,8 +78,19 @@ void visit_end_alternate(Visitor *v);
  */
 bool visit_optional(Visitor *v, const char *name, bool *present);
 
+/*
+ * Visit an enum value.
+ *
+ * @strings expresses the mapping between C enum values and QAPI enum
+ * names; it should be the ENUM_lookup array from visit-types.h.
+ *
+ * May call visit_type_str() under the hood, and the enum visit may
+ * fail even if the corresponding string visit succeeded; this implies
+ * that visit_type_str() must have no unwelcome side effects.
+ */
 void visit_type_enum(Visitor *v, const char *name, int *obj,
                      const char *const strings[], Error **errp);
+
 void visit_type_int(Visitor *v, const char *name, int64_t *obj, Error **errp);
 void visit_type_uint8(Visitor *v, const char *name, uint8_t *obj,
                       Error **errp);

diff --git a/qapi/opts-visitor.c b/qapi/opts-visitor.c
index 602f2609cc46c1622e34eef0403bfddd57333f13..66aeaed87e4f1038fe7507ffd5bd281d20c826d1 100644 (file)
--- a/qapi/opts-visitor.c
+++ b/qapi/opts-visitor.c
@@ -317,6 +317,11 @@ opts_type_str(Visitor *v, const char *name, char **obj, Error **errp)
         return;
     }
     *obj = g_strdup(opt->str ? opt->str : "");
+    /* Note that we consume a string even if this is called as part of
+     * an enum visit that later fails because the string is not a
+     * valid enum value; this is harmless because tracking what gets
+     * consumed only matters to visit_end_struct() as the final error
+     * check if there were no other failures during the visit.  */
     processed(ov, name);
 }
 
@@ -507,6 +512,8 @@ opts_visitor_new(const QemuOpts *opts)
 
     ov = g_malloc0(sizeof *ov);
 
+    ov->visitor.type = VISITOR_INPUT;
+
     ov->visitor.start_struct = &opts_start_struct;
     ov->visitor.end_struct   = &opts_end_struct;
 
@@ -514,16 +521,6 @@ opts_visitor_new(const QemuOpts *opts)
     ov->visitor.next_list  = &opts_next_list;
     ov->visitor.end_list   = &opts_end_list;
 
-    /* input_type_enum() covers both "normal" enums and union discriminators.
-     * The union discriminator field is always generated as "type"; it should
-     * match the "type" QemuOpt child of any QemuOpts.
-     *
-     * input_type_enum() will remove the looked-up key from the
-     * "unprocessed_opts" hash even if the lookup fails, because the removal is
-     * done earlier in opts_type_str(). This should be harmless.
-     */
-    ov->visitor.type_enum = &input_type_enum;
-
     ov->visitor.type_int64  = &opts_type_int64;
     ov->visitor.type_uint64 = &opts_type_uint64;
     ov->visitor.type_size   = &opts_type_size;

diff --git a/qapi/qapi-dealloc-visitor.c b/qapi/qapi-dealloc-visitor.c
index 69221794ec34f4b603d62bbe6eef334e01bad3c9..c19a459391b18b684feec10b88e04c0559aa0ca6 100644 (file)
--- a/qapi/qapi-dealloc-visitor.c
+++ b/qapi/qapi-dealloc-visitor.c
@@ -163,11 +163,6 @@ static void qapi_dealloc_type_anything(Visitor *v, const char *name,
     }
 }
 
-static void qapi_dealloc_type_enum(Visitor *v, const char *name, int *obj,
-                                   const char * const strings[], Error **errp)
-{
-}
-
 Visitor *qapi_dealloc_get_visitor(QapiDeallocVisitor *v)
 {
     return &v->visitor;
@@ -184,6 +179,7 @@ QapiDeallocVisitor *qapi_dealloc_visitor_new(void)
 
     v = g_malloc0(sizeof(*v));
 
+    v->visitor.type = VISITOR_DEALLOC;
     v->visitor.start_struct = qapi_dealloc_start_struct;
     v->visitor.end_struct = qapi_dealloc_end_struct;
     v->visitor.start_alternate = qapi_dealloc_start_alternate;
@@ -191,7 +187,6 @@ QapiDeallocVisitor *qapi_dealloc_visitor_new(void)
     v->visitor.start_list = qapi_dealloc_start_list;
     v->visitor.next_list = qapi_dealloc_next_list;
     v->visitor.end_list = qapi_dealloc_end_list;
-    v->visitor.type_enum = qapi_dealloc_type_enum;
     v->visitor.type_int64 = qapi_dealloc_type_int64;
     v->visitor.type_uint64 = qapi_dealloc_type_uint64;
     v->visitor.type_bool = qapi_dealloc_type_bool;

diff --git a/qapi/qapi-visit-core.c b/qapi/qapi-visit-core.c
index fa680c9991d686b313a409d112b7819cb170996b..3cd7edcc12a254420dfcf89cefa22047f598c2d5 100644 (file)
--- a/qapi/qapi-visit-core.c
+++ b/qapi/qapi-visit-core.c
@@ -72,12 +72,6 @@ bool visit_optional(Visitor *v, const char *name, bool *present)
     return *present;
 }
 
-void visit_type_enum(Visitor *v, const char *name, int *obj,
-                     const char *const strings[], Error **errp)
-{
-    v->type_enum(v, name, obj, strings, errp);
-}
-
 void visit_type_int(Visitor *v, const char *name, int64_t *obj, Error **errp)
 {
     v->type_int64(v, name, obj, errp);
@@ -208,14 +202,13 @@ void visit_type_any(Visitor *v, const char *name, QObject **obj, Error **errp)
     v->type_any(v, name, obj, errp);
 }
 
-void output_type_enum(Visitor *v, const char *name, int *obj,
-                      const char *const strings[], Error **errp)
+static void output_type_enum(Visitor *v, const char *name, int *obj,
+                             const char *const strings[], Error **errp)
 {
     int i = 0;
     int value = *obj;
     char *enum_str;
 
-    assert(strings);
     while (strings[i++] != NULL);
     if (value < 0 || value >= i - 1) {
         error_setg(errp, QERR_INVALID_PARAMETER, name ? name : "null");
@@ -226,15 +219,13 @@ void output_type_enum(Visitor *v, const char *name, int *obj,
     visit_type_str(v, name, &enum_str, errp);
 }
 
-void input_type_enum(Visitor *v, const char *name, int *obj,
-                     const char *const strings[], Error **errp)
+static void input_type_enum(Visitor *v, const char *name, int *obj,
+                            const char *const strings[], Error **errp)
 {
     Error *local_err = NULL;
     int64_t value = 0;
     char *enum_str;
 
-    assert(strings);
-
     visit_type_str(v, name, &enum_str, &local_err);
     if (local_err) {
         error_propagate(errp, local_err);
@@ -257,3 +248,14 @@ void input_type_enum(Visitor *v, const char *name, int *obj,
     g_free(enum_str);
     *obj = value;
 }
+
+void visit_type_enum(Visitor *v, const char *name, int *obj,
+                     const char *const strings[], Error **errp)
+{
+    assert(strings);
+    if (v->type == VISITOR_INPUT) {
+        input_type_enum(v, name, obj, strings, errp);
+    } else if (v->type == VISITOR_OUTPUT) {
+        output_type_enum(v, name, obj, strings, errp);
+    }
+}

diff --git a/qapi/qmp-input-visitor.c b/qapi/qmp-input-visitor.c
index 7cd1b777a08fb1381f06def76d6a6dae73707f84..02d42334636a81ed8980b9fd9990a293b7100cf7 100644 (file)
--- a/qapi/qmp-input-visitor.c
+++ b/qapi/qmp-input-visitor.c
@@ -339,13 +339,13 @@ QmpInputVisitor *qmp_input_visitor_new(QObject *obj)
 
     v = g_malloc0(sizeof(*v));
 
+    v->visitor.type = VISITOR_INPUT;
     v->visitor.start_struct = qmp_input_start_struct;
     v->visitor.end_struct = qmp_input_end_struct;
     v->visitor.start_list = qmp_input_start_list;
     v->visitor.next_list = qmp_input_next_list;
     v->visitor.end_list = qmp_input_end_list;
     v->visitor.start_alternate = qmp_input_start_alternate;
-    v->visitor.type_enum = input_type_enum;
     v->visitor.type_int64 = qmp_input_type_int64;
     v->visitor.type_uint64 = qmp_input_type_uint64;
     v->visitor.type_bool = qmp_input_type_bool;

diff --git a/qapi/qmp-output-visitor.c b/qapi/qmp-output-visitor.c
index d44c676317d033cc5b264a36921c1a75ceaa61f8..1f2a7ba646975d3b579970b12232f5934104a527 100644 (file)
--- a/qapi/qmp-output-visitor.c
+++ b/qapi/qmp-output-visitor.c
@@ -234,12 +234,12 @@ QmpOutputVisitor *qmp_output_visitor_new(void)
 
     v = g_malloc0(sizeof(*v));
 
+    v->visitor.type = VISITOR_OUTPUT;
     v->visitor.start_struct = qmp_output_start_struct;
     v->visitor.end_struct = qmp_output_end_struct;
     v->visitor.start_list = qmp_output_start_list;
     v->visitor.next_list = qmp_output_next_list;
     v->visitor.end_list = qmp_output_end_list;
-    v->visitor.type_enum = output_type_enum;
     v->visitor.type_int64 = qmp_output_type_int64;
     v->visitor.type_uint64 = qmp_output_type_uint64;
     v->visitor.type_bool = qmp_output_type_bool;

diff --git a/qapi/string-input-visitor.c b/qapi/string-input-visitor.c
index 5ea2d77b5ad95f9645640d706db4cc47e9403cd4..97009a6dc710dd5ab179fea29127833c8c4b353c 100644 (file)
--- a/qapi/string-input-visitor.c
+++ b/qapi/string-input-visitor.c
@@ -348,7 +348,7 @@ StringInputVisitor *string_input_visitor_new(const char *str)
 
     v = g_malloc0(sizeof(*v));
 
-    v->visitor.type_enum = input_type_enum;
+    v->visitor.type = VISITOR_INPUT;
     v->visitor.type_int64 = parse_type_int64;
     v->visitor.type_uint64 = parse_type_uint64;
     v->visitor.type_size = parse_type_size;

diff --git a/qapi/string-output-visitor.c b/qapi/string-output-visitor.c
index c2e5c5b92b2c890f9f9c110ec0f77d57d2939725..0d44d7e6a566a6d54351848d3d1d5feaa311d0c0 100644 (file)
--- a/qapi/string-output-visitor.c
+++ b/qapi/string-output-visitor.c
@@ -351,7 +351,7 @@ StringOutputVisitor *string_output_visitor_new(bool human)
 
     v->string = g_string_new(NULL);
     v->human = human;
-    v->visitor.type_enum = output_type_enum;
+    v->visitor.type = VISITOR_OUTPUT;
     v->visitor.type_int64 = print_type_int64;
     v->visitor.type_uint64 = print_type_uint64;
     v->visitor.type_size = print_type_size;