migration: Move qjson.[ch] to migration/

Type QJSON lets you build JSON text.  Its interface mirrors (a subset
of) abstract JSON syntax.

QAPI output visitors also produce JSON text.  They assert their
preconditions and invariants, and therefore abort on incorrect use.

Contrastingly, QJSON does *not* detect incorrect use.  It happily
produces invalid JSON then.  This is what migration wants.

QJSON was designed for migration, and migration is its only user.
Move it to migration/ for proper coverage by MAINTAINERS, and to deter
accidental use outside migration.

[Pointed out by Eric: QJSON was added in commits 0457d07..b174257
 -- Amit]

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Message-Id: <1462380558-2030-2-git-send-email-armbru@redhat.com>
Signed-off-by: Amit Shah <amit.shah@redhat.com>

3 files changed, 141 insertions, 1 deletions

diff --git a/migration/Makefile.objs b/migration/Makefile.objs
index 0cac6d707a..d25ff483eb 100644
--- a/migration/Makefile.objs
+++ b/migration/Makefile.objs
@@ -2,6 +2,7 @@ common-obj-y += migration.o tcp.o
 common-obj-y += vmstate.o
 common-obj-y += qemu-file.o qemu-file-buf.o qemu-file-unix.o qemu-file-stdio.o
 common-obj-y += xbzrle.o postcopy-ram.o
+common-obj-y += qjson.o
 
 common-obj-$(CONFIG_RDMA) += rdma.o
 common-obj-$(CONFIG_POSIX) += exec.o unix.o fd.o
diff --git a/migration/qjson.c b/migration/qjson.c
new file mode 100644
index 0000000000..cb479fe0eb
--- /dev/null
+++ b/migration/qjson.c
@@ -0,0 +1,140 @@
+/*
+ * A simple JSON writer
+ *
+ * Copyright Alexander Graf
+ *
+ * Authors:
+ *  Alexander Graf <agraf@suse.de>
+ *
+ * This work is licensed under the terms of the GNU LGPL, version 2.1 or later.
+ * See the COPYING.LIB file in the top-level directory.
+ *
+ */
+
+/*
+ * Type QJSON lets you build JSON text.  Its interface mirrors (a
+ * subset of) abstract JSON syntax.
+ *
+ * It does *not* detect incorrect use.  It happily produces invalid
+ * JSON then.  This is what migration wants.
+ *
+ * QAPI output visitors also produce JSON text.  However, they do
+ * assert their preconditions and invariants, and therefore abort on
+ * incorrect use.
+ */
+
+#include "qemu/osdep.h"
+#include "qapi/qmp/qstring.h"
+#include "migration/qjson.h"
+#include "qemu/module.h"
+#include "qom/object.h"
+
+struct QJSON {
+    Object obj;
+    QString *str;
+    bool omit_comma;
+};
+
+#define QJSON(obj) OBJECT_CHECK(QJSON, (obj), TYPE_QJSON)
+
+static void json_emit_element(QJSON *json, const char *name)
+{
+    /* Check whether we need to print a , before an element */
+    if (json->omit_comma) {
+        json->omit_comma = false;
+    } else {
+        qstring_append(json->str, ", ");
+    }
+
+    if (name) {
+        qstring_append(json->str, "\"");
+        qstring_append(json->str, name);
+        qstring_append(json->str, "\" : ");
+    }
+}
+
+void json_start_object(QJSON *json, const char *name)
+{
+    json_emit_element(json, name);
+    qstring_append(json->str, "{ ");
+    json->omit_comma = true;
+}
+
+void json_end_object(QJSON *json)
+{
+    qstring_append(json->str, " }");
+    json->omit_comma = false;
+}
+
+void json_start_array(QJSON *json, const char *name)
+{
+    json_emit_element(json, name);
+    qstring_append(json->str, "[ ");
+    json->omit_comma = true;
+}
+
+void json_end_array(QJSON *json)
+{
+    qstring_append(json->str, " ]");
+    json->omit_comma = false;
+}
+
+void json_prop_int(QJSON *json, const char *name, int64_t val)
+{
+    json_emit_element(json, name);
+    qstring_append_int(json->str, val);
+}
+
+void json_prop_str(QJSON *json, const char *name, const char *str)
+{
+    json_emit_element(json, name);
+    qstring_append_chr(json->str, '"');
+    qstring_append(json->str, str);
+    qstring_append_chr(json->str, '"');
+}
+
+const char *qjson_get_str(QJSON *json)
+{
+    return qstring_get_str(json->str);
+}
+
+QJSON *qjson_new(void)
+{
+    QJSON *json = QJSON(object_new(TYPE_QJSON));
+    return json;
+}
+
+void qjson_finish(QJSON *json)
+{
+    json_end_object(json);
+}
+
+static void qjson_initfn(Object *obj)
+{
+    QJSON *json = QJSON(obj);
+
+    json->str = qstring_from_str("{ ");
+    json->omit_comma = true;
+}
+
+static void qjson_finalizefn(Object *obj)
+{
+    QJSON *json = QJSON(obj);
+
+    qobject_decref(QOBJECT(json->str));
+}
+
+static const TypeInfo qjson_type_info = {
+    .name = TYPE_QJSON,
+    .parent = TYPE_OBJECT,
+    .instance_size = sizeof(QJSON),
+    .instance_init = qjson_initfn,
+    .instance_finalize = qjson_finalizefn,
+};
+
+static void qjson_register_types(void)
+{
+    type_register_static(&qjson_type_info);
+}
+
+type_init(qjson_register_types)
diff --git a/migration/vmstate.c b/migration/vmstate.c
index bf3d5db301..46dc55ea40 100644
--- a/migration/vmstate.c
+++ b/migration/vmstate.c
@@ -6,7 +6,6 @@
 #include "qemu/bitops.h"
 #include "qemu/error-report.h"
 #include "trace.h"
-#include "qjson.h"
 
 static void vmstate_subsection_save(QEMUFile *f, const VMStateDescription *vmsd,
                                     void *opaque, QJSON *vmdesc);