qobject: Change qobject_to_json()'s value to GString

qobject_to_json() and qobject_to_json_pretty() build a GString, then
covert it to QString.  Just one of the callers actually needs a
QString: qemu_rbd_parse_filename().  A few others need a string they
can modify: qmp_send_response(), qga's send_response(), to_json_str(),
and qmp_fd_vsend_fds().  The remainder just need a string.

Change qobject_to_json() and qobject_to_json_pretty() to return the
GString.

qemu_rbd_parse_filename() now has to convert to QString.  All others
save a QString temporary.  to_json_str() actually becomes a bit
simpler, because GString provides more convenient modification
functions.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20201211171152.146877-6-armbru@redhat.com>

3 files changed, 39 insertions, 43 deletions

diff --git a/tests/check-qjson.c b/tests/check-qjson.c
index ca8fb81..337add0 100644
--- a/tests/check-qjson.c
+++ b/tests/check-qjson.c
@@ -35,17 +35,15 @@ static QString *from_json_str(const char *jstr, bool single, Error **errp)
 
 static char *to_json_str(QString *str)
 {
-    QString *json = qobject_to_json(QOBJECT(str));
-    char *jstr;
+    GString *json = qobject_to_json(QOBJECT(str));
 
     if (!json) {
         return NULL;
     }
     /* peel off double quotes */
-    jstr = g_strndup(qstring_get_str(json) + 1,
-                     qstring_get_length(json) - 2);
-    qobject_unref(json);
-    return jstr;
+    g_string_truncate(json, json->len - 1);
+    g_string_erase(json, 0, 1);
+    return g_string_free(json, false);
 }
 
 static void escaped_string(void)
@@ -809,7 +807,7 @@ static void int_number(void)
     QNum *qnum;
     int64_t ival;
     uint64_t uval;
-    QString *str;
+    GString *str;
 
     for (i = 0; test_cases[i].encoded; i++) {
         qnum = qobject_to(QNum,
@@ -828,9 +826,9 @@ static void int_number(void)
                           (double)test_cases[i].decoded);
 
         str = qobject_to_json(QOBJECT(qnum));
-        g_assert_cmpstr(qstring_get_str(str), ==,
+        g_assert_cmpstr(str->str, ==,
                         test_cases[i].reencoded ?: test_cases[i].encoded);
-        qobject_unref(str);
+        g_string_free(str, true);
 
         qobject_unref(qnum);
     }
@@ -851,7 +849,7 @@ static void uint_number(void)
     QNum *qnum;
     int64_t ival;
     uint64_t uval;
-    QString *str;
+    GString *str;
 
     for (i = 0; test_cases[i].encoded; i++) {
         qnum = qobject_to(QNum,
@@ -865,9 +863,9 @@ static void uint_number(void)
                           (double)test_cases[i].decoded);
 
         str = qobject_to_json(QOBJECT(qnum));
-        g_assert_cmpstr(qstring_get_str(str), ==,
+        g_assert_cmpstr(str->str, ==,
                         test_cases[i].reencoded ?: test_cases[i].encoded);
-        qobject_unref(str);
+        g_string_free(str, true);
 
         qobject_unref(qnum);
     }
@@ -892,7 +890,7 @@ static void float_number(void)
     QNum *qnum;
     int64_t ival;
     uint64_t uval;
-    QString *str;
+    GString *str;
 
     for (i = 0; test_cases[i].encoded; i++) {
         qnum = qobject_to(QNum,
@@ -904,9 +902,9 @@ static void float_number(void)
         g_assert(!qnum_get_try_uint(qnum, &uval));
 
         str = qobject_to_json(QOBJECT(qnum));
-        g_assert_cmpstr(qstring_get_str(str), ==,
+        g_assert_cmpstr(str->str, ==,
                         test_cases[i].reencoded ?: test_cases[i].encoded);
-        qobject_unref(str);
+        g_string_free(str, true);
 
         qobject_unref(qnum);
     }
@@ -917,7 +915,7 @@ static void keyword_literal(void)
     QObject *obj;
     QBool *qbool;
     QNull *null;
-    QString *str;
+    GString *str;
 
     obj = qobject_from_json("true", &error_abort);
     qbool = qobject_to(QBool, obj);
@@ -925,8 +923,8 @@ static void keyword_literal(void)
     g_assert(qbool_get_bool(qbool) == true);
 
     str = qobject_to_json(obj);
-    g_assert(strcmp(qstring_get_str(str), "true") == 0);
-    qobject_unref(str);
+    g_assert_cmpstr(str->str, ==, "true");
+    g_string_free(str, true);
 
     qobject_unref(qbool);
 
@@ -936,8 +934,8 @@ static void keyword_literal(void)
     g_assert(qbool_get_bool(qbool) == false);
 
     str = qobject_to_json(obj);
-    g_assert(strcmp(qstring_get_str(str), "false") == 0);
-    qobject_unref(str);
+    g_assert_cmpstr(str->str, ==, "false");
+    g_string_free(str, true);
 
     qobject_unref(qbool);
 
@@ -1087,7 +1085,7 @@ static void simple_dict(void)
 
     for (i = 0; test_cases[i].encoded; i++) {
         QObject *obj;
-        QString *str;
+        GString *str;
 
         obj = qobject_from_json(test_cases[i].encoded, &error_abort);
         g_assert(qlit_equal_qobject(&test_cases[i].decoded, obj));
@@ -1095,10 +1093,10 @@ static void simple_dict(void)
         str = qobject_to_json(obj);
         qobject_unref(obj);
 
-        obj = qobject_from_json(qstring_get_str(str), &error_abort);
+        obj = qobject_from_json(str->str, &error_abort);
         g_assert(qlit_equal_qobject(&test_cases[i].decoded, obj));
         qobject_unref(obj);
-        qobject_unref(str);
+        g_string_free(str, true);
     }
 }
 
@@ -1196,7 +1194,7 @@ static void simple_list(void)
 
     for (i = 0; test_cases[i].encoded; i++) {
         QObject *obj;
-        QString *str;
+        GString *str;
 
         obj = qobject_from_json(test_cases[i].encoded, &error_abort);
         g_assert(qlit_equal_qobject(&test_cases[i].decoded, obj));
@@ -1204,10 +1202,10 @@ static void simple_list(void)
         str = qobject_to_json(obj);
         qobject_unref(obj);
 
-        obj = qobject_from_json(qstring_get_str(str), &error_abort);
+        obj = qobject_from_json(str->str, &error_abort);
         g_assert(qlit_equal_qobject(&test_cases[i].decoded, obj));
         qobject_unref(obj);
-        qobject_unref(str);
+        g_string_free(str, true);
     }
 }
 
@@ -1258,7 +1256,7 @@ static void simple_whitespace(void)
 
     for (i = 0; test_cases[i].encoded; i++) {
         QObject *obj;
-        QString *str;
+        GString *str;
 
         obj = qobject_from_json(test_cases[i].encoded, &error_abort);
         g_assert(qlit_equal_qobject(&test_cases[i].decoded, obj));
@@ -1266,11 +1264,11 @@ static void simple_whitespace(void)
         str = qobject_to_json(obj);
         qobject_unref(obj);
 
-        obj = qobject_from_json(qstring_get_str(str), &error_abort);
+        obj = qobject_from_json(str->str, &error_abort);
         g_assert(qlit_equal_qobject(&test_cases[i].decoded, obj));
 
         qobject_unref(obj);
-        qobject_unref(str);
+        g_string_free(str, true);
     }
 }
 
diff --git a/tests/qtest/libqtest.c b/tests/qtest/libqtest.c
index 213fa4f..8e93b0a 100644
--- a/tests/qtest/libqtest.c
+++ b/tests/qtest/libqtest.c
@@ -652,27 +652,25 @@ void qmp_fd_vsend_fds(int fd, int *fds, size_t fds_num,
     /* No need to send anything for an empty QObject.  */
     if (qobj) {
         int log = getenv("QTEST_LOG") != NULL;
-        QString *qstr = qobject_to_json(qobj);
-        const char *str;
+        GString *str = qobject_to_json(qobj);
 
         /*
          * BUG: QMP doesn't react to input until it sees a newline, an
          * object, or an array.  Work-around: give it a newline.
          */
-        qstring_append_chr(qstr, '\n');
-        str = qstring_get_str(qstr);
+        g_string_append_c(str, '\n');
 
         if (log) {
-            fprintf(stderr, "%s", str);
+            fprintf(stderr, "%s", str->str);
         }
         /* Send QMP request */
         if (fds && fds_num > 0) {
-            socket_send_fds(fd, fds, fds_num, str, qstring_get_length(qstr));
+            socket_send_fds(fd, fds, fds_num, str->str, str->len);
         } else {
-            socket_send(fd, str, qstring_get_length(qstr));
+            socket_send(fd, str->str, str->len);
         }
 
-        qobject_unref(qstr);
+        g_string_free(str, true);
         qobject_unref(qobj);
     }
 }
@@ -1197,9 +1195,9 @@ void qtest_qmp_assert_success(QTestState *qts, const char *fmt, ...)
 
     g_assert(response);
     if (!qdict_haskey(response, "return")) {
-        QString *s = qobject_to_json_pretty(QOBJECT(response), true);
-        g_test_message("%s", qstring_get_str(s));
-        qobject_unref(s);
+        GString *s = qobject_to_json_pretty(QOBJECT(response), true);
+        g_test_message("%s", s->str);
+        g_string_free(s, true);
     }
     g_assert(qdict_haskey(response, "return"));
     qobject_unref(response);
diff --git a/tests/test-visitor-serialization.c b/tests/test-visitor-serialization.c
index dfe120a..4629958 100644
--- a/tests/test-visitor-serialization.c
+++ b/tests/test-visitor-serialization.c
@@ -957,15 +957,15 @@ static void qmp_deserialize(void **native_out, void *datap,
                             VisitorFunc visit, Error **errp)
 {
     QmpSerializeData *d = datap;
-    QString *output_json;
+    GString *output_json;
     QObject *obj_orig, *obj;
 
     visit_complete(d->qov, &d->obj);
     obj_orig = d->obj;
     output_json = qobject_to_json(obj_orig);
-    obj = qobject_from_json(qstring_get_str(output_json), &error_abort);
+    obj = qobject_from_json(output_json->str, &error_abort);
 
-    qobject_unref(output_json);
+    g_string_free(output_json, true);
     d->qiv = qobject_input_visitor_new(obj);
     qobject_unref(obj_orig);
     qobject_unref(obj);