[Qemu-devel] [PATCH V13 2/6] avoid duplication of default value in QemuOpts

[Dong Xu Wang]

According Markus's comments, his patch will move the default value entirely
to QemuOptDesc.

When getting the value of an option that hasn't been set, and
QemuOptDesc has a default value, return that.  Else, behave as
before.

Example: qemu_opt_get_number(opts, "foo", 42)

   If "foo" has been set in opts, return its value.

   Else, if opt's QemuOptDesc has a default value for "foo", return
   that.

   Else, return 42.

   Note that the last argument is useless when QemuOptDesc has a
   default value.  Ugly.  If it bothers us, assert that the argument
   equals the default from QemuOptDesc.

Example: qemu_opt_get(opts, "bar")

   If "bar" has been set in opts, return its value.

   Else, if opt's QemuOptDesc has a default value for "bar", return
   that.

   Else, return NULL.

Signed-off-by: Dong Xu Wang <address@hidden>
---
 util/qemu-option.c | 58 +++++++++++++++++++++++++++++++++++++-----------------
 1 file changed, 40 insertions(+), 18 deletions(-)

diff --git a/util/qemu-option.c b/util/qemu-option.c
index 57cdd57..4f94000 100644
--- a/util/qemu-option.c
+++ b/util/qemu-option.c
@@ -525,10 +525,28 @@ static QemuOpt *qemu_opt_find(QemuOpts *opts, const char 
*name)
     return NULL;
 }
 
+static const QemuOptDesc *find_desc_by_name(const QemuOptDesc *desc,
+                                            const char *name)
+{
+    int i;
+
+    for (i = 0; desc[i].name != NULL; i++) {
+        if (strcmp(desc[i].name, name) == 0) {
+            return &desc[i];
+        }
+    }
+
+    return NULL;
+}
+
 const char *qemu_opt_get(QemuOpts *opts, const char *name)
 {
     QemuOpt *opt = qemu_opt_find(opts, name);
-    return opt ? opt->str : NULL;
+    const QemuOptDesc *desc;
+    desc = find_desc_by_name(opts->list->desc, name);
+
+    return opt ? opt->str :
+        (desc && desc->def_value_str ? desc->def_value_str : NULL);
 }
 
 bool qemu_opt_has_help_opt(QemuOpts *opts)
@@ -546,9 +564,15 @@ bool qemu_opt_has_help_opt(QemuOpts *opts)
 bool qemu_opt_get_bool(QemuOpts *opts, const char *name, bool defval)
 {
     QemuOpt *opt = qemu_opt_find(opts, name);
+    const QemuOptDesc *desc;
 
-    if (opt == NULL)
+    if (opt == NULL) {
+        desc = find_desc_by_name(opts->list->desc, name);
+        if (desc && desc->def_value_str) {
+            parse_option_bool(name, desc->def_value_str, &defval, NULL);
+        }
         return defval;
+    }
     assert(opt->desc && opt->desc->type == QEMU_OPT_BOOL);
     return opt->value.boolean;
 }
@@ -556,9 +580,15 @@ bool qemu_opt_get_bool(QemuOpts *opts, const char *name, 
bool defval)
 uint64_t qemu_opt_get_number(QemuOpts *opts, const char *name, uint64_t defval)
 {
     QemuOpt *opt = qemu_opt_find(opts, name);
+    const QemuOptDesc *desc;
 
-    if (opt == NULL)
+    if (opt == NULL) {
+        desc = find_desc_by_name(opts->list->desc, name);
+        if (desc && desc->def_value_str) {
+            parse_option_number(name, desc->def_value_str, &defval, NULL);
+        }
         return defval;
+    }
     assert(opt->desc && opt->desc->type == QEMU_OPT_NUMBER);
     return opt->value.uint;
 }
@@ -566,9 +596,15 @@ uint64_t qemu_opt_get_number(QemuOpts *opts, const char 
*name, uint64_t defval)
 uint64_t qemu_opt_get_size(QemuOpts *opts, const char *name, uint64_t defval)
 {
     QemuOpt *opt = qemu_opt_find(opts, name);
+    const QemuOptDesc *desc;
 
-    if (opt == NULL)
+    if (opt == NULL) {
+        desc = find_desc_by_name(opts->list->desc, name);
+        if (desc && desc->def_value_str) {
+            parse_option_size(name, desc->def_value_str, &defval, NULL);
+        }
         return defval;
+    }
     assert(opt->desc && opt->desc->type == QEMU_OPT_SIZE);
     return opt->value.uint;
 }
@@ -609,20 +645,6 @@ static bool opts_accepts_any(const QemuOpts *opts)
     return opts->list->desc[0].name == NULL;
 }
 
-static const QemuOptDesc *find_desc_by_name(const QemuOptDesc *desc,
-                                            const char *name)
-{
-    int i;
-
-    for (i = 0; desc[i].name != NULL; i++) {
-        if (strcmp(desc[i].name, name) == 0) {
-            return &desc[i];
-        }
-    }
-
-    return NULL;
-}
-
 static void opt_set(QemuOpts *opts, const char *name, const char *value,
                     bool prepend, Error **errp)
 {
-- 
1.7.11.7