qapi: Add qobject_is_equal()

This generic function (along with its implementations for different
types) determines whether two QObjects are equal.

Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Alberto Garcia <berto@igalia.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Message-id: 20171114180128.17076-4-mreitz@redhat.com
Signed-off-by: Max Reitz <mreitz@redhat.com>

7 files changed, 170 insertions, 0 deletions

diff --git a/qobject/qbool.c b/qobject/qbool.c
index 0606bbd2a3..ac825fc5a2 100644
--- a/qobject/qbool.c
+++ b/qobject/qbool.c
@@ -52,6 +52,14 @@ QBool *qobject_to_qbool(const QObject *obj)
 }
 
 /**
+ * qbool_is_equal(): Test whether the two QBools are equal
+ */
+bool qbool_is_equal(const QObject *x, const QObject *y)
+{
+    return qobject_to_qbool(x)->value == qobject_to_qbool(y)->value;
+}
+
+/**
  * qbool_destroy_obj(): Free all memory allocated by a
  * QBool object
  */
diff --git a/qobject/qdict.c b/qobject/qdict.c
index 576018e531..e8f15f1132 100644
--- a/qobject/qdict.c
+++ b/qobject/qdict.c
@@ -403,6 +403,35 @@ void qdict_del(QDict *qdict, const char *key)
 }
 
 /**
+ * qdict_is_equal(): Test whether the two QDicts are equal
+ *
+ * Here, equality means whether they contain the same keys and whether
+ * the respective values are in turn equal (i.e. invoking
+ * qobject_is_equal() on them yields true).
+ */
+bool qdict_is_equal(const QObject *x, const QObject *y)
+{
+    const QDict *dict_x = qobject_to_qdict(x);
+    const QDict *dict_y = qobject_to_qdict(y);
+    const QDictEntry *e;
+
+    if (qdict_size(dict_x) != qdict_size(dict_y)) {
+        return false;
+    }
+
+    for (e = qdict_first(dict_x); e; e = qdict_next(dict_x, e)) {
+        const QObject *obj_x = qdict_entry_value(e);
+        const QObject *obj_y = qdict_get(dict_y, qdict_entry_key(e));
+
+        if (!qobject_is_equal(obj_x, obj_y)) {
+            return false;
+        }
+    }
+
+    return true;
+}
+
+/**
  * qdict_destroy_obj(): Free all the memory allocated by a QDict
  */
 void qdict_destroy_obj(QObject *obj)
diff --git a/qobject/qlist.c b/qobject/qlist.c
index 86b60cb88c..3ef57d31d1 100644
--- a/qobject/qlist.c
+++ b/qobject/qlist.c
@@ -140,6 +140,38 @@ QList *qobject_to_qlist(const QObject *obj)
 }
 
 /**
+ * qlist_is_equal(): Test whether the two QLists are equal
+ *
+ * In order to be considered equal, the respective two objects at each
+ * index of the two lists have to compare equal (regarding
+ * qobject_is_equal()), and both lists have to have the same number of
+ * elements.
+ * That means both lists have to contain equal objects in equal order.
+ */
+bool qlist_is_equal(const QObject *x, const QObject *y)
+{
+    const QList *list_x = qobject_to_qlist(x);
+    const QList *list_y = qobject_to_qlist(y);
+    const QListEntry *entry_x, *entry_y;
+
+    entry_x = qlist_first(list_x);
+    entry_y = qlist_first(list_y);
+
+    while (entry_x && entry_y) {
+        if (!qobject_is_equal(qlist_entry_obj(entry_x),
+                              qlist_entry_obj(entry_y)))
+        {
+            return false;
+        }
+
+        entry_x = qlist_next(entry_x);
+        entry_y = qlist_next(entry_y);
+    }
+
+    return !entry_x && !entry_y;
+}
+
+/**
  * qlist_destroy_obj(): Free all the memory allocated by a QList
  */
 void qlist_destroy_obj(QObject *obj)
diff --git a/qobject/qnull.c b/qobject/qnull.c
index bc9fd31626..f6f55f11ea 100644
--- a/qobject/qnull.c
+++ b/qobject/qnull.c
@@ -20,3 +20,12 @@ QNull qnull_ = {
         .refcnt = 1,
     },
 };
+
+/**
+ * qnull_is_equal(): Always return true because any two QNull objects
+ * are equal.
+ */
+bool qnull_is_equal(const QObject *x, const QObject *y)
+{
+    return true;
+}
diff --git a/qobject/qnum.c b/qobject/qnum.c
index 476e81c93b..410686a611 100644
--- a/qobject/qnum.c
+++ b/qobject/qnum.c
@@ -213,6 +213,60 @@ QNum *qobject_to_qnum(const QObject *obj)
 }
 
 /**
+ * qnum_is_equal(): Test whether the two QNums are equal
+ *
+ * Negative integers are never considered equal to unsigned integers,
+ * but positive integers in the range [0, INT64_MAX] are considered
+ * equal independently of whether the QNum's kind is i64 or u64.
+ *
+ * Doubles are never considered equal to integers.
+ */
+bool qnum_is_equal(const QObject *x, const QObject *y)
+{
+    QNum *num_x = qobject_to_qnum(x);
+    QNum *num_y = qobject_to_qnum(y);
+
+    switch (num_x->kind) {
+    case QNUM_I64:
+        switch (num_y->kind) {
+        case QNUM_I64:
+            /* Comparison in native int64_t type */
+            return num_x->u.i64 == num_y->u.i64;
+        case QNUM_U64:
+            /* Implicit conversion of x to uin64_t, so we have to
+             * check its sign before */
+            return num_x->u.i64 >= 0 && num_x->u.i64 == num_y->u.u64;
+        case QNUM_DOUBLE:
+            return false;
+        }
+        abort();
+    case QNUM_U64:
+        switch (num_y->kind) {
+        case QNUM_I64:
+            return qnum_is_equal(y, x);
+        case QNUM_U64:
+            /* Comparison in native uint64_t type */
+            return num_x->u.u64 == num_y->u.u64;
+        case QNUM_DOUBLE:
+            return false;
+        }
+        abort();
+    case QNUM_DOUBLE:
+        switch (num_y->kind) {
+        case QNUM_I64:
+        case QNUM_U64:
+            return false;
+        case QNUM_DOUBLE:
+            /* Comparison in native double type */
+            return num_x->u.dbl == num_y->u.dbl;
+        }
+        abort();
+    }
+
+    abort();
+}
+
+/**
  * qnum_destroy_obj(): Free all memory allocated by a
  * QNum object
  */
diff --git a/qobject/qobject.c b/qobject/qobject.c
index b0cafb66f1..b2a536041d 100644
--- a/qobject/qobject.c
+++ b/qobject/qobject.c
@@ -27,3 +27,32 @@ void qobject_destroy(QObject *obj)
     assert(QTYPE_QNULL < obj->type && obj->type < QTYPE__MAX);
     qdestroy[obj->type](obj);
 }
+
+
+static bool (*qis_equal[QTYPE__MAX])(const QObject *, const QObject *) = {
+    [QTYPE_NONE] = NULL,               /* No such object exists */
+    [QTYPE_QNULL] = qnull_is_equal,
+    [QTYPE_QNUM] = qnum_is_equal,
+    [QTYPE_QSTRING] = qstring_is_equal,
+    [QTYPE_QDICT] = qdict_is_equal,
+    [QTYPE_QLIST] = qlist_is_equal,
+    [QTYPE_QBOOL] = qbool_is_equal,
+};
+
+bool qobject_is_equal(const QObject *x, const QObject *y)
+{
+    /* We cannot test x == y because an object does not need to be
+     * equal to itself (e.g. NaN floats are not). */
+
+    if (!x && !y) {
+        return true;
+    }
+
+    if (!x || !y || x->type != y->type) {
+        return false;
+    }
+
+    assert(QTYPE_NONE < x->type && x->type < QTYPE__MAX);
+
+    return qis_equal[x->type](x, y);
+}
diff --git a/qobject/qstring.c b/qobject/qstring.c
index 5da7b5f37c..74182a1c02 100644
--- a/qobject/qstring.c
+++ b/qobject/qstring.c
@@ -129,6 +129,15 @@ const char *qstring_get_str(const QString *qstring)
 }
 
 /**
+ * qstring_is_equal(): Test whether the two QStrings are equal
+ */
+bool qstring_is_equal(const QObject *x, const QObject *y)
+{
+    return !strcmp(qobject_to_qstring(x)->string,
+                   qobject_to_qstring(y)->string);
+}
+
+/**
  * qstring_destroy_obj(): Free all memory allocated by a QString
  * object
  */