QString: Introduce qstring_from_substr()

Note that we can now write qstring_from_str() as a wrapper.

Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

qstring.c

@@ -30,6 +30,29 @@ QString *qstring_new(void)
     return qstring_from_str("");
 }
 
+/**
+ * qstring_from_substr(): Create a new QString from a C string substring
+ *
+ * Return string reference
+ */
+QString *qstring_from_substr(const char *str, int start, int end)
+{
+    QString *qstring;
+
+    qstring = qemu_malloc(sizeof(*qstring));
+
+    qstring->length = end - start + 1;
+    qstring->capacity = qstring->length;
+
+    qstring->string = qemu_malloc(qstring->capacity + 1);
+    memcpy(qstring->string, str + start, qstring->length);
+    qstring->string[qstring->length] = 0;
+
+    QOBJECT_INIT(qstring, &qstring_type);
+
+    return qstring;
+}
+
 /**
  * qstring_from_str(): Create a new QString from a regular C string
  *
@@ -37,20 +60,7 @@ QString *qstring_new(void)
  */
 QString *qstring_from_str(const char *str)
 {
-    QString *qstring;
-
-    qstring = qemu_malloc(sizeof(*qstring));
-
-    qstring->length = strlen(str);
-    qstring->capacity = qstring->length;
-
-    qstring->string = qemu_malloc(qstring->capacity + 1);
-    memcpy(qstring->string, str, qstring->length);
-    qstring->string[qstring->length] = 0;
-
-    QOBJECT_INIT(qstring, &qstring_type);
-
-    return qstring;
+    return qstring_from_substr(str, 0, strlen(str) - 1);
 }
 
 static void capacity_increase(QString *qstring, size_t len)

qstring.h

@@ -13,6 +13,7 @@ typedef struct QString {
 
 QString *qstring_new(void);
 QString *qstring_from_str(const char *str);
+QString *qstring_from_substr(const char *str, int start, int end);
 const char *qstring_get_str(const QString *qstring);
 void qstring_append_int(QString *qstring, int64_t value);
 void qstring_append(QString *qstring, const char *str);