Diff: source/types/RefCounted.cpp

Revision:

1:8aa5cdb4ab67

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/source/types/RefCounted.cpp	Thu Apr 07 01:33:22 2016 +0100
@@ -0,0 +1,98 @@
+/*
+The MIT License (MIT)
+
+Copyright (c) 2016 British Broadcasting Corporation.
+This software is provided by Lancaster University by arrangement with the BBC.
+
+Permission is hereby granted, free of charge, to any person obtaining a
+copy of this software and associated documentation files (the "Software"),
+to deal in the Software without restriction, including without limitation
+the rights to use, copy, modify, merge, publish, distribute, sublicense,
+and/or sell copies of the Software, and to permit persons to whom the
+Software is furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+DEALINGS IN THE SOFTWARE.
+*/
+
+/**
+  * Base class for payload for ref-counted objects. Used by ManagedString and MicroBitImage.
+  * There is no constructor, as this struct is typically malloc()ed.
+  */
+#include "mbed.h"
+#include "MicroBitConfig.h"
+#include "RefCounted.h"
+#include "MicroBitDisplay.h"
+
+/**
+  * Initializes for one outstanding reference.
+  */
+void RefCounted::init()
+{
+    // Initialize to one reference (lowest bit set to 1)
+    refCount = 3;
+}
+
+/**
+  * Checks if the object resides in flash memory.
+  *
+  * @param t the object to check.
+  *
+  * @return true if the object resides in flash memory, false otherwise.
+  */
+static inline bool isReadOnlyInline(RefCounted *t)
+{
+    uint32_t refCount = t->refCount;
+
+    if (refCount == 0xffff)
+        return true; // object in flash
+
+    // Do some sanity checking while we're here
+    if (refCount == 1 ||        // object should have been deleted
+        (refCount & 1) == 0)    // refCount doesn't look right
+        microbit_panic(MICROBIT_HEAP_ERROR);
+
+    // Not read only
+    return false;
+}
+
+/**
+  * Checks if the object resides in flash memory.
+  *
+  * @return true if the object resides in flash memory, false otherwise.
+  */
+bool RefCounted::isReadOnly()
+{
+    return isReadOnlyInline(this);
+}
+
+/**
+  * Increment reference count.
+  */
+void RefCounted::incr()
+{
+    if (!isReadOnlyInline(this))
+        refCount += 2;
+}
+
+/**
+  * Decrement reference count.
+  */
+void RefCounted::decr()
+{
+    if (isReadOnlyInline(this))
+        return;
+
+    refCount -= 2;
+    if (refCount == 1) {
+        free(this);
+    }
+}