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diff --git a/gfx/2d/UserData.h b/gfx/2d/UserData.h
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+/* -*- Mode: c++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef MOZILLA_GFX_USERDATA_H_
+#define MOZILLA_GFX_USERDATA_H_
+
+#include <stdlib.h>
+#include "Types.h"
+#include "mozilla/Assertions.h"
+
+namespace mozilla {
+namespace gfx {
+
+struct UserDataKey {
+ int unused;
+};
+
+/* this class is basically a clone of the user data concept from cairo */
+class UserData
+{
+ typedef void (*destroyFunc)(void *data);
+public:
+ UserData() : count(0), entries(nullptr) {}
+
+ /* Attaches untyped userData associated with key. destroy is called on destruction */
+ void Add(UserDataKey *key, void *userData, destroyFunc destroy)
+ {
+ for (int i=0; i<count; i++) {
+ if (key == entries[i].key) {
+ if (entries[i].destroy) {
+ entries[i].destroy(entries[i].userData);
+ }
+ entries[i].userData = userData;
+ entries[i].destroy = destroy;
+ return;
+ }
+ }
+
+ // We could keep entries in a std::vector instead of managing it by hand
+ // but that would propagate an stl dependency out which we'd rather not
+ // do (see bug 666609). Plus, the entries array is expect to stay small
+ // so doing a realloc everytime we add a new entry shouldn't be too costly
+ entries = static_cast<Entry*>(realloc(entries, sizeof(Entry)*(count+1)));
+
+ if (!entries) {
+ MOZ_CRASH("GFX: UserData::Add");
+ }
+
+ entries[count].key = key;
+ entries[count].userData = userData;
+ entries[count].destroy = destroy;
+
+ count++;
+ }
+
+ /* Remove and return user data associated with key, without destroying it */
+ void* Remove(UserDataKey *key)
+ {
+ for (int i=0; i<count; i++) {
+ if (key == entries[i].key) {
+ void *userData = entries[i].userData;
+ // decrement before looping so entries[i+1] doesn't read past the end:
+ --count;
+ for (;i<count; i++) {
+ entries[i] = entries[i+1];
+ }
+ return userData;
+ }
+ }
+ return nullptr;
+ }
+
+ /* Retrives the userData for the associated key */
+ void *Get(UserDataKey *key) const
+ {
+ for (int i=0; i<count; i++) {
+ if (key == entries[i].key) {
+ return entries[i].userData;
+ }
+ }
+ return nullptr;
+ }
+
+ bool Has(UserDataKey *key)
+ {
+ for (int i=0; i<count; i++) {
+ if (key == entries[i].key) {
+ return true;
+ }
+ }
+ return false;
+ }
+
+ void Destroy()
+ {
+ for (int i=0; i<count; i++) {
+ if (entries[i].destroy) {
+ entries[i].destroy(entries[i].userData);
+ }
+ }
+ free(entries);
+ entries = nullptr;
+ count = 0;
+ }
+
+ ~UserData()
+ {
+ Destroy();
+ }
+
+private:
+ struct Entry {
+ const UserDataKey *key;
+ void *userData;
+ destroyFunc destroy;
+ };
+
+ int count;
+ Entry *entries;
+
+};
+
+} // namespace gfx
+} // namespace mozilla
+
+#endif /* MOZILLA_GFX_USERDATA_H_ */