gfx/2d/UserData.h

   1 /* -*- Mode: c++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
   2  * This Source Code Form is subject to the terms of the Mozilla Public
   3  * License, v. 2.0. If a copy of the MPL was not distributed with this
   4  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   5
   6 #ifndef MOZILLA_GFX_USERDATA_H_
   7 #define MOZILLA_GFX_USERDATA_H_
   8
   9 #include <stdlib.h>
  10 #include "Types.h"
  11 #include "mozilla/Assertions.h"
  12
  13 namespace mozilla {
  14 namespace gfx {
  15
  16 struct UserDataKey {
  17   int unused;
  18 };
  19
  20 /* this class is basically a clone of the user data concept from cairo */
  21 class UserData
  22 {
  23   typedef void (*destroyFunc)(void *data);
  24 public:
  25   UserData() : count(0), entries(nullptr) {}
  26
  27   /* Attaches untyped userData associated with key. destroy is called on destruction */
  28   void Add(UserDataKey *key, void *userData, destroyFunc destroy)
  29   {
  30     for (int i=0; i<count; i++) {
  31       if (key == entries[i].key) {
  32         if (entries[i].destroy) {
  33           entries[i].destroy(entries[i].userData);
  34         }
  35         entries[i].userData = userData;
  36         entries[i].destroy = destroy;
  37         return;
  38       }
  39     }
  40
  41     // We could keep entries in a std::vector instead of managing it by hand
  42     // but that would propagate an stl dependency out which we'd rather not
  43     // do (see bug 666609). Plus, the entries array is expect to stay small
  44     // so doing a realloc everytime we add a new entry shouldn't be too costly
  45     entries = static_cast<Entry*>(realloc(entries, sizeof(Entry)*(count+1)));
  46
  47     if (!entries) {
  48       MOZ_CRASH();
  49     }
  50
  51     entries[count].key      = key;
  52     entries[count].userData = userData;
  53     entries[count].destroy  = destroy;
  54
  55     count++;
  56   }
  57
  58   /* Remove and return user data associated with key, without destroying it */
  59   void* Remove(UserDataKey *key)
  60   {
  61     for (int i=0; i<count; i++) {
  62       if (key == entries[i].key) {
  63         void *userData = entries[i].userData;
  64         // decrement before looping so entries[i+1] doesn't read past the end:
  65         --count;
  66         for (;i<count; i++) {
  67           entries[i] = entries[i+1];
  68         }
  69         return userData;
  70       }
  71     }
  72     return nullptr;
  73   }
  74
  75   /* Retrives the userData for the associated key */
  76   void *Get(UserDataKey *key) const
  77   {
  78     for (int i=0; i<count; i++) {
  79       if (key == entries[i].key) {
  80         return entries[i].userData;
  81       }
  82     }
  83     return nullptr;
  84   }
  85
  86   bool Has(UserDataKey *key)
  87   {
  88     for (int i=0; i<count; i++) {
  89       if (key == entries[i].key) {
  90         return true;
  91       }
  92     }
  93     return false;
  94   }
  95
  96   void Destroy()
  97   {
  98     for (int i=0; i<count; i++) {
  99       if (entries[i].destroy) {
 100         entries[i].destroy(entries[i].userData);
 101       }
 102     }
 103     free(entries);
 104     entries = nullptr;
 105     count = 0;
 106   }
 107
 108   ~UserData()
 109   {
 110     Destroy();
 111   }
 112
 113 private:
 114   struct Entry {
 115     const UserDataKey *key;
 116     void *userData;
 117     destroyFunc destroy;
 118   };
 119
 120   int count;
 121   Entry *entries;
 122
 123 };
 124
 125 }
 126 }
 127
 128 #endif /* MOZILLA_GFX_USERDATA_H_ */