aboutsummaryrefslogtreecommitdiffhomepage
path: root/include/core/SkTInternalLList.h
blob: a6b6f153530796097c1f92a7294220f2209bd481 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
/*
 * Copyright 2012 Google Inc.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#ifndef SkTInternalLList_DEFINED
#define SkTInternalLList_DEFINED

#include "SkTypes.h"

/**
 * Helper class to automatically initialize the doubly linked list created pointers.
 */
template <typename T> class SkPtrWrapper {
  public:
      SkPtrWrapper() : fPtr(NULL) {}
      SkPtrWrapper& operator =(T* ptr) { fPtr = ptr; return *this; }
      operator T*() const { return fPtr; }
      T* operator->() { return fPtr; }
  private:
      T* fPtr;
};


/**
 * This macro creates the member variables required by the SkTInternalLList class. It should be
 * placed in the private section of any class that will be stored in a double linked list.
 */
#define SK_DECLARE_INTERNAL_LLIST_INTERFACE(ClassName)              \
    friend class SkTInternalLList<ClassName>;                       \
    /* back pointer to the owning list - for debugging */           \
    SkDEBUGCODE(SkPtrWrapper<SkTInternalLList<ClassName> > fList;)  \
    SkPtrWrapper<ClassName> fPrev;                                  \
    SkPtrWrapper<ClassName> fNext

/**
 * This class implements a templated internal doubly linked list data structure.
 */
template <class T> class SkTInternalLList : public SkNoncopyable {
public:
    SkTInternalLList()
        : fHead(NULL)
        , fTail(NULL) {
    }

    void remove(T* entry) {
        SkASSERT(NULL != fHead && NULL != fTail);
        SkASSERT(this->isInList(entry));

        T* prev = entry->fPrev;
        T* next = entry->fNext;

        if (NULL != prev) {
            prev->fNext = next;
        } else {
            fHead = next;
        }
        if (NULL != next) {
            next->fPrev = prev;
        } else {
            fTail = prev;
        }

        entry->fPrev = NULL;
        entry->fNext = NULL;

#ifdef SK_DEBUG
        entry->fList = NULL;
#endif
    }

    void addToHead(T* entry) {
        SkASSERT(NULL == entry->fPrev && NULL == entry->fNext);
        SkASSERT(NULL == entry->fList);

        entry->fPrev = NULL;
        entry->fNext = fHead;
        if (NULL != fHead) {
            fHead->fPrev = entry;
        }
        fHead = entry;
        if (NULL == fTail) {
            fTail = entry;
        }

#ifdef SK_DEBUG
        entry->fList = this;
#endif
    }

    void addToTail(T* entry) {
        SkASSERT(NULL == entry->fPrev && NULL == entry->fNext);
        SkASSERT(NULL == entry->fList);

        entry->fPrev = fTail;
        entry->fNext = NULL;
        if (NULL != fTail) {
            fTail->fNext = entry;
        }
        fTail = entry;
        if (NULL == fHead) {
            fHead = entry;
        }

#ifdef SK_DEBUG
        entry->fList = this;
#endif
    }

    /**
     * Inserts a new list entry before an existing list entry. The new entry must not already be
     * a member of this or any other list. If existingEntry is NULL then the new entry is added
     * at the tail.
     */
    void addBefore(T* newEntry, T* existingEntry) {
        SkASSERT(NULL != newEntry);

        if (NULL == existingEntry) {
            this->addToTail(newEntry);
            return;
        }

        SkASSERT(this->isInList(existingEntry));
        newEntry->fNext = existingEntry;
        T* prev = existingEntry->fPrev;
        existingEntry->fPrev = newEntry;
        newEntry->fPrev = prev;
        if (NULL == prev) {
            SkASSERT(fHead == existingEntry);
            fHead = newEntry;
        } else {
            prev->fNext = newEntry;
        }
#ifdef SK_DEBUG
        newEntry->fList = this;
#endif
    }

    /**
     * Inserts a new list entry after an existing list entry. The new entry must not already be
     * a member of this or any other list. If existingEntry is NULL then the new entry is added
     * at the head.
     */
    void addAfter(T* newEntry, T* existingEntry) {
        SkASSERT(NULL != newEntry);

        if (NULL == existingEntry) {
            this->addToHead(newEntry);
            return;
        }

        SkASSERT(this->isInList(existingEntry));
        newEntry->fPrev = existingEntry;
        T* next = existingEntry->fNext;
        existingEntry->fNext = newEntry;
        newEntry->fNext = next;
        if (NULL == next) {
            SkASSERT(fTail == existingEntry);
            fTail = newEntry;
        } else {
            next->fPrev = newEntry;
        }
#ifdef SK_DEBUG
        newEntry->fList = this;
#endif
    }

    bool isEmpty() const {
        return NULL == fHead && NULL == fTail;
    }

    T* head() { return fHead; }
    T* tail() { return fTail; }

    class Iter {
    public:
        enum IterStart {
            kHead_IterStart,
            kTail_IterStart
        };

        Iter() : fCurr(NULL) {}
        Iter(const Iter& iter) : fCurr(iter.fCurr) {}
        Iter& operator= (const Iter& iter) { fCurr = iter.fCurr; return *this; }

        T* init(const SkTInternalLList& list, IterStart startLoc) {
            if (kHead_IterStart == startLoc) {
                fCurr = list.fHead;
            } else {
                SkASSERT(kTail_IterStart == startLoc);
                fCurr = list.fTail;
            }

            return fCurr;
        }

        T* get() { return fCurr; }

        /**
         * Return the next/previous element in the list or NULL if at the end.
         */
        T* next() {
            if (NULL == fCurr) {
                return NULL;
            }

            fCurr = fCurr->fNext;
            return fCurr;
        }

        T* prev() {
            if (NULL == fCurr) {
                return NULL;
            }

            fCurr = fCurr->fPrev;
            return fCurr;
        }

    private:
        T* fCurr;
    };

#ifdef SK_DEBUG
    void validate() const {
        SkASSERT(!fHead == !fTail);
        Iter iter;
        for (T* item = iter.init(*this, Iter::kHead_IterStart); NULL != (item = iter.next()); ) {
            SkASSERT(this->isInList(item));
            if (NULL == item->fPrev) {
                SkASSERT(fHead == item);
            } else {
                SkASSERT(item->fPrev->fNext == item);
            }
            if (NULL == item->fNext) {
                SkASSERT(fTail == item);
            } else {
                SkASSERT(item->fNext->fPrev == item);
            }
        }
    }

    /**
     * Debugging-only method that uses the list back pointer to check if 'entry' is indeed in 'this'
     * list.
     */
    bool isInList(const T* entry) const {
        return entry->fList == this;
    }

    /**
     * Debugging-only method that laboriously counts the list entries.
     */
    int countEntries() const {
        int count = 0;
        for (T* entry = fHead; NULL != entry; entry = entry->fNext) {
            ++count;
        }
        return count;
    }
#endif // SK_DEBUG

private:
    T* fHead;
    T* fTail;

    typedef SkNoncopyable INHERITED;
};

#endif