The Tor Browser: gfx/skia/trunk/src/core/SkTDynamicHash.h@129ffea94266 (annotated)

gfx/skia/trunk/src/core/SkTDynamicHash.h@129ffea94266 (annotated)

gfx/skia/trunk/src/core/SkTDynamicHash.h

Sat, 03 Jan 2015 20:18:00 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Sat, 03 Jan 2015 20:18:00 +0100
branch: TOR_BUG_3246
changeset 7: 129ffea94266
permissions: -rw-r--r--

Conditionally enable double key logic according to:
private browsing mode or privacy.thirdparty.isolate preference and
implement in GetCookieStringCommon and FindCookie where it counts...
With some reservations of how to convince FindCookie users to test
condition and pass a nullptr when disabling double key logic.

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 #ifndef SkTDynamicHash_DEFINED
 #define SkTDynamicHash_DEFINED
 #include "SkMath.h"
 #include "SkTemplates.h"
 #include "SkTypes.h"
 template <typename T,
           typename Key,
           const Key& (GetKey)(const T&),
           uint32_t (Hash)(const Key&),
           bool (Equal)(const T&, const Key&),
           int kGrowPercent = 75>  // Larger -> more memory efficient, but slower.
 class SkTDynamicHash {
 public:
     SkTDynamicHash() : fCount(0), fDeleted(0), fCapacity(0), fArray(NULL) {
         SkASSERT(this->validate());
     }
     ~SkTDynamicHash() {
         sk_free(fArray);
     }
     class Iter {
     public:
         explicit Iter(SkTDynamicHash* hash) : fHash(hash), fCurrentIndex(-1) {
             SkASSERT(hash);
             ++(*this);
         }
         bool done() const {
             SkASSERT(fCurrentIndex <= fHash->fCapacity);
             return fCurrentIndex == fHash->fCapacity;
         }
         T& operator*() const {
             SkASSERT(!this->done());
             return *this->current();
         }
         void operator++() {
             do {
                 fCurrentIndex++;
             } while (!this->done() && (this->current() == Empty() || this->current() == Deleted()));
         }
     private:
         T* current() const { return fHash->fArray[fCurrentIndex]; }
         SkTDynamicHash* fHash;
         int fCurrentIndex;
     };
     int count() const { return fCount; }
     // Return the entry with this key if we have it, otherwise NULL.
     T* find(const Key& key) const {
         int index = this->firstIndex(key);
         for (int round = 0; round < fCapacity; round++) {
             T* candidate = fArray[index];
             if (Empty() == candidate) {
                 return NULL;
             }
             if (Deleted() != candidate && Equal(*candidate, key)) {
                 return candidate;
             }
             index = this->nextIndex(index, round);
         }
         SkASSERT(fCapacity == 0);
         return NULL;
     }
     // Add an entry with this key.  We require that no entry with newEntry's key is already present.
     void add(T* newEntry) {
         SkASSERT(NULL == this->find(GetKey(*newEntry)));
         this->maybeGrow();
         this->innerAdd(newEntry);
         SkASSERT(this->validate());
     }
     // Remove the entry with this key.  We reqire that an entry with this key is present.
     void remove(const Key& key) {
         SkASSERT(NULL != this->find(key));
         this->innerRemove(key);
         SkASSERT(this->validate());
     }
 protected:
     // These methods are used by tests only.
     int capacity() const { return fCapacity; }
     // How many collisions do we go through before finding where this entry should be inserted?
     int countCollisions(const Key& key) const {
         int index = this->firstIndex(key);
         for (int round = 0; round < fCapacity; round++) {
             const T* candidate = fArray[index];
             if (Empty() == candidate || Deleted() == candidate || Equal(*candidate, key)) {
                 return round;
             }
             index = this->nextIndex(index, round);
         }
         SkASSERT(fCapacity == 0);
         return 0;
     }
 private:
     // We have two special values to indicate an empty or deleted entry.
     static T* Empty()   { return reinterpret_cast<T*>(0); }  // i.e. NULL
     static T* Deleted() { return reinterpret_cast<T*>(1); }  // Also an invalid pointer.
     bool validate() const {
         #define SKTDYNAMICHASH_CHECK(x) SkASSERT((x)); if (!(x)) return false
         static const int kLarge = 50;  // Arbitrary, tweak to suit your patience.
         // O(1) checks, always done.
         // Is capacity sane?
         SKTDYNAMICHASH_CHECK(SkIsPow2(fCapacity));
         // O(N) checks, skipped when very large.
         if (fCount < kLarge * kLarge) {
             // Are fCount and fDeleted correct, and are all elements findable?
             int count = 0, deleted = 0;
             for (int i = 0; i < fCapacity; i++) {
                 if (Deleted() == fArray[i]) {
                     deleted++;
                 } else if (Empty() != fArray[i]) {
                     count++;
                     SKTDYNAMICHASH_CHECK(NULL != this->find(GetKey(*fArray[i])));
                 }
             }
             SKTDYNAMICHASH_CHECK(count == fCount);
             SKTDYNAMICHASH_CHECK(deleted == fDeleted);
         }
         // O(N^2) checks, skipped when large.
         if (fCount < kLarge) {
             // Are all entries unique?
             for (int i = 0; i < fCapacity; i++) {
                 if (Empty() == fArray[i] || Deleted() == fArray[i]) {
                     continue;
                 }
                 for (int j = i+1; j < fCapacity; j++) {
                     if (Empty() == fArray[j] || Deleted() == fArray[j]) {
                         continue;
                     }
                     SKTDYNAMICHASH_CHECK(fArray[i] != fArray[j]);
                     SKTDYNAMICHASH_CHECK(!Equal(*fArray[i], GetKey(*fArray[j])));
                     SKTDYNAMICHASH_CHECK(!Equal(*fArray[j], GetKey(*fArray[i])));
                 }
             }
         }
         #undef SKTDYNAMICHASH_CHECK
         return true;
     }
     void innerAdd(T* newEntry) {
         const Key& key = GetKey(*newEntry);
         int index = this->firstIndex(key);
         for (int round = 0; round < fCapacity; round++) {
             const T* candidate = fArray[index];
             if (Empty() == candidate || Deleted() == candidate) {
                 if (Deleted() == candidate) {
                     fDeleted--;
                 }
                 fCount++;
                 fArray[index] = newEntry;
                 return;
             }
             index = this->nextIndex(index, round);
         }
         SkASSERT(fCapacity == 0);
     }
     void innerRemove(const Key& key) {
         const int firstIndex = this->firstIndex(key);
         int index = firstIndex;
         for (int round = 0; round < fCapacity; round++) {
             const T* candidate = fArray[index];
             if (Deleted() != candidate && Equal(*candidate, key)) {
                 fDeleted++;
                 fCount--;
                 fArray[index] = Deleted();
                 return;
             }
             index = this->nextIndex(index, round);
         }
         SkASSERT(fCapacity == 0);
     }
     void maybeGrow() {
         if (100 * (fCount + fDeleted + 1) > fCapacity * kGrowPercent) {
             this->resize(fCapacity > 0 ? fCapacity * 2 : 4);
         }
     }
     void resize(int newCapacity) {
         SkDEBUGCODE(int oldCount = fCount;)
         int oldCapacity = fCapacity;
         SkAutoTMalloc<T*> oldArray(fArray);
         fCount = fDeleted = 0;
         fCapacity = newCapacity;
         fArray = (T**)sk_calloc_throw(sizeof(T*) * fCapacity);
         for (int i = 0; i < oldCapacity; i++) {
             T* entry = oldArray[i];
             if (Empty() != entry && Deleted() != entry) {
                 this->innerAdd(entry);
             }
         }
         SkASSERT(oldCount == fCount);
     }
     // fCapacity is always a power of 2, so this masks the correct low bits to index into our hash.
     uint32_t hashMask() const { return fCapacity - 1; }
     int firstIndex(const Key& key) const {
         return Hash(key) & this->hashMask();
     }
     // Given index at round N, what is the index to check at N+1?  round should start at 0.
     int nextIndex(int index, int round) const {
         // This will search a power-of-two array fully without repeating an index.
         return (index + round + 1) & this->hashMask();
     }
     int fCount;     // Number of non Empty(), non Deleted() entries in fArray.
     int fDeleted;   // Number of Deleted() entries in fArray.
     int fCapacity;  // Number of entries in fArray.  Always a power of 2.
     T** fArray;
 };
 #endif

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gfx/skia/trunk/src/core/SkTDynamicHash.h@129ffea94266 (annotated)

gfx/skia/trunk/src/core/SkTDynamicHash.h