Move SkTHash.h to include/private.

src/core/SkTHash.h

-/*
- * Copyright 2015 Google Inc.
- *
- * Use of this source code is governed by a BSD-style license that can be
- * found in the LICENSE file.
- */
-
-#ifndef SkTHash_DEFINED
-#define SkTHash_DEFINED
-
-#include "SkChecksum.h"
-#include "SkTypes.h"
-#include "SkTemplates.h"
-
-// Before trying to use SkTHashTable, look below to see if SkTHashMap or SkTHashSet works for you.
-// They're easier to use, usually perform the same, and have fewer sharp edges.
-
-// T and K are treated as ordinary copyable C++ types.
-// Traits must have:
-//   - static K GetKey(T)
-//   - static uint32_t Hash(K)
-// If the key is large and stored inside T, you may want to make K a const&.
-// Similarly, if T is large you might want it to be a pointer.
-template <typename T, typename K, typename Traits = T>
-class SkTHashTable : SkNoncopyable {
-public:
-    SkTHashTable() : fCount(0), fRemoved(0), fCapacity(0) {}
-
-    // Clear the table.
-    void reset() {
-        this->~SkTHashTable();
-        SkNEW_PLACEMENT(this, SkTHashTable);
-    }
-
-    // How many entries are in the table?
-    int count() const { return fCount; }
-
-    // !!!!!!!!!!!!!!!!!                 CAUTION                   !!!!!!!!!!!!!!!!!
-    // set(), find() and foreach() all allow mutable access to table entries.
-    // If you change an entry so that it no longer has the same key, all hell
-    // will break loose.  Do not do that!
-    //
-    // Please prefer to use SkTHashMap or SkTHashSet, which do not have this danger.
-
-    // The pointers returned by set() and find() are valid only until the next call to set().
-    // The pointers you receive in foreach() are only valid for its duration.
-
-    // Copy val into the hash table, returning a pointer to the copy now in the table.
-    // If there already is an entry in the table with the same key, we overwrite it.
-    T* set(const T& val) {
-        if (4 * (fCount+fRemoved) >= 3 * fCapacity) {
-            this->resize(fCapacity > 0 ? fCapacity * 2 : 4);
-        }
-        return this->uncheckedSet(val);
-    }
-
-    // If there is an entry in the table with this key, return a pointer to it.  If not, NULL.
-    T* find(const K& key) const {
-        uint32_t hash = Hash(key);
-        int index = hash & (fCapacity-1);
-        for (int n = 0; n < fCapacity; n++) {
-            Slot& s = fSlots[index];
-            if (s.empty()) {
-                return NULL;
-            }
-            if (!s.removed() && hash == s.hash && key == Traits::GetKey(s.val)) {
-                return &s.val;
-            }
-            index = this->next(index, n);
-        }
-        SkASSERT(fCapacity == 0);
-        return NULL;
-    }
-
-    // Remove the value with this key from the hash table.
-    void remove(const K& key) {
-        SkASSERT(this->find(key));
-
-        uint32_t hash = Hash(key);
-        int index = hash & (fCapacity-1);
-        for (int n = 0; n < fCapacity; n++) {
-            Slot& s = fSlots[index];
-            SkASSERT(!s.empty());
-            if (!s.removed() && hash == s.hash && key == Traits::GetKey(s.val)) {
-                fRemoved++;
-                fCount--;
-                s.markRemoved();
-                return;
-            }
-            index = this->next(index, n);
-        }
-        SkASSERT(fCapacity == 0);
-    }
-
-    // Call fn on every entry in the table.  You may mutate the entries, but be very careful.
-    template <typename Fn>  // f(T*)
-    void foreach(Fn&& fn) {
-        for (int i = 0; i < fCapacity; i++) {
-            if (!fSlots[i].empty() && !fSlots[i].removed()) {
-                fn(&fSlots[i].val);
-            }
-        }
-    }
-
-    // Call fn on every entry in the table.  You may not mutate anything.
-    template <typename Fn>  // f(T) or f(const T&)
-    void foreach(Fn&& fn) const {
-        for (int i = 0; i < fCapacity; i++) {
-            if (!fSlots[i].empty() && !fSlots[i].removed()) {
-                fn(fSlots[i].val);
-            }
-        }
-    }
-
-private:
-    T* uncheckedSet(const T& val) {
-        const K& key = Traits::GetKey(val);
-        uint32_t hash = Hash(key);
-        int index = hash & (fCapacity-1);
-        for (int n = 0; n < fCapacity; n++) {
-            Slot& s = fSlots[index];
-            if (s.empty() || s.removed()) {
-                // New entry.
-                if (s.removed()) {
-                    fRemoved--;
-                }
-                s.val  = val;
-                s.hash = hash;
-                fCount++;
-                return &s.val;
-            }
-            if (hash == s.hash && key == Traits::GetKey(s.val)) {
-                // Overwrite previous entry.
-                // Note: this triggers extra copies when adding the same value repeatedly.
-                s.val = val;
-                return &s.val;
-            }
-            index = this->next(index, n);
-        }
-        SkASSERT(false);
-        return NULL;
-    }
-
-    void resize(int capacity) {
-        int oldCapacity = fCapacity;
-        SkDEBUGCODE(int oldCount = fCount);
-
-        fCount = fRemoved = 0;
-        fCapacity = capacity;
-        SkAutoTArray<Slot> oldSlots(capacity);
-        oldSlots.swap(fSlots);
-
-        for (int i = 0; i < oldCapacity; i++) {
-            const Slot& s = oldSlots[i];
-            if (!s.empty() && !s.removed()) {
-                this->uncheckedSet(s.val);
-            }
-        }
-        SkASSERT(fCount == oldCount);
-    }
-
-    int next(int index, int n) const {
-        // A valid strategy explores all slots in [0, fCapacity) as n walks from 0 to fCapacity-1.
-        // Both of these strategies are valid:
-        //return (index + 0 + 1) & (fCapacity-1);      // Linear probing.
-        return (index + n + 1) & (fCapacity-1);        // Quadratic probing.
-    }
-
-    static uint32_t Hash(const K& key) {
-        uint32_t hash = Traits::Hash(key);
-        return hash < 2 ? hash+2 : hash;  // We reserve hash 0 and 1 to mark empty or removed slots.
-    }
-
-    struct Slot {
-        Slot() : hash(0) {}
-        bool   empty() const { return this->hash == 0; }
-        bool removed() const { return this->hash == 1; }
-
-        void markRemoved() { this->hash = 1; }
-
-        T val;
-        uint32_t hash;
-    };
-
-    int fCount, fRemoved, fCapacity;
-    SkAutoTArray<Slot> fSlots;
-};
-
-// Maps K->V.  A more user-friendly wrapper around SkTHashTable, suitable for most use cases.
-// K and V are treated as ordinary copyable C++ types, with no assumed relationship between the two.
-template <typename K, typename V, uint32_t(*HashK)(const K&) = &SkGoodHash>
-class SkTHashMap : SkNoncopyable {
-public:
-    SkTHashMap() {}
-
-    // Clear the map.
-    void reset() { fTable.reset(); }
-
-    // How many key/value pairs are in the table?
-    int count() const { return fTable.count(); }
-
-    // N.B. The pointers returned by set() and find() are valid only until the next call to set().
-
-    // Set key to val in the table, replacing any previous value with the same key.
-    // We copy both key and val, and return a pointer to the value copy now in the table.
-    V* set(const K& key, const V& val) {
-        Pair in = { key, val };
-        Pair* out = fTable.set(in);
-        return &out->val;
-    }
-
-    // If there is key/value entry in the table with this key, return a pointer to the value.
-    // If not, return NULL.
-    V* find(const K& key) const {
-        if (Pair* p = fTable.find(key)) {
-            return &p->val;
-        }
-        return NULL;
-    }
-
-    // Remove the key/value entry in the table with this key.
-    void remove(const K& key) {
-        SkASSERT(this->find(key));
-        fTable.remove(key);
-    }
-
-    // Call fn on every key/value pair in the table.  You may mutate the value but not the key.
-    template <typename Fn>  // f(K, V*) or f(const K&, V*)
-    void foreach(Fn&& fn) {
-        fTable.foreach([&fn](Pair* p){ fn(p->key, &p->val); });
-    }
-
-    // Call fn on every key/value pair in the table.  You may not mutate anything.
-    template <typename Fn>  // f(K, V), f(const K&, V), f(K, const V&) or f(const K&, const V&).
-    void foreach(Fn&& fn) const {
-        fTable.foreach([&fn](const Pair& p){ fn(p.key, p.val); });
-    }
-
-private:
-    struct Pair {
-        K key;
-        V val;
-        static const K& GetKey(const Pair& p) { return p.key; }
-        static uint32_t Hash(const K& key) { return HashK(key); }
-    };
-
-    SkTHashTable<Pair, K> fTable;
-};
-
-// A set of T.  T is treated as an ordiary copyable C++ type.
-template <typename T, uint32_t(*HashT)(const T&) = &SkGoodHash>
-class SkTHashSet : SkNoncopyable {
-public:
-    SkTHashSet() {}
-
-    // Clear the set.
-    void reset() { fTable.reset(); }
-
-    // How many items are in the set?
-    int count() const { return fTable.count(); }
-
-    // Copy an item into the set.
-    void add(const T& item) { fTable.set(item); }
-
-    // Is this item in the set?
-    bool contains(const T& item) const { return SkToBool(this->find(item)); }
-
-    // If an item equal to this is in the set, return a pointer to it, otherwise null.
-    // This pointer remains valid until the next call to add().
-    const T* find(const T& item) const { return fTable.find(item); }
-
-    // Remove the item in the set equal to this.
-    void remove(const T& item) {
-        SkASSERT(this->contains(item));
-        fTable.remove(item);
-    }
-
-    // Call fn on every item in the set.  You may not mutate anything.
-    template <typename Fn>  // f(T), f(const T&)
-    void foreach (Fn&& fn) const {
-        fTable.foreach(fn);
-    }
-
-private:
-    struct Traits {
-        static const T& GetKey(const T& item) { return item; }
-        static uint32_t Hash(const T& item) { return HashT(item); }
-    };
-    SkTHashTable<T, T, Traits> fTable;
-};
-
-#endif//SkTHash_DEFINED