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// Copyright (C) 2014 The Android Open Source Project
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#ifndef EMUGL_COMMON_UNIQUE_INTEGER_MAP_H
#define EMUGL_COMMON_UNIQUE_INTEGER_MAP_H
#include "emugl/common/pod_vector.h"
#include <stdint.h>
namespace emugl {
// Helper template class that implements a bi-directional mapping between
// two integer types |A| and |B|. More specifically:
//
// - The map allocates values of type |B| when a key of type |A| is entered
// in the map.
//
// - keys and values cannot be 0, which is reserved (i.e. means 'invalid').
//
// This is used in EmuGL to map liberal 'void*' values (e.g. EGLimages ones)
// to unique 32-bit IDs that can be written to / read from the wire protocol.
template <typename A, typename B>
class UniqueIntegerMap {
public:
UniqueIntegerMap() : mForwardPairs(), mBackwardPairs() {}
~UniqueIntegerMap() {}
// Return true iff the map is empty.
const bool empty() const { return mForwardPairs.empty(); }
// Return the number of (key,value) pairs in the map.
size_t size() const { return mForwardPairs.size(); }
// Find the value associated with |key| in the map.
// Returns 0 in case of failure, or if |key| is 0.
B find(const A key) const;
// Find the key associated with a given |value| in the map.
// Returns 0 if |value| is 0, or in case of failure.
A findKeyFor(const B value) const;
// Add |key| to the map and return an automatically-allocated
// unique value for it. Return 0 if |key| is 0.
B add(const A key);
// Delete the entry associated with a given |key|. The
// corresponding value may be recycled by future calls to add().
void del(const A key);
private:
typedef struct {
A first;
B second;
} ForwardPair;
typedef struct {
B first;
A second;
} BackwardPair;
size_t findKeyIndexPlusOne(const A key) const;
size_t findValueIndexPlusOne(const B value) const;
B allocValue();
void freeValue(B value);
PodVector<ForwardPair> mForwardPairs;
PodVector<BackwardPair> mBackwardPairs;
B mLastValue;
PodVector<B> mFreeValues;
};
template <typename A, typename B>
B UniqueIntegerMap<A,B>::find(const A key) const {
size_t keyIndex = findKeyIndexPlusOne(key);
if (!keyIndex) {
return 0;
}
return mForwardPairs[keyIndex - 1U].second;
}
template <typename A, typename B>
A UniqueIntegerMap<A,B>::findKeyFor(const B value) const {
size_t valueIndex = findValueIndexPlusOne(value);
if (!valueIndex) {
return 0;
}
return mBackwardPairs[valueIndex - 1U].second;
}
template <typename A, typename B>
B UniqueIntegerMap<A,B>::add(const A key) {
// Binary search to find the proper insertion point for the key.
// Also checks that the key isn't already in the set.
size_t min = 0;
size_t max = mForwardPairs.size();
while (min < max) {
size_t mid = min + ((max - min) >> 1);
A midKey = mForwardPairs[mid].first;
if (midKey < key) {
min = mid + 1U;
} else if (midKey > key) {
max = mid;
} else {
// Already in the set.
return 0;
}
}
// Generate new unique value
B value = allocValue();
ForwardPair* pair = mForwardPairs.emplace(min);
pair->first = key;
pair->second = value;
// Binary search to find proper insertion point for the value.
min = 0;
max = mBackwardPairs.size();
while (min < max) {
size_t mid = min + ((max - min) >> 1);
B midValue = mBackwardPairs[mid].first;
if (midValue < value) {
min = mid + 1U;
} else {
max = mid;
}
}
BackwardPair* backPair = mBackwardPairs.emplace(min);
backPair->first = value;
backPair->second = key;
return value;
}
template <typename A, typename B>
void UniqueIntegerMap<A,B>::del(const A key) {
size_t keyIndex = findKeyIndexPlusOne(key);
if (!keyIndex) {
return;
}
B value = mForwardPairs[keyIndex - 1U].second;
size_t valueIndex = findValueIndexPlusOne(value);
mForwardPairs.remove(keyIndex - 1U);
mBackwardPairs.remove(valueIndex - 1U);
freeValue(value);
}
template <typename A, typename B>
size_t UniqueIntegerMap<A,B>::findKeyIndexPlusOne(const A key) const {
// Binary search in forward pair array.
size_t min = 0;
size_t max = mForwardPairs.size();
while (min < max) {
size_t mid = min + ((max - min) >> 1);
A midKey = mForwardPairs[mid].first;
if (midKey < key) {
min = mid + 1U;
} else if (midKey > key) {
max = mid;
} else {
return mid + 1U;
}
}
return 0U;
}
template <typename A, typename B>
size_t UniqueIntegerMap<A,B>::findValueIndexPlusOne(const B value) const {
// Binary search in revere pair array.
size_t min = 0;
size_t max = mBackwardPairs.size();
while (min < max) {
size_t mid = min + ((max - min) >> 1);
B midValue = mBackwardPairs[mid].first;
if (midValue < value) {
min = mid + 1U;
} else if (midValue > value) {
max = mid;
} else {
return mid + 1U;
}
}
return 0U;
}
template <typename A, typename B>
B UniqueIntegerMap<A,B>::allocValue() {
if (!mFreeValues.empty()) {
B result = mFreeValues[0];
mFreeValues.pop();
return result;
}
return ++mLastValue;
}
template <typename A, typename B>
void UniqueIntegerMap<A,B>::freeValue(B value) {
if (!value) {
return;
}
if (value == mLastValue) {
mLastValue--;
return;
}
mFreeValues.append(value);
}
} // namespace emugl
#endif // EMUGL_COMMON_INTEGER_MAP_H
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