OVMS3-idf/components/nvs_flash/src/compressed_enum_table.hpp

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2016-08-17 15:08:22 +00:00
// Copyright 2015-2016 Espressif Systems (Shanghai) PTE LTD
//
// 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 compressed_enum_table_h
#define compressed_enum_table_h
#include <cstdint>
#include <cassert>
#include <type_traits>
template<typename Tenum, size_t Nbits, size_t Nitems>
class CompressedEnumTable
{
public:
uint32_t* data()
{
return mData;
}
const uint32_t* data() const
{
return mData;
}
Tenum get(size_t index) const
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{
assert(index >= 0 && index < Nitems);
size_t wordIndex = index / ITEMS_PER_WORD;
size_t offset = (index % ITEMS_PER_WORD) * Nbits;
return static_cast<Tenum>((mData[wordIndex] >> offset) & VALUE_MASK);
}
void set(size_t index, Tenum val)
{
assert(index >= 0 && index < Nitems);
size_t wordIndex = index / ITEMS_PER_WORD;
size_t offset = (index % ITEMS_PER_WORD) * Nbits;
uint32_t v = static_cast<uint32_t>(val) << offset;
mData[wordIndex] = (mData[wordIndex] & ~(VALUE_MASK << offset)) | v;
}
static constexpr size_t getWordIndex(size_t index)
{
return index / ITEMS_PER_WORD;
}
static constexpr size_t byteSize()
{
return WORD_COUNT * 4;
}
static constexpr size_t count()
{
return Nitems;
}
protected:
static_assert(32 % Nbits == 0, "Nbits must divide 32");
static const size_t ITEMS_PER_WORD = 32 / Nbits;
static const size_t WORD_COUNT = ( Nbits * Nitems + 31 ) / 32;
static const uint32_t VALUE_MASK = (1 << Nbits) - 1;
uint32_t mData[WORD_COUNT];
};
#endif /* compressed_enum_table_h */