126 lines
4.6 KiB
C
126 lines
4.6 KiB
C
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/*
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* Copyright (C) 2013, The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#ifndef LATINIME_BUFFER_WITH_EXTENDABLE_BUFFER_H
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#define LATINIME_BUFFER_WITH_EXTENDABLE_BUFFER_H
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#include <cstddef>
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#include <cstdint>
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#include <vector>
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#include "defines.h"
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#include "dictionary/utils/byte_array_utils.h"
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#include "utils/byte_array_view.h"
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namespace latinime {
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// This is used as a buffer that can be extended for updatable dictionaries.
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// To optimize performance, raw pointer is directly used for reading buffer. The position has to be
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// adjusted to access additional buffer. On the other hand, this class does not provide writable
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// raw pointer but provides several methods that handle boundary checking for writing data.
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class BufferWithExtendableBuffer {
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public:
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static const size_t DEFAULT_MAX_ADDITIONAL_BUFFER_SIZE;
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BufferWithExtendableBuffer(const ReadWriteByteArrayView originalBuffer,
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const int maxAdditionalBufferSize)
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: mOriginalBuffer(originalBuffer), mAdditionalBuffer(), mUsedAdditionalBufferSize(0),
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mMaxAdditionalBufferSize(maxAdditionalBufferSize) {}
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// Without original buffer.
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BufferWithExtendableBuffer(const int maxAdditionalBufferSize)
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: mOriginalBuffer(), mAdditionalBuffer(), mUsedAdditionalBufferSize(0),
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mMaxAdditionalBufferSize(maxAdditionalBufferSize) {}
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AK_FORCE_INLINE int getTailPosition() const {
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return mOriginalBuffer.size() + mUsedAdditionalBufferSize;
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}
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AK_FORCE_INLINE int getUsedAdditionalBufferSize() const {
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return mUsedAdditionalBufferSize;
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}
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/**
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* For reading.
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*/
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AK_FORCE_INLINE bool isInAdditionalBuffer(const int position) const {
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return position >= static_cast<int>(mOriginalBuffer.size());
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}
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// TODO: Resolve the issue that the address can be changed when the vector is resized.
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// CAVEAT!: Be careful about array out of bound access with buffers
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AK_FORCE_INLINE const uint8_t *getBuffer(const bool usesAdditionalBuffer) const {
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if (usesAdditionalBuffer) {
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return mAdditionalBuffer.data();
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} else {
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return mOriginalBuffer.data();
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}
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}
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uint32_t readUint(const int size, const int pos) const;
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uint32_t readUintAndAdvancePosition(const int size, int *const pos) const;
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void readCodePointsAndAdvancePosition(const int maxCodePointCount,
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int *const outCodePoints, int *outCodePointCount, int *const pos) const;
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AK_FORCE_INLINE int getOriginalBufferSize() const {
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return mOriginalBuffer.size();
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}
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AK_FORCE_INLINE bool isNearSizeLimit() const {
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return mAdditionalBuffer.size() >= ((mMaxAdditionalBufferSize
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* NEAR_BUFFER_LIMIT_THRESHOLD_PERCENTILE) / 100);
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}
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bool extend(const int size);
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/**
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* For writing.
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*
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* Writing is allowed for original buffer, already written region of additional buffer and the
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* tail of additional buffer.
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*/
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bool writeUint(const uint32_t data, const int size, const int pos);
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bool writeUintAndAdvancePosition(const uint32_t data, const int size, int *const pos);
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bool writeCodePointsAndAdvancePosition(const int *const codePoints, const int codePointCount,
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const bool writesTerminator, int *const pos);
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bool copy(const BufferWithExtendableBuffer *const sourceBuffer);
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private:
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DISALLOW_COPY_AND_ASSIGN(BufferWithExtendableBuffer);
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static const int NEAR_BUFFER_LIMIT_THRESHOLD_PERCENTILE;
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static const size_t EXTEND_ADDITIONAL_BUFFER_SIZE_STEP;
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const ReadWriteByteArrayView mOriginalBuffer;
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std::vector<uint8_t> mAdditionalBuffer;
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int mUsedAdditionalBufferSize;
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const size_t mMaxAdditionalBufferSize;
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// Return if the buffer is successfully extended or not.
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bool extendBuffer(const size_t size);
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// Returns if it is possible to write size-bytes from pos. When pos is at the tail position of
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// the additional buffer, try extending the buffer.
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bool checkAndPrepareWriting(const int pos, const int size);
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};
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}
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#endif /* LATINIME_BUFFER_WITH_EXTENDABLE_BUFFER_H */
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