105 lines
2.7 KiB
C
105 lines
2.7 KiB
C
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/*
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* Tencent is pleased to support the open source community by making
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* MMKV available.
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*
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* Copyright (C) 2018 THL A29 Limited, a Tencent company.
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* All rights reserved.
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*
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* Licensed under the BSD 3-Clause License (the "License"); you may not use
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* this file except in compliance with the License. You may obtain a copy of
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* the License at
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*
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* https://opensource.org/licenses/BSD-3-Clause
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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 MMKV_MMBUFFER_H
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#define MMKV_MMBUFFER_H
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#ifdef __cplusplus
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#include "MMKVPredef.h"
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#include <cstdint>
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#include <cstdlib>
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namespace mmkv {
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enum MMBufferCopyFlag : bool {
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MMBufferCopy = false,
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MMBufferNoCopy = true,
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};
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#pragma pack(push, 1)
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#ifndef MMKV_DISABLE_CRYPT
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struct KeyValueHolderCrypt;
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#endif
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class MMBuffer {
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enum MMBufferType : uint8_t {
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MMBufferType_Small, // store small buffer in stack memory
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MMBufferType_Normal, // store in heap memory
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};
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MMBufferType type;
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union {
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struct {
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MMBufferCopyFlag isNoCopy;
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size_t size;
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void *ptr;
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#ifdef MMKV_APPLE
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NSData *m_data;
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#endif
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};
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struct {
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uint8_t paddedSize;
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// make at least 10 bytes to hold all primitive types (negative int32, int64, double etc) on 32 bit device
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// on 64 bit device it's guaranteed larger than 10 bytes
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uint8_t paddedBuffer[10];
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};
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};
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static constexpr size_t SmallBufferSize() {
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return sizeof(MMBuffer) - offsetof(MMBuffer, paddedBuffer);
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}
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public:
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explicit MMBuffer(size_t length = 0);
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MMBuffer(void *source, size_t length, MMBufferCopyFlag flag = MMBufferCopy);
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#ifdef MMKV_APPLE
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explicit MMBuffer(NSData *data, MMBufferCopyFlag flag = MMBufferCopy);
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#endif
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MMBuffer(MMBuffer &&other) noexcept;
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MMBuffer &operator=(MMBuffer &&other) noexcept;
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~MMBuffer();
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void *getPtr() const { return (type == MMBufferType_Small) ? (void *) paddedBuffer : ptr; }
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size_t length() const { return (type == MMBufferType_Small) ? paddedSize : size; }
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// transfer ownership to others
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void detach();
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// those are expensive, just forbid it for possibly misuse
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explicit MMBuffer(const MMBuffer &other) = delete;
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MMBuffer &operator=(const MMBuffer &other) = delete;
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#ifndef MMKV_DISABLE_CRYPT
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friend KeyValueHolderCrypt;
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#endif
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};
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#pragma pack(pop)
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} // namespace mmkv
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#endif
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#endif //MMKV_MMBUFFER_H
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