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111 рядки
2.6 KiB
111 рядки
2.6 KiB
#ifndef VTABLE_FORMAT_H
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#define VTABLE_FORMAT_H
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#include "leveldb/slice.h"
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#include "leveldb/status.h"
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#include "table/format.h"
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namespace leveldb {
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const uint64_t kRecordHeaderSize = 4;
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// VTable最基本的存储单位，表示存储的一个key和一个value
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struct VTableRecord {
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Slice key;
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Slice value;
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// 将record编码为str
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void Encode(std::string* target) const;
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// 将Slice解码为record
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Status Decode(Slice* input);
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// 该record的size
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size_t size() const { return key.size() + value.size(); }
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friend bool operator==(const VTableRecord& a, const VTableRecord& b) {
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return a.key == b.key && a.value == b.value;
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}
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};
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class RecordEncoder {
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public:
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// TODO: Support compression while encoding a record
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RecordEncoder() = default;
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// 编码一条vTable record
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void Encode(const VTableRecord& record);
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// 获得编码后的records的size
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size_t GetEncodedSize() const { return sizeof(header_) + record_.size(); }
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// 获取编码后的header
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Slice GetHeader() const { return {header_, sizeof(header_)}; }
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// 获得编码后的record
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Slice GetRecord() const { return record_; }
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private:
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char header_[kRecordHeaderSize];
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Slice record_;
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std::string record_buff_;
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};
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class RecordDecoder {
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public:
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// 解码出record的header
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Status DecodeHeader(Slice* input);
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// 解码出record
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Status DecodeRecord(Slice* input, VTableRecord* record) const;
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// 获得解码后的record size
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size_t GetDecodedSize() const { return record_size_; }
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private:
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uint32_t record_size_{0};
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};
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struct VTableHandle {
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// 表示某个record在VTable中的位置
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uint64_t offset{0};
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uint64_t size{0};
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void Encode(std::string* target) const;
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Status Decode(Slice* input);
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friend bool operator==(const VTableHandle& a, const VTableHandle& b) {
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return a.offset == b.offset && a.size == b.size;
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}
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};
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struct VTableIndex {
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// 存入sstable中的index
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enum Type : unsigned char {
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kVTableIndex = 1,
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};
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uint64_t file_number{0};
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VTableHandle vtable_handle;
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void Encode(std::string* target) const;
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Status Decode(Slice* input);
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friend bool operator==(const VTableIndex& a, const VTableIndex& b) {
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return a.file_number == b.file_number && a.vtable_handle == b.vtable_handle;
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}
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};
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// 便利的调用解码方法的函数
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template <typename T>
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Status DecodeSrcIntoObj(const Slice& src, T* target) {
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Slice input = src;
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Status s = target->Decode(&input);
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if (s.ok() && !input.empty()) {
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s = Status::Corruption(Slice());
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}
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return s;
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}
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} // namespace leveldb
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#endif //VTABLE_FORMAT_H
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