// Copyright (c) 2011 The LevelDB Authors. All rights reserved. // Use of this source code is governed by a BSD-style license that can be // found in the LICENSE file. See the AUTHORS file for names of contributors. #include "db/memtable.h" #include "db/dbformat.h" #include "leveldb/comparator.h" #include "leveldb/env.h" #include "leveldb/iterator.h" #include "util/coding.h" #include "include/leveldb/write_batch.h" namespace leveldb { static Slice GetLengthPrefixedSlice(const char* data) { uint32_t len; const char* p = data; p = GetVarint32Ptr(p, p + 5, &len); // +5: we assume "p" is not corrupted return Slice(p, len); } MemTable::MemTable(const InternalKeyComparator& comparator) : comparator_(comparator), refs_(0), table_(comparator_, &arena_) {} MemTable::~MemTable() { assert(refs_ == 0); } size_t MemTable::ApproximateMemoryUsage() { return arena_.MemoryUsage(); } int MemTable::KeyComparator::operator()(const char* aptr, const char* bptr) const { // Internal keys are encoded as length-prefixed strings. Slice a = GetLengthPrefixedSlice(aptr); Slice b = GetLengthPrefixedSlice(bptr); return comparator.Compare(a, b); } // Encode a suitable internal key target for "target" and return it. // Uses *scratch as scratch space, and the returned pointer will point // into this scratch space. static const char* EncodeKey(std::string* scratch, const Slice& target) { scratch->clear(); PutVarint32(scratch, target.size()); scratch->append(target.data(), target.size()); return scratch->data(); } class MemTableIterator : public Iterator { public: explicit MemTableIterator(MemTable::Table* table) : iter_(table) {} MemTableIterator(const MemTableIterator&) = delete; MemTableIterator& operator=(const MemTableIterator&) = delete; ~MemTableIterator() override = default; bool Valid() const override { return iter_.Valid(); } void Seek(const Slice& k) override { iter_.Seek(EncodeKey(&tmp_, k)); } void SeekToFirst() override { iter_.SeekToFirst(); } void SeekToLast() override { iter_.SeekToLast(); } void Next() override { iter_.Next(); } void Prev() override { iter_.Prev(); } Slice key() const override { return GetLengthPrefixedSlice(iter_.key()); } Slice value() const override { Slice key_slice = GetLengthPrefixedSlice(iter_.key()); return GetLengthPrefixedSlice(key_slice.data() + key_slice.size()); } Status status() const override { return Status::OK(); } private: MemTable::Table::Iterator iter_; std::string tmp_; // For passing to EncodeKey }; Iterator* MemTable::NewIterator() { return new MemTableIterator(&table_); } void MemTable::Add(SequenceNumber s, ValueType type, const Slice& key, const Slice& value) { // Format of an entry is concatenation of: // key_size : varint32 of internal_key.size() // key bytes : char[internal_key.size()] // tag : uint64((sequence << 8) | type) // value_size : varint32 of value.size() // value bytes : char[value.size()] size_t key_size = key.size(); size_t val_size = value.size(); size_t internal_key_size = key_size + 8; const size_t encoded_len = VarintLength(internal_key_size) + internal_key_size + VarintLength(val_size) + val_size; char* buf = arena_.Allocate(encoded_len); char* p = EncodeVarint32(buf, internal_key_size); std::memcpy(p, key.data(), key_size); p += key_size; EncodeFixed64(p, (s << 8) | type); p += 8; p = EncodeVarint32(p, val_size); std::memcpy(p, value.data(), val_size); assert(p + val_size == buf + encoded_len); table_.Insert(buf); } // bool MemTable::Get(const LookupKey& key, std::string* value, Status* s) { //燕改 // Slice memkey = key.memtable_key(); // Table::Iterator iter(&table_); // iter.Seek(memkey.data()); // if (iter.Valid()) {// 获取跳表项的内容 // // entry format is: // // klength varint32 // // userkey char[klength] // // tag uint64 // // vlength varint32 // // value char[vlength] // // Check that it belongs to same user key. We do not check the // // sequence number since the Seek() call above should have skipped // // all entries with overly large sequence numbers. // const char* entry = iter.key(); // uint32_t key_length; // const char* key_ptr = GetVarint32Ptr(entry, entry + 5, &key_length); // if (comparator_.comparator.user_comparator()->Compare(// 比较键值 // Slice(key_ptr, key_length - 8), key.user_key()) == 0) { // // Correct user key // const uint64_t tag = DecodeFixed64(key_ptr + key_length - 8); // switch (static_cast(tag & 0xff)) { // case kTypeValue: { // // Slice v = GetLengthPrefixedSlice(key_ptr + key_length); // // value->assign(v.data(), v.size()); // // return true; // // 获取过期时间戳，燕改 // Slice v = GetLengthPrefixedSlice(key_ptr + key_length); // uint64_t expire_time = DecodeFixed64(v.data() + v.size() - sizeof(uint64_t)); // // 检查是否已过期 // uint64_t current_time = Env::Default()->NowMicros() / 1000000; // 当前时间（秒） // if (expire_time > 0 && expire_time < current_time) { // *s = Status::NotFound("Key has expired"); // 已过期 // return false; // } // // 未过期，返回值 // value->assign(v.data() + 8, v.size() - 8); // 去除前8字节的时间戳 // return true; // } // case kTypeDeletion: // *s = Status::NotFound(Slice()); // return true; // } // } // } // return false; // } bool MemTable::Get(const LookupKey& key, std::string* value, Status* s) { Slice memkey = key.memtable_key(); Table::Iterator iter(&table_); iter.Seek(memkey.data()); if (iter.Valid()) { // 获取跳表项的内容 const char* entry = iter.key(); uint32_t key_length; const char* key_ptr = GetVarint32Ptr(entry, entry + 5, &key_length); if (comparator_.comparator.user_comparator()->Compare( Slice(key_ptr, key_length - 8), key.user_key()) == 0) { const uint64_t tag = DecodeFixed64(key_ptr + key_length - 8); switch (static_cast(tag & 0xff)) { case kTypeValue: { // 获取存储的值和时间戳 Slice v = GetLengthPrefixedSlice(key_ptr + key_length); std::string combined_str(v.data(), v.size()); // 根据存储格式分离原始值和时间戳 std::string actual_value = combined_str.substr(0, combined_str.size() - 20); std::string time_str = combined_str.substr(combined_str.size() - 19, 19); // 获取当前时间（字符串格式） auto now = std::chrono::system_clock::now(); auto now_time_t = std::chrono::system_clock::to_time_t(now); std::tm* now_tm = std::localtime(&now_time_t); char buffer[20]; std::strftime(buffer, sizeof(buffer), "%Y-%m-%d %H:%M:%S", now_tm); std::string current_time_str(buffer); // 检查过期 if (time_str <= current_time_str) { *s = Status::NotFound("Key has expired"); // 已过期 return true; } // 未过期，返回实际值 value->assign(actual_value); return true; } case kTypeDeletion: *s = Status::NotFound(Slice()); return true; } } } return false; } } // namespace leveldb