levelDB-LAB1-pzy_ckx/table/table.cc

// 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 "leveldb/table.h"

#include <sstream>   // For std::istringstream
#include <iomanip>   // For std::get_time
#include <ctime>     // For std::tm and std::mktime


#include "leveldb/cache.h"
#include "leveldb/comparator.h"
#include "leveldb/env.h"
#include "leveldb/filter_policy.h"
#include "leveldb/options.h"
#include "table/block.h"
#include "table/filter_block.h"
#include "table/format.h"
#include "table/two_level_iterator.h"
#include "util/coding.h"

namespace leveldb {

struct Table::Rep {
  ~Rep() {
    delete filter;
    delete[] filter_data;
    delete index_block;
  }

  Options options;
  Status status;
  RandomAccessFile* file;
  uint64_t cache_id;
  FilterBlockReader* filter;
  const char* filter_data;

  BlockHandle metaindex_handle;  // Handle to metaindex_block: saved from footer
  Block* index_block;
};

Status Table::Open(const Options& options, RandomAccessFile* file,
                   uint64_t size, Table** table) {
  *table = nullptr;
  if (size < Footer::kEncodedLength) {
    return Status::Corruption("file is too short to be an sstable");
  }

  char footer_space[Footer::kEncodedLength];
  Slice footer_input;
  Status s = file->Read(size - Footer::kEncodedLength, Footer::kEncodedLength,
                        &footer_input, footer_space);
  if (!s.ok()) return s;

  Footer footer;
  s = footer.DecodeFrom(&footer_input);
  if (!s.ok()) return s;

  // Read the index block
  BlockContents index_block_contents;
  ReadOptions opt;
  if (options.paranoid_checks) {
    opt.verify_checksums = true;
  }
  s = ReadBlock(file, opt, footer.index_handle(), &index_block_contents);

  if (s.ok()) {
    // We've successfully read the footer and the index block: we're
    // ready to serve requests.
    Block* index_block = new Block(index_block_contents);
    Rep* rep = new Table::Rep;
    rep->options = options;
    rep->file = file;
    rep->metaindex_handle = footer.metaindex_handle();
    rep->index_block = index_block;
    rep->cache_id = (options.block_cache ? options.block_cache->NewId() : 0);
    rep->filter_data = nullptr;
    rep->filter = nullptr;
    *table = new Table(rep);
    (*table)->ReadMeta(footer);
  }

  return s;
}

void Table::ReadMeta(const Footer& footer) {
  if (rep_->options.filter_policy == nullptr) {
    return;  // Do not need any metadata
  }

  // TODO(sanjay): Skip this if footer.metaindex_handle() size indicates
  // it is an empty block.
  ReadOptions opt;
  if (rep_->options.paranoid_checks) {
    opt.verify_checksums = true;
  }
  BlockContents contents;
  if (!ReadBlock(rep_->file, opt, footer.metaindex_handle(), &contents).ok()) {
    // Do not propagate errors since meta info is not needed for operation
    return;
  }
  Block* meta = new Block(contents);

  Iterator* iter = meta->NewIterator(BytewiseComparator());
  std::string key = "filter.";
  key.append(rep_->options.filter_policy->Name());
  iter->Seek(key);
  if (iter->Valid() && iter->key() == Slice(key)) {
    ReadFilter(iter->value());
  }
  delete iter;
  delete meta;
}

void Table::ReadFilter(const Slice& filter_handle_value) {
  Slice v = filter_handle_value;
  BlockHandle filter_handle;
  if (!filter_handle.DecodeFrom(&v).ok()) {
    return;
  }

  // We might want to unify with ReadBlock() if we start
  // requiring checksum verification in Table::Open.
  ReadOptions opt;
  if (rep_->options.paranoid_checks) {
    opt.verify_checksums = true;
  }
  BlockContents block;
  if (!ReadBlock(rep_->file, opt, filter_handle, &block).ok()) {
    return;
  }
  if (block.heap_allocated) {
    rep_->filter_data = block.data.data();  // Will need to delete later
  }
  rep_->filter = new FilterBlockReader(rep_->options.filter_policy, block.data);
}

Table::~Table() { delete rep_; }

static void DeleteBlock(void* arg, void* ignored) {
  delete reinterpret_cast<Block*>(arg);
}

static void DeleteCachedBlock(const Slice& key, void* value) {
  Block* block = reinterpret_cast<Block*>(value);
  delete block;
}

static void ReleaseBlock(void* arg, void* h) {
  Cache* cache = reinterpret_cast<Cache*>(arg);
  Cache::Handle* handle = reinterpret_cast<Cache::Handle*>(h);
  cache->Release(handle);
}

// Convert an index iterator value (i.e., an encoded BlockHandle)
// into an iterator over the contents of the corresponding block.
Iterator* Table::BlockReader(void* arg, const ReadOptions& options,
                             const Slice& index_value) {
  Table* table = reinterpret_cast<Table*>(arg);
  Cache* block_cache = table->rep_->options.block_cache;
  Block* block = nullptr;
  Cache::Handle* cache_handle = nullptr;

  BlockHandle handle;
  Slice input = index_value;
  Status s = handle.DecodeFrom(&input);
  // We intentionally allow extra stuff in index_value so that we
  // can add more features in the future.

  if (s.ok()) {
    BlockContents contents;
    if (block_cache != nullptr) {
      char cache_key_buffer[16];
      EncodeFixed64(cache_key_buffer, table->rep_->cache_id);
      EncodeFixed64(cache_key_buffer + 8, handle.offset());
      Slice key(cache_key_buffer, sizeof(cache_key_buffer));
      cache_handle = block_cache->Lookup(key);
      if (cache_handle != nullptr) {
        block = reinterpret_cast<Block*>(block_cache->Value(cache_handle));
      } else {
        s = ReadBlock(table->rep_->file, options, handle, &contents);
        if (s.ok()) {
          block = new Block(contents);
          if (contents.cachable && options.fill_cache) {
            cache_handle = block_cache->Insert(key, block, block->size(),
                                               &DeleteCachedBlock);
          }
        }
      }
    } else {
      s = ReadBlock(table->rep_->file, options, handle, &contents);
      if (s.ok()) {
        block = new Block(contents);
      }
    }
  }

  Iterator* iter;
  if (block != nullptr) {
    iter = block->NewIterator(table->rep_->options.comparator);
    if (cache_handle == nullptr) {
      iter->RegisterCleanup(&DeleteBlock, block, nullptr);
    } else {
      iter->RegisterCleanup(&ReleaseBlock, block_cache, cache_handle);
    }
  } else {
    iter = NewErrorIterator(s);
  }
  return iter;
}

Iterator* Table::NewIterator(const ReadOptions& options) const {
  return NewTwoLevelIterator(
      rep_->index_block->NewIterator(rep_->options.comparator),
      &Table::BlockReader, const_cast<Table*>(this), options);
}

// Status Table::InternalGet(const ReadOptions& options, const Slice& k, void* arg,
//                           void (*handle_result)(void*, const Slice&,
//                                                 const Slice&)) {
//   Status s;
//   Iterator* iiter = rep_->index_block->NewIterator(rep_->options.comparator);
//   iiter->Seek(k);
//   if (iiter->Valid()) {
//     Slice handle_value = iiter->value();
//     FilterBlockReader* filter = rep_->filter;
//     BlockHandle handle;
//     if (filter != nullptr && handle.DecodeFrom(&handle_value).ok() &&
//         !filter->KeyMayMatch(handle.offset(), k)) {
//       // Not found
//     } else {
//       Iterator* block_iter = BlockReader(this, options, iiter->value());
//       block_iter->Seek(k);
//       if (block_iter->Valid()) {
//         (*handle_result)(arg, block_iter->key(), block_iter->value());
//       }
//       s = block_iter->status();
//       delete block_iter;
//     }
//   }
//   if (s.ok()) {
//     s = iiter->status();
//   }
//   delete iiter;
//   return s;
// }
Status Table::InternalGet(const ReadOptions& options, const Slice& k, void* arg,
                          void (*handle_result)(void*, const Slice&,
                                                const Slice&)) {
    Status s;
    Iterator* iiter = rep_->index_block->NewIterator(rep_->options.comparator);
    iiter->Seek(k);
    if (iiter->Valid()) {
        Slice handle_value = iiter->value();
        FilterBlockReader* filter = rep_->filter;
        BlockHandle handle;
        if (filter != nullptr && handle.DecodeFrom(&handle_value).ok() &&
            !filter->KeyMayMatch(handle.offset(), k)) {
            // Not found
        } else {
            Iterator* block_iter = BlockReader(this, options, iiter->value());
            block_iter->Seek(k);
            if (block_iter->Valid()) {
                // 这里获取存储的组合字符串
                s = Status::OK();  // 确保状态为 OK
                Slice combined_value = block_iter->value();
                
                // 获取实际的值和过期时间
                std::string combined_str = combined_value.ToString();
                
                // 假设过期时间是字符串的最后19个字符
                std::string expiration_time_str = combined_str.substr(combined_str.size() - 19, 19); // 获取过期时间字符串
                std::string actual_value = combined_str.substr(0, combined_str.size() - 19); // 获取实际值
                
                // 解析过期时间为时间戳
                std::tm tm = {};
                std::istringstream ss(expiration_time_str);
                ss >> std::get_time(&tm, "%Y-%m-%d %H:%M:%S");
                std::time_t expiration_time = std::mktime(&tm);

                // 获取当前时间并与过期时间进行比较
                auto now = std::chrono::system_clock::now();
                auto now_time_t = std::chrono::system_clock::to_time_t(now);
                
                // 检查是否过期
                if (expiration_time > now_time_t) {
                    // 调用结果处理函数，返回实际值
                    (*handle_result)(arg, block_iter->key(), Slice(actual_value));//, Slice(expiration_time_str));
                    s = block_iter->status();
                    if (! s.ok()) printf("291\n");
                } else {
                    // 数据已过期，处理过期情况
                    s = Status::NotFound("Key has expired");
                }
            }
            else {
              s = block_iter->status();
              if (! s.ok()) printf("299\n");
            }
            delete block_iter;
        }
    }
    if (s.ok()) {
        s = iiter->status();
        if (! s.ok()) printf("306\n");
    }
    delete iiter;
    if (! s.ok()) printf("!!!!!!!!!!!"); // 如果不在sstable里
    return s;
}


uint64_t Table::ApproximateOffsetOf(const Slice& key) const {
  Iterator* index_iter =
      rep_->index_block->NewIterator(rep_->options.comparator);
  index_iter->Seek(key);
  uint64_t result;
  if (index_iter->Valid()) {
    BlockHandle handle;
    Slice input = index_iter->value();
    Status s = handle.DecodeFrom(&input);
    if (s.ok()) {
      result = handle.offset();
    } else {
      // Strange: we can't decode the block handle in the index block.
      // We'll just return the offset of the metaindex block, which is
      // close to the whole file size for this case.
      result = rep_->metaindex_handle.offset();
    }
  } else {
    // key is past the last key in the file.  Approximate the offset
    // by returning the offset of the metaindex block (which is
    // right near the end of the file).
    result = rep_->metaindex_handle.offset();
  }
  delete index_iter;
  return result;
}

}  // namespace leveldb