1  // Copyright (c) 2011 The LevelDB Authors. All rights reserved.
  2  // Use of this source code is governed by a BSD-style license that can be
  3  // found in the LICENSE file. See the AUTHORS file for names of contributors.
  4  
  5  #include "db/dbformat.h"
  6  
  7  #include <stdio.h>
  8  
  9  #include <sstream>
 10  
 11  #include "port/port.h"
 12  #include "util/coding.h"
 13  
 14  namespace leveldb {
 15  
 16  static uint64_t PackSequenceAndType(uint64_t seq, ValueType t) {
 17    assert(seq <= kMaxSequenceNumber);
 18    assert(t <= kValueTypeForSeek);
 19    return (seq << 8) | t;
 20  }
 21  
 22  void AppendInternalKey(std::string* result, const ParsedInternalKey& key) {
 23    result->append(key.user_key.data(), key.user_key.size());
 24    PutFixed64(result, PackSequenceAndType(key.sequence, key.type));
 25  }
 26  
 27  std::string ParsedInternalKey::DebugString() const {
 28    std::ostringstream ss;
 29    ss << '\'' << EscapeString(user_key.ToString()) << "' @ " << sequence << " : "
 30       << static_cast<int>(type);
 31    return ss.str();
 32  }
 33  
 34  std::string InternalKey::DebugString() const {
 35    ParsedInternalKey parsed;
 36    if (ParseInternalKey(rep_, &parsed)) {
 37      return parsed.DebugString();
 38    }
 39    std::ostringstream ss;
 40    ss << "(bad)" << EscapeString(rep_);
 41    return ss.str();
 42  }
 43  
 44  const char* InternalKeyComparator::Name() const {
 45    return "leveldb.InternalKeyComparator";
 46  }
 47  
 48  int InternalKeyComparator::Compare(const Slice& akey, const Slice& bkey) const {
 49    // Order by:
 50    //    increasing user key (according to user-supplied comparator)
 51    //    decreasing sequence number
 52    //    decreasing type (though sequence# should be enough to disambiguate)
 53    int r = user_comparator_->Compare(ExtractUserKey(akey), ExtractUserKey(bkey));
 54    if (r == 0) {
 55      const uint64_t anum = DecodeFixed64(akey.data() + akey.size() - 8);
 56      const uint64_t bnum = DecodeFixed64(bkey.data() + bkey.size() - 8);
 57      if (anum > bnum) {
 58        r = -1;
 59      } else if (anum < bnum) {
 60        r = +1;
 61      }
 62    }
 63    return r;
 64  }
 65  
 66  void InternalKeyComparator::FindShortestSeparator(std::string* start,
 67                                                    const Slice& limit) const {
 68    // Attempt to shorten the user portion of the key
 69    Slice user_start = ExtractUserKey(*start);
 70    Slice user_limit = ExtractUserKey(limit);
 71    std::string tmp(user_start.data(), user_start.size());
 72    user_comparator_->FindShortestSeparator(&tmp, user_limit);
 73    if (tmp.size() < user_start.size() &&
 74        user_comparator_->Compare(user_start, tmp) < 0) {
 75      // User key has become shorter physically, but larger logically.
 76      // Tack on the earliest possible number to the shortened user key.
 77      PutFixed64(&tmp,
 78                 PackSequenceAndType(kMaxSequenceNumber, kValueTypeForSeek));
 79      assert(this->Compare(*start, tmp) < 0);
 80      assert(this->Compare(tmp, limit) < 0);
 81      start->swap(tmp);
 82    }
 83  }
 84  
 85  void InternalKeyComparator::FindShortSuccessor(std::string* key) const {
 86    Slice user_key = ExtractUserKey(*key);
 87    std::string tmp(user_key.data(), user_key.size());
 88    user_comparator_->FindShortSuccessor(&tmp);
 89    if (tmp.size() < user_key.size() &&
 90        user_comparator_->Compare(user_key, tmp) < 0) {
 91      // User key has become shorter physically, but larger logically.
 92      // Tack on the earliest possible number to the shortened user key.
 93      PutFixed64(&tmp,
 94                 PackSequenceAndType(kMaxSequenceNumber, kValueTypeForSeek));
 95      assert(this->Compare(*key, tmp) < 0);
 96      key->swap(tmp);
 97    }
 98  }
 99  
100  const char* InternalFilterPolicy::Name() const { return user_policy_->Name(); }
101  
102  void InternalFilterPolicy::CreateFilter(const Slice* keys, int n,
103                                          std::string* dst) const {
104    // We rely on the fact that the code in table.cc does not mind us
105    // adjusting keys[].
106    Slice* mkey = const_cast<Slice*>(keys);
107    for (int i = 0; i < n; i++) {
108      mkey[i] = ExtractUserKey(keys[i]);
109      // TODO(sanjay): Suppress dups?
110    }
111    user_policy_->CreateFilter(keys, n, dst);
112  }
113  
114  bool InternalFilterPolicy::KeyMayMatch(const Slice& key, const Slice& f) const {
115    return user_policy_->KeyMayMatch(ExtractUserKey(key), f);
116  }
117  
118  LookupKey::LookupKey(const Slice& user_key, SequenceNumber s) {
119    size_t usize = user_key.size();
120    size_t needed = usize + 13;  // A conservative estimate
121    char* dst;
122    if (needed <= sizeof(space_)) {
123      dst = space_;
124    } else {
125      dst = new char[needed];
126    }
127    start_ = dst;
128    dst = EncodeVarint32(dst, usize + 8);
129    kstart_ = dst;
130    memcpy(dst, user_key.data(), usize);
131    dst += usize;
132    EncodeFixed64(dst, PackSequenceAndType(s, kValueTypeForSeek));
133    dst += 8;
134    end_ = dst;
135  }
136  
137  }  // namespace leveldb