src/dbwrapper.h

   1 // Copyright (c) 2012-2016 The Bitcoin Core developers
   2 // Distributed under the MIT software license, see the accompanying
   3 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
   4
   5 #ifndef BITCOIN_DBWRAPPER_H
   6 #define BITCOIN_DBWRAPPER_H
   7
   8 #include "clientversion.h"
   9 #include "fs.h"
  10 #include "serialize.h"
  11 #include "streams.h"
  12 #include "util.h"
  13 #include "utilstrencodings.h"
  14 #include "version.h"
  15
  16 #include <leveldb/db.h>
  17 #include <leveldb/write_batch.h>
  18
  19 static const size_t DBWRAPPER_PREALLOC_KEY_SIZE = 64;
  20 static const size_t DBWRAPPER_PREALLOC_VALUE_SIZE = 1024;
  21
  22 class dbwrapper_error : public std::runtime_error
  23 {
  24 public:
  25     dbwrapper_error(const std::string& msg) : std::runtime_error(msg) {}
  26 };
  27
  28 class CDBWrapper;
  29
  30 /** These should be considered an implementation detail of the specific database.
  31  */
  32 namespace dbwrapper_private {
  33
  34 /** Handle database error by throwing dbwrapper_error exception.
  35  */
  36 void HandleError(const leveldb::Status& status);
  37
  38 /** Work around circular dependency, as well as for testing in dbwrapper_tests.
  39  * Database obfuscation should be considered an implementation detail of the
  40  * specific database.
  41  */
  42 const std::vector<unsigned char>& GetObfuscateKey(const CDBWrapper &w);
  43
  44 };
  45
  46 /** Batch of changes queued to be written to a CDBWrapper */
  47 class CDBBatch
  48 {
  49     friend class CDBWrapper;
  50
  51 private:
  52     const CDBWrapper &parent;
  53     leveldb::WriteBatch batch;
  54
  55     CDataStream ssKey;
  56     CDataStream ssValue;
  57
  58     size_t size_estimate;
  59
  60 public:
  61     /**
  62      * @param[in] _parent   CDBWrapper that this batch is to be submitted to
  63      */
  64     CDBBatch(const CDBWrapper &_parent) : parent(_parent), ssKey(SER_DISK, CLIENT_VERSION), ssValue(SER_DISK, CLIENT_VERSION), size_estimate(0) { };
  65
  66     void Clear()
  67     {
  68         batch.Clear();
  69         size_estimate = 0;
  70     }
  71
  72     template <typename K, typename V>
  73     void Write(const K& key, const V& value)
  74     {
  75         ssKey.reserve(DBWRAPPER_PREALLOC_KEY_SIZE);
  76         ssKey << key;
  77         leveldb::Slice slKey(ssKey.data(), ssKey.size());
  78
  79         ssValue.reserve(DBWRAPPER_PREALLOC_VALUE_SIZE);
  80         ssValue << value;
  81         ssValue.Xor(dbwrapper_private::GetObfuscateKey(parent));
  82         leveldb::Slice slValue(ssValue.data(), ssValue.size());
  83
  84         batch.Put(slKey, slValue);
  85         // LevelDB serializes writes as:
  86         // - byte: header
  87         // - varint: key length (1 byte up to 127B, 2 bytes up to 16383B, ...)
  88         // - byte[]: key
  89         // - varint: value length
  90         // - byte[]: value
  91         // The formula below assumes the key and value are both less than 16k.
  92         size_estimate += 3 + (slKey.size() > 127) + slKey.size() + (slValue.size() > 127) + slValue.size();
  93         ssKey.clear();
  94         ssValue.clear();
  95     }
  96
  97     template <typename K>
  98     void Erase(const K& key)
  99     {
 100         ssKey.reserve(DBWRAPPER_PREALLOC_KEY_SIZE);
 101         ssKey << key;
 102         leveldb::Slice slKey(ssKey.data(), ssKey.size());
 103
 104         batch.Delete(slKey);
 105         // LevelDB serializes erases as:
 106         // - byte: header
 107         // - varint: key length
 108         // - byte[]: key
 109         // The formula below assumes the key is less than 16kB.
 110         size_estimate += 2 + (slKey.size() > 127) + slKey.size();
 111         ssKey.clear();
 112     }
 113
 114     size_t SizeEstimate() const { return size_estimate; }
 115 };
 116
 117 class CDBIterator
 118 {
 119 private:
 120     const CDBWrapper &parent;
 121     leveldb::Iterator *piter;
 122
 123 public:
 124
 125     /**
 126      * @param[in] _parent          Parent CDBWrapper instance.
 127      * @param[in] _piter           The original leveldb iterator.
 128      */
 129     CDBIterator(const CDBWrapper &_parent, leveldb::Iterator *_piter) :
 130         parent(_parent), piter(_piter) { };
 131     ~CDBIterator();
 132
 133     bool Valid() const;
 134
 135     void SeekToFirst();
 136
 137     template<typename K> void Seek(const K& key) {
 138         CDataStream ssKey(SER_DISK, CLIENT_VERSION);
 139         ssKey.reserve(DBWRAPPER_PREALLOC_KEY_SIZE);
 140         ssKey << key;
 141         leveldb::Slice slKey(ssKey.data(), ssKey.size());
 142         piter->Seek(slKey);
 143     }
 144
 145     void Next();
 146
 147     template<typename K> bool GetKey(K& key) {
 148         leveldb::Slice slKey = piter->key();
 149         try {
 150             CDataStream ssKey(slKey.data(), slKey.data() + slKey.size(), SER_DISK, CLIENT_VERSION);
 151             ssKey >> key;
 152         } catch (const std::exception&) {
 153             return false;
 154         }
 155         return true;
 156     }
 157
 158     template<typename V> bool GetValue(V& value) {
 159         leveldb::Slice slValue = piter->value();
 160         try {
 161             CDataStream ssValue(slValue.data(), slValue.data() + slValue.size(), SER_DISK, CLIENT_VERSION);
 162             ssValue.Xor(dbwrapper_private::GetObfuscateKey(parent));
 163             ssValue >> value;
 164         } catch (const std::exception&) {
 165             return false;
 166         }
 167         return true;
 168     }
 169
 170     unsigned int GetValueSize() {
 171         return piter->value().size();
 172     }
 173
 174 };
 175
 176 class CDBWrapper
 177 {
 178     friend const std::vector<unsigned char>& dbwrapper_private::GetObfuscateKey(const CDBWrapper &w);
 179 private:
 180     //! custom environment this database is using (may be NULL in case of default environment)
 181     leveldb::Env* penv;
 182
 183     //! database options used
 184     leveldb::Options options;
 185
 186     //! options used when reading from the database
 187     leveldb::ReadOptions readoptions;
 188
 189     //! options used when iterating over values of the database
 190     leveldb::ReadOptions iteroptions;
 191
 192     //! options used when writing to the database
 193     leveldb::WriteOptions writeoptions;
 194
 195     //! options used when sync writing to the database
 196     leveldb::WriteOptions syncoptions;
 197
 198     //! the database itself
 199     leveldb::DB* pdb;
 200
 201     //! a key used for optional XOR-obfuscation of the database
 202     std::vector<unsigned char> obfuscate_key;
 203
 204     //! the key under which the obfuscation key is stored
 205     static const std::string OBFUSCATE_KEY_KEY;
 206
 207     //! the length of the obfuscate key in number of bytes
 208     static const unsigned int OBFUSCATE_KEY_NUM_BYTES;
 209
 210     std::vector<unsigned char> CreateObfuscateKey() const;
 211
 212 public:
 213     /**
 214      * @param[in] path        Location in the filesystem where leveldb data will be stored.
 215      * @param[in] nCacheSize  Configures various leveldb cache settings.
 216      * @param[in] fMemory     If true, use leveldb's memory environment.
 217      * @param[in] fWipe       If true, remove all existing data.
 218      * @param[in] obfuscate   If true, store data obfuscated via simple XOR. If false, XOR
 219      *                        with a zero'd byte array.
 220      */
 221     CDBWrapper(const fs::path& path, size_t nCacheSize, bool fMemory = false, bool fWipe = false, bool obfuscate = false);
 222     ~CDBWrapper();
 223
 224     template <typename K, typename V>
 225     bool Read(const K& key, V& value) const
 226     {
 227         CDataStream ssKey(SER_DISK, CLIENT_VERSION);
 228         ssKey.reserve(DBWRAPPER_PREALLOC_KEY_SIZE);
 229         ssKey << key;
 230         leveldb::Slice slKey(ssKey.data(), ssKey.size());
 231
 232         std::string strValue;
 233         leveldb::Status status = pdb->Get(readoptions, slKey, &strValue);
 234         if (!status.ok()) {
 235             if (status.IsNotFound())
 236                 return false;
 237             LogPrintf("LevelDB read failure: %s\n", status.ToString());
 238             dbwrapper_private::HandleError(status);
 239         }
 240         try {
 241             CDataStream ssValue(strValue.data(), strValue.data() + strValue.size(), SER_DISK, CLIENT_VERSION);
 242             ssValue.Xor(obfuscate_key);
 243             ssValue >> value;
 244         } catch (const std::exception&) {
 245             return false;
 246         }
 247         return true;
 248     }
 249
 250     template <typename K, typename V>
 251     bool Write(const K& key, const V& value, bool fSync = false)
 252     {
 253         CDBBatch batch(*this);
 254         batch.Write(key, value);
 255         return WriteBatch(batch, fSync);
 256     }
 257
 258     template <typename K>
 259     bool Exists(const K& key) const
 260     {
 261         CDataStream ssKey(SER_DISK, CLIENT_VERSION);
 262         ssKey.reserve(DBWRAPPER_PREALLOC_KEY_SIZE);
 263         ssKey << key;
 264         leveldb::Slice slKey(ssKey.data(), ssKey.size());
 265
 266         std::string strValue;
 267         leveldb::Status status = pdb->Get(readoptions, slKey, &strValue);
 268         if (!status.ok()) {
 269             if (status.IsNotFound())
 270                 return false;
 271             LogPrintf("LevelDB read failure: %s\n", status.ToString());
 272             dbwrapper_private::HandleError(status);
 273         }
 274         return true;
 275     }
 276
 277     template <typename K>
 278     bool Erase(const K& key, bool fSync = false)
 279     {
 280         CDBBatch batch(*this);
 281         batch.Erase(key);
 282         return WriteBatch(batch, fSync);
 283     }
 284
 285     bool WriteBatch(CDBBatch& batch, bool fSync = false);
 286
 287     // not available for LevelDB; provide for compatibility with BDB
 288     bool Flush()
 289     {
 290         return true;
 291     }
 292
 293     bool Sync()
 294     {
 295         CDBBatch batch(*this);
 296         return WriteBatch(batch, true);
 297     }
 298
 299     CDBIterator *NewIterator()
 300     {
 301         return new CDBIterator(*this, pdb->NewIterator(iteroptions));
 302     }
 303
 304     /**
 305      * Return true if the database managed by this class contains no entries.
 306      */
 307     bool IsEmpty();
 308
 309     template<typename K>
 310     size_t EstimateSize(const K& key_begin, const K& key_end) const
 311     {
 312         CDataStream ssKey1(SER_DISK, CLIENT_VERSION), ssKey2(SER_DISK, CLIENT_VERSION);
 313         ssKey1.reserve(DBWRAPPER_PREALLOC_KEY_SIZE);
 314         ssKey2.reserve(DBWRAPPER_PREALLOC_KEY_SIZE);
 315         ssKey1 << key_begin;
 316         ssKey2 << key_end;
 317         leveldb::Slice slKey1(ssKey1.data(), ssKey1.size());
 318         leveldb::Slice slKey2(ssKey2.data(), ssKey2.size());
 319         uint64_t size = 0;
 320         leveldb::Range range(slKey1, slKey2);
 321         pdb->GetApproximateSizes(&range, 1, &size);
 322         return size;
 323     }
 324 };
 325
 326 #endif // BITCOIN_DBWRAPPER_H