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Diffstat (limited to 'src/leveldb/db/dbformat.h')
-rw-r--r-- | src/leveldb/db/dbformat.h | 227 |
1 files changed, 0 insertions, 227 deletions
diff --git a/src/leveldb/db/dbformat.h b/src/leveldb/db/dbformat.h deleted file mode 100644 index f7f64dafb6..0000000000 --- a/src/leveldb/db/dbformat.h +++ /dev/null @@ -1,227 +0,0 @@ -// 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. - -#ifndef STORAGE_LEVELDB_DB_FORMAT_H_ -#define STORAGE_LEVELDB_DB_FORMAT_H_ - -#include <stdio.h> -#include "leveldb/comparator.h" -#include "leveldb/db.h" -#include "leveldb/filter_policy.h" -#include "leveldb/slice.h" -#include "leveldb/table_builder.h" -#include "util/coding.h" -#include "util/logging.h" - -namespace leveldb { - -// Grouping of constants. We may want to make some of these -// parameters set via options. -namespace config { -static const int kNumLevels = 7; - -// Level-0 compaction is started when we hit this many files. -static const int kL0_CompactionTrigger = 4; - -// Soft limit on number of level-0 files. We slow down writes at this point. -static const int kL0_SlowdownWritesTrigger = 8; - -// Maximum number of level-0 files. We stop writes at this point. -static const int kL0_StopWritesTrigger = 12; - -// Maximum level to which a new compacted memtable is pushed if it -// does not create overlap. We try to push to level 2 to avoid the -// relatively expensive level 0=>1 compactions and to avoid some -// expensive manifest file operations. We do not push all the way to -// the largest level since that can generate a lot of wasted disk -// space if the same key space is being repeatedly overwritten. -static const int kMaxMemCompactLevel = 2; - -} // namespace config - -class InternalKey; - -// Value types encoded as the last component of internal keys. -// DO NOT CHANGE THESE ENUM VALUES: they are embedded in the on-disk -// data structures. -enum ValueType { - kTypeDeletion = 0x0, - kTypeValue = 0x1 -}; -// kValueTypeForSeek defines the ValueType that should be passed when -// constructing a ParsedInternalKey object for seeking to a particular -// sequence number (since we sort sequence numbers in decreasing order -// and the value type is embedded as the low 8 bits in the sequence -// number in internal keys, we need to use the highest-numbered -// ValueType, not the lowest). -static const ValueType kValueTypeForSeek = kTypeValue; - -typedef uint64_t SequenceNumber; - -// We leave eight bits empty at the bottom so a type and sequence# -// can be packed together into 64-bits. -static const SequenceNumber kMaxSequenceNumber = - ((0x1ull << 56) - 1); - -struct ParsedInternalKey { - Slice user_key; - SequenceNumber sequence; - ValueType type; - - ParsedInternalKey() { } // Intentionally left uninitialized (for speed) - ParsedInternalKey(const Slice& u, const SequenceNumber& seq, ValueType t) - : user_key(u), sequence(seq), type(t) { } - std::string DebugString() const; -}; - -// Return the length of the encoding of "key". -inline size_t InternalKeyEncodingLength(const ParsedInternalKey& key) { - return key.user_key.size() + 8; -} - -// Append the serialization of "key" to *result. -extern void AppendInternalKey(std::string* result, - const ParsedInternalKey& key); - -// Attempt to parse an internal key from "internal_key". On success, -// stores the parsed data in "*result", and returns true. -// -// On error, returns false, leaves "*result" in an undefined state. -extern bool ParseInternalKey(const Slice& internal_key, - ParsedInternalKey* result); - -// Returns the user key portion of an internal key. -inline Slice ExtractUserKey(const Slice& internal_key) { - assert(internal_key.size() >= 8); - return Slice(internal_key.data(), internal_key.size() - 8); -} - -inline ValueType ExtractValueType(const Slice& internal_key) { - assert(internal_key.size() >= 8); - const size_t n = internal_key.size(); - uint64_t num = DecodeFixed64(internal_key.data() + n - 8); - unsigned char c = num & 0xff; - return static_cast<ValueType>(c); -} - -// A comparator for internal keys that uses a specified comparator for -// the user key portion and breaks ties by decreasing sequence number. -class InternalKeyComparator : public Comparator { - private: - const Comparator* user_comparator_; - public: - explicit InternalKeyComparator(const Comparator* c) : user_comparator_(c) { } - virtual const char* Name() const; - virtual int Compare(const Slice& a, const Slice& b) const; - virtual void FindShortestSeparator( - std::string* start, - const Slice& limit) const; - virtual void FindShortSuccessor(std::string* key) const; - - const Comparator* user_comparator() const { return user_comparator_; } - - int Compare(const InternalKey& a, const InternalKey& b) const; -}; - -// Filter policy wrapper that converts from internal keys to user keys -class InternalFilterPolicy : public FilterPolicy { - private: - const FilterPolicy* const user_policy_; - public: - explicit InternalFilterPolicy(const FilterPolicy* p) : user_policy_(p) { } - virtual const char* Name() const; - virtual void CreateFilter(const Slice* keys, int n, std::string* dst) const; - virtual bool KeyMayMatch(const Slice& key, const Slice& filter) const; -}; - -// Modules in this directory should keep internal keys wrapped inside -// the following class instead of plain strings so that we do not -// incorrectly use string comparisons instead of an InternalKeyComparator. -class InternalKey { - private: - std::string rep_; - public: - InternalKey() { } // Leave rep_ as empty to indicate it is invalid - InternalKey(const Slice& user_key, SequenceNumber s, ValueType t) { - AppendInternalKey(&rep_, ParsedInternalKey(user_key, s, t)); - } - - void DecodeFrom(const Slice& s) { rep_.assign(s.data(), s.size()); } - Slice Encode() const { - assert(!rep_.empty()); - return rep_; - } - - Slice user_key() const { return ExtractUserKey(rep_); } - - void SetFrom(const ParsedInternalKey& p) { - rep_.clear(); - AppendInternalKey(&rep_, p); - } - - void Clear() { rep_.clear(); } - - std::string DebugString() const; -}; - -inline int InternalKeyComparator::Compare( - const InternalKey& a, const InternalKey& b) const { - return Compare(a.Encode(), b.Encode()); -} - -inline bool ParseInternalKey(const Slice& internal_key, - ParsedInternalKey* result) { - const size_t n = internal_key.size(); - if (n < 8) return false; - uint64_t num = DecodeFixed64(internal_key.data() + n - 8); - unsigned char c = num & 0xff; - result->sequence = num >> 8; - result->type = static_cast<ValueType>(c); - result->user_key = Slice(internal_key.data(), n - 8); - return (c <= static_cast<unsigned char>(kTypeValue)); -} - -// A helper class useful for DBImpl::Get() -class LookupKey { - public: - // Initialize *this for looking up user_key at a snapshot with - // the specified sequence number. - LookupKey(const Slice& user_key, SequenceNumber sequence); - - ~LookupKey(); - - // Return a key suitable for lookup in a MemTable. - Slice memtable_key() const { return Slice(start_, end_ - start_); } - - // Return an internal key (suitable for passing to an internal iterator) - Slice internal_key() const { return Slice(kstart_, end_ - kstart_); } - - // Return the user key - Slice user_key() const { return Slice(kstart_, end_ - kstart_ - 8); } - - private: - // We construct a char array of the form: - // klength varint32 <-- start_ - // userkey char[klength] <-- kstart_ - // tag uint64 - // <-- end_ - // The array is a suitable MemTable key. - // The suffix starting with "userkey" can be used as an InternalKey. - const char* start_; - const char* kstart_; - const char* end_; - char space_[200]; // Avoid allocation for short keys - - // No copying allowed - LookupKey(const LookupKey&); - void operator=(const LookupKey&); -}; - -inline LookupKey::~LookupKey() { - if (start_ != space_) delete[] start_; -} - -} // namespace leveldb - -#endif // STORAGE_LEVELDB_DB_FORMAT_H_ |