You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
198 lines
6.8 KiB
198 lines
6.8 KiB
// 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 "include/comparator.h"
|
|
#include "include/db.h"
|
|
#include "include/slice.h"
|
|
#include "include/table_builder.h"
|
|
#include "util/coding.h"
|
|
#include "util/logging.h"
|
|
|
|
namespace leveldb {
|
|
|
|
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,
|
|
kTypeLargeValueRef = 0x2,
|
|
};
|
|
// 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 = kTypeLargeValueRef;
|
|
|
|
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;
|
|
};
|
|
|
|
// 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(); }
|
|
};
|
|
|
|
inline int InternalKeyComparator::Compare(
|
|
const InternalKey& a, const InternalKey& b) const {
|
|
return Compare(a.Encode(), b.Encode());
|
|
}
|
|
|
|
// LargeValueRef is a 160-bit hash value (20 bytes), plus an 8 byte
|
|
// uncompressed size, and a 1 byte CompressionType code. An
|
|
// encoded form of it is embedded in the filenames of large value
|
|
// files stored in the database, and the raw binary form is stored as
|
|
// the iter->value() result for values of type kTypeLargeValueRef in
|
|
// the table and log files that make up the database.
|
|
struct LargeValueRef {
|
|
char data[29];
|
|
|
|
// Initialize a large value ref for the given data
|
|
static LargeValueRef Make(const Slice& data,
|
|
CompressionType compression_type);
|
|
|
|
// Initialize a large value ref from a serialized, 29-byte reference value
|
|
static LargeValueRef FromRef(const Slice& ref) {
|
|
LargeValueRef result;
|
|
assert(ref.size() == sizeof(result.data));
|
|
memcpy(result.data, ref.data(), sizeof(result.data));
|
|
return result;
|
|
}
|
|
|
|
// Return the number of bytes in a LargeValueRef (not the
|
|
// number of bytes in the value referenced).
|
|
static size_t ByteSize() { return sizeof(LargeValueRef().data); }
|
|
|
|
// Return the number of bytes in the value referenced by "*this".
|
|
uint64_t ValueSize() const { return DecodeFixed64(&data[20]); }
|
|
|
|
CompressionType compression_type() const {
|
|
return static_cast<CompressionType>(data[28]);
|
|
}
|
|
|
|
bool operator==(const LargeValueRef& b) const {
|
|
return memcmp(data, b.data, sizeof(data)) == 0;
|
|
}
|
|
bool operator<(const LargeValueRef& b) const {
|
|
return memcmp(data, b.data, sizeof(data)) < 0;
|
|
}
|
|
};
|
|
|
|
// Convert the large value ref to a human-readable string suitable
|
|
// for embedding in a large value filename.
|
|
extern std::string LargeValueRefToFilenameString(const LargeValueRef& h);
|
|
|
|
// Parse the large value filename string in "input" and store it in
|
|
// "*h". If successful, returns true. Otherwise returns false.
|
|
extern bool FilenameStringToLargeValueRef(const Slice& in, LargeValueRef* ref);
|
|
|
|
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>(kTypeLargeValueRef));
|
|
}
|
|
|
|
}
|
|
|
|
#endif // STORAGE_LEVELDB_DB_FORMAT_H_
|