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修改部分readme文件
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‎db/dbformat.cc

Lines changed: 119 additions & 119 deletions
Original file line numberDiff line numberDiff line change
@@ -12,125 +12,125 @@
1212

1313
namespace leveldb {
1414

15-
static uint64_t PackSequenceAndType(uint64_t seq, ValueType t) {
16-
assert(seq <= kMaxSequenceNumber);
17-
assert(t <= kValueTypeForSeek);
18-
return (seq << 8) | t;
19-
}
20-
21-
void AppendInternalKey(std::string* result, const ParsedInternalKey& key) {
22-
result->append(key.user_key.data(), key.user_key.size());
23-
PutFixed64(result, PackSequenceAndType(key.sequence, key.type));
24-
}
25-
26-
std::string ParsedInternalKey::DebugString() const {
27-
std::ostringstream ss;
28-
ss << '\'' << EscapeString(user_key.ToString()) << "' @ " << sequence << " : "
29-
<< static_cast<int>(type);
30-
return ss.str();
31-
}
32-
33-
std::string InternalKey::DebugString() const {
34-
ParsedInternalKey parsed;
35-
if (ParseInternalKey(rep_, &parsed)) {
36-
return parsed.DebugString();
37-
}
38-
std::ostringstream ss;
39-
ss << "(bad)" << EscapeString(rep_);
40-
return ss.str();
41-
}
42-
43-
const char* InternalKeyComparator::Name() const {
44-
return "leveldb.InternalKeyComparator";
45-
}
46-
47-
int InternalKeyComparator::Compare(const Slice& akey, const Slice& bkey) const {
48-
// Order by:
49-
// increasing user key (according to user-supplied comparator)
50-
// decreasing sequence number
51-
// decreasing type (though sequence# should be enough to disambiguate)
52-
int r = user_comparator_->Compare(ExtractUserKey(akey), ExtractUserKey(bkey));
53-
if (r == 0) {
54-
const uint64_t anum = DecodeFixed64(akey.data() + akey.size() - 8);
55-
const uint64_t bnum = DecodeFixed64(bkey.data() + bkey.size() - 8);
56-
if (anum > bnum) {
57-
r = -1;
58-
} else if (anum < bnum) {
59-
r = +1;
15+
static uint64_t PackSequenceAndType(uint64_t seq, ValueType t) {
16+
assert(seq <= kMaxSequenceNumber);
17+
assert(t <= kValueTypeForSeek);
18+
return (seq << 8) | t;
19+
}
20+
21+
void AppendInternalKey(std::string *result, const ParsedInternalKey &key) {
22+
result->append(key.user_key.data(), key.user_key.size());
23+
PutFixed64(result, PackSequenceAndType(key.sequence, key.type));
24+
}
25+
26+
std::string ParsedInternalKey::DebugString() const {
27+
std::ostringstream ss;
28+
ss << '\'' << EscapeString(user_key.ToString()) << "' @ " << sequence << " : "
29+
<< static_cast<int>(type);
30+
return ss.str();
31+
}
32+
33+
std::string InternalKey::DebugString() const {
34+
ParsedInternalKey parsed;
35+
if (ParseInternalKey(rep_, &parsed)) {
36+
return parsed.DebugString();
37+
}
38+
std::ostringstream ss;
39+
ss << "(bad)" << EscapeString(rep_);
40+
return ss.str();
41+
}
42+
43+
const char *InternalKeyComparator::Name() const {
44+
return "leveldb.InternalKeyComparator";
45+
}
46+
47+
int InternalKeyComparator::Compare(const Slice &akey, const Slice &bkey) const {
48+
// Order by:
49+
// increasing user key (according to user-supplied comparator)
50+
// decreasing sequence number
51+
// decreasing type (though sequence# should be enough to disambiguate)
52+
int r = user_comparator_->Compare(ExtractUserKey(akey), ExtractUserKey(bkey));
53+
if (r == 0) {
54+
const uint64_t anum = DecodeFixed64(akey.data() + akey.size() - 8);
55+
const uint64_t bnum = DecodeFixed64(bkey.data() + bkey.size() - 8);
56+
if (anum > bnum) {
57+
r = -1;
58+
} else if (anum < bnum) {
59+
r = +1;
60+
}
61+
}
62+
return r;
63+
}
64+
65+
void InternalKeyComparator::FindShortestSeparator(std::string *start,
66+
const Slice &limit) const {
67+
// Attempt to shorten the user portion of the key
68+
Slice user_start = ExtractUserKey(*start);
69+
Slice user_limit = ExtractUserKey(limit);
70+
std::string tmp(user_start.data(), user_start.size());
71+
user_comparator_->FindShortestSeparator(&tmp, user_limit);
72+
if (tmp.size() < user_start.size() &&
73+
user_comparator_->Compare(user_start, tmp) < 0) {
74+
// User key has become shorter physically, but larger logically.
75+
// Tack on the earliest possible number to the shortened user key.
76+
PutFixed64(&tmp,
77+
PackSequenceAndType(kMaxSequenceNumber, kValueTypeForSeek));
78+
assert(this->Compare(*start, tmp) < 0);
79+
assert(this->Compare(tmp, limit) < 0);
80+
start->swap(tmp);
81+
}
82+
}
83+
84+
void InternalKeyComparator::FindShortSuccessor(std::string *key) const {
85+
Slice user_key = ExtractUserKey(*key);
86+
std::string tmp(user_key.data(), user_key.size());
87+
user_comparator_->FindShortSuccessor(&tmp);
88+
if (tmp.size() < user_key.size() &&
89+
user_comparator_->Compare(user_key, tmp) < 0) {
90+
// User key has become shorter physically, but larger logically.
91+
// Tack on the earliest possible number to the shortened user key.
92+
PutFixed64(&tmp,
93+
PackSequenceAndType(kMaxSequenceNumber, kValueTypeForSeek));
94+
assert(this->Compare(*key, tmp) < 0);
95+
key->swap(tmp);
96+
}
97+
}
98+
99+
const char *InternalFilterPolicy::Name() const { return user_policy_->Name(); }
100+
101+
void InternalFilterPolicy::CreateFilter(const Slice *keys, int n,
102+
std::string *dst) const {
103+
// We rely on the fact that the code in table.cc does not mind us
104+
// adjusting keys[].
105+
Slice *mkey = const_cast<Slice *>(keys);
106+
for (int i = 0; i < n; i++) {
107+
mkey[i] = ExtractUserKey(keys[i]);
108+
// TODO(sanjay): Suppress dups?
109+
}
110+
user_policy_->CreateFilter(keys, n, dst);
111+
}
112+
113+
bool InternalFilterPolicy::KeyMayMatch(const Slice &key, const Slice &f) const {
114+
return user_policy_->KeyMayMatch(ExtractUserKey(key), f);
115+
}
116+
117+
LookupKey::LookupKey(const Slice &user_key, SequenceNumber s) {
118+
size_t usize = user_key.size();
119+
size_t needed = usize + 13; // A conservative estimate
120+
char *dst;
121+
if (needed <= sizeof(space_)) {
122+
dst = space_;
123+
} else {
124+
dst = new char[needed];
125+
}
126+
start_ = dst;
127+
dst = EncodeVarint32(dst, usize + 8);
128+
kstart_ = dst;
129+
std::memcpy(dst, user_key.data(), usize);
130+
dst += usize;
131+
EncodeFixed64(dst, PackSequenceAndType(s, kValueTypeForSeek));
132+
dst += 8;
133+
end_ = dst;
60134
}
61-
}
62-
return r;
63-
}
64-
65-
void InternalKeyComparator::FindShortestSeparator(std::string* start,
66-
const Slice& limit) const {
67-
// Attempt to shorten the user portion of the key
68-
Slice user_start = ExtractUserKey(*start);
69-
Slice user_limit = ExtractUserKey(limit);
70-
std::string tmp(user_start.data(), user_start.size());
71-
user_comparator_->FindShortestSeparator(&tmp, user_limit);
72-
if (tmp.size() < user_start.size() &&
73-
user_comparator_->Compare(user_start, tmp) < 0) {
74-
// User key has become shorter physically, but larger logically.
75-
// Tack on the earliest possible number to the shortened user key.
76-
PutFixed64(&tmp,
77-
PackSequenceAndType(kMaxSequenceNumber, kValueTypeForSeek));
78-
assert(this->Compare(*start, tmp) < 0);
79-
assert(this->Compare(tmp, limit) < 0);
80-
start->swap(tmp);
81-
}
82-
}
83-
84-
void InternalKeyComparator::FindShortSuccessor(std::string* key) const {
85-
Slice user_key = ExtractUserKey(*key);
86-
std::string tmp(user_key.data(), user_key.size());
87-
user_comparator_->FindShortSuccessor(&tmp);
88-
if (tmp.size() < user_key.size() &&
89-
user_comparator_->Compare(user_key, tmp) < 0) {
90-
// User key has become shorter physically, but larger logically.
91-
// Tack on the earliest possible number to the shortened user key.
92-
PutFixed64(&tmp,
93-
PackSequenceAndType(kMaxSequenceNumber, kValueTypeForSeek));
94-
assert(this->Compare(*key, tmp) < 0);
95-
key->swap(tmp);
96-
}
97-
}
98-
99-
const char* InternalFilterPolicy::Name() const { return user_policy_->Name(); }
100-
101-
void InternalFilterPolicy::CreateFilter(const Slice* keys, int n,
102-
std::string* dst) const {
103-
// We rely on the fact that the code in table.cc does not mind us
104-
// adjusting keys[].
105-
Slice* mkey = const_cast<Slice*>(keys);
106-
for (int i = 0; i < n; i++) {
107-
mkey[i] = ExtractUserKey(keys[i]);
108-
// TODO(sanjay): Suppress dups?
109-
}
110-
user_policy_->CreateFilter(keys, n, dst);
111-
}
112-
113-
bool InternalFilterPolicy::KeyMayMatch(const Slice& key, const Slice& f) const {
114-
return user_policy_->KeyMayMatch(ExtractUserKey(key), f);
115-
}
116-
117-
LookupKey::LookupKey(const Slice& user_key, SequenceNumber s) {
118-
size_t usize = user_key.size();
119-
size_t needed = usize + 13; // A conservative estimate
120-
char* dst;
121-
if (needed <= sizeof(space_)) {
122-
dst = space_;
123-
} else {
124-
dst = new char[needed];
125-
}
126-
start_ = dst;
127-
dst = EncodeVarint32(dst, usize + 8);
128-
kstart_ = dst;
129-
std::memcpy(dst, user_key.data(), usize);
130-
dst += usize;
131-
EncodeFixed64(dst, PackSequenceAndType(s, kValueTypeForSeek));
132-
dst += 8;
133-
end_ = dst;
134-
}
135135

136136
} // namespace leveldb

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