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本文主要研究一下claudb的importRDB
importRDB
claudb-1.7.1/src/main/java/com/github/tonivade/claudb/DBServerState.java
public class DBServerState {
//......
public void importRDB(InputStream input) throws IOException {
RDBInputStream rdb = new RDBInputStream(input);
Map> load = rdb.parse();
for (Map.Entry> entry : load.entrySet()) {
databases.get(entry.getKey()).overrideAll(ImmutableMap.from(entry.getValue()));
}
}
//......
} - importRDB方法创建RDBInputStream，然后执行其parse方法进行解析，之后遍历解析结果，挨个执行databases.get(entry.getKey()).overrideAll(ImmutableMap.from(entry.getValue()))
RDBInputStream
claudb-1.7.1/src/main/java/com/github/tonivade/claudb/persistence/RDBInputStream.java
public class RDBInputStream {
private static final SafeString REDIS_PREAMBLE = safeString("REDIS");
private static final long TO_MILLIS = 1000L;
private static final int HASH = 0x04;
private static final int SORTED_SET = 0x03;
private static final int SET = 0x02;
private static final int LIST = 0x01;
private static final int STRING = 0x00;
private static final int TTL_MILLISECONDS = 0xFC;
private static final int TTL_SECONDS = 0xFD;
private static final int SELECT = 0xFE;
private static final int END_OF_STREAM = 0xFF;
private static final int REDIS_VERSION = 6;
private static final int VERSION_LENGTH = 4;
private static final int REDIS_LENGTH = 5;
private final CheckedInputStream in;
public RDBInputStream(InputStream in) {
this.in = new CheckedInputStream(in, new CRC64());
}
public Map> parse() throws IOException {
Map> databases = new HashMap<>();
int version = version();
if (version > REDIS_VERSION) {
throw new IOException("invalid version: " + version);
}
Long expireTime = null;
HashMap db = null;
for (boolean end = false; !end;) {
int read = in.read();
switch (read) {
case SELECT:
db = new HashMap<>();
databases.put(readLength(), db);
break;
case TTL_SECONDS:
expireTime = parseTimeSeconds();
break;
case TTL_MILLISECONDS:
expireTime = parseTimeMillis();
break;
case STRING:
ensure(db, readKey(), readString(expireTime));
expireTime = null;
break;
case LIST:
ensure(db, readKey(), readList(expireTime));
expireTime = null;
break;
case SET:
ensure(db, readKey(), readSet(expireTime));
expireTime = null;
break;
case SORTED_SET:
ensure(db, readKey(), readSortedSet(expireTime));
expireTime = null;
break;
case HASH:
ensure(db, readKey(), readHash(expireTime));
expireTime = null;
break;
case END_OF_STREAM:
// end of stream
end = true;
db = null;
expireTime = null;
break;
default:
throw new IOException("not supported: " + read);
}
}
verifyChecksum();
return databases;
}
private int version() throws IOException {
SafeString redis = new SafeString(read(REDIS_LENGTH));
if (!redis.equals(REDIS_PREAMBLE)) {
throw new IOException("not valid stream");
}
return parseVersion(read(VERSION_LENGTH));
}
private int parseVersion(byte[] version) {
StringBuilder sb = new StringBuilder();
for (byte b : version) {
sb.append((char) b);
}
return Integer.parseInt(sb.toString());
}
private void verifyChecksum() throws IOException {
long calculated = in.getChecksum().getValue();
long readed = parseChecksum();
if (calculated != readed) {
throw new IOException("invalid checksum: " + readed);
}
}
private long parseChecksum() throws IOException {
return ByteUtils.byteArrayToLong(read(Long.BYTES));
}
//......
} - RDBInputStream的构造器使用CheckedInputStream对InputStream进行包装；其parse方法先解析version进行校验，之后循环进行in.read()，分别解析SELECT、TTL_SECONDS、TTL_MILLISECONDS、STRING、LIST、SET、SORTED_SET、HASH、END_OF_STREAM；最后执行verifyChecksum校验checksum
readKey
claudb-1.7.1/src/main/java/com/github/tonivade/claudb/persistence/RDBInputStream.java
private DatabaseKey readKey() throws IOException {
return new DatabaseKey(readSafeString());
}
private SafeString readSafeString() throws IOException {
int length = readLength();
return new SafeString(read(length));
}
private int readLength() throws IOException {
int length = in.read();
if (length < 0x40) {
// 1 byte: 00XXXXXX
return length;
} else if (length < 0x80) {
// 2 bytes: 01XXXXXX XXXXXXXX
int next = in.read();
return readLength(length, next);
} else {
// 5 bytes: 10...... XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX
return byteArrayToInt(read(Integer.BYTES));
}
}
private byte[] read(int size) throws IOException {
byte[] array = new byte[size];
int read = in.read(array);
if (read != size) {
throw new IOException("error reading stream");
}
return array;
} - readKey方法执行readSafeString，先readLength，在根据length进行read
readString
claudb-1.7.1/src/main/java/com/github/tonivade/claudb/persistence/RDBInputStream.java
private DatabaseValue readString(Long expireTime) throws IOException {
return string(readSafeString()).expiredAt(expireTime != null ? ofEpochMilli(expireTime) : null);
}- readString方法先readSafeString，然后转为DatabaseValue再设置expiredAt
readList
claudb-1.7.1/src/main/java/com/github/tonivade/claudb/persistence/RDBInputStream.java
private DatabaseValue readList(Long expireTime) throws IOException {
int size = readLength();
List list = new LinkedList<>();
for (int i = 0; i < size; i++) {
list.add(readSafeString());
}
return list(list).expiredAt(expireTime != null ? ofEpochMilli(expireTime) : null);
} - readList方法先通过readLength读取list元素个数，在挨个执行readSafeString，最后将list转为DatabaseValue再设置expiredAt
readSet
claudb-1.7.1/src/main/java/com/github/tonivade/claudb/persistence/RDBInputStream.java
private DatabaseValue readSet(Long expireTime) throws IOException {
int size = readLength();
Set set = new LinkedHashSet<>();
for (int i = 0; i < size; i++) {
set.add(readSafeString());
}
return set(set).expiredAt(expireTime != null ? ofEpochMilli(expireTime) : null);
} - readSet方法先通过readLength读取set元素个数，在挨个执行readSafeString，最后将set转为DatabaseValue再设置expiredAt
readSortedSet
claudb-1.7.1/src/main/java/com/github/tonivade/claudb/persistence/RDBInputStream.java
private DatabaseValue readSortedSet(Long expireTime) throws IOException {
int size = readLength();
Set> entries = new LinkedHashSet<>();
for (int i = 0; i < size; i++) {
SafeString value = readSafeString();
Double score = readDouble();
entries.add(score(score, value));
}
return zset(entries).expiredAt(expireTime != null ? ofEpochMilli(expireTime) : null);
} - readSortedSet方法先通过readLength读取set元素个数，在挨个执行readSafeString、readDouble，添加到LinkedHashSet，最后将entries转为DatabaseValue再设置expiredAt；与readSet的差别在于多读取了score
readHash
private DatabaseValue readHash(Long expireTime) throws IOException {
int size = readLength();
Set> entries = new LinkedHashSet<>();
for (int i = 0; i < size; i++) {
entries.add(entry(readSafeString(), readSafeString()));
}
return hash(entries).expiredAt(expireTime != null ? ofEpochMilli(expireTime) : null);
} - readHash方法先通过readLength读取hash元素个数，在挨个执行readSafeString、readSafeString，转为entry添加到LinkedHashSet，最后将entries转为DatabaseValue再设置expiredAt
小结
importRDB方法创建RDBInputStream，然后执行其parse方法进行解析，之后遍历解析结果，挨个执行databases.get(entry.getKey()).overrideAll(ImmutableMap.from(entry.getValue()))