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Safe handling of sequence number #13

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Safe handling of sequence number #13

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2 changes: 1 addition & 1 deletion ...e/src/main/java/com/github/rholder/fauxflake/provider/twitter/SnowflakeDecodingUtils.java
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Original file line number Diff line number Diff line change
Expand Up @@ -48,6 +48,6 @@ public static long decodeMachineId(long id) {
* @param id the id to decode from
*/
public static int decodeSequence(long id) {
return (int)(id & 0x0000000000000FFF);
return (int)(id & SnowflakeEncodingProvider.SEQUENCE_MASK);
}
}
12 changes: 11 additions & 1 deletion ...rc/main/java/com/github/rholder/fauxflake/provider/twitter/SnowflakeEncodingProvider.java
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Original file line number Diff line number Diff line change
Expand Up @@ -47,6 +47,12 @@ public class SnowflakeEncodingProvider implements EncodingProvider {
*/
public static final int MAX_SEQUENCE_NUMBERS = 4096;

/**
* Number of bits needed to represent all sequence numbers
*/
public static final int SEQUENCE_BITS = 12;
public static final int SEQUENCE_MASK = ~(-1 << SEQUENCE_BITS);

/**
* Number of bits to shift the time over
*/
Expand All @@ -68,9 +74,13 @@ public SnowflakeEncodingProvider(long machineId) {
this.shiftedMachineId = ((machineId % MACHINE_CODES) << SHIFT_MACHINE_CODE_BITS);
}

/**
* Returns a Snowflake ID. Note that only the lower order 12 bits of the sequence number are
* used
*/
@Override
public byte[] encodeAsBytes(long time, int sequence) {
long v = ((time - EPOCH) << SHIFT_TIME_BITS) | shiftedMachineId | sequence;
long v = ((time - EPOCH) << SHIFT_TIME_BITS) | shiftedMachineId | (sequence & SEQUENCE_MASK);

byte[] buffer = new byte[8];
buffer[0] = (byte)(v >>> 56);
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