Yuta HIGUCHI | 8f18219 | 2014-08-02 18:47:42 -0700 | [diff] [blame] | 1 | package net.onrc.onos.core.util.distributed.sharedlog; |
| 2 | |
| 3 | import static com.google.common.base.Preconditions.checkArgument; |
| 4 | import static com.google.common.base.Preconditions.checkNotNull; |
| 5 | |
| 6 | import javax.annotation.concurrent.Immutable; |
| 7 | |
| 8 | import com.google.common.annotations.Beta; |
| 9 | import com.google.common.primitives.Longs; |
| 10 | import com.google.common.primitives.UnsignedLong; |
| 11 | import com.google.common.primitives.UnsignedLongs; |
| 12 | |
| 13 | // TODO register to Kryo |
| 14 | /** |
| 15 | * Sequence number used as log entry key. |
| 16 | */ |
| 17 | @Beta |
| 18 | @Immutable |
| 19 | public final class SeqNum extends Number implements Comparable<SeqNum> { |
| 20 | |
| 21 | /** |
| 22 | * Long value reserved for {@link #INITIAL}. |
| 23 | */ |
| 24 | public static final long ZERO = 0L; |
| 25 | |
| 26 | /** |
| 27 | * Special sequence number which will never have LogValue. |
| 28 | */ |
| 29 | public static final SeqNum INITIAL = new SeqNum(ZERO); |
| 30 | |
| 31 | |
| 32 | private final long seq; |
| 33 | |
| 34 | /** |
| 35 | * Constructor. |
| 36 | * |
| 37 | * @param number sequence number. |
| 38 | */ |
| 39 | protected SeqNum(final long number) { |
| 40 | this.seq = number; |
| 41 | } |
| 42 | |
| 43 | /** |
| 44 | * Gets an instance for specified number. |
| 45 | * |
| 46 | * @param number must not be {@link #ZERO} |
| 47 | * @return SeqNum |
| 48 | * |
| 49 | * @throws IllegalArgumentException if given number was {@link #ZERO} |
| 50 | */ |
| 51 | public static SeqNum valueOf(final long number) { |
| 52 | checkArgument(number != ZERO); |
| 53 | return new SeqNum(number); |
| 54 | } |
| 55 | |
| 56 | // TODO give better name? |
| 57 | /** |
| 58 | * Gets an instance for specified number. |
| 59 | * |
| 60 | * @param number sequence number. Can be {@link #ZERO} |
| 61 | * @return SeqNum |
| 62 | */ |
| 63 | public static SeqNum anyValueOf(final long number) { |
| 64 | return new SeqNum(number); |
| 65 | } |
| 66 | |
| 67 | /** |
Yuta HIGUCHI | 8cc4169 | 2014-08-20 21:47:03 -0700 | [diff] [blame] | 68 | * Gets an instance for specified string. |
| 69 | * |
| 70 | * @param str parsed result must not be {@link #ZERO} |
| 71 | * @return SeqNum |
| 72 | */ |
| 73 | public static SeqNum valueOf(final String str) { |
| 74 | return valueOf(UnsignedLongs.decode(str)); |
| 75 | } |
| 76 | |
| 77 | /** |
| 78 | * Gets an instance for specified string. |
| 79 | * |
| 80 | * @param str string representation of unsigned long |
| 81 | * @return SeqNum |
| 82 | */ |
| 83 | public static SeqNum anyValueOf(final String str) { |
| 84 | return anyValueOf(UnsignedLongs.decode(str)); |
| 85 | } |
| 86 | |
| 87 | /** |
Yuta HIGUCHI | 8f18219 | 2014-08-02 18:47:42 -0700 | [diff] [blame] | 88 | * Gets the next sequence number. |
| 89 | * <p> |
| 90 | * WARN: This is not a atomic sequencer, |
| 91 | * this method just returns the next number in sequence. |
| 92 | * |
| 93 | * @return next sequence number |
| 94 | */ |
| 95 | public SeqNum next() { |
| 96 | return step(1); |
| 97 | } |
| 98 | |
| 99 | /** |
| 100 | * Gets the previous sequence number. |
| 101 | * <p> |
| 102 | * WARN: This is not a atomic sequencer, |
| 103 | * this method just returns the previous number in sequence. |
| 104 | * |
| 105 | * @return prev sequence number |
| 106 | */ |
| 107 | public SeqNum prev() { |
| 108 | return step(-1); |
| 109 | } |
| 110 | |
| 111 | /** |
| 112 | * Gets the sequence number stepping forward/backward by {@code delta}. |
| 113 | * |
| 114 | * @param delta step |
| 115 | * @return sequence number |
| 116 | */ |
| 117 | public SeqNum step(long delta) { |
| 118 | long next = seq + delta; |
| 119 | if (next == SeqNum.ZERO) { |
| 120 | if (delta >= 0) { |
| 121 | return SeqNum.valueOf(next + 1); |
| 122 | } else { |
| 123 | // XXX Revisit this behavior |
| 124 | return SeqNum.valueOf(next - 1); |
| 125 | } |
| 126 | } |
| 127 | return SeqNum.valueOf(next); |
| 128 | } |
| 129 | |
| 130 | // TODO comparator which treats long as ring? |
| 131 | |
| 132 | @Override |
| 133 | public int intValue() { |
| 134 | return UnsignedLong.valueOf(seq).intValue(); |
| 135 | } |
| 136 | |
| 137 | @Override |
| 138 | public long longValue() { |
| 139 | return seq; |
| 140 | } |
| 141 | |
| 142 | @Override |
| 143 | public float floatValue() { |
| 144 | return UnsignedLong.valueOf(seq).floatValue(); |
| 145 | } |
| 146 | |
| 147 | @Override |
| 148 | public double doubleValue() { |
| 149 | return UnsignedLong.valueOf(seq).doubleValue(); |
| 150 | } |
| 151 | |
| 152 | @Override |
| 153 | public int hashCode() { |
| 154 | return Longs.hashCode(seq); |
| 155 | } |
| 156 | |
| 157 | @Override |
| 158 | public boolean equals(Object obj) { |
| 159 | if (this == obj) { |
| 160 | return true; |
| 161 | } |
| 162 | if (obj == null) { |
| 163 | return false; |
| 164 | } |
| 165 | if (getClass() != obj.getClass()) { |
| 166 | return false; |
| 167 | } |
| 168 | SeqNum other = (SeqNum) obj; |
| 169 | return seq == other.seq; |
| 170 | } |
| 171 | |
| 172 | @Override |
| 173 | public String toString() { |
| 174 | return UnsignedLongs.toString(seq); |
| 175 | } |
| 176 | |
| 177 | @Override |
| 178 | public int compareTo(final SeqNum o) { |
| 179 | checkNotNull(o); |
| 180 | |
| 181 | return Long.signum(-this.distance(o)); |
| 182 | } |
| 183 | |
| 184 | /** |
| 185 | * Returns the distance between other and this SeqNum. |
| 186 | * |
| 187 | * @param other other SeqNum |
| 188 | * @return {@code other - this} |
| 189 | * or -Long.MAX_VALUE, Log.MAX_VALUE if too far apart. |
| 190 | */ |
| 191 | public long distance(final SeqNum other) { |
| 192 | checkNotNull(other); |
| 193 | |
| 194 | // distance from INITIAL is always measured clockwise on the ring |
| 195 | if (this.equals(INITIAL)) { |
| 196 | return (other.seq >= 0) ? other.seq : Long.MAX_VALUE; |
| 197 | } else if (other.equals(INITIAL)) { |
| 198 | return (this.seq >= 0) ? -this.seq : -Long.MAX_VALUE; |
| 199 | } |
| 200 | |
| 201 | /// other cases measures using "shorter" half of the ring |
| 202 | final long diff = other.seq - this.seq; |
| 203 | if (diff == Long.MIN_VALUE) { |
| 204 | // both arc is same distance |
| 205 | // treat arc including INITIAL as shorter |
| 206 | if (this.seq < 0) { |
| 207 | // clock wise arc contain INITIAL |
| 208 | return Long.MAX_VALUE; |
| 209 | } else { |
| 210 | // counter clock wise arc contain INITIAL |
| 211 | return -Long.MAX_VALUE; |
| 212 | } |
| 213 | } else { |
| 214 | return diff; |
| 215 | } |
| 216 | } |
| 217 | } |