ByteSizeUnit.java

package net.csdn.common.unit;

/**
 * BlogInfo: william
 * Date: 11-9-1
 * Time: 下午4:16
 */
public enum ByteSizeUnit {
    BYTES {
        @Override
        public long toBytes(long size) {
            return size;
        }

        @Override
        public long toKB(long size) {
            return size / (C1 / C0);
        }

        @Override
        public long toMB(long size) {
            return size / (C2 / C0);
        }

        @Override
        public long toGB(long size) {
            return size / (C3 / C0);
        }
    },
    KB {
        @Override
        public long toBytes(long size) {
            return x(size, C1 / C0, MAX / (C1 / C0));
        }

        @Override
        public long toKB(long size) {
            return size;
        }

        @Override
        public long toMB(long size) {
            return size / (C2 / C1);
        }

        @Override
        public long toGB(long size) {
            return size / (C3 / C1);
        }
    },
    MB {
        @Override
        public long toBytes(long size) {
            return x(size, C2 / C0, MAX / (C2 / C0));
        }

        @Override
        public long toKB(long size) {
            return x(size, C2 / C1, MAX / (C2 / C1));
        }

        @Override
        public long toMB(long size) {
            return size;
        }

        @Override
        public long toGB(long size) {
            return size / (C3 / C2);
        }
    },
    GB {
        @Override
        public long toBytes(long size) {
            return x(size, C3 / C0, MAX / (C3 / C0));
        }

        @Override
        public long toKB(long size) {
            return x(size, C3 / C1, MAX / (C3 / C1));
        }

        @Override
        public long toMB(long size) {
            return x(size, C3 / C2, MAX / (C3 / C2));
        }

        @Override
        public long toGB(long size) {
            return size;
        }
    };

    static final long C0 = 1L;
    static final long C1 = C0 * 1024L;
    static final long C2 = C1 * 1024L;
    static final long C3 = C2 * 1024L;

    static final long MAX = Long.MAX_VALUE;

    /**
     * Scale d by m, checking for overflow.
     * This has a short name to make above code more readable.
     */
    static long x(long d, long m, long over) {
        if (d > over) return Long.MAX_VALUE;
        if (d < -over) return Long.MIN_VALUE;
        return d * m;
    }


    public long toBytes(long size) {
        throw new AbstractMethodError();
    }

    public long toKB(long size) {
        throw new AbstractMethodError();
    }

    public long toMB(long size) {
        throw new AbstractMethodError();
    }

    public long toGB(long size) {
        throw new AbstractMethodError();
    }
}