protected static long extractSnapshotSize(byte[] data, int offset, int length)
    throws InvalidProtocolBufferException {
    ByteString byteStr = UnsafeByteOperations.unsafeWrap(data, offset, length);
    return org.apache.hadoop.hbase.shaded.protobuf.generated.QuotaProtos.SpaceQuotaSnapshot
      .parseFrom(byteStr).getQuotaUsage();
  }
Returns the current space quota snapshot of the given {@code tableName} from
{@code QuotaTableUtil.QUOTA_TABLE_NAME} or null if the no quota information is available for
that tableName.
@param conn      connection to re-use
@param tableName name of the table whose current snapshot is to be retreived
hbase-client/src/main/java/org/apache/hadoop/hbase/quotas/QuotaTableUtil.java