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Java > Open Source Codes > org > apache > derby > iapi > services > io > FormatIdUtil


1 /*
2
3    Derby - Class org.apache.derby.iapi.services.io.FormatIdUtil
4
5    Licensed to the Apache Software Foundation (ASF) under one or more
6    contributor license agreements. See the NOTICE file distributed with
7    this work for additional information regarding copyright ownership.
8    The ASF licenses this file to you under the Apache License, Version 2.0
9    (the "License"); you may not use this file except in compliance with
10    the License. You may obtain a copy of the License at
11
12       http://www.apache.org/licenses/LICENSE-2.0
13
14    Unless required by applicable law or agreed to in writing, software
15    distributed under the License is distributed on an "AS IS" BASIS,
16    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
17    See the License for the specific language governing permissions and
18    limitations under the License.
19
20  */
21
22 package org.apache.derby.iapi.services.io;
23
24 import java.io.DataInput JavaDoc;
25 import java.io.DataOutput JavaDoc;
26 import java.io.IOException JavaDoc;
27
28 /**
29   Utility class with static methods for constructing and reading the byte array
30   representation of format id's.
31
32   <P>This utility supports a number of families of format ids. The byte array
33   form of each family is a different length. In all cases the first two bits
34   of the first byte indicate the family for an id. The list below describes
35   each family and gives its two bit identifier in parens.
36
37   <UL>
38   <LI> (0) - The format id is a one byte number between 0 and 63 inclusive.
39              The byte[] encoding fits in one byte.
40   <LI> (1) - The format id is a two byte number between 16384 to 32767
41              inclusive. The byte[] encoding stores the high order byte
42              first.
43   <LI> (2) - The format id is four byte number between 2147483648 and
44              3221225471 inclusive. The byte[] encoding stores the high
45              order byte first.
46   <LI> (3) - Future expansion.
47   </UL>
48  */
49 public final class FormatIdUtil
50 {
51     private FormatIdUtil() {
52     }
53
54     public static int getFormatIdByteLength(int formatId) {
55             return 2;
56     }
57
58     public static void writeFormatIdInteger(DataOutput JavaDoc out, int formatId) throws IOException JavaDoc {
59         out.writeShort(formatId);
60     }
61
62     public static int readFormatIdInteger(DataInput JavaDoc in)
63         throws IOException JavaDoc {
64
65         return in.readUnsignedShort();
66     }
67
68     public static int readFormatIdInteger(byte[] data) {
69
70         int a = data[0];
71         int b = data[1];
72         return (((a & 0xff) << 8) | (b & 0xff));
73     }
74
75     public static String JavaDoc formatIdToString(int fmtId) {
76
77         return Integer.toString(fmtId);
78     }
79 }
80
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