1 /*
2  * Copyright (c) 2006, Oracle and/or its affiliates. All rights reserved.
3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4  *
5  * This code is free software; you can redistribute it and/or modify it
6  * under the terms of the GNU General Public License version 2 only, as
7  * published by the Free Software Foundation.  Oracle designates this
8  * particular file as subject to the "Classpath" exception as provided
9  * by Oracle in the LICENSE file that accompanied this code.
10  *
11  * This code is distributed in the hope that it will be useful, but WITHOUT
12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
14  * version 2 for more details (a copy is included in the LICENSE file that
15  * accompanied this code).
16  *
17  * You should have received a copy of the GNU General Public License version
18  * 2 along with this work; if not, write to the Free Software Foundation,
19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20  *
21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22  * or visit www.oracle.com if you need additional information or have any
23  * questions.
24  */
25 
26 
27 import java.nio.ByteBuffer;
28 import java.nio.CharBuffer;
29 import java.nio.charset.Charset;
30 import java.nio.charset.CharsetDecoder;
31 import java.nio.charset.CoderResult;
32 
33 /**
34  * An abstract base class for subclasses which decode
35  * IBM double byte only ebcdic host encodings such as ibm
36  * code pages 834 835 837 300,... etc
37  *
38  * The structure of IBM DBCS-only charsets is defined by the
39  * IBM Character Data Representation Architecture (CDRA) document
40  *
41  * http://www-306.ibm.com/software/globalization/cdra/appendix_a.jsp#HDRHEBDBST
42  *
43  */
44 
45 public abstract class DBCS_ONLY_IBM_EBCDIC_Decoder extends CharsetDecoder
46 {
47     protected static final char REPLACE_CHAR='\uFFFD';
48 
49     protected short   index1[];
50     protected String  index2;
51     protected int     mask1;
52     protected int     mask2;
53     protected int     shift;
54 
DBCS_ONLY_IBM_EBCDIC_Decoder(Charset cs)55     protected DBCS_ONLY_IBM_EBCDIC_Decoder(Charset cs) {
56         super(cs, 0.5f, 1.0f);
57     }
58 
59     // Check validity of dbcs ebcdic byte pair values
isValidDoubleByte(int b1, int b2)60     private static boolean isValidDoubleByte(int b1, int b2) {
61         return (b1 == 0x40 && b2 == 0x40) // DBCS-HOST SPACE
62             || (0x41 <= b1 && b1 <= 0xfe &&
63                 0x41 <= b2 && b2 <= 0xfe);
64     }
65 
decodeArrayLoop(ByteBuffer src, CharBuffer dst)66     private CoderResult decodeArrayLoop(ByteBuffer src, CharBuffer dst) {
67         byte[] sa = src.array();
68         int sp = src.arrayOffset() + src.position();
69         int sl = src.arrayOffset() + src.limit();
70         assert (sp <= sl);
71         sp = (sp <= sl ? sp : sl);
72         char[] da = dst.array();
73         int dp = dst.arrayOffset() + dst.position();
74         int dl = dst.arrayOffset() + dst.limit();
75         assert (dp <= dl);
76         dp = (dp <= dl ? dp : dl);
77 
78         try {
79             while (sp + 1 < sl) {
80                 int b1 = sa[sp] & 0xff;
81                 int b2 = sa[sp + 1] & 0xff;
82 
83                 if (!isValidDoubleByte(b1, b2)) {
84                     return CoderResult.malformedForLength(2);
85                 }
86                 // Lookup in the two level index
87                 int v = b1 * 256 + b2;
88                 char outputChar = index2.charAt(index1[((v & mask1) >> shift)]
89                                                 + (v & mask2));
90                 if (outputChar == REPLACE_CHAR)
91                     return CoderResult.unmappableForLength(2);
92                 if (dl - dp < 1)
93                     return CoderResult.OVERFLOW;
94                 da[dp++] = outputChar;
95                 sp += 2;
96             }
97             return CoderResult.UNDERFLOW;
98         } finally {
99             src.position(sp - src.arrayOffset());
100             dst.position(dp - dst.arrayOffset());
101         }
102     }
103 
decodeBufferLoop(ByteBuffer src, CharBuffer dst)104     private CoderResult decodeBufferLoop(ByteBuffer src, CharBuffer dst) {
105         int mark = src.position();
106         try {
107             while (src.remaining() > 1) {
108                 int b1 = src.get() & 0xff;
109                 int b2 = src.get() & 0xff;
110 
111                 if (!isValidDoubleByte(b1, b2)) {
112                     return CoderResult.malformedForLength(2);
113                 }
114                 // Lookup in the two level index
115                 int v = b1 * 256 + b2;
116                 char outputChar = index2.charAt(index1[((v & mask1) >> shift)]
117                                                 + (v & mask2));
118                 if (outputChar == REPLACE_CHAR)
119                     return CoderResult.unmappableForLength(2);
120 
121                 if (!dst.hasRemaining())
122                     return CoderResult.OVERFLOW;
123                 dst.put(outputChar);
124                 mark += 2;
125             }
126             return CoderResult.UNDERFLOW;
127         } finally {
128             src.position(mark);
129         }
130     }
131 
decodeLoop(ByteBuffer src, CharBuffer dst)132     protected CoderResult decodeLoop(ByteBuffer src, CharBuffer dst) {
133         if (src.hasArray() && dst.hasArray())
134             return decodeArrayLoop(src, dst);
135         else
136             return decodeBufferLoop(src, dst);
137     }
138 }
139