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package sun.nio.cs.ext;

import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.nio.charset.Charset;
import java.nio.charset.CharsetDecoder;
import java.nio.charset.CoderResult;

An abstract base class for subclasses which decode IBM double byte only ebcdic host encodings such as ibm code pages 834 835 837 300,... etc The structure of IBM DBCS-only charsets is defined by the IBM Character Data Representation Architecture (CDRA) document http://www-306.ibm.com/software/globalization/cdra/appendix_a.jsp#HDRHEBDBST
/** * An abstract base class for subclasses which decode * IBM double byte only ebcdic host encodings such as ibm * code pages 834 835 837 300,... etc * * The structure of IBM DBCS-only charsets is defined by the * IBM Character Data Representation Architecture (CDRA) document * * http://www-306.ibm.com/software/globalization/cdra/appendix_a.jsp#HDRHEBDBST * */
public abstract class DBCS_ONLY_IBM_EBCDIC_Decoder extends CharsetDecoder { protected static final char REPLACE_CHAR='\uFFFD'; protected short index1[]; protected String index2; protected int mask1; protected int mask2; protected int shift; protected DBCS_ONLY_IBM_EBCDIC_Decoder(Charset cs) { super(cs, 0.5f, 1.0f); } // Check validity of dbcs ebcdic byte pair values private static boolean isValidDoubleByte(int b1, int b2) { return (b1 == 0x40 && b2 == 0x40) // DBCS-HOST SPACE || (0x41 <= b1 && b1 <= 0xfe && 0x41 <= b2 && b2 <= 0xfe); } private CoderResult decodeArrayLoop(ByteBuffer src, CharBuffer dst) { byte[] sa = src.array(); int sp = src.arrayOffset() + src.position(); int sl = src.arrayOffset() + src.limit(); assert (sp <= sl); sp = (sp <= sl ? sp : sl); char[] da = dst.array(); int dp = dst.arrayOffset() + dst.position(); int dl = dst.arrayOffset() + dst.limit(); assert (dp <= dl); dp = (dp <= dl ? dp : dl); try { while (sp + 1 < sl) { int b1 = sa[sp] & 0xff; int b2 = sa[sp + 1] & 0xff; if (!isValidDoubleByte(b1, b2)) { return CoderResult.malformedForLength(2); } // Lookup in the two level index int v = b1 * 256 + b2; char outputChar = index2.charAt(index1[((v & mask1) >> shift)] + (v & mask2)); if (outputChar == REPLACE_CHAR) return CoderResult.unmappableForLength(2); if (dl - dp < 1) return CoderResult.OVERFLOW; da[dp++] = outputChar; sp += 2; } return CoderResult.UNDERFLOW; } finally { src.position(sp - src.arrayOffset()); dst.position(dp - dst.arrayOffset()); } } private CoderResult decodeBufferLoop(ByteBuffer src, CharBuffer dst) { int mark = src.position(); try { while (src.remaining() > 1) { int b1 = src.get() & 0xff; int b2 = src.get() & 0xff; if (!isValidDoubleByte(b1, b2)) { return CoderResult.malformedForLength(2); } // Lookup in the two level index int v = b1 * 256 + b2; char outputChar = index2.charAt(index1[((v & mask1) >> shift)] + (v & mask2)); if (outputChar == REPLACE_CHAR) return CoderResult.unmappableForLength(2); if (!dst.hasRemaining()) return CoderResult.OVERFLOW; dst.put(outputChar); mark += 2; } return CoderResult.UNDERFLOW; } finally { src.position(mark); } } protected CoderResult decodeLoop(ByteBuffer src, CharBuffer dst) { if (src.hasArray() && dst.hasArray()) return decodeArrayLoop(src, dst); else return decodeBufferLoop(src, dst); } }