大五碼(Big5)編碼自學筆記 - v3.14，楊和榮
Warning: GB2312 encoding used!
從大五碼到 Unicode 轉換表製作程式
本章介紹了 Big5Unicode.java 源程式。它可以用來製作大五碼 (Big5) 到 Unicode 編碼轉換表。
本書列出的從大五碼到 Unicode 編碼轉換表由下面的程式所產生。這個程式採用了 Java 內部編碼轉換函數 CharsetDecoder.encode() 和 CharsetDecoder.decode()，
/* Big5Unicode.java
- Copyright (c) 2015, HerongYang.com, All Rights Reserved.
*/
import java.io.*;
import java.nio.*;
import java.nio.charset.*;
class Big5Unicode {
static OutputStream out = null;
static char hexDigit[] = {'0', '1', '2', '3', '4', '5', '6', '7',
'8', '9', 'A', 'B', 'C', 'D', 'E', 'F'};
static String blk_name[] = {"Special Symbols",
"Level 1 Characters", "Level 2 Characters"};
static int blk_first[] = {0xA140, 0xA440, 0xC940};
static int blk_last[] = {0xA3BF, 0xC67E, 0xF9D5};
static int blk_size[] = {408, 5401, 7652};
static int blk_count[] = {0, 0, 0};
public static void main(String[] args) {
try {
out = new FileOutputStream("big5-unicode.big5");
writeCode();
out.close();
} catch (IOException e) {
System.out.println(e.toString());
}
}
public static void writeCode() throws IOException {
String name = null;
CharsetDecoder b5dc = Charset.forName("Big5").newDecoder();
CharsetEncoder uxec = Charset.forName("UTF-16BE").newEncoder();
ByteBuffer b5bb = null;
ByteBuffer uxbb = null;
CharBuffer cb = null;
for (int i=0xA1; i<=0xFF; i++) {
int blk = getBlock(i);
if (blk==-1) continue;
name = blk_name[blk];
writeln();
writeString("<p><b>Row ");
writeHex((byte)i);
writeString(": "+name+"</b></p>");
writeln();
writeln();
writeHeader();
for (int j=0x40; j<=0xFF; j++) {
byte hi = (byte)(i);
byte lo = (byte)(j);
if (validBig5(i, j, blk)) {
b5bb = ByteBuffer.wrap(new byte[]{hi, lo});
try {
cb = b5dc.decode(b5bb);
uxbb = uxec.encode(cb);
writeByte(hi);
writeByte(lo);
writeString(" ");
writeHex(hi);
writeHex(lo);
blk_count[blk] = blk_count[blk] + 1;
} catch (CharacterCodingException e) {
cb = null;
uxbb = null;
writeBig5Space();
writeString(" fail");
}
} else {
cb = null;
uxbb = null;
writeBig5Space();
writeString(" null");
}
writeString(" ");
writeByteBuffer(uxbb, 2);
if ((j+1)%4 == 0) {
writeln();
} else {
writeString(" ");
}
}
writeFooter();
}
for (int l=0; l<blk_name.length; l++) {
System.out.println(blk_name[l]+": "
+ blk_count[l]+" of "+blk_size[l]);
}
}
public static void writeln() throws IOException {
out.write(0x0D);
out.write(0x0A);
}
public static void writeByte(byte b) throws IOException {
out.write(b & 0xFF);
}
public static void writeByteBuffer(ByteBuffer b, int l)
throws IOException {
int i = 0;
if (b==null) {
writeString("null");
i = 2;
} else {
for (i=0; i<b.limit(); i++) writeHex(b.get(i));
}
for (int j=i; j<l; j++) writeString(" ");
}
public static void writeBig5Space() throws IOException {
out.write(0xA1);
out.write(0x40);
}
public static void writeString(String s) throws IOException {
if (s!=null) {
for (int i=0; i<s.length(); i++) {
out.write((int) (s.charAt(i) & 0xFF));
}
}
}
public static void writeNumber(int i) throws IOException {
String s = "00" + String.valueOf(i);
writeString(s.substring(s.length()-2,s.length()));
}
public static void writeHex(byte b) throws IOException {
out.write((int) hexDigit[(b >> 4) & 0x0F]);
out.write((int) hexDigit[b & 0x0F]);
}
public static void writeHeader() throws IOException {
writeString("<pre class=\"chinese\">");
writeBig5Space();
writeString(" Big5 Uni.");
writeString(" ");
writeBig5Space();
writeString(" Big5 Uni.");
writeString(" ");
writeBig5Space();
writeString(" Big5 Uni.");
writeString(" ");
writeBig5Space();
writeString(" Big5 Uni.");
writeln();
writeln();
}
public static void writeFooter() throws IOException {
writeString("</pre>");
writeln();
}
public static boolean validBig5(int i, int j, int blk) {
// valid ranges for j: 0x40 - 0x7E and 0xA1 - 0xFE.
if (j<0x40) return false;
if (j>0x7E && j<0xA1) return false;
if (j>0xFE) return false;
int last_i = blk_last[blk] >> 8;
int last_j = blk_last[blk] & 0xFF;
if (i==last_i && j>last_j) return false;
return true;
}
public static int getBlock(int i) {
for (int l=0; l<blk_first.length; l++) {
int first = blk_first[l] >> 8;
int last = blk_last[l] >> 8;
if (i>=first && i<=last) return l;
}
return -1;
}
}
關於程式的幾點註解:
程式可以在 JDK 8 到 JDK 20 的任何一個版本中編譯和執行。 程式的輸出結果如下：
herong$ javac Big5Unicode.java herong$ java Big5Unicode Special Symbols: 406 of 408 Level 1 Characters: 5401 of 5401 Level 2 Characters: 7652 of 7652
結果顯示，JDK 無法處理兩個大五碼符號： 0xA1C3 (��) 和 0xA1C5 (��)。 我們只好在輸出的轉換錶中，做下列修改：
�� A1C3 U+FFE3 �� A1C5 U+02CD
另外，JDK 還有三個解碼錯誤，需要修改：
A1FE: Java bug - wrong mapping (／ A1FE U+2571, ╱ A2AC U+2571) It should be: ／ A1FE U+FF0F A240: Java bug - wrong mapping (＼ A240 U+2572, ╲ A2AD U+2572) It should be: ＼ A240 U+FF3C A15A: Java bug - wrong mapping (＿ A15A U+FF3F, ＿ A1C4 U+FF3F) It should be: ＿ A15A U+2574
程式輸出的轉換錶將列入本書的後面部分。
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