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/**
* Unicode字符集转换
* 提取于JDK 1.5.0_08 java.util.Properties类的私有方法（loadConvert，saveConvert）
*
* @date 2009-4-7 17:09
*/
public class CharacterSetToolkit {

/**
* 从 Unicode 码转换成编码前的特殊字符串。
* @param in Unicode编码的字符数组。
* @param off 转换的起始偏移量。
* @param len 转换的字符长度。
* @param convtBuf 转换的缓存字符数组。
* @return 完成转换，返回编码前的特殊字符串。
*/
/*
* Converts encoded \uxxxx to unicode chars
* and changes special saved chars to their original forms
*/
public static String unicodeToString(char[] in, int off, int len, char[] convtBuf) {
if (convtBuf.length < len) {
int newLen = len * 2;
if (newLen < 0) {
newLen = Integer.MAX_VALUE;
}
convtBuf = new char[newLen];
}
char aChar;
char[] out = convtBuf;
int outLen = 0;
int end = off + len;

while (off < end) {
aChar = in[off++];
if (aChar == '\\') {
aChar = in[off++];
if(aChar == 'u') {
// Read the xxxx
int value=0;
for (int i=0; i<4; i++) {
aChar = in[off++];
switch (aChar) {
case '0': case '1': case '2': case '3': case '4':
case '5': case '6': case '7': case '8': case '9':
value = (value << 4) + aChar - '0';
break;
case 'a': case 'b': case 'c':
case 'd': case 'e': case 'f':
value = (value << 4) + 10 + aChar - 'a';
break;
case 'A': case 'B': case 'C':
case 'D': case 'E': case 'F':
value = (value << 4) + 10 + aChar - 'A';
break;
default:
throw new IllegalArgumentException(
"Malformed \\uxxxx encoding.");
}
}
out[outLen++] = (char)value;
} else {
if (aChar == 't') aChar = '\t';
else if (aChar == 'r') aChar = '\r';
else if (aChar == 'n') aChar = '\n';
else if (aChar == 'f') aChar = '\f';
out[outLen++] = aChar;
}
} else {
out[outLen++] = (char)aChar;
}
}
return new String (out, 0, outLen);
}

/**
* 将字符串编码成 Unicode 。
* @param theString 待转换成Unicode编码的字符串。
* @param escapeSpace 是否忽略空格。
* @return 返回转换后Unicode编码的字符串。
*/
/*
* Converts unicodes to encoded \uxxxx and escapes
* special characters with a preceding slash
*/
public static String stringToUnicode(String theString, boolean escapeSpace) {
int len = theString.length();
int bufLen = len * 2;
if (bufLen < 0) {
bufLen = Integer.MAX_VALUE;
}
StringBuffer outBuffer = new StringBuffer(bufLen);

for(int x=0; x<len; x++) {
char aChar = theString.charAt(x);
// Handle common case first, selecting largest block that
// avoids the specials below
if ((aChar > 61) && (aChar < 127)) {
if (aChar == '\\') {
outBuffer.append('\\'); outBuffer.append('\\');
continue;
}
outBuffer.append(aChar);
continue;
}
switch(aChar) {
case ' ':
if (x == 0 || escapeSpace)
outBuffer.append('\\');
outBuffer.append(' ');
break;
case '\t':outBuffer.append('\\'); outBuffer.append('t');
break;
case '\n':outBuffer.append('\\'); outBuffer.append('n');
break;
case '\r':outBuffer.append('\\'); outBuffer.append('r');
break;
case '\f':outBuffer.append('\\'); outBuffer.append('f');
break;
case '=': // Fall through
case ':': // Fall through
case '#': // Fall through
case '!':
outBuffer.append('\\'); outBuffer.append(aChar);
break;
default:
if ((aChar < 0x0020) || (aChar > 0x007e)) {
outBuffer.append('\\');
outBuffer.append('u');
outBuffer.append(toHex((aChar >> 12) & 0xF));
outBuffer.append(toHex((aChar >>  8) & 0xF));
outBuffer.append(toHex((aChar >>  4) & 0xF));
outBuffer.append(toHex( aChar        & 0xF));
} else {
outBuffer.append(aChar);
}
}
}
return outBuffer.toString();
}

/**
* Convert a nibble to a hex character
* @param	nibble	the nibble to convert.
*/
private static char toHex(int nibble) {
return hexDigit[(nibble & 0xF)];
}

/** A table of hex digits */
private static final char[] hexDigit = {
'0','1','2','3','4','5','6','7','8','9','A','B','C','D','E','F'
};
}