packN.java

    //60,67
    //45 81
    //32,95
    private String convertCharPack(int value, int charnum , int base , int packsize){
        int b;
        char[] ret = new char[charnum];
        for (int i = 0; i < charnum; i++) {
            b = value % packsize;
            ret[i] = (char)(b+base);
            value = value / packsize;
        }
        return new String(ret);
    }
    private int convertCharDepack(String chars, int base , int packsize){
        int l = chars.length();
        int v  = chars.charAt(l-1)-base;
        for (int i = l-2; i >= 0; i--) {
            v = v * packsize + chars.charAt(i)-base;
        }
        return v;
    }

    //60 -> 64 = 2^6 , ? % 64 = ? & 63
    private String convertCharPack2(int value, int charnum , int base, int packbeki, int packm){
        int b;
        int fb = value;
        char[] ret = new char[charnum];
        if (value < 0){
            Log.d(LOGID, "not plus parameter: pack:" + value);
        }
        for (int i = 0; i < charnum; i++) {
            b = value & packm;
            ret[i] = (char)(b+base);
            value = value >> packbeki;
        }
        if (value > 0){
            Log.d(LOGID, "too big parameter: pack:" + fb);
        }
        return new String(ret);
    }
    private int convertCharDepack2(String chars, int base, int packbeki){
        int l = chars.length();
        int v  = chars.charAt(l-1)-base;
        for (int i = l-2; i >= 0; i--) {
            v = (v <<packbeki) + chars.charAt(i)-base;
        }
        return v;
    }

Outline:
Convert string to N-index.
like perl's pack64 function.
There are two type method and each type has two method.
version 1:More Flexible.
version 2:More Fast. (It can pack only 2^n pack-range type)

数値を文字に変換し圧縮します。
2typeあり、柔軟性のあるバージョンと、2のべき乗に制限した高速バージョンです。

Usecase:
For compressing string at save or through network.
保存時/ 通信時などの文字圧縮などに。

IN/OUT example
60 <-> x (base 60 : pack 64 (2^6), charnum 1 : int range 64^1)
333333 <-> QTM= (base 60 : pack 64 (2^6), charnum 4: int range 64^4)
assemble from upper side 'Q' (with small int value '333333 mod 64')

range example:
char('<') ASCII(60) ～ char('~') ASCII(60+67)
char('A') ASCII(65) ～ char('Z') ASCII(65+25) : ONLY BIG LETTER ASCII

Usage:
sb.append(convertCharPack2( value,4,60,6,63))
or
convertCharDepack2(data.substring(i + 1,i+3),60,6)

Recommend pack pattern
//60,67 base 60 ~ 60+67
//45 81
//32,95

License:
For free at your own risk.