Add baseEncode, baseDecode

std/StringTools.hx

@@ -182,10 +182,86 @@ class StringTools {
 		return s.split(sub).join(by);
 	}
 
+	/**
+		Encode a string using the specified base. The base length must be a power of two.
+	**/
+	public static function baseEncode( s : String, base : String ) : String {
+		#if neko
+		return new String(_baseEncode(untyped s.__s,untyped base.__s));
+		#else true
+		var len = base.length;
+		var nbits = 1;
+		while( len > 1 << nbits )
+			nbits++;
+		if( nbits > 8 || len != 1 << nbits )
+			throw "baseEncode: base must be a power of two.";
+		var size = Std.int((s.length * 8 + nbits - 1) / nbits);
+		var out = new StringBuf();
+		var buf = 0;
+		var curbits = 0;
+		var mask = ((1 << nbits) - 1);
+		var pin = 0;
+		while( size-- > 0 ){
+			while( curbits < nbits ){
+				curbits += 8;
+				buf <<= 8;
+				var t = s.charCodeAt(pin++);
+				if( t > 255 )
+					throw "baseEncode: bad chars";
+				buf |= t;
+			}
+			curbits -= nbits;
+			out.addChar(base.charCodeAt((buf >> curbits) & mask));
+		}
+		return out.toString();
+		#end
+	}
+
+	/**
+		Decode a string encoded in the specified base. The base length must be a power of two.
+	**/
+	public static function baseDecode( s : String, base : String ) : String {
+		#if neko
+		return new String(_baseDecode(untyped s.__s,untyped base.__s));
+		#else true
+		var len = base.length;
+		var nbits = 1;
+		while( len > 1 << nbits )
+			nbits++;
+		if( nbits > 8 || len != 1 << nbits )
+			throw "baseDecode: base must be a power of two.";
+		var size = (s.length * 8 + nbits - 1) / nbits;
+		var tbl = new Array();
+		for( i in 0...256 )
+			tbl[i] = -1;
+		for( i in 0...len )
+			tbl[base.charCodeAt(i)] = i;
+		var size = (s.length * nbits) / 8;
+		var out = new StringBuf();
+		var buf = 0;
+		var curbits = 0;
+		var pin = 0;
+		while( size-- > 0 ){
+			while( curbits < 8 ){
+				curbits += nbits;
+				buf <<= nbits;
+				var i = tbl[s.charCodeAt(pin++)];
+				if( i == -1 )
+					throw "baseDecode: bad chars";
+				buf |= i;
+			}
+			curbits -= 8;
+			out.addChar((buf >> curbits) & 0xFF);
+		}
+		return out.toString();
+		#end
+	}
 
 	#if neko
 	private static var _urlEncode = neko.Lib.load("std","url_encode",1);
 	private static var _urlDecode = neko.Lib.load("std","url_decode",1);
+	private static var _baseEncode = neko.Lib.load("std","base_encode",2);
+	private static var _baseDecode = neko.Lib.load("std","base_decode",2);
 	#end
 
 }