java - IllegalArgumentException using Java8 Base64 decoder -

i wanted use base64.java encode , decode files. encode.wrap(inputstream) , decode.wrap(inputstream) worked runned slowly. used following code.

public static void decodefile(string inputfilename,         string outputfilename)         throws filenotfoundexception, ioexception {      base64.decoder decoder = base64.getdecoder();     inputstream in = new fileinputstream(inputfilename);     outputstream out = new fileoutputstream(outputfilename);      byte[] inbuff = new byte[buff_size];  //final int buff_size = 1024;     byte[] outbuff = null;     while (in.read(inbuff) > 0) {         outbuff = decoder.decode(inbuff);         out.write(outbuff);     }     out.flush();     out.close();     in.close(); } 

however, throws

exception in thread "awt-eventqueue-0" java.lang.illegalargumentexception: input byte array has wrong 4-byte ending unit     @ java.util.base64$decoder.decode0(base64.java:704)     @ java.util.base64$decoder.decode(base64.java:526)     @ base64coder.javabase64filecoder.decodefile(javabase64filecoder.java:69)     ... 

after changed final int buff_size = 1024; final int buff_size = 3*1024;, code worked. since "buff_size" used encode file, believe there wrong file encoded (1024 % 3 = 1, means paddings added in middle of file).

also, @jon skeet , @tagir valeev mentioned, should not ignore return value inputstream.read(). so, modified code below.

(however, have mention code run faster using wrap(). noticed speed difference because had coded , intensively used base64.encodefile()/decodefile() long before jdk8 released. now, buffed jdk8 code runs fast original code. so, not know going on wrap()... )

public static void decodefile(string inputfilename,         string outputfilename)         throws filenotfoundexception, ioexception {      base64.decoder decoder = base64.getdecoder();     inputstream in = new fileinputstream(inputfilename);     outputstream out = new fileoutputstream(outputfilename);      byte[] inbuff = new byte[buff_size];     byte[] outbuff = null;     int bytesread = 0;     while (true)     {         bytesread = in.read(inbuff);         if (bytesread == buff_size)         {             outbuff = decoder.decode(inbuff);         }         else if (bytesread > 0)         {             byte[] tempbuff = new byte[bytesread];             system.arraycopy(inbuff, 0, tempbuff, 0, bytesread);             outbuff = decoder.decode(tempbuff);         }         else         {             out.flush();             out.close();             in.close();             return;         }         out.write(outbuff);     } } 

special @jon skeet , @tagir valeev.

i suspect problem you're ignoring return value inputstream.read, other check end of stream. this:

while (in.read(inbuff) > 0) {     // decodes *complete* buffer     outbuff = decoder.decode(inbuff);     out.write(outbuff); } 

should be

int bytesread; while ((bytesread = in.read(inbuff)) > 0) {     outbuff = decoder.decode(inbuff, 0, bytesread);     out.write(outbuff); } 

i wouldn't expect faster using wrap though.