java - Convert long to "unsigned, 4 byte integer in network byte order" with ByteBuffer -

the protocol i'm using requires sending current position in file "unsigned, 4 byte integer in network byte order". there several questions on this, assuming i'm using integers, not longs

i attempting port nio's bytebuffer can sent in socket channel:

long bytestransfered = ... number of bytes transfered... //todo: do? outbuffer[0] = (byte) ((bytestransfered >> 24) & 0xff); outbuffer[1] = (byte) ((bytestransfered >> 16) & 0xff); outbuffer[2] = (byte) ((bytestransfered >> 8) & 0xff); //todo: why netbeans nothing? outbuffer[3] = (byte) ((bytestransfered >> 0) & 0xff); 

are methods in bytebuffer accomplish this? in more obvious, self-descriptive way bit-shifting magic above?

whether signed or unsigned, bits same.

if cast long int, jvm discards high-order bits. issue comes when promoting int long: java sign-extend value, filling in high-order bits of long most-significant bit of int.

to resolve problem, apply mask long. following should make clear:

long value = integer.max_value + 1234l; system.out.println("original value    = " + value);  int ivalue = (int)value; system.out.println("value int      = " + ivalue); byte[] array = new byte[4];  bytebuffer buf = bytebuffer.wrap(array); buf.putint(0, ivalue);  int iretrieved = buf.getint(0); system.out.println("int buf      = " + iretrieved);  long retrieved = iretrieved; system.out.println("converted long = " + retrieved);  retrieved = retrieved & 0xffffffffl; system.out.println("high bytes masked = " + retrieved); 

however, aware still have 32 bits. if filesizes greater 4gb won't able fit 4 bytes (and if have worry files > 2g, should worry files > 4g).