How to send by socket C++ compatible struct from Java? -


suppose there written, unchangeable host program, receives such c++ struct socket:

#pragma pack(push, 2) struct data {   double x;   double y;   double z;   long framenumber; }; #pragma pack(pop)

platform: c++ / 32-bit windows application compiled in visual studio 2008

how send such data java socket? have attemted fill bytebuffer putdouble(), , putlong(), putint() assuming long 32-bit, cannot produce valid values.

i have generated , sended data randomly, , structure-level bytes assignment looks fine(i can randomize 1 value, example x), cannot produce exact value (propably different double representation?), random stuff sending math.random() * double.max_value;

can use google protocol buffers on 1 side (client producing data) solve problem?

remember, cannot change server (receiving) side

i know can move sending data c++ , use jni, i'm searching simpler solution.

i see @ least 2 possible problems here:

  • double representation @ byte-level (like 01234567 , 76543210 on other side)
  • bits representation in 1 byte (like 00000001 , 1000000 on other side)

what things in java in c++?

in several hours provide exact sample data "byte-hacking" (exact java value before send , value of received double in c++)

about server bad-design answering

i know such implemented , unchangeable server bad software, environment in problem inject data small old application @ "hobbistic-level"

java representation

maybe bits-level c++ expert:

long.tobinarystring( double.doubletorawlongbits( (double) 0 ) ); // 000000000000000000000000000000000000000000000000000000000000000  long.tobinarystring( double.doubletorawlongbits( 1 ) ); // 011111111110000000000000000000000000000000000000000000000000000  long.tobinarystring( double.doubletorawlongbits( 1.1 ) ); // 011111111110001100110011001100110011001100110011001100110011010  long.tobinarystring( double.doubletorawlongbits( 1024 ) ); // 100000010010000000000000000000000000000000000000000000000000000  long.tobinarystring( double.doubletorawlongbits( 1024.1024 ) ); // 100000010010000000000000110100011011011100010111010110001110001  long.tobinarystring( double.doubletorawlongbits( double.max_value ) ); // 111111111101111111111111111111111111111111111111111111111111111

suppose there written, unchangeable host program, receives such c++ struct socket

then have major problem unknown person has kindly left legacy. have produce java code conform specific c++ compiler's conception of wire format of specific struct, depends on:

  • the hardware
  • the compiler vendor
  • the compiler version
  • the compilation options
  • the surrounding #pragmas
  • ...

i strongly suggest you take opportunity fix whole megillah , define proper wire format transaction.

once you've done can emulate enough facilities of dataoutputstream, or if problem worse , endian-ness involved, nio plus bytebuffer.


Comments

Post a Comment

Popular posts from this blog

php - cannot display multiple markers in google maps v3 from traceroute result -

i'm newbie in php mysql , google maps v3. have problems in google maps v3. made traceroute web based , map traceroute's result in google maps v3 final project of college education. have try many tutorials didn't work. have tried tutorials in forum nothing worked. problem cannot display multiple markers got location data database. maybe because i'm newbie , not know how do. confuse looping show markers. here code <?php error_reporting(e_all ^ (e_notice)); ini_set('max_execution_time', 360); $enable_log_user = false; global $ip, $host_name, $host_ip; $host = @$_post['host']; $trace = @$_post['trace']; $self = $_server['php_self']; include("phpsqlajax_dbinfo.php"); $connection = mysql_connect ('127.0.0.1', $username, $password); if (!$connection) { die('not connected : ' . mysql_error());} $db_selected = mysql_select_db($database, $connection); if (!$db_selected) { die ('can\'t use db : ...
Read more

c# - DetailsView in ASP.Net - How to add another column on the side/add a control in each row? -

i have detailsview control on page used edit various fields of record, works in respect. i looking way add 1 column (and if works, why not more) right, absolutely read-only, show same fields of record comparison purposes. i aware there no obvious way such thing out of box detailsview . have looked other controls (transposed gridview , recommended formview , listview ), nothing satisfies. have special data binding setup using detailsview , can't out of without losing features. anyone on how "hack in" additional columns (for display only) on detailsview ? the solution have now, use second detailsview , visible set false in aspx. in code, make sure databind hidden detailsview hosts data third column first, initial detailsview named itemdetails . and in item created event, pass third column html rendering of hidden controls (in last code block) : protected void itemdetails_itemcreated(object sender, eventargs e) { if (dataite...
Read more

javascript - firefox memory leak -

i have following script (i use raphaeljs also) draws circle, waits 1 second, draws circle again, etc (you can copy paste - functional, need include raphael raphaeljs.com): <div id="holder"> </div> <script src="raphael.js" type="text/javascript"></script> <script> var paper = raphael(10, 50, 320, 200); var rad = math.pi / 180; var finangle = 0; function sector(cx, cy, r, startangle, endangle, params) { var x1 = cx + r * math.cos(-startangle * rad), x2 = cx + r * math.cos(-endangle * rad), y1 = cy + r * math.sin(-startangle * rad), y2 = cy + r * math.sin(-endangle * rad); return ["m", cx, cy, "l", x1, y1, "a", r, r, 0, +(endangle - startangle > 180), 0, x2, y2]; } var path = sector(100,100,50,0,180); var arc = paper.path(path); function draw() { path = sector(100,100,50,0,finangle); ...
Read more