c - raw socket. ip header when to use hton -


i new raw socket, , playing around ip header. noticed ip->ip_hl = sizeof(struct ip) >> 2 //works fine; ip->ip_hl = hton(sizeof(struct ip) >> 2) //will not work;

what dont understand why not convert numbers network order instead of host order in case? what's general rule judge when use network order/host order?

thanks

htons 16-bit values. htonl 32-bit values. hton (no suffix), i'm not sure exists.

the header length occupies 1 byte (actually part of 1 byte). don't need flip bytes right form. accordingly, there no macro htons or htonl 8-bit values.


Comments

Post a Comment

Popular posts from this blog

javascript - backbone.js Collection.add() doesn't `construct` (`initialize`) an object -

<!doctype html public "-//w3c//dtd xhtml 1.0 strict//en" "http://www.w3.org/tr/xhtml1/dtd/xhtml1-strict.dtd"> <html> <head> <script src="https://ajax.googleapis.com/ajax/libs/jquery/1.7.2/jquery.min.js"></script> <script src="http://documentcloud.github.com/underscore/underscore-min.js"></script> <script src="http://documentcloud.github.com/backbone/backbone-min.js"></script> </head> <body> <button id="cmd_create_event" name="cmd_create_event" type="button">create new `event`</button> <script type="text/javascript"> var eventmodel = backbone.model.extend({ initialize : function() { console.log("`event` initialized. id: " + this.cid); this.bind("change:status", function() { console.log(this.get("status") + " value `status`"); }); this.bind("error", function(model, e...
Read more

c++ - Accessing inactive union member and undefined behavior? -

i under impression accessing union member other last 1 set ub, can't seem find solid reference (other answers claiming it's ub without support standard). so, undefined behavior? the confusion c explicitly permits type-punning through union, whereas c++ ( c++11 ) has no such permission. c11 6.5.2.3 structure , union members 95) if member used read contents of union object not same member last used store value in object, appropriate part of object representation of value reinterpreted object representation in new type described in 6.2.6 (a process called ‘‘type punning’’). might trap representation. the situation c++: c++11 9.5 unions [class.union] in union, @ 1 of non-static data members can active @ time, is, value of @ 1 of non-static data members can stored in union @ time. c++ later has language permitting use of unions containing struct s common initial sequences; doesn't permit type-punning. to determine whether union type-punning is allowe...
Read more

php - Get uncommon values from two or more arrays -

is there function in php give array of uncommon values 2 or more arrays? for example: $array1 = array( "green", "red", "blue"); $array2 = array( "green", "yellow", "red"); .... $result = function_needed($array1, $array2,...); print_r($result); should give output: array("blue", "yellow", ...); use array_diff , array_merge : $result = array_merge(array_diff($array1, $array2), array_diff($array2, $array1)); here's demo. for multiple arrays, combine callback , array_reduce : function unique(&$a, $b) { return $a ? array_merge(array_diff($a, $b), array_diff($b, $a)) : $b; } $arrays = array( array('green', 'red', 'blue'), array('green', 'yellow', 'red') ); $result = array_reduce($arrays, 'unique'); and here's demo of that.
Read more