c - Does the complement have any impact on Fletcher's checksum? -

-

the wikipedia article fletcher's checksum states:

these examples assume two's complement arithmetic, fletcher's algorithm incorrect on one's complement machines.

this question provides scan book says:

addition performed modulo 255 (1's complement arithmetic)

fletcher's checksum uses running sum, don't see need negative numbers, , aim identify differences, long same number system (one's complement, two's complement, neither) used on checking system matter? examples given on wikipedia page specify unsigned integer types too.

i've tagged c examples given on wikipedia page in c perhaps has bearing in this. i'm not mathematician , barely competent programmer it's quite possible there blindingly obvious reason why complement have impact.

any insight grateful received.

the number system matters lot.

although fletcher's checksum works using both two's complement arithmetic (integer computations modulo 256) , one's complement arithmetic (integer computations modulo 255), resulting algorithms have different error-detection properties. one's complement version has minimum separation of undetected double bit errors of 2040 bits while two's complement has minimum separation of 16 bits (table 1 in paper).

therefore, fletcher explicitely recommends against using two's complement version.


Comments

Post a Comment

Popular posts from this blog

javascript - Chart.js (Radar Chart) different scaleLineColor for each scaleLine -

-
Image
i try , create radar chart using chart.js has various colours each scaleline, or coloured between scalelines. wondering if possible? from: to: i have working graph, though there doesn't seem method change individual scale lines. kind regards leigh you can extend radar chart type this, so chart.types.radar.extend({ name: "radaralt", initialize: function (data) { chart.types.radar.prototype.initialize.apply(this, arguments); var originalscaledraw = this.scale.draw; var ctx = this.chart.ctx; this.scale.draw = function () { var linewidth = this.linewidth; // bypasses line drawing in originalscaledraw this.linewidth = linewidth; originalscaledraw.apply(this, arguments); ctx.linewidth = this.linewidth; var scale = this; // draw chart.helpers.each(scale.ylabels, function (label, index) { // color of ...
Read more

apache - Error with PHP mail(): Multiple or malformed newlines found in additional_header -

-
suddenly have started receiving above error without changes having been made script. host 1and1 (i know...) the script still works fine on different server, , suspicion there must have been server config change has lead this, although hosts plead ignorance. there's no information on above error @ in google can find - have ideas? server running apache if helps. had similar problem. came out of blue. no php code changed. what changed: php upgraded 5.5.25-1 5.5.26. a security risk in php mail() function has been fixed , newlines in additional_headers allowed no more. because newlines mean: starts email message (and surely don't want inject newlines through headers followed evil message). what have worked fine, e.g. having newlines after headers or passing whole message additional_headers , function no more. solution : sanitize headers. no multiple newlines in additional_headers argument. these count "multiple or malformed newlines":...
Read more

java - Android – MapFragment overlay button shadow, just like MyLocation button -

-
Image
i'm struggling add shadow custom overlay button on google map. goal make custom button google's mylocation button. here's how app looks now: layout.xml <relativelayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" xmlns:map="http://schemas.android.com/apk/res-auto" android:layout_height="match_parent" android:layout_width="match_parent" style="@style/apptheme"> <fragment android:layout_width="match_parent" android:layout_height="match_parent" android:id="@+id/map" tools:context=".mapsactivity" android:name="com.google.android.gms.maps.supportmapfragment" android:layout_alignparentend="true" android:layout_alignparentstart="true" android:layout_alignparentbottom="true" ...
Read more