.net - md5 hash for file without File Attributes -

-

using following code compute md5 hashs of files:

 private _md5hash string  dim _binarydata byte() = new byte(fileupload1.postedfile.inputstream.length) {}  fileupload1.postedfile.inputstream.read(_binarydata, 0, _binarydata.length)   dim md5 new system.security.cryptography.md5cryptoserviceprovider  dim md5hash() byte  md5hash = md5.computehash(me._binarydata)  me._md5hash = bytearraytostring(md5hash)    private function bytearraytostring(byval arrinput() byte) string      dim sb new system.text.stringbuilder(arrinput.length * 2)      integer = 0 arrinput.length - 1        sb.append(arrinput(i).tostring("x2"))      next      return sb.tostring().tolower   end function

we getting different hashes depending on create-date , modify-date of file. storing hash , binary file in sql db. works fine when upload same instance of file. when save new instance of file db (with today's date create/modify) on file-system , check new hash versus md5 stored in db not match, , therefor fail duplicate check.

how can check file hash excluding file attributes? or there different issue here?

i suspect me._binarydata getting initialized more contents of file...

ultimately way hash can change if byte array changes.

another possibility character set / encoding differences when persist/restore file db.


Comments

Post a Comment

Popular posts from this blog

javascript - Enclosure Memory Copies -

-
function myclass() { //lots , lots of vars , code here. this.bar = function() { //do numerous enclosed myclass vars } this.foo = function() { alert('hello'); //don't enclosed variables. } } each instance of myclass gets own copy of bar , foo, why prototyped methods use less memory. however, know more memory use of inner methods. it seems obvious me (1) below must true. agree? not distinct myclass instances have own distinct copies of bar, must have own distinct copies of myclass enclosure. (or else how bar method keep myclass variables straight on per instance basis?) now (2) question i'm after. since inner foo method doesn't use in myclass enclosure natural qustion is: javascript smart enough not keep myclass enclosure in memory use of foo? this depend entirely on implementation not language. naive implementations keep far more around others. answer true e.g. v8 (chrome's js engine) may not true spider...
Read more

php - Replacing tags in braces, even nested tags, with regex -

-
example preg_replace('/\{[a-za-z.,\(\)0-9]+\}/', 'replaced', 'lorem ipsum dolor sit {tag1({tag2()})}, consectetur adipiscing elit.'); the result: lorem ipsum dolor sit {tag1(replaced)}, consectetur adipiscing elit. question as can see "tag2" has been replaced, want replace "tag1" know how can this? (in cases might this: {tag1({tag2({tag3()})})}) , on.) btw using preg_replace_callback, easier show preg_replace here site can test code: http://www.spaweditor.com/scripts/regex/index.php you need add curly braces character set. here's pattern used: /\{[a-za-z.,\(\)\{\}0-9]+\}/ and here result: "lorem ipsum dolor sit replaced, consectetur adipiscing elit."
Read more