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czmaster

Binary file and string

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czmaster

Hi,

If I remove some data (from a binary file) with the String functions (Stringregexp, StringMid, ...) some data are changed by 0x.

If I open the file and show the data without using the String functions the data doesn't change.

For example if I open a GIF file instead of the line GIF89 I have GI0x123456.

Do you know why ?

Thx !

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Jos

Hi,

If I remove some data (from a binary file) with the String functions (Stringregexp, StringMid, ...) some data are changed by 0x.

If I open the file and show the data without using the String functions the data doesn't change.

For example if I open a GIF file instead of the line GIF89 I have GI0x123456.

Do you know why ?

Thx !

You are probably doing something wrong but you will have to show the script to be able to see what is happening.

Jos


SciTE4AutoIt3 Full installer Download page   - Beta files       Read before posting     How to post scriptsource        Forum Rules
 
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Melba23

czmaster,

Because Autoit variables are not "typed" (that is forced to be something specific like an integer, string, float, etc) you sometimes get the "best guess" of the interpreter as to what a type particular variable is supposed to be. If you open a file in binary mode, Autoit presumes you want the contents as a hex string - and that is what you get: the hex bytes preceded by "0x" to indicate it is hex. Look at this example:

$sFilename = "Your_File_Path"

Global $hFileHandle = FileOpen($sFilename, 16)
$bFileContents = FileRead($hFileHandle)

$bFirstBytes = StringLeft($bFileContents, 16)
$bFirstHex = StringMid($bFileContents, 3, 14)

MsgBox(0, "", $bFirstBytes & @CRLF & "    " & $bFirstHex)

You can see that the "normal" return has the "0x" at the beginning - it is up to you to remove it if you want to manipulate the bytes themselves.

I know it sounds a pain, but it is the price to pay for having un-typed variables - one that I am very happy to pay given the flexibility that it offers. There are a number of commands which force variables into a specifiic type: Dec, Hex, Number, Binary, String, etc - these can be used if you want to change the type. For example, InputBox returns a string - so if you want to compare the result to a number, you need to reset the type first:

$sResult = InputBox(.....
If Number($sResult) > 5 Then
; .....

I hope that answers your question. If not, post your code so we can see what is going on and offer more advice. :)

M23


Any of my own code posted anywhere on the forum is available for use by others without any restriction of any kind._______My UDFs:

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czmaster

While 1

        $recv = TCPRecv($socket, 8)
        If @error <> 0 Then
            ExitLoop
        EndIf
        If ($x = 1) Then
            $txt &= $recv
        EndIf
        ConsoleWrite($recv)
    WEnd
    $f = FileOpen("123.txt", 1)

    $b = 1
    While $b <> 0
        $a = $b + 1
        $b = StringInStr($txt, @CRLF, 0, 1, $a)
        $t = StringMid($txt, $a, $b - $a)
        FileWrite($f, $t & @CRLF)
    Wend

This is a part of code, the entire program donwload a file from an HTTP server and remove chunk information.

When I show value of $recv it looks good, but in my file it isn't the same value.

Thx,

Edited by czmaster

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Authenticity

The file on the server is a binary or text file? Can you post the first few bytes?

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czmaster

The file on the server is a binary or text file? Can you post the first few bytes?

The file is a GIF but it can also be other format. The server return ASCII character but it isn't really text.

Authentic file bytes (copy/paste does not work with all character) :

GIF89a çÿ×é³ûÛüÿöÍå’þþý

Result file bytes :

G0x49463839612000200x00E7FF00EE9D93EDøØ
Edited by czmaster

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