Luigi Auriemma

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 Post subject: PutDString and nul bytes
PostPosted: 09 Apr 2011 15:04 

Joined: 09 Apr 2011 14:41
Posts: 1
Hi Luigi,

I encountered an issue when trying to use PutDString.
I would like to write a blob of data to a memoryfile.

Apparently, the GetDString and PutDString show a different behavior.
Code:
PutDString VAR LENGTH [FILENUM]


example :

GetDString NAME 0x100
SetDString NAME 0x100 MEMORY_FILE



When writing a VAR that has NUL bytes embedded (because the input had them in the first place), data is padded with NUL bytes after the first \x00.

if input is :
01 02 03 04 05 00 01 02 03 04 etc.
output is (unfortunately) :
01 02 03 04 05 00 00 00 00 00 etc.

Here is the reason:
Code:
    if(size > datasz) { // fill with zeroes, I avoided to use myfputc(0x00, fd);
        size -= datasz;
        myalloc(&buff, size, &buffsz);
        memset(buff, 0, size);
        if(myfw(fd, buff, size) < 0) return(-1);
    }



on the other hand, GetDString does not seem to bother:
Code:
    myalloc(&buff, size + 1, &buffsz);
    myfr(fd, buff, size);
    buff[size] = 0;



My question is, would it be possible to bypass the datasz check?
If backward compatibility is a concern, how about having an additional arg to toggle the behavior?


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 Post subject: Re: PutDString and nul bytes
PostPosted: 10 Apr 2011 05:47 

Joined: 13 Aug 2007 21:44
Posts: 4068
Location: http://aluigi.org
the variables are strings so when there is a NULL delimiter they get truncated.
the only exception is the set VARIABLE binary "blahblah\x00blah\x0d\x0a" command that allows to store the variable including any byte.
I should check your specific case to know what solution would be better (exist many ways to do the same thing) anyway let me know if the set/binary command is ok


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