Crypto Error

[Saj]

I've put a small program together to explore crypto. I can seem to apply crypto but not the reverse. In the attached program press 'Create File' followed by 'Read File' to see the error.

 

[Erel]

You cannot safely convert an array of bytes to a string. This will only work if the bytes do represent a string. Otherwise some of the data gets lost. For example is there is a 0 bytes in the array the string will be trimmed to this byte.

 

[Saj]

So, can you suggest what I should do to save an array bytes to a file such that it can be read back safely?

 

[Erel]

You should use BinaryFile.WriteBytes / BinaryFile.ReadBytes. Sometimes it is useful to first write an int value with the array length.

 

[Saj]

Sometimes it is useful to first write an int value with the array length.

Sorry Erel, can you elaborate on this a bit more?

 

[Erel]

If you are writing several arrays one after another then you later need a way to separate the arrays when reading. In this case you can write the array size before each array and then when you read the data you first read the length and then know how many bytes you should read.
If you are only writing a single array to a file then it is simpler as you only need to read the whole file.

 

[Saj]

Thanks Erel. I've had a go at what you suggested. I think i'm getting an error reading an array. Could you take another look?

 

[Erel]

Which error do you get?

 

[Saj]

Hi Erel

I'm getting an error (line 100) which seems to be related to reading the number of saved bytes in the binary file - as you previously suggested.

Thanks

 

[agraham]

Your buffer() array is only 16 bytes long but you are trying to read 32 bytes into it.

 

[Saj]

Whats the syntax for redeclaring the size of an array on the fly after it has been declared in Globals? Ive tried 'Dim buffer(32)' and it don't like it.

 

[agraham]

Always read the error messages carefully. It has already told you what the problem is whether you ran it in the IDE or tried to compile it.

 

[Saj]

ah yes, gotcha