A Byte copy command similar to Mid?

TSEYFARTH · Joined: 01 Jul 2006 Posts: 1054

Hello all,

I need to selectively copy some bytes from one variable to another. I tried MEMCOPY but that did not work.

Paulvk · Joined: 28 Jul 2006 Posts: 1257 Location: SYDNEY

Hello Tim

I would overlay a byte array onto the variables then select the elements in the arrays to swap/move

Regards paul

TSEYFARTH · Joined: 01 Jul 2006 Posts: 1054

Hi Paul,
Thanks for the tip. But it already is a bytes array:

Paulvk · Joined: 28 Jul 2006 Posts: 1257 Location: SYDNEY

Hello Tim

then just copy the elements you want from buffer array to the other
I thought with your question that they were not byte arrays just variables.
Yes if you have bytes that are ASCII characters as I have in the web servers you can overlay a byte array on a string variable
then use string functions on the string to search for characters this is what I do in the web servers
I take bytes from the wiznet/enc28j60 chips put them into the overlay-ed byte array then they are also in the string.
eg
dim thestring as string * 100
dim bytesof(101) as byte at thestring overlay
Note there is an extra byte at the end of the string as a terminator you need to set this byte see web servers.
Also note you can put the ASCII value as a number into a byte then in the string it is a character.

regards Paul

MWS · Joined: 22 Aug 2009 Posts: 2262

TSEYFARTH · Joined: 01 Jul 2006 Posts: 1054

Hi MWS.
Yes, I am guilty as charged..... The medium gentility is sometimes a good idea - not preachy put downs, but a reminder of what can make a difference to the reader and the poster. The poster will get more responses with more complete information, as you have pointed out.

I was actually going to make post today (just got up after a long night) that I was able to solve the problem. I was not getting the answer that I was expecting but was blind by the use of the MEMCOPY command. I had reviewed the help which was only a little help. Had the results been shown in the help for each of the lines of code that would have been more clarifying. And of course having not made a simple trial, as you suggested too, may have helped.

This is the code that works properly

albertsm · Joined: 09 Apr 2004 Posts: 5921 Location: Holland

TSEYFARTH · Joined: 01 Jul 2006 Posts: 1054

HI Mark,

Please understand I am/was not throwing rocks at you or the tools you created - they ARE really GREAT! I cannot wait for the next tool set to become available - I will be one of the first to buy it! The problem was not with the help, and it was *of* help; but it would have been of even more help had it had just a tiny bit more.

I will try to explain specifically what I mean. This is from the MEMCOPY in help.

"///
option
An optional numeric constant with one of the following values :
1 - only the source address will be increased after each copied byte
2 - only the target address will be increased after each copied byte
3 - both the source and target address will be increased after each copied byte
"///
What is meant by "increased"?? Does this mean "changed to"? Or "incremented"?

"///
Dim Ars(10) As Byte 'source bytes
Dim Art(10) As Byte 'target bytes
Dim J As Byte 'index

For J = 1 To 10 'fill array
Ars(j) = J
Next
J = Memcopy(ars(1) , Art(1) , 4) 'copy 4 bytes
Print J ; " bytes copied"
"///
what the new value of Art(1) Art(2) Art(3) Art(4) ? Is it the value 1, 2, 3, 4 or all 1's - I am 99% sure it is 1234.

"///
Dim W As Word , L As Long
W = 65511
J = Memcopy(w , L , 2) 'copy 2 bytes from word to long
End
"///
What is the new value of L?

If the result was shown, ie what the new value of Art(1) Art(2) Art(3) Art(4) and L becomes, it would be clearer - at least to me.

"///
For J = 1 To 10
Print Art(j)
Next
J = Memcopy(ars(1) , Art(1) , 10 , 2) 'assign them all with element 1
"///
In this case, when using option 2 how is the second array Art(1) set to the value of element 1? option 2 says that the target address (Art()) is "incremented", so how it is set to a 1 in each element of its array?

If this is obvious to everyone else, please excuse my ignorance. And, perhaps this is deemed redundant, obvious or something else; but when fighting with a problem and one referrs to the help, which is what it is there for, the expected result is absolutely spelled out, leaving nothing to ambiguity. Having that absolute, would have said to me, that to look elsewhere in my code to find the problem.

In the above cases, the two things that are confusing are the words "increased" in the options and in the last example understanding how they call get to a 1. Finally in this same help example, it says "MEMCOPY can also be used to clear an array quickly". How? After now having used this, I suppose I can assume that both the target and/or the source would be set to some new value like 255, or 0 etc. But spelling it out would complete the effort you made when you created and updated the Help.

As a final example, from the help for MID:
Dim S As String * 15 , Z As String * 15
S ="ABCDEFG"
Z = Left(s , 5)
Print Z 'ABCDE

This spells out that the value of Z will be "ABCDE"! Leaving nothing to guess.

Again Mark, I hope you do not take offense to the comments. In the above, you asked for a response and that is what I have tried to provide.

Thank you,
Tim

albertsm · Joined: 09 Apr 2004 Posts: 5921 Location: Holland

- first of all, when having doubts of what is meant in the help : ask. it is the only way to clear it up and to improve it.

TSEYFARTH · Joined: 01 Jul 2006 Posts: 1054

Thank you Mark,
Tim