Binary File Access

You *definiately* do NOT want to read a file *ONE BYTE* at a time. It will be slow as *MUD*. This is due to the overhead of multiple calls. Generally you want to read in blocks that are the same size as a disk cluster. This will give overall best performance from the heads of the drive up to your app. The disk controller is going to read a cluster at a time no matter what so you might as well keep your disk buffers the same size range. On the *last* cluster your returned string will be *shorter* than your cluster size (this is one way to tell you're at the end).

If you want to create a new file as you go you need to kill the file off explicitly prior to opening with BINARY.

M

Ok I guess I have two questions.

1)  How do I tell the length of the file.

2) I want to feed the to a winsock program tha I wrote.  I want to be able to read in 2048 byte sections.  How do I do that.     Also if the program doesn't happen to end exactly at the end of the block how does the read know that.


I will up the points since I am being such a newbie on this topic

filelen() will give you the length before you open the file.
Set your character buffer to 2048 like this:

IsLastBlock = False

(repeat this loop as required)

Buffer$ = Space$( 2048 )   ' Fill with 2k of empty
GET #1,,Buffer$                'Replace with data from disk
IF LEN( Buffer$ ) <> 2048 THEN IsLastBlock = True
.

Would you want to use LOF for this???

Would you want to use LOF for this???

Ok then so I take everything in a nice blocks off 2048 bytes of information.  What happens to that last little bit when I don't hage 2048 bytes of information.

Ok then so I take everything in a nice blocks off 2048 bytes of information.  What happens to that last little bit when I don't hage 2048 bytes of information.

Then you send a short block to finish up.

LOF is used when the file is OPEN. FILELEN when the file is closed.

The length of Buffer$ will be 2048 if you read a full block or something less if you're at the end of the file. Here is some nice code for binary file copying:

'
' FileSpec$ = Full name/path of original file
' filnam$ = Root file name in local directory
'
' Ok, we want to copy in large blocks for speed, but we
' can't get too big or we'll run out of buffer
'
If Len(filnam$) > 0 Then
    rawsize = FileLen(filespec$)
    numblocks = Int(rawsize / 4096)
    fraction = rawsize Mod 4096
    Open filespec$ For Binary As #1
    Open maildir$ + filnam$ For Binary As #2
'
    If numblocks < 1 Then GoTo copytail
    '
    For cindex = 1 To numblocks
        bite$ = Space$(4096)
        Get #1, , bite$
        Put #2, , bite$
    Next cindex
    '
copytail:
    If fraction > 0 Then
        bite$ = Space$(fraction)
        Get #1, , bite$
        Put #2, , bite$
    End If
'
    Close
End If
'