Splitting a file

[some dude]

I need to split a file into multiple parts. Let's say you have a 3.8 MB file and need to split it into 500 KB segments; how would I do this?

Thanks.

[czimmerman]

See http://www.freevbcode.com/ShowCode.Asp?ID=449

[xxMariusxx]

The following code should do what you're asking. I wrote it on the fly so I don't know how efficient it really is. Regarding the code, though, maybe someone can answer this for me. When you split up the files, the sum total size of all the files is larger than the original file...and when you reconstruct the original from the smaller chunks, the new file is actually larger in size than the original, but is virtually identical in every other respect. I have a version of Jasc Paint Shop Pro I tested the code with. After reconstruction, the new executable was exactly 32767 bytes larger than the original, but it ran just the same as before.

It wouldn't really matter except that 32767 bytes is too much of a coincidence in this case. During splitting up the file, I transferred data in exactly 32K chunks...and now my new file is 32K larger than the original. I gotta go skiing in a bit here so I don't have time to sit and pick apart the code looking for the mysterious 32K, but if someone wants a neat little puzzle to figure out then they can find out where this is coming from and why it doesn't affect the end result file and email me at butlerc@tdssd.com with your answer.



public Sub Split_Up_File()
Dim smallChunkSize as Long
Dim position1 as Long
Dim position2 as Long
Dim filesize as Long
Dim numTmpFiles as Integer
Dim theData as string
Dim sizeCopied as Long

' initialize state variables
smallChunkSize = 32767 ' break off 32K chunks at a time to write to a temp file
sizeCopied = 0 ' keep track of how much data has been copied from the source file
numTmpFiles = 1 ' helps determine the name of our temp files
position1 = 1 ' keeps track of the byte position to read from in the source file
position2 = 1 ' keeps track of the byte position to write to in the temp file
Open "YOUR_FILE" for binary as #1
filesize = LOF(1)
Open "SOME_DIRECTORY\tempfile1.tmp" for binary as #2
Do While filesize - sizeCopied >= smallChunkSize
If position2 >= 512000 then ' position2 starts out at 1, so we ignore this
Close #2 ' the first run through. Later when the temp file
position2 = 1 ' size exceeds 512000 (500K), we close it and
numTmpFiles = numTmpFiles + 1 ' open another file to write to
Open "SOME_DIRECTORY\tempfile" & numTmpFiles & ".tmp" for binary as #2
End If
theData = string(smallChunkSize, " ")
get #1, position1, theData ' read the 32K chunk of data from the source file
Put #2, position2, theData ' and write it to the temp file
sizeCopied = position1 - 1
position1 = position1 + smallChunkSize ' increment the byte position of
position2 = position2 + smallChunkSize ' read/write in each file
Loop
If filesize - sizeCopied > 0 then ' if there was data left over
theData = string(filesize - sizeCopied, " ") ' that didn't fit neatly into
get #1, position1, theData ' our 32K chunk, read it out of the source file and
Put #2, position2, theData ' write it to the end of our temp file
End If
Close #1
Close #2
End Sub

public Sub Reconstruct_File()
Dim smallChunkSize as Long
Dim position1 as Long
Dim position2 as Long
Dim howManyFiles as Integer
Dim s as string
Dim i as Integer
Dim filesize as Long
Dim sizeCopied as Long
Dim theData as string

howManyFiles = 0
s = Dir("SAME_DIRECTORY_YOU_USED_BEFORE\*.tmp") ' determine the number
Do While s <> "" ' of files we will be using to reconstruct our original
howManyFiles = howManyFiles + 1
s = Dir
Loop
position1 = 1
smallChunkSize = 32767
Open "RECONSTRUCTION_FILE_NAME" for binary as #1 ' open the outfile
for i = 1 to howManyFiles
' open the the temp file corresponding to the current index of the loop
' to be read into the outfile
Open "SAME_DIRECTORY_YOU_USED_BEFORE\tempfile" & i & ".tmp" for binary as #2
position2 = 1
filesize = LOF(2)
sizeCopied = 0
Do While filesize - sizeCopied >= smallChunkSize ' begin reading data
theData = string(smallChunkSize, " ") ' from the temp file and writing it
get #2, position2, theData ' to the outfile in 32K chunks
Put #1, position1, theData
position2 = position2 + smallChunkSize
position1 = position1 + smallChunkSize
sizeCopied = position2 - 1
Loop
If filesize - sizeCopied > 0 then ' again, account for leftover
theData = string(filesize - sizeCopied, " ") ' bytes of data that did not
get #2, position2, theData ' neatly into our 32K chunks
Put #1, position1, theData
End If
Close #2 ' close the temp file and increment the loop to start working
next i ' with the next temp file, leaving the outfile open
Close #1 ' close the outfile
End Sub




xxMariusxx