I want to pull a 3.5 meg file into a Byte Array in Fox, make some changes to individual bytes, and write the array back to another file.
The only way I have found to do so is to build the array one character at a time. Is there a better way to do this?
Thanks in advance for any input ,
Joe
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A "ByteArray" is just a stream of Bytes (i.e. a file) and you can address any position directly by offset.
cBytes = FileToStr(Getfile()) ? LEN(cBytes)
cBytes = STUFF(cBytes, 5648, 5, "Hello") && replace 5 Bytes at 5648 with a string; or insert or delete bytes. See help on that STUFF :)
StrToFile(cBytes, PutFile()) && write Bytestream back to disk with new name
Another option is just using LLFFs (LowLevelFileFunctions):
nHandle = FOPEN(GetFile()) FSEEK(nHandle, 5648, 0) FRWITE(nHandle, "Hello") FCLOSE(nHandle)
wOOdy
-----Ursprüngliche Nachricht----- Von: ProFox profox-bounces@leafe.com Im Auftrag von Joe Yoder Gesendet: Dienstag, 2. Mai 2023 04:33 An: profoxtech@leafe.com Betreff: Byte Arrays in VFP
I want to pull a 3.5 meg file into a Byte Array in Fox, make some changes to individual bytes, and write the array back to another file. The only way I have found to do so is to build the array one character at a time. Is there a better way to do this? Thanks in advance for any input ,
Joe
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Couldn't you leave the file on disk and make the changes directly to the file with low level file functions https://hackfox.github.io/section4/s4g194.html?
Eric
On Mon, May 1, 2023 at 9:33 PM Joe Yoder joe@wheypower.com wrote:
I want to pull a 3.5 meg file into a Byte Array in Fox, make some changes to individual bytes, and write the array back to another file.
The only way I have found to do so is to build the array one character at a time. Is there a better way to do this?
Thanks in advance for any input ,
Joe
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Coincidentally as I was preparing my VFP2C32 presentation just now for next week's Virtual Fox Fest, I was reading about the Windows API's support for memory mapped files.
"Memory-mapped files: The Windows API also provides support for memory-mapped files, which allow developers to map a file directly into memory and access it as if it were an array."
I'm going to see if I can contrive an example of how to do this in VFP.
Eric
On Tue, May 2, 2023 at 8:31 AM Eric Selje Eric@saltydogllc.com wrote:
Couldn't you leave the file on disk and make the changes directly to the file with low level file functions https://hackfox.github.io/section4/s4g194.html?
Eric
On Mon, May 1, 2023 at 9:33 PM Joe Yoder joe@wheypower.com wrote:
I want to pull a 3.5 meg file into a Byte Array in Fox, make some changes to individual bytes, and write the array back to another file.
The only way I have found to do so is to build the array one character at a time. Is there a better way to do this?
Thanks in advance for any input ,
Joe
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