Re: Byte Arrays in VFP

[Eric Selje]

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  wrote:

> Couldn't you leave the file on disk and make the changes directly to the
> file with low level file functions
> ?
>
> Eric
>
> On Mon, May 1, 2023 at 9:33 PM Joe Yoder  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
>>
>>
>> --- StripMime Report -- processed MIME parts ---
>> multipart/alternative
>>   text/plain (text body -- kept)
>>   text/html
>> ---
>>
[excessive quoting removed by server]

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Re: Byte Arrays in VFP

[Eric Selje]

Couldn't you leave the file on disk and make the changes directly to the
file with low level file functions
?

Eric

On Mon, May 1, 2023 at 9:33 PM Joe Yoder  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
>
>
> --- StripMime Report -- processed MIME parts ---
> multipart/alternative
>   text/plain (text body -- kept)
>   text/html
> ---
>
[excessive quoting removed by server]

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AW: Byte Arrays in VFP

[Jürgen Wondzinski]

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  Im Auftrag von Joe Yoder
Gesendet: Dienstag, 2. Mai 2023 04:33
An: profoxt...@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


[excessive quoting removed by server]

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Byte Arrays in VFP

[Joe Yoder]

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


--- StripMime Report -- processed MIME parts ---
multipart/alternative
  text/plain (text body -- kept)
  text/html
---

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