> Steve B. <steve_beauge@com.msn_swap_com_and_msn> wrote:
>> I'm building an application that use a binary file format with a
>> proprietary
>> format.
>> Files can grow up to several GBytes...
>>
>> The mecanism of building the data is quite complex and I'd like to know
>> if
>> multiple threads can -simultaneously- write into the data file...
>>
>> For example, I know in advance thread one will write the first 100MB,
>> thread
>> two 50 next MB, and so on. Can I write from multiple threads ?
>> What objects Have I to use ?
>> One FileStream and seeking as needing ? One FileStream and several
>> StreamWriters ? etc ...
>
> I suspect there *are* ways of doing it from multiple threads, but it
> feels like the kind of thing which could very easily go wrong. An
> alternative which may well be simpler would be to have a single thread
> which had a queue of write requests. The other threads would add jobs
> to the queue, and then the single thread could process those requests.
>
> --
> Jon Skeet - <sk***@pobox.com>
> http://www.pobox.com/~skeet   Blog: http://www.msmvps.com/jon.skeet
> If replying to the group, please do not mail me too

> After some tests, I found a solution which seems to work :
>
> lock (outputStream)
> {
> outputStream.Seek(
> dataOffset + numberObBytesWritten
> SeekOrigin.Begin
> );
>
> outputStream.Write(
> buffer,
> 0,
> read
> );
>
> I'm not sure this is a very smart solution.

> Steve B. <steve_beauge@com.msn_swap_com_and_msn> wrote:
>> After some tests, I found a solution which seems to work :
>>
>> lock (outputStream)
>> {
>> outputStream.Seek(
>> dataOffset + numberObBytesWritten
>> SeekOrigin.Begin
>> );
>>
>> outputStream.Write(
>> buffer,
>> 0,
>> read
>> );
>>
>> I'm not sure this is a very smart solution.
>
> It's not particularly safe, as if you have two streams pointing at the
> same file, they could still both update it simultaneously.
>
>> Your solution should look like this :
>>
>> WriterClass.QueueWriteOperation(Stream s, int offset, byte[] buffer)...
>> That's it ?
>
> I wouldn't pass the stream - I'd create one WriterClass (or whatever)
> per file I wanted to write to, and have it maintain the stream. Now,
> admittedly you'd still need to make sure you didn't create two
> WriterClasses for the same file, but that's probably easier to do than
> the stream equivalent. (You could easily provide a factory method, in
> fact.)
>
> Note that an easier way of seeking is often to use the Position
> property:
>
> outputStream.Position = dataOffset+numberOfBytesWritten;
>
> --
> Jon Skeet - <sk***@pobox.com>
> http://www.pobox.com/~skeet   Blog: http://www.msmvps.com/jon.skeet
> If replying to the group, please do not mail me too