Simplest way to truncate a file

I suspect Joerg and Colin were suggesting that these kinds of APIs deserve to be better exposed via the filename ;)

-Boris (via BlackBerry)

----- Original Message -----
From: [hidden email] <[hidden email]>
To: [hidden email] <[hidden email]>
Sent: Wed Mar 03 13:34:35 2010
Subject: Re: [vwnc] Simplest way to truncate a file

True, if you want to truncate it to a specific size - then the original
example is probably the fastest way to do it.

On 3/3/10 1:12 PM, Colin Putney, DeepCove Labs (YVR) wrote:
> That'll only truncate to size 0, though. Say a file is 10 bytes long and
> you want it to be 7 bytes long. #truncateTo: seems to be the only way to
> do that.
>
> -----Original Message-----
> From: [hidden email] [[hidden email]] On
> Behalf Of Michael Lucas-Smith
> Sent: Wednesday, March 03, 2010 10:57 AM
> To: [hidden email]
> Subject: Re: [vwnc] Simplest way to truncate a file
>
> On 3/3/10 10:49 AM, Joerg Beekmann, DeepCove Labs (YVR) wrote:
>   
>> This is the simplest way I could see to truncate an external file. Is
>> there a more obvious approach?
>>
>>     
> You don't need to do the truncateTo:, simply opening an existing file
> for write only will truncate it. You just need to close it after that.
>
> (IOAccessor
>       openFileNamed: aFilename
>       direction: IOAccessor writeOnly
>       creation: IOAccessor truncateNoCreate)
>           close
>
> Cheers,
> Michael
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Heh. Well, actually, this came up because I wanted to truncate a file that I had an ExternalReadWriteStream on. I figured it would be something like  [stream position: 7; truncate].

 

But #truncate doesn’t exist. So I poked around and found IOAccessor>>truncateTo:, which has no senders. I tried implementing #truncate, but found that buffering gets in the way – as soon as you close the file, the buffer gets flushed, undoing the truncation. Updating the buffer state of an ExternalReadWriteStream is decidedly non-trivial, so I went in a different direction and did something that didn’t require truncating the file.

 

I’m a bit surprised that such a fundamental operation isn’t implemented, but I guess folks find work-arounds, just like I did.

 

Colin

 

 

From: [hidden email] [[hidden email]] On Behalf Of Boris Popov, DeepCove Labs (YVR)
Sent: Wednesday, March 03, 2010 2:09 PM
To: [hidden email]; [hidden email]
Subject: Re: [vwnc] Simplest way to truncate a file

 

I suspect Joerg and Colin were suggesting that these kinds of APIs deserve to be better exposed via the filename ;)

-Boris (via BlackBerry)

----- Original Message -----
From: [hidden email] [hidden email]
To: [hidden email] [hidden email]
Sent: Wed Mar 03 13:34:35 2010
Subject: Re: [vwnc] Simplest way to truncate a file

True, if you want to truncate it to a specific size - then the original
example is probably the fastest way to do it.

On 3/3/10 1:12 PM, Colin Putney, DeepCove Labs (YVR) wrote:
> That'll only truncate to size 0, though. Say a file is 10 bytes long and
> you want it to be 7 bytes long. #truncateTo: seems to be the only way to
> do that.
>
> -----Original Message-----
> From: [hidden email] [[hidden email]] On
> Behalf Of Michael Lucas-Smith
> Sent: Wednesday, March 03, 2010 10:57 AM
> To: [hidden email]
> Subject: Re: [vwnc] Simplest way to truncate a file
>
> On 3/3/10 10:49 AM, Joerg Beekmann, DeepCove Labs (YVR) wrote:
>   
>> This is the simplest way I could see to truncate an external file. Is
>> there a more obvious approach?
>>
>>     
> You don't need to do the truncateTo:, simply opening an existing file
> for write only will truncate it. You just need to close it after that.
>
> (IOAccessor
>       openFileNamed: aFilename
>       direction: IOAccessor writeOnly
>       creation: IOAccessor truncateNoCreate)
>           close
>
> Cheers,
> Michael
> _______________________________________________
> vwnc mailing list
> [hidden email]
> http://lists.cs.uiuc.edu/mailman/listinfo/vwnc
>
> _______________________________________________
> vwnc mailing list
> [hidden email]
> http://lists.cs.uiuc.edu/mailman/listinfo/vwnc
>
>   

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I suspect Joerg and Colin were suggesting that these kinds of APIs deserve to be better exposed via the filename ;)

-Boris (via BlackBerry)

----- Original Message -----
From: [hidden email] <[hidden email]>
To: [hidden email] <[hidden email]>
Sent: Wed Mar 03 13:34:35 2010
Subject: Re: [vwnc] Simplest way to truncate a file

True, if you want to truncate it to a specific size - then the original
example is probably the fastest way to do it.

On 3/3/10 1:12 PM, Colin Putney, DeepCove Labs (YVR) wrote: