Re: [Boost-users] Seekg on a gzip'd file...Is this possible?

Subject: Re: [Boost-users] Seekg on a gzip'd file...Is this possible?
From: Gerrick Bivins (gbivins_at_[hidden])
Date: 2009-03-14 14:25:16

I'd actually like to "skip" (move forward) in the stream. "Rewind"
functionality would not be necessary. As I stated earlier, I'm porting code
from java to c++ that has this functionality via
java.util.zip.GZIPInputStream.  My desired functionality would be something
like this:
1) read some header info
2) read meta data that tells me which parts of the data I care about
3) Continue read through file sequentially:
    a) extract needed data as it is encountered
    b) use meta data to skipping over unneeded data to the next set of
needed data.  
So maybe a "skip" method would be appropriate?
Gerrick

On 3/13/09 11:05 PM, "Cory Nelson" <phrosty_at_[hidden]> wrote:

> On Fri, Mar 13, 2009 at 7:59 PM, Gerrick Bivins
> <gbivins_at_[hidden]> wrote:
>> Hi Steven,
>> Thanks for the response. Does that mean that the gzip_decompressor in boost
>> doesn't' support seeking or does gzip in general not support seekeing? Any
>> suggestions for working around this problem?
>> Gerrick
> 
> Gzip steams can only move forward.  I see no reason why at least this
> couldn't be supported other than most people expect seek to be
> instant, whereas gzip will have to decompress all the way to that
> point.  Does seek have some complexity requirements that make this a
> bad idea?