Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.lang.c > #8515

Re: skipping bytes

Show all headers | View raw

blmblm@myrealbox.com wrote:
> In article <4e25d86a$0$1975$bbae4d71@news.suddenlink.net>,
> Bill Cunningham <nospam@nspam.invalid> wrote:
>> blmblm@myrealbox.com wrote:
>>> In article <4e24a90b$0$8602$bbae4d71@news.suddenlink.net>,
>>> Bill Cunningham <nospam@nspam.invalid> wrote:
>>>> John Gordon wrote:
>>>>> In <4e24a281$0$1929$bbae4d71@news.suddenlink.net> "Bill
>>>>> Cunningham" <nospam@nspam.invalid> writes:
>>>>>
>>>>>>     I want to take a 700MB file and skip evey 200MB, so I thought
>>>>>> of this.
>>>>>
>>>>> You mean you want to copy the 700MB file to another file, omitting
>>>>> 200MB chunks?
>>>>>
>>>>>> long * space=malloc(sizeof(long)*500000);
>>>>>
>>>>> There's no need to allocate that much space for a simple copy
>>>>> operation.
>>>>> You can copy, say, 8K or 16K at a time without allocating a huge
>>>>> buffer.
>>>>
>>>>     I actually wanted to do something a little more difficult than
>>>> just copy the file. Every 200MB I want to save in a buffer about 8
>>>> bytes of data and exchange 0x0000 for it. It doesn't have to be
>>>> every 200M but it's such a large file I thought of 200MB. Not using
>>>> malloc() makes things so much easier. It doesn't have to be exactly
>>>> 8 bytes it could be 32. The important thing is to correctly store
>>>> the data read and save it correctly so it could be put back.
>>>
>>> Do you have some end goal in mind, or are you doing this because it
>>> somehow strikes you as an interesting or entertaining problem in its
>>> own right?  I can't make much sense of the above description and am
>>> (mildly) curious.
>>
>>     Please don't say "don't reinvent the wheel" it's all been done.
>> Everything is a learning experience. By punching "holes" in a file
>> you make it unreadable. By saving that information and reinserting
>> it it becomes readable again.
>
> Oh!  Okay, well, that's not a task I'd have set myself, but this
> description is *almost* enough for me to imagine what the code
> might be like, and I guess I can sort of understand how it might
> seem like an interesting problem.  (Depending on what kind of file
> it is, just replacing some of the data might or might not make it
> totally unreadable.  But that may not matter to you.)
>
> One question you might ask yourself is where you're going to
> save the data you overwrite and want to put back later -- will
> it go in some separate file, or in some predetermined place in
> the original, or what?

    Exactly. I was thinking about saving it in another file. This would be 
to complicted for me to simply put into main() and I would have to break it 
down into function. I can almost imagine how to do it. I'm not bad with C 
functions; the ones I use mostly but counting and reading and writing would 
be more complicated for me.

    Anyway. Interesting learning experience.

Bill

Back to comp.lang.c | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

skipping bytes "Bill Cunningham" <nospam@nspam.invalid> - 2011-07-19 05:15 -0400
  Re: skipping bytes John Gordon <gordon@panix.com> - 2011-07-18 21:35 +0000
    Re: skipping bytes "Bill Cunningham" <nospam@nspam.invalid> - 2011-07-19 05:43 -0400
      Re: skipping bytes blmblm@myrealbox.com <blmblm.myrealbox@gmail.com> - 2011-07-19 17:27 +0000
        Re: skipping bytes Chad <cdalten@gmail.com> - 2011-07-19 12:09 -0700
          Re: skipping bytes blmblm@myrealbox.com <blmblm.myrealbox@gmail.com> - 2011-07-19 21:34 +0000
        Re: skipping bytes "Bill Cunningham" <nospam@nspam.invalid> - 2011-07-20 03:17 -0400
          Re: skipping bytes blmblm@myrealbox.com <blmblm.myrealbox@gmail.com> - 2011-07-19 21:35 +0000
            Re: skipping bytes "Bill Cunningham" <nospam@nspam.invalid> - 2011-07-20 07:01 -0400
            Re: skipping bytes "Bill Cunningham" <nospam@nspam.invalid> - 2011-07-22 11:25 -0400
  Re: skipping bytes Ian Collins <ian-news@hotmail.com> - 2011-07-19 09:42 +1200

csiph-web