Re: Insert data in a file
On Dec 20, 12:56 am, Paavo Helde <pa...@nospam.please.ee> wrote:
The Doctor <TheDoc...@imnotemailable.org> kirjutas:
I am writing an application, which has to insert and remove
data from a file. I have a quite big file (~500 mb), and I
want to insert and remove data from it. How do I do this
without having to move huge blocks of data manually? That
would really cost a lot of time.
If you want to move data inside the file to other location,
then you have to do it, nobody else is doing that for you
(except maybe DMA can do it faster? never tried...).
I would map the file in memory (partially at least) and worked
in that interface, but this depends on OS and is not on topic
here. In portable C/C++ you would have to open the file in
binary mode, seek around in the file, read some parts into a
buffer, seek to somewhere else, write them out there, etc.
Even that doesn't really work. You can't insert data into a
file, nor remove it. Period. You can only overwrite it.
Note that C++ stream abstraction is probably just nuisance
here, you might want to work directly on C level (FILE*
interface).
There's no difference with regards to what you can do with FILE*
or with an fstream; the same constraints hold. For that matter,
the fact that you can't insert or remove data also holds at the
system level (int or HANDLE as a file descriptor) under Unix or
Windows.
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