[Libguestfs] [PATCH 8/12] hivex: Add HIVEX_OPEN_WRITE flag to allow hive to be opened for writing.
Matthew Booth
mbooth at redhat.com
Thu Feb 4 13:34:10 UTC 2010
On 03/02/10 18:34, Richard W.M. Jones wrote:
> Subject: [PATCH 08/12] hivex: Add HIVEX_OPEN_WRITE flag to allow hive to be opened for writing.
>
> If this flag is omitted (as in the case for all existing callers)
> then the hive is still opened read-only.
>
> We add a 'writable' flag to the hive handle, and we change the way
> that the hive file (data) is stored. The data is still mmapped if
> the file is opened read-only, since that is more efficient and allows
> us to handle larger hives. However if we need to write to the file
> then we have to read it all into memory, since if we had to extend the
> file we need to realloc that data.
>
> Note the manpage section L</WRITING TO HIVE FILES> comes in a later
> commit.
I'm not convinced this is a good idea. It introduces an asymmetry which
is like to lead to head-scratching bugs down the line.
Why can't we mremap where realloc would be necessary?
Matt
--
Matthew Booth, RHCA, RHCSS
Red Hat Engineering, Virtualisation Team
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