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Re: Faster StrNCpy

From: Markus Schaber <schabi(at)logix-tt(dot)com>
To: pgsql-hackers(at)postgresql(dot)org
Subject: Re: Faster StrNCpy
Date: 2006-09-29 09:21:21
Message-ID: 451CE591.9030108@logix-tt.com (view raw or flat)
Thread:
Lists: pgsql-hackerspgsql-patches
Hi, Tom,

Tom Lane wrote:
> "Strong, David" <david(dot)strong(at)unisys(dot)com> writes:
>> Just wondering - are any of these cases where a memcpy() would work
>> just as well? Or are you not sure that the source string is at least
>> 64 bytes in length?
> 
> In most cases, we're pretty sure that it's *not* --- it'll just be a
> palloc'd C string.
> 
> I'm disinclined to fool with the restriction that namestrcpy zero-pad
> Name values, because they might end up on disk, and allowing random
> memory contents to get written out is ungood from a security point of
> view.

There's another disadvantage of always copying 64 bytes:

It may be that the 64-byte range crosses a page boundary. Now guess what
happens when this next page is not mapped -> segfault.

Markus
-- 
Markus Schaber | Logical Tracking&Tracing International AG
Dipl. Inf.     | Software Development GIS

Fight against software patents in Europe! www.ffii.org
www.nosoftwarepatents.org

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