From: Simon Cozens <simon@netthink.co.uk>
Date: Sat, 31 Mar 2001 13:09:59 +0000 (+0100)
Subject: Re: [PATCH] av.h cosmetics
X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=commitdiff_plain;h=319cef53be1e4f9b9d5f4c92c429de1b9c0b0640;p=p5sagit%2Fp5-mst-13.2.git

Re: [PATCH] av.h cosmetics
Message-ID: <20010331130959.A22000@netthink.co.uk>

Document AvALLOC.

p4raw-id: //depot/perl@9490
---

diff --git a/pod/perlguts.pod b/pod/perlguts.pod
index 35741c6..e18abba 100644
--- a/pod/perlguts.pod
+++ b/pod/perlguts.pod
@@ -247,6 +247,15 @@ portion of the string between the "real" and the "fake" beginnings is
 shown in parentheses, and the values of C<SvCUR> and C<SvLEN> reflect
 the fake beginning, not the real one.
 
+Something similar to the offset hack is perfomed on AVs to enable
+efficient shifting and splicing off the beginning of the array; while
+C<AvARRAY> points to the first element in the array that is visible from
+Perl, C<AvALLOC> points to the real start of the C array. These are
+usually the same, but a C<shift> operation can be carried out by
+increasing C<AvARRAY> by one and decreasing C<AvFILL> and C<AvLEN>.
+Again, the location of the real start of the C array only comes into
+play when freeing the array. See C<av_shift> in F<av.c>.
+
 =head2 What's Really Stored in an SV?
 
 Recall that the usual method of determining the type of scalar you have is