# [PATCH] block-sha1: make the size member first in the context struct 3 messages from 2009-08-18 to 2009-08-18. Participants: Nicolas Pitre, Johannes Schindelin. Thread: https://gitlist.dev/t/20648 ## Nicolas Pitre, 2009-08-18 00:18 Subject: [PATCH] block-sha1: make the size member first in the context struct Message-ID: URL: https://gitlist.dev/e/alpine.LFD.2.00.0908172012591.6044%40xanadu.home ``` This is a 64-bit value, hence having it first provides a better alignment. Signed-off-by: Nicolas Pitre diff --git a/block-sha1/sha1.h b/block-sha1/sha1.h index 6ff59b2..b864df6 100644 --- a/block-sha1/sha1.h +++ b/block-sha1/sha1.h @@ -7,9 +7,9 @@ */ typedef struct { + unsigned long long size; unsigned int H[5]; unsigned int W[16]; - unsigned long long size; } blk_SHA_CTX; void blk_SHA1_Init(blk_SHA_CTX *ctx); ``` ## Johannes Schindelin, 2009-08-18 00:24 Subject: Re: [PATCH] block-sha1: make the size member first in the context struct Message-ID: URL: https://gitlist.dev/e/alpine.DEB.1.00.0908180223280.8306%40pacific.mpi-cbg.de In-Reply-To: ``` Hi, On Mon, 17 Aug 2009, Nicolas Pitre wrote: > This is a 64-bit value, hence having it first provides a better > alignment. > > Signed-off-by: Nicolas Pitre > > diff --git a/block-sha1/sha1.h b/block-sha1/sha1.h > index 6ff59b2..b864df6 100644 > --- a/block-sha1/sha1.h > +++ b/block-sha1/sha1.h > @@ -7,9 +7,9 @@ > */ > > typedef struct { > + unsigned long long size; > unsigned int H[5]; > unsigned int W[16]; > - unsigned long long size; > } blk_SHA_CTX; By the reasoning suggested in the commit message, should H[5] not go to the end? Ciao, Dscho ``` ## Nicolas Pitre, 2009-08-18 00:39 Subject: Re: [PATCH] block-sha1: make the size member first in the context struct Message-ID: URL: https://gitlist.dev/e/alpine.LFD.2.00.0908172035320.6044%40xanadu.home In-Reply-To: ``` On Tue, 18 Aug 2009, Johannes Schindelin wrote: > Hi, > > On Mon, 17 Aug 2009, Nicolas Pitre wrote: > > > This is a 64-bit value, hence having it first provides a better > > alignment. > > > > Signed-off-by: Nicolas Pitre > > > > diff --git a/block-sha1/sha1.h b/block-sha1/sha1.h > > index 6ff59b2..b864df6 100644 > > --- a/block-sha1/sha1.h > > +++ b/block-sha1/sha1.h > > @@ -7,9 +7,9 @@ > > */ > > > > typedef struct { > > + unsigned long long size; > > unsigned int H[5]; > > unsigned int W[16]; > > - unsigned long long size; > > } blk_SHA_CTX; > > By the reasoning suggested in the commit message, should H[5] not go to > the end? Both arrays are based of unsigned ints which have the same alignment rules. Furthermore the size and H members are much more used than the W member, and keeping them close should help with CPU cache locality. Nicolas ```