X-Git-Url: http://git.maemo.org/git/?p=samba;a=blobdiff_plain;f=source%2Finclude%2Fbyteorder.h;fp=source%2Finclude%2Fbyteorder.h;h=0eef55730662e97ccb831de6bb37bad00caeee61;hp=0000000000000000000000000000000000000000;hb=6bca4ca307d55b6dc888e56cee47aebcddbce786;hpb=7fd70fa738b636089bcc6c961aa3eaa02f20dda2

diff --git a/source/include/byteorder.h b/source/include/byteorder.h
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+++ b/source/include/byteorder.h
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+/* 
+   Unix SMB/CIFS implementation.
+   SMB Byte handling
+   Copyright (C) Andrew Tridgell 1992-1998
+   
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 2 of the License, or
+   (at your option) any later version.
+   
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+   
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+*/
+
+#ifndef _BYTEORDER_H
+#define _BYTEORDER_H
+
+/*
+   This file implements macros for machine independent short and 
+   int manipulation
+
+Here is a description of this file that I emailed to the samba list once:
+
+> I am confused about the way that byteorder.h works in Samba. I have
+> looked at it, and I would have thought that you might make a distinction
+> between LE and BE machines, but you only seem to distinguish between 386
+> and all other architectures.
+> 
+> Can you give me a clue?
+
+sure.
+
+The distinction between 386 and other architectures is only there as
+an optimisation. You can take it out completely and it will make no
+difference. The routines (macros) in byteorder.h are totally byteorder
+independent. The 386 optimsation just takes advantage of the fact that
+the x86 processors don't care about alignment, so we don't have to
+align ints on int boundaries etc. If there are other processors out
+there that aren't alignment sensitive then you could also define
+CAREFUL_ALIGNMENT=0 on those processors as well.
+
+Ok, now to the macros themselves. I'll take a simple example, say we
+want to extract a 2 byte integer from a SMB packet and put it into a
+type called uint16 that is in the local machines byte order, and you
+want to do it with only the assumption that uint16 is _at_least_ 16
+bits long (this last condition is very important for architectures
+that don't have any int types that are 2 bytes long)
+
+You do this:
+
+#define CVAL(buf,pos) (((unsigned char *)(buf))[pos])
+#define PVAL(buf,pos) ((unsigned)CVAL(buf,pos))
+#define SVAL(buf,pos) (PVAL(buf,pos)|PVAL(buf,(pos)+1)<<8)
+
+then to extract a uint16 value at offset 25 in a buffer you do this:
+
+char *buffer = foo_bar();
+uint16 xx = SVAL(buffer,25);
+
+We are using the byteoder independence of the ANSI C bitshifts to do
+the work. A good optimising compiler should turn this into efficient
+code, especially if it happens to have the right byteorder :-)
+
+I know these macros can be made a bit tidier by removing some of the
+casts, but you need to look at byteorder.h as a whole to see the
+reasoning behind them. byteorder.h defines the following macros:
+
+SVAL(buf,pos) - extract a 2 byte SMB value
+IVAL(buf,pos) - extract a 4 byte SMB value
+SVALS(buf,pos) signed version of SVAL()
+IVALS(buf,pos) signed version of IVAL()
+
+SSVAL(buf,pos,val) - put a 2 byte SMB value into a buffer
+SIVAL(buf,pos,val) - put a 4 byte SMB value into a buffer
+SSVALS(buf,pos,val) - signed version of SSVAL()
+SIVALS(buf,pos,val) - signed version of SIVAL()
+
+RSVAL(buf,pos) - like SVAL() but for NMB byte ordering
+RSVALS(buf,pos) - like SVALS() but for NMB byte ordering
+RIVAL(buf,pos) - like IVAL() but for NMB byte ordering
+RIVALS(buf,pos) - like IVALS() but for NMB byte ordering
+RSSVAL(buf,pos,val) - like SSVAL() but for NMB ordering
+RSIVAL(buf,pos,val) - like SIVAL() but for NMB ordering
+RSIVALS(buf,pos,val) - like SIVALS() but for NMB ordering
+
+it also defines lots of intermediate macros, just ignore those :-)
+
+*/
+
+#undef CAREFUL_ALIGNMENT
+
+/* we know that the 386 can handle misalignment and has the "right" 
+   byteorder */
+#ifdef __i386__
+#define CAREFUL_ALIGNMENT 0
+#endif
+
+#ifndef CAREFUL_ALIGNMENT
+#define CAREFUL_ALIGNMENT 1
+#endif
+
+#define CVAL(buf,pos) ((unsigned)(((const unsigned char *)(buf))[pos]))
+#define CVAL_NC(buf,pos) (((unsigned char *)(buf))[pos]) /* Non-const version of CVAL */
+#define PVAL(buf,pos) (CVAL(buf,pos))
+#define SCVAL(buf,pos,val) (CVAL_NC(buf,pos) = (val))
+
+
+#if CAREFUL_ALIGNMENT
+
+#define SVAL(buf,pos) (PVAL(buf,pos)|PVAL(buf,(pos)+1)<<8)
+#define IVAL(buf,pos) (SVAL(buf,pos)|SVAL(buf,(pos)+2)<<16)
+#define SSVALX(buf,pos,val) (CVAL_NC(buf,pos)=(unsigned char)((val)&0xFF),CVAL_NC(buf,pos+1)=(unsigned char)((val)>>8))
+#define SIVALX(buf,pos,val) (SSVALX(buf,pos,val&0xFFFF),SSVALX(buf,pos+2,val>>16))
+#define SVALS(buf,pos) ((int16)SVAL(buf,pos))
+#define IVALS(buf,pos) ((int32)IVAL(buf,pos))
+#define SSVAL(buf,pos,val) SSVALX((buf),(pos),((uint16)(val)))
+#define SIVAL(buf,pos,val) SIVALX((buf),(pos),((uint32)(val)))
+#define SSVALS(buf,pos,val) SSVALX((buf),(pos),((int16)(val)))
+#define SIVALS(buf,pos,val) SIVALX((buf),(pos),((int32)(val)))
+
+#else /* CAREFUL_ALIGNMENT */
+
+/* this handles things for architectures like the 386 that can handle
+   alignment errors */
+/*
+   WARNING: This section is dependent on the length of int16 and int32
+   being correct 
+*/
+
+/* get single value from an SMB buffer */
+#define SVAL(buf,pos) (*(const uint16 *)((const char *)(buf) + (pos)))
+#define SVAL_NC(buf,pos) (*(uint16 *)((char *)(buf) + (pos))) /* Non const version of above. */
+#define IVAL(buf,pos) (*(const uint32 *)((const char *)(buf) + (pos)))
+#define IVAL_NC(buf,pos) (*(uint32 *)((char *)(buf) + (pos))) /* Non const version of above. */
+#define SVALS(buf,pos) (*(const int16 *)((const char *)(buf) + (pos)))
+#define SVALS_NC(buf,pos) (*(int16 *)((char *)(buf) + (pos))) /* Non const version of above. */
+#define IVALS(buf,pos) (*(const int32 *)((const char *)(buf) + (pos)))
+#define IVALS_NC(buf,pos) (*(int32 *)((char *)(buf) + (pos))) /* Non const version of above. */
+
+/* store single value in an SMB buffer */
+#define SSVAL(buf,pos,val) SVAL_NC(buf,pos)=((uint16)(val))
+#define SIVAL(buf,pos,val) IVAL_NC(buf,pos)=((uint32)(val))
+#define SSVALS(buf,pos,val) SVALS_NC(buf,pos)=((int16)(val))
+#define SIVALS(buf,pos,val) IVALS_NC(buf,pos)=((int32)(val))
+
+#endif /* CAREFUL_ALIGNMENT */
+
+/* now the reverse routines - these are used in nmb packets (mostly) */
+#define SREV(x) ((((x)&0xFF)<<8) | (((x)>>8)&0xFF))
+#define IREV(x) ((SREV(x)<<16) | (SREV((x)>>16)))
+
+#define RSVAL(buf,pos) SREV(SVAL(buf,pos))
+#define RSVALS(buf,pos) SREV(SVALS(buf,pos))
+#define RIVAL(buf,pos) IREV(IVAL(buf,pos))
+#define RIVALS(buf,pos) IREV(IVALS(buf,pos))
+#define RSSVAL(buf,pos,val) SSVAL(buf,pos,SREV(val))
+#define RSSVALS(buf,pos,val) SSVALS(buf,pos,SREV(val))
+#define RSIVAL(buf,pos,val) SIVAL(buf,pos,IREV(val))
+#define RSIVALS(buf,pos,val) SIVALS(buf,pos,IREV(val))
+
+/* Alignment macros. */
+#define ALIGN4(p,base) ((p) + ((4 - (PTR_DIFF((p), (base)) & 3)) & 3))
+#define ALIGN2(p,base) ((p) + ((2 - (PTR_DIFF((p), (base)) & 1)) & 1))
+
+#endif /* _BYTEORDER_H */