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04bf12b176
(This used to be commit 3101c236b8
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172 lines
6.8 KiB
C
172 lines
6.8 KiB
C
/*
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Unix SMB/CIFS implementation.
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SMB Byte handling
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Copyright (C) Andrew Tridgell 1992-1998
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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#ifndef _BYTEORDER_H
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#define _BYTEORDER_H
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/*
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This file implements macros for machine independent short and
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int manipulation
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Here is a description of this file that I emailed to the samba list once:
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> I am confused about the way that byteorder.h works in Samba. I have
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> looked at it, and I would have thought that you might make a distinction
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> between LE and BE machines, but you only seem to distinguish between 386
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> and all other architectures.
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>
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> Can you give me a clue?
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sure.
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The distinction between 386 and other architectures is only there as
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an optimisation. You can take it out completely and it will make no
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difference. The routines (macros) in byteorder.h are totally byteorder
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independent. The 386 optimsation just takes advantage of the fact that
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the x86 processors don't care about alignment, so we don't have to
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align ints on int boundaries etc. If there are other processors out
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there that aren't alignment sensitive then you could also define
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CAREFUL_ALIGNMENT=0 on those processors as well.
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Ok, now to the macros themselves. I'll take a simple example, say we
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want to extract a 2 byte integer from a SMB packet and put it into a
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type called uint16 that is in the local machines byte order, and you
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want to do it with only the assumption that uint16 is _at_least_ 16
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bits long (this last condition is very important for architectures
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that don't have any int types that are 2 bytes long)
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You do this:
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#define CVAL(buf,pos) (((unsigned char *)(buf))[pos])
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#define PVAL(buf,pos) ((unsigned)CVAL(buf,pos))
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#define SVAL(buf,pos) (PVAL(buf,pos)|PVAL(buf,(pos)+1)<<8)
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then to extract a uint16 value at offset 25 in a buffer you do this:
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char *buffer = foo_bar();
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uint16 xx = SVAL(buffer,25);
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We are using the byteoder independence of the ANSI C bitshifts to do
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the work. A good optimising compiler should turn this into efficient
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code, especially if it happens to have the right byteorder :-)
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I know these macros can be made a bit tidier by removing some of the
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casts, but you need to look at byteorder.h as a whole to see the
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reasoning behind them. byteorder.h defines the following macros:
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SVAL(buf,pos) - extract a 2 byte SMB value
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IVAL(buf,pos) - extract a 4 byte SMB value
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SVALS(buf,pos) signed version of SVAL()
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IVALS(buf,pos) signed version of IVAL()
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SSVAL(buf,pos,val) - put a 2 byte SMB value into a buffer
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SIVAL(buf,pos,val) - put a 4 byte SMB value into a buffer
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SSVALS(buf,pos,val) - signed version of SSVAL()
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SIVALS(buf,pos,val) - signed version of SIVAL()
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RSVAL(buf,pos) - like SVAL() but for NMB byte ordering
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RSVALS(buf,pos) - like SVALS() but for NMB byte ordering
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RIVAL(buf,pos) - like IVAL() but for NMB byte ordering
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RIVALS(buf,pos) - like IVALS() but for NMB byte ordering
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RSSVAL(buf,pos,val) - like SSVAL() but for NMB ordering
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RSIVAL(buf,pos,val) - like SIVAL() but for NMB ordering
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RSIVALS(buf,pos,val) - like SIVALS() but for NMB ordering
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it also defines lots of intermediate macros, just ignore those :-)
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*/
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#undef CAREFUL_ALIGNMENT
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/* we know that the 386 can handle misalignment and has the "right"
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byteorder */
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#ifdef __i386__
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#define CAREFUL_ALIGNMENT 0
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#endif
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#ifndef CAREFUL_ALIGNMENT
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#define CAREFUL_ALIGNMENT 1
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#endif
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#define CVAL(buf,pos) ((unsigned)(((const unsigned char *)(buf))[pos]))
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#define CVAL_NC(buf,pos) (((unsigned char *)(buf))[pos]) /* Non-const version of CVAL */
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#define PVAL(buf,pos) (CVAL(buf,pos))
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#define SCVAL(buf,pos,val) (CVAL_NC(buf,pos) = (val))
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#if CAREFUL_ALIGNMENT
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#define SVAL(buf,pos) (PVAL(buf,pos)|PVAL(buf,(pos)+1)<<8)
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#define IVAL(buf,pos) (SVAL(buf,pos)|SVAL(buf,(pos)+2)<<16)
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#define SSVALX(buf,pos,val) (CVAL_NC(buf,pos)=(unsigned char)((val)&0xFF),CVAL_NC(buf,pos+1)=(unsigned char)((val)>>8))
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#define SIVALX(buf,pos,val) (SSVALX(buf,pos,val&0xFFFF),SSVALX(buf,pos+2,val>>16))
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#define SVALS(buf,pos) ((int16)SVAL(buf,pos))
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#define IVALS(buf,pos) ((int32)IVAL(buf,pos))
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#define SSVAL(buf,pos,val) SSVALX((buf),(pos),((uint16)(val)))
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#define SIVAL(buf,pos,val) SIVALX((buf),(pos),((uint32)(val)))
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#define SSVALS(buf,pos,val) SSVALX((buf),(pos),((int16)(val)))
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#define SIVALS(buf,pos,val) SIVALX((buf),(pos),((int32)(val)))
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#else /* CAREFUL_ALIGNMENT */
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/* this handles things for architectures like the 386 that can handle
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alignment errors */
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/*
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WARNING: This section is dependent on the length of int16 and int32
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being correct
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*/
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/* get single value from an SMB buffer */
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#define SVAL(buf,pos) (*(const uint16 *)((const char *)(buf) + (pos)))
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#define SVAL_NC(buf,pos) (*(uint16 *)((char *)(buf) + (pos))) /* Non const version of above. */
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#define IVAL(buf,pos) (*(const uint32 *)((const char *)(buf) + (pos)))
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#define IVAL_NC(buf,pos) (*(uint32 *)((char *)(buf) + (pos))) /* Non const version of above. */
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#define SVALS(buf,pos) (*(const int16 *)((const char *)(buf) + (pos)))
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#define SVALS_NC(buf,pos) (*(int16 *)((char *)(buf) + (pos))) /* Non const version of above. */
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#define IVALS(buf,pos) (*(const int32 *)((const char *)(buf) + (pos)))
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#define IVALS_NC(buf,pos) (*(int32 *)((char *)(buf) + (pos))) /* Non const version of above. */
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/* store single value in an SMB buffer */
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#define SSVAL(buf,pos,val) SVAL_NC(buf,pos)=((uint16)(val))
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#define SIVAL(buf,pos,val) IVAL_NC(buf,pos)=((uint32)(val))
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#define SSVALS(buf,pos,val) SVALS_NC(buf,pos)=((int16)(val))
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#define SIVALS(buf,pos,val) IVALS_NC(buf,pos)=((int32)(val))
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#endif /* CAREFUL_ALIGNMENT */
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/* now the reverse routines - these are used in nmb packets (mostly) */
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#define SREV(x) ((((x)&0xFF)<<8) | (((x)>>8)&0xFF))
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#define IREV(x) ((SREV(x)<<16) | (SREV((x)>>16)))
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#define RSVAL(buf,pos) SREV(SVAL(buf,pos))
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#define RSVALS(buf,pos) SREV(SVALS(buf,pos))
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#define RIVAL(buf,pos) IREV(IVAL(buf,pos))
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#define RIVALS(buf,pos) IREV(IVALS(buf,pos))
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#define RSSVAL(buf,pos,val) SSVAL(buf,pos,SREV(val))
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#define RSSVALS(buf,pos,val) SSVALS(buf,pos,SREV(val))
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#define RSIVAL(buf,pos,val) SIVAL(buf,pos,IREV(val))
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#define RSIVALS(buf,pos,val) SIVALS(buf,pos,IREV(val))
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/* Alignment macros. */
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#define ALIGN4(p,base) ((p) + ((4 - (PTR_DIFF((p), (base)) & 3)) & 3))
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#define ALIGN2(p,base) ((p) + ((2 - (PTR_DIFF((p), (base)) & 1)) & 1))
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#endif /* _BYTEORDER_H */
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