OpenVAS Libraries
4.0+rc3.SVN
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00001 /* 00002 Unix SMB/CIFS implementation. 00003 SMB Byte handling 00004 Copyright (C) Andrew Tridgell 1992-1998 00005 00006 This program is free software; you can redistribute it and/or modify 00007 it under the terms of the GNU General Public License as published by 00008 the Free Software Foundation; either version 2 of the License, or 00009 (at your option) any later version. 00010 00011 This program is distributed in the hope that it will be useful, 00012 but WITHOUT ANY WARRANTY; without even the implied warranty of 00013 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 00014 GNU General Public License for more details. 00015 00016 You should have received a copy of the GNU General Public License 00017 along with this program; if not, write to the Free Software 00018 Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. 00019 */ 00020 00021 #ifndef _BYTEORDER_H 00022 #define _BYTEORDER_H 00023 00024 /* 00025 This file implements macros for machine independent short and 00026 int manipulation 00027 00028 Here is a description of this file that I emailed to the samba list once: 00029 00030 > I am confused about the way that byteorder.h works in Samba. I have 00031 > looked at it, and I would have thought that you might make a distinction 00032 > between LE and BE machines, but you only seem to distinguish between 386 00033 > and all other architectures. 00034 > 00035 > Can you give me a clue? 00036 00037 sure. 00038 00039 The distinction between 386 and other architectures is only there as 00040 an optimisation. You can take it out completely and it will make no 00041 difference. The routines (macros) in byteorder.h are totally byteorder 00042 independent. The 386 optimsation just takes advantage of the fact that 00043 the x86 processors don't care about alignment, so we don't have to 00044 align ints on int boundaries etc. If there are other processors out 00045 there that aren't alignment sensitive then you could also define 00046 CAREFUL_ALIGNMENT=0 on those processors as well. 00047 00048 Ok, now to the macros themselves. I'll take a simple example, say we 00049 want to extract a 2 byte integer from a SMB packet and put it into a 00050 type called uint16 that is in the local machines byte order, and you 00051 want to do it with only the assumption that uint16 is _at_least_ 16 00052 bits long (this last condition is very important for architectures 00053 that don't have any int types that are 2 bytes long) 00054 00055 You do this: 00056 00057 #define CVAL(buf,pos) (((unsigned char *)(buf))[pos]) 00058 #define PVAL(buf,pos) ((unsigned)CVAL(buf,pos)) 00059 #define SVAL(buf,pos) (PVAL(buf,pos)|PVAL(buf,(pos)+1)<<8) 00060 00061 then to extract a uint16 value at offset 25 in a buffer you do this: 00062 00063 char *buffer = foo_bar(); 00064 uint16 xx = SVAL(buffer,25); 00065 00066 We are using the byteoder independence of the ANSI C bitshifts to do 00067 the work. A good optimising compiler should turn this into efficient 00068 code, especially if it happens to have the right byteorder :-) 00069 00070 I know these macros can be made a bit tidier by removing some of the 00071 casts, but you need to look at byteorder.h as a whole to see the 00072 reasoning behind them. byteorder.h defines the following macros: 00073 00074 SVAL(buf,pos) - extract a 2 byte SMB value 00075 IVAL(buf,pos) - extract a 4 byte SMB value 00076 SVALS(buf,pos) signed version of SVAL() 00077 IVALS(buf,pos) signed version of IVAL() 00078 00079 SSVAL(buf,pos,val) - put a 2 byte SMB value into a buffer 00080 SIVAL(buf,pos,val) - put a 4 byte SMB value into a buffer 00081 SSVALS(buf,pos,val) - signed version of SSVAL() 00082 SIVALS(buf,pos,val) - signed version of SIVAL() 00083 00084 RSVAL(buf,pos) - like SVAL() but for NMB byte ordering 00085 RSVALS(buf,pos) - like SVALS() but for NMB byte ordering 00086 RIVAL(buf,pos) - like IVAL() but for NMB byte ordering 00087 RIVALS(buf,pos) - like IVALS() but for NMB byte ordering 00088 RSSVAL(buf,pos,val) - like SSVAL() but for NMB ordering 00089 RSIVAL(buf,pos,val) - like SIVAL() but for NMB ordering 00090 RSIVALS(buf,pos,val) - like SIVALS() but for NMB ordering 00091 00092 it also defines lots of intermediate macros, just ignore those :-) 00093 00094 */ 00095 00096 #undef CAREFUL_ALIGNMENT 00097 00098 /* we know that the 386 can handle misalignment and has the "right" 00099 byteorder */ 00100 #ifdef __i386__ 00101 #define CAREFUL_ALIGNMENT 0 00102 #endif 00103 00104 #ifndef CAREFUL_ALIGNMENT 00105 #define CAREFUL_ALIGNMENT 1 00106 #endif 00107 00108 #define CVAL(buf,pos) ((unsigned)(((const unsigned char *)(buf))[pos])) 00109 #define CVAL_NC(buf,pos) (((unsigned char *)(buf))[pos]) /* Non-const version of CVAL */ 00110 #define PVAL(buf,pos) (CVAL(buf,pos)) 00111 #define SCVAL(buf,pos,val) (CVAL_NC(buf,pos) = (val)) 00112 00113 00114 #if CAREFUL_ALIGNMENT 00115 00116 #define SVAL(buf,pos) (PVAL(buf,pos)|PVAL(buf,(pos)+1)<<8) 00117 #define IVAL(buf,pos) (SVAL(buf,pos)|SVAL(buf,(pos)+2)<<16) 00118 #define SSVALX(buf,pos,val) (CVAL_NC(buf,pos)=(unsigned char)((val)&0xFF),CVAL_NC(buf,pos+1)=(unsigned char)((val)>>8)) 00119 #define SIVALX(buf,pos,val) (SSVALX(buf,pos,val&0xFFFF),SSVALX(buf,pos+2,val>>16)) 00120 #define SVALS(buf,pos) ((int16)SVAL(buf,pos)) 00121 #define IVALS(buf,pos) ((int32)IVAL(buf,pos)) 00122 #define SSVAL(buf,pos,val) SSVALX((buf),(pos),((uint16)(val))) 00123 #define SIVAL(buf,pos,val) SIVALX((buf),(pos),((uint32)(val))) 00124 #define SSVALS(buf,pos,val) SSVALX((buf),(pos),((int16)(val))) 00125 #define SIVALS(buf,pos,val) SIVALX((buf),(pos),((int32)(val))) 00126 00127 #else /* CAREFUL_ALIGNMENT */ 00128 00129 /* this handles things for architectures like the 386 that can handle 00130 alignment errors */ 00131 /* 00132 WARNING: This section is dependent on the length of int16 and int32 00133 being correct 00134 */ 00135 00136 /* get single value from an SMB buffer */ 00137 #define SVAL(buf,pos) (*(const uint16 *)((const char *)(buf) + (pos))) 00138 #define SVAL_NC(buf,pos) (*(uint16 *)((char *)(buf) + (pos))) /* Non const version of above. */ 00139 #define IVAL(buf,pos) (*(const uint32 *)((const char *)(buf) + (pos))) 00140 #define IVAL_NC(buf,pos) (*(uint32 *)((char *)(buf) + (pos))) /* Non const version of above. */ 00141 #define SVALS(buf,pos) (*(const int16 *)((const char *)(buf) + (pos))) 00142 #define SVALS_NC(buf,pos) (*(int16 *)((char *)(buf) + (pos))) /* Non const version of above. */ 00143 #define IVALS(buf,pos) (*(const int32 *)((const char *)(buf) + (pos))) 00144 #define IVALS_NC(buf,pos) (*(int32 *)((char *)(buf) + (pos))) /* Non const version of above. */ 00145 00146 /* store single value in an SMB buffer */ 00147 #define SSVAL(buf,pos,val) SVAL_NC(buf,pos)=((uint16)(val)) 00148 #define SIVAL(buf,pos,val) IVAL_NC(buf,pos)=((uint32)(val)) 00149 #define SSVALS(buf,pos,val) SVALS_NC(buf,pos)=((int16)(val)) 00150 #define SIVALS(buf,pos,val) IVALS_NC(buf,pos)=((int32)(val)) 00151 00152 #endif /* CAREFUL_ALIGNMENT */ 00153 00154 /* now the reverse routines - these are used in nmb packets (mostly) */ 00155 #define SREV(x) ((((x)&0xFF)<<8) | (((x)>>8)&0xFF)) 00156 #define IREV(x) ((SREV(x)<<16) | (SREV((x)>>16))) 00157 00158 #define RSVAL(buf,pos) SREV(SVAL(buf,pos)) 00159 #define RSVALS(buf,pos) SREV(SVALS(buf,pos)) 00160 #define RIVAL(buf,pos) IREV(IVAL(buf,pos)) 00161 #define RIVALS(buf,pos) IREV(IVALS(buf,pos)) 00162 #define RSSVAL(buf,pos,val) SSVAL(buf,pos,SREV(val)) 00163 #define RSSVALS(buf,pos,val) SSVALS(buf,pos,SREV(val)) 00164 #define RSIVAL(buf,pos,val) SIVAL(buf,pos,IREV(val)) 00165 #define RSIVALS(buf,pos,val) SIVALS(buf,pos,IREV(val)) 00166 00167 /* Alignment macros. */ 00168 #define ALIGN4(p,base) ((p) + ((4 - (PTR_DIFF((p), (base)) & 3)) & 3)) 00169 #define ALIGN2(p,base) ((p) + ((2 - (PTR_DIFF((p), (base)) & 1)) & 1)) 00170 00171 #endif /* _BYTEORDER_H */