lib/util/byteorder.h

   1 /*
   2    Unix SMB/CIFS implementation.
   3    SMB Byte handling
   4    Copyright (C) Andrew Tridgell 1992-1998
   5
   6    This program is free software; you can redistribute it and/or modify
   7    it under the terms of the GNU General Public License as published by
   8    the Free Software Foundation; either version 3 of the License, or
   9    (at your option) any later version.
  10
  11    This program is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14    GNU General Public License for more details.
  15
  16    You should have received a copy of the GNU General Public License
  17    along with this program.  If not, see <http://www.gnu.org/licenses/>.
  18 */
  19
  20 #ifndef _BYTEORDER_H
  21 #define _BYTEORDER_H
  22
  23 /*
  24    This file implements macros for machine independent short and
  25    int manipulation
  26
  27 Here is a description of this file that I emailed to the samba list once:
  28
  29 > I am confused about the way that byteorder.h works in Samba. I have
  30 > looked at it, and I would have thought that you might make a distinction
  31 > between LE and BE machines, but you only seem to distinguish between 386
  32 > and all other architectures.
  33 >
  34 > Can you give me a clue?
  35
  36 sure.
  37
  38 The distinction between 386 and other architectures is only there as
  39 an optimisation. You can take it out completely and it will make no
  40 difference. The routines (macros) in byteorder.h are totally byteorder
  41 independent. The 386 optimsation just takes advantage of the fact that
  42 the x86 processors don't care about alignment, so we don't have to
  43 align ints on int boundaries etc. If there are other processors out
  44 there that aren't alignment sensitive then you could also define
  45 CAREFUL_ALIGNMENT=0 on those processors as well.
  46
  47 Ok, now to the macros themselves. I'll take a simple example, say we
  48 want to extract a 2 byte integer from a SMB packet and put it into a
  49 type called uint16_t that is in the local machines byte order, and you
  50 want to do it with only the assumption that uint16_t is _at_least_ 16
  51 bits long (this last condition is very important for architectures
  52 that don't have any int types that are 2 bytes long)
  53
  54 You do this:
  55
  56 #define CVAL(buf,pos) (((uint8_t *)(buf))[pos])
  57 #define PVAL(buf,pos) ((unsigned int)CVAL(buf,pos))
  58 #define SVAL(buf,pos) (PVAL(buf,pos)|PVAL(buf,(pos)+1)<<8)
  59
  60 then to extract a uint16_t value at offset 25 in a buffer you do this:
  61
  62 char *buffer = foo_bar();
  63 uint16_t xx = SVAL(buffer,25);
  64
  65 We are using the byteoder independence of the ANSI C bitshifts to do
  66 the work. A good optimising compiler should turn this into efficient
  67 code, especially if it happens to have the right byteorder :-)
  68
  69 I know these macros can be made a bit tidier by removing some of the
  70 casts, but you need to look at byteorder.h as a whole to see the
  71 reasoning behind them. byteorder.h defines the following macros:
  72
  73 SVAL(buf,pos) - extract a 2 byte SMB value
  74 IVAL(buf,pos) - extract a 4 byte SMB value
  75 BVAL(buf,pos) - extract a 8 byte SMB value
  76 SVALS(buf,pos) - signed version of SVAL()
  77 IVALS(buf,pos) - signed version of IVAL()
  78 BVALS(buf,pos) - signed version of BVAL()
  79
  80 SSVAL(buf,pos,val) - put a 2 byte SMB value into a buffer
  81 SIVAL(buf,pos,val) - put a 4 byte SMB value into a buffer
  82 SBVAL(buf,pos,val) - put a 8 byte SMB value into a buffer
  83 SSVALS(buf,pos,val) - signed version of SSVAL()
  84 SIVALS(buf,pos,val) - signed version of SIVAL()
  85 SBVALS(buf,pos,val) - signed version of SBVAL()
  86
  87 RSVAL(buf,pos) - like SVAL() but for NMB byte ordering
  88 RSVALS(buf,pos) - like SVALS() but for NMB byte ordering
  89 RIVAL(buf,pos) - like IVAL() but for NMB byte ordering
  90 RIVALS(buf,pos) - like IVALS() but for NMB byte ordering
  91 RSSVAL(buf,pos,val) - like SSVAL() but for NMB ordering
  92 RSIVAL(buf,pos,val) - like SIVAL() but for NMB ordering
  93 RSIVALS(buf,pos,val) - like SIVALS() but for NMB ordering
  94
  95 it also defines lots of intermediate macros, just ignore those :-)
  96
  97 */
  98
  99
 100 /*
 101   on powerpc we can use the magic instructions to load/store
 102   in little endian
 103 */
 104 #if (defined(__powerpc__) && defined(__GNUC__))
 105 static __inline__ uint16_t ld_le16(const uint16_t *addr)
 106 {
 107         uint16_t val;
 108         __asm__ ("lhbrx %0,0,%1" : "=r" (val) : "r" (addr), "m" (*addr));
 109         return val;
 110 }
 111
 112 static __inline__ void st_le16(uint16_t *addr, const uint16_t val)
 113 {
 114         __asm__ ("sthbrx %1,0,%2" : "=m" (*addr) : "r" (val), "r" (addr));
 115 }
 116
 117 static __inline__ uint32_t ld_le32(const uint32_t *addr)
 118 {
 119         uint32_t val;
 120         __asm__ ("lwbrx %0,0,%1" : "=r" (val) : "r" (addr), "m" (*addr));
 121         return val;
 122 }
 123
 124 static __inline__ void st_le32(uint32_t *addr, const uint32_t val)
 125 {
 126         __asm__ ("stwbrx %1,0,%2" : "=m" (*addr) : "r" (val), "r" (addr));
 127 }
 128 #define HAVE_ASM_BYTEORDER 1
 129 #else
 130 #define HAVE_ASM_BYTEORDER 0
 131 #endif
 132
 133
 134
 135 #undef CAREFUL_ALIGNMENT
 136
 137 /* we know that the 386 can handle misalignment and has the "right"
 138    byteorder */
 139 #if defined(__i386__)
 140 #define CAREFUL_ALIGNMENT 0
 141 #endif
 142
 143 #ifndef CAREFUL_ALIGNMENT
 144 #define CAREFUL_ALIGNMENT 1
 145 #endif
 146
 147 #define CVAL(buf,pos) ((unsigned int)(((const uint8_t *)(buf))[pos]))
 148 #define CVAL_NC(buf,pos) (((uint8_t *)(buf))[pos]) /* Non-const version of CVAL */
 149 #define PVAL(buf,pos) (CVAL(buf,pos))
 150 #define SCVAL(buf,pos,val) (CVAL_NC(buf,pos) = (val))
 151
 152 #if HAVE_ASM_BYTEORDER
 153
 154 #define  _PTRPOS(buf,pos) (((const uint8_t *)(buf))+(pos))
 155 #define SVAL(buf,pos) ld_le16((const uint16_t *)_PTRPOS(buf,pos))
 156 #define IVAL(buf,pos) ld_le32((const uint32_t *)_PTRPOS(buf,pos))
 157 #define SSVAL(buf,pos,val) st_le16((uint16_t *)_PTRPOS(buf,pos), val)
 158 #define SIVAL(buf,pos,val) st_le32((uint32_t *)_PTRPOS(buf,pos), val)
 159 #define SVALS(buf,pos) ((int16_t)SVAL(buf,pos))
 160 #define IVALS(buf,pos) ((int32_t)IVAL(buf,pos))
 161 #define SSVALS(buf,pos,val) SSVAL((buf),(pos),((int16_t)(val)))
 162 #define SIVALS(buf,pos,val) SIVAL((buf),(pos),((int32_t)(val)))
 163
 164 #elif CAREFUL_ALIGNMENT
 165
 166 #define SVAL(buf,pos) (PVAL(buf,pos)|PVAL(buf,(pos)+1)<<8)
 167 #define IVAL(buf,pos) (SVAL(buf,pos)|SVAL(buf,(pos)+2)<<16)
 168 #define SSVALX(buf,pos,val) (CVAL_NC(buf,pos)=(uint8_t)((val)&0xFF),CVAL_NC(buf,pos+1)=(uint8_t)((val)>>8))
 169 #define SIVALX(buf,pos,val) (SSVALX(buf,pos,val&0xFFFF),SSVALX(buf,pos+2,val>>16))
 170 #define SVALS(buf,pos) ((int16_t)SVAL(buf,pos))
 171 #define IVALS(buf,pos) ((int32_t)IVAL(buf,pos))
 172 #define SSVAL(buf,pos,val) SSVALX((buf),(pos),((uint16_t)(val)))
 173 #define SIVAL(buf,pos,val) SIVALX((buf),(pos),((uint32_t)(val)))
 174 #define SSVALS(buf,pos,val) SSVALX((buf),(pos),((int16_t)(val)))
 175 #define SIVALS(buf,pos,val) SIVALX((buf),(pos),((int32_t)(val)))
 176
 177 #else /* not CAREFUL_ALIGNMENT */
 178
 179 /* this handles things for architectures like the 386 that can handle
 180    alignment errors */
 181 /*
 182    WARNING: This section is dependent on the length of int16_t and int32_t
 183    being correct
 184 */
 185
 186 /* get single value from an SMB buffer */
 187 #define SVAL(buf,pos) (*(const uint16_t *)((const char *)(buf) + (pos)))
 188 #define SVAL_NC(buf,pos) (*(uint16_t *)((void *)((char *)(buf) + (pos)))) /* Non const version of above. */
 189 #define IVAL(buf,pos) (*(const uint32_t *)((const char *)(buf) + (pos)))
 190 #define IVAL_NC(buf,pos) (*(uint32_t *)((void *)((char *)(buf) + (pos)))) /* Non const version of above. */
 191 #define SVALS(buf,pos) (*(const int16_t *)((const char *)(buf) + (pos)))
 192 #define SVALS_NC(buf,pos) (*(int16_t *)((void *)((char *)(buf) + (pos)))) /* Non const version of above. */
 193 #define IVALS(buf,pos) (*(const int32_t *)((const char *)(buf) + (pos)))
 194 #define IVALS_NC(buf,pos) (*(int32_t *)((void *)((char *)(buf) + (pos)))) /* Non const version of above. */
 195
 196 /* store single value in an SMB buffer */
 197 #define SSVAL(buf,pos,val) SVAL_NC(buf,pos)=((uint16_t)(val))
 198 #define SIVAL(buf,pos,val) IVAL_NC(buf,pos)=((uint32_t)(val))
 199 #define SSVALS(buf,pos,val) SVALS_NC(buf,pos)=((int16_t)(val))
 200 #define SIVALS(buf,pos,val) IVALS_NC(buf,pos)=((int32_t)(val))
 201
 202 #endif /* not CAREFUL_ALIGNMENT */
 203
 204 /* 64 bit macros */
 205 #define BVAL(p, ofs) (IVAL(p,ofs) | (((uint64_t)IVAL(p,(ofs)+4)) << 32))
 206 #define BVALS(p, ofs) ((int64_t)BVAL(p,ofs))
 207 #define SBVAL(p, ofs, v) (SIVAL(p,ofs,(v)&0xFFFFFFFF), SIVAL(p,(ofs)+4,((uint64_t)(v))>>32))
 208 #define SBVALS(p, ofs, v) (SBVAL(p,ofs,(uint64_t)v))
 209
 210 /* now the reverse routines - these are used in nmb packets (mostly) */
 211 #define SREV(x) ((((x)&0xFF)<<8) | (((x)>>8)&0xFF))
 212 #define IREV(x) ((SREV(x)<<16) | (SREV((x)>>16)))
 213 #define BREV(x) ((IREV(x)<<32) | (IREV((x)>>32)))
 214
 215 #define RSVAL(buf,pos) SREV(SVAL(buf,pos))
 216 #define RSVALS(buf,pos) SREV(SVALS(buf,pos))
 217 #define RIVAL(buf,pos) IREV(IVAL(buf,pos))
 218 #define RIVALS(buf,pos) IREV(IVALS(buf,pos))
 219 #define RBVAL(buf,pos) BREV(BVAL(buf,pos))
 220 #define RBVALS(buf,pos) BREV(BVALS(buf,pos))
 221 #define RSSVAL(buf,pos,val) SSVAL(buf,pos,SREV(val))
 222 #define RSSVALS(buf,pos,val) SSVALS(buf,pos,SREV(val))
 223 #define RSIVAL(buf,pos,val) SIVAL(buf,pos,IREV(val))
 224 #define RSIVALS(buf,pos,val) SIVALS(buf,pos,IREV(val))
 225 #define RSBVAL(buf,pos,val) SBVAL(buf,pos,BREV(val))
 226 #define RSBVALS(buf,pos,val) SBVALS(buf,pos,BREV(val))
 227
 228 /* Alignment macros. */
 229 #define ALIGN4(p,base) ((p) + ((4 - (PTR_DIFF((p), (base)) & 3)) & 3))
 230 #define ALIGN2(p,base) ((p) + ((2 - (PTR_DIFF((p), (base)) & 1)) & 1))
 231
 232
 233 /* macros for accessing SMB protocol elements */
 234 #define VWV(vwv) ((vwv)*2)
 235
 236 #endif /* _BYTEORDER_H */