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 Ok, now to the macros themselves. I'll take a simple example, say we
  39 want to extract a 2 byte integer from a SMB packet and put it into a
  40 type called uint16_t that is in the local machines byte order, and you
  41 want to do it with only the assumption that uint16_t is _at_least_ 16
  42 bits long (this last condition is very important for architectures
  43 that don't have any int types that are 2 bytes long)
  44
  45 You do this:
  46
  47 #define CVAL(buf,pos) (((uint8_t *)(buf))[pos])
  48 #define PVAL(buf,pos) ((unsigned int)CVAL(buf,pos))
  49 #define SVAL(buf,pos) (PVAL(buf,pos)|PVAL(buf,(pos)+1)<<8)
  50
  51 then to extract a uint16_t value at offset 25 in a buffer you do this:
  52
  53 char *buffer = foo_bar();
  54 uint16_t xx = SVAL(buffer,25);
  55
  56 We are using the byteoder independence of the ANSI C bitshifts to do
  57 the work. A good optimising compiler should turn this into efficient
  58 code, especially if it happens to have the right byteorder :-)
  59
  60 I know these macros can be made a bit tidier by removing some of the
  61 casts, but you need to look at byteorder.h as a whole to see the
  62 reasoning behind them. byteorder.h defines the following macros:
  63
  64 SVAL(buf,pos) - extract a 2 byte SMB value
  65 IVAL(buf,pos) - extract a 4 byte SMB value
  66 BVAL(buf,pos) - extract a 8 byte SMB value
  67 SVALS(buf,pos) - signed version of SVAL()
  68 IVALS(buf,pos) - signed version of IVAL()
  69 BVALS(buf,pos) - signed version of BVAL()
  70
  71 SSVAL(buf,pos,val) - put a 2 byte SMB value into a buffer
  72 SIVAL(buf,pos,val) - put a 4 byte SMB value into a buffer
  73 SBVAL(buf,pos,val) - put a 8 byte SMB value into a buffer
  74 SSVALS(buf,pos,val) - signed version of SSVAL()
  75 SIVALS(buf,pos,val) - signed version of SIVAL()
  76 SBVALS(buf,pos,val) - signed version of SBVAL()
  77
  78 RSVAL(buf,pos) - like SVAL() but for NMB byte ordering
  79 RSVALS(buf,pos) - like SVALS() but for NMB byte ordering
  80 RIVAL(buf,pos) - like IVAL() but for NMB byte ordering
  81 RIVALS(buf,pos) - like IVALS() but for NMB byte ordering
  82 RSSVAL(buf,pos,val) - like SSVAL() but for NMB ordering
  83 RSIVAL(buf,pos,val) - like SIVAL() but for NMB ordering
  84 RSIVALS(buf,pos,val) - like SIVALS() but for NMB ordering
  85
  86 it also defines lots of intermediate macros, just ignore those :-)
  87
  88 */
  89
  90
  91 #define CVAL(buf,pos) ((unsigned int)(((const uint8_t *)(buf))[pos]))
  92 #define CVAL_NC(buf,pos) (((uint8_t *)(buf))[pos]) /* Non-const version of CVAL */
  93 #define PVAL(buf,pos) (CVAL(buf,pos))
  94 #define SCVAL(buf,pos,val) (CVAL_NC(buf,pos) = (val))
  95
  96 #define SVAL(buf,pos) (PVAL(buf,pos)|PVAL(buf,(pos)+1)<<8)
  97 #define IVAL(buf,pos) (SVAL(buf,pos)|SVAL(buf,(pos)+2)<<16)
  98 #define SSVALX(buf,pos,val) (CVAL_NC(buf,pos)=(uint8_t)((val)&0xFF),CVAL_NC(buf,pos+1)=(uint8_t)((val)>>8))
  99 #define SIVALX(buf,pos,val) (SSVALX(buf,pos,val&0xFFFF),SSVALX(buf,pos+2,val>>16))
 100 #define SVALS(buf,pos) ((int16_t)SVAL(buf,pos))
 101 #define IVALS(buf,pos) ((int32_t)IVAL(buf,pos))
 102 #define SSVAL(buf,pos,val) SSVALX((buf),(pos),((uint16_t)(val)))
 103 #define SIVAL(buf,pos,val) SIVALX((buf),(pos),((uint32_t)(val)))
 104 #define SSVALS(buf,pos,val) SSVALX((buf),(pos),((int16_t)(val)))
 105 #define SIVALS(buf,pos,val) SIVALX((buf),(pos),((int32_t)(val)))
 106
 107 /* 64 bit macros */
 108 #define BVAL(p, ofs) (IVAL(p,ofs) | (((uint64_t)IVAL(p,(ofs)+4)) << 32))
 109 #define BVALS(p, ofs) ((int64_t)BVAL(p,ofs))
 110 #define SBVAL(p, ofs, v) (SIVAL(p,ofs,(v)&0xFFFFFFFF), SIVAL(p,(ofs)+4,((uint64_t)(v))>>32))
 111 #define SBVALS(p, ofs, v) (SBVAL(p,ofs,(uint64_t)v))
 112
 113 /* now the reverse routines - these are used in nmb packets (mostly) */
 114 #define SREV(x) ((((x)&0xFF)<<8) | (((x)>>8)&0xFF))
 115 #define IREV(x) ((SREV(x)<<16) | (SREV((x)>>16)))
 116 #define BREV(x) ((IREV((uint64_t)x)<<32) | (IREV(((uint64_t)x)>>32)))
 117
 118 #define RSVAL(buf,pos) SREV(SVAL(buf,pos))
 119 #define RSVALS(buf,pos) SREV(SVALS(buf,pos))
 120 #define RIVAL(buf,pos) IREV(IVAL(buf,pos))
 121 #define RIVALS(buf,pos) IREV(IVALS(buf,pos))
 122 #define RBVAL(buf,pos) BREV(BVAL(buf,pos))
 123 #define RBVALS(buf,pos) BREV(BVALS(buf,pos))
 124 #define RSSVAL(buf,pos,val) SSVAL(buf,pos,SREV(val))
 125 #define RSSVALS(buf,pos,val) SSVALS(buf,pos,SREV(val))
 126 #define RSIVAL(buf,pos,val) SIVAL(buf,pos,IREV(val))
 127 #define RSIVALS(buf,pos,val) SIVALS(buf,pos,IREV(val))
 128 #define RSBVAL(buf,pos,val) SBVAL(buf,pos,BREV(val))
 129 #define RSBVALS(buf,pos,val) SBVALS(buf,pos,BREV(val))
 130
 131 #endif /* _BYTEORDER_H */