root/src/vfs/smbfs/helpers/include/byteorder.h

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INCLUDED FROM


   1 /*
   2    Unix SMB/Netbios implementation.
   3    Version 1.9.
   4    SMB Byte handling
   5  */
   6 
   7 #ifndef _BYTEORDER_H
   8 #define _BYTEORDER_H
   9 
  10 /*
  11    This file implements macros for machine independent short and 
  12    int manipulation
  13 
  14    Here is a description of this file that I emailed to the samba list once:
  15 
  16    > I am confused about the way that byteorder.h works in Samba. I have
  17    > looked at it, and I would have thought that you might make a distinction
  18    > between LE and BE machines, but you only seem to distinguish between 386
  19    > and all other architectures.
  20    > 
  21    > Can you give me a clue?
  22 
  23    sure.
  24 
  25    The distinction between 386 and other architectures is only there as
  26    an optimisation. You can take it out completely and it will make no
  27    difference. The routines (macros) in byteorder.h are totally byteorder
  28    independent. The 386 optimsation just takes advantage of the fact that
  29    the x86 processors don't care about alignment, so we don't have to
  30    align ints on int boundaries etc. If there are other processors out
  31    there that aren't alignment sensitive then you could also define
  32    CAREFUL_ALIGNMENT=0 on those processors as well.
  33 
  34    Ok, now to the macros themselves. I'll take a simple example, say we
  35    want to extract a 2 byte integer from a SMB packet and put it into a
  36    type called uint16 that is in the local machines byte order, and you
  37    want to do it with only the assumption that uint16 is _at_least_ 16
  38    bits long (this last condition is very important for architectures
  39    that don't have any int types that are 2 bytes long)
  40 
  41    You do this:
  42 
  43    #define CVAL(buf,pos) (((unsigned char *)(buf))[pos])
  44    #define PVAL(buf,pos) ((unsigned)CVAL(buf,pos))
  45    #define SVAL(buf,pos) (PVAL(buf,pos)|PVAL(buf,(pos)+1)<<8)
  46 
  47    then to extract a uint16 value at offset 25 in a buffer you do this:
  48 
  49    char *buffer = foo_bar();
  50    uint16 xx = SVAL(buffer,25);
  51 
  52    We are using the byteoder independence of the ANSI C bitshifts to do
  53    the work. A good optimising compiler should turn this into efficient
  54    code, especially if it happens to have the right byteorder :-)
  55 
  56    I know these macros can be made a bit tidier by removing some of the
  57    casts, but you need to look at byteorder.h as a whole to see the
  58    reasoning behind them. byteorder.h defines the following macros:
  59 
  60    SVAL(buf,pos) - extract a 2 byte SMB value
  61    IVAL(buf,pos) - extract a 4 byte SMB value
  62    SVALS(buf,pos) signed version of SVAL()
  63    IVALS(buf,pos) signed version of IVAL()
  64 
  65    SSVAL(buf,pos,val) - put a 2 byte SMB value into a buffer
  66    SIVAL(buf,pos,val) - put a 4 byte SMB value into a buffer
  67    SSVALS(buf,pos,val) - signed version of SSVAL()
  68    SIVALS(buf,pos,val) - signed version of SIVAL()
  69 
  70    RSVAL(buf,pos) - like SVAL() but for NMB byte ordering
  71    RSVALS(buf,pos) - like SVALS() but for NMB byte ordering
  72    RIVAL(buf,pos) - like IVAL() but for NMB byte ordering
  73    RIVALS(buf,pos) - like IVALS() but for NMB byte ordering
  74    RSSVAL(buf,pos,val) - like SSVAL() but for NMB ordering
  75    RSIVAL(buf,pos,val) - like SIVAL() but for NMB ordering
  76    RSIVALS(buf,pos,val) - like SIVALS() but for NMB ordering
  77 
  78    it also defines lots of intermediate macros, just ignore those :-)
  79 
  80  */
  81 
  82 /* some switch macros that do both store and read to and from SMB buffers */
  83 
  84 #define RW_PCVAL(read,inbuf,outbuf,len) \
  85         { if (read) { PCVAL (inbuf,0,outbuf,len); } \
  86         else      { PSCVAL(inbuf,0,outbuf,len); } }
  87 
  88 #define RW_PIVAL(read,big_endian,inbuf,outbuf,len) \
  89         { if (read) { if (big_endian) { RPIVAL(inbuf,0,outbuf,len); } else { PIVAL(inbuf,0,outbuf,len); } } \
  90         else      { if (big_endian) { RPSIVAL(inbuf,0,outbuf,len); } else { PSIVAL(inbuf,0,outbuf,len); } } }
  91 
  92 #define RW_PSVAL(read,big_endian,inbuf,outbuf,len) \
  93         { if (read) { if (big_endian) { RPSVAL(inbuf,0,outbuf,len); } else { PSVAL(inbuf,0,outbuf,len); } } \
  94         else      { if (big_endian) { RPSSVAL(inbuf,0,outbuf,len); } else { PSSVAL(inbuf,0,outbuf,len); } } }
  95 
  96 #define RW_CVAL(read, inbuf, outbuf, offset) \
  97         { if (read) { (outbuf) = CVAL (inbuf,offset); } \
  98         else      { SCVAL(inbuf,offset,outbuf); } }
  99 
 100 #define RW_IVAL(read, big_endian, inbuf, outbuf, offset) \
 101         { if (read) { (outbuf) = ((big_endian) ? RIVAL(inbuf,offset) : IVAL (inbuf,offset)); } \
 102         else      { if (big_endian) { RSIVAL(inbuf,offset,outbuf); } else { SIVAL(inbuf,offset,outbuf); } } }
 103 
 104 #define RW_SVAL(read, big_endian, inbuf, outbuf, offset) \
 105         { if (read) { (outbuf) = ((big_endian) ? RSVAL(inbuf,offset) : SVAL (inbuf,offset)); } \
 106         else      { if (big_endian) { RSSVAL(inbuf,offset,outbuf); } else { SSVAL(inbuf,offset,outbuf); } } }
 107 
 108 #undef CAREFUL_ALIGNMENT
 109 
 110 /* we know that the 386 can handle misalignment and has the "right" 
 111    byteorder */
 112 #ifdef __i386__
 113 #define CAREFUL_ALIGNMENT 0
 114 #endif
 115 
 116 #ifndef CAREFUL_ALIGNMENT
 117 #define CAREFUL_ALIGNMENT 1
 118 #endif
 119 
 120 #define CVAL(buf,pos) (((unsigned char *)(buf))[pos])
 121 #define PVAL(buf,pos) ((unsigned)CVAL(buf,pos))
 122 #define SCVAL(buf,pos,val) (CVAL(buf,pos) = (val))
 123 
 124 
 125 #if CAREFUL_ALIGNMENT
 126 
 127 #define SVAL(buf,pos) (PVAL(buf,pos)|PVAL(buf,(pos)+1)<<8)
 128 #define IVAL(buf,pos) (SVAL(buf,pos)|SVAL(buf,(pos)+2)<<16)
 129 #define SSVALX(buf,pos,val) (CVAL(buf,pos)=(val)&0xFF,CVAL(buf,pos+1)=(val)>>8)
 130 #define SIVALX(buf,pos,val) (SSVALX(buf,pos,val&0xFFFF),SSVALX(buf,pos+2,val>>16))
 131 #define SVALS(buf,pos) ((int16)SVAL(buf,pos))
 132 #define IVALS(buf,pos) ((int32)IVAL(buf,pos))
 133 #define SSVAL(buf,pos,val) SSVALX((buf),(pos),((uint16)(val)))
 134 #define SIVAL(buf,pos,val) SIVALX((buf),(pos),((uint32)(val)))
 135 #define SSVALS(buf,pos,val) SSVALX((buf),(pos),((int16)(val)))
 136 #define SIVALS(buf,pos,val) SIVALX((buf),(pos),((int32)(val)))
 137 
 138 #else /* CAREFUL_ALIGNMENT */
 139 
 140 /* this handles things for architectures like the 386 that can handle
 141    alignment errors */
 142 /*
 143    WARNING: This section is dependent on the length of int16 and int32
 144    being correct 
 145  */
 146 
 147 /* get single value from an SMB buffer */
 148 #define SVAL(buf,pos) (*(uint16 *)((char *)(buf) + (pos)))
 149 #define IVAL(buf,pos) (*(uint32 *)((char *)(buf) + (pos)))
 150 #define SVALS(buf,pos) (*(int16 *)((char *)(buf) + (pos)))
 151 #define IVALS(buf,pos) (*(int32 *)((char *)(buf) + (pos)))
 152 
 153 /* store single value in an SMB buffer */
 154 #define SSVAL(buf,pos,val) SVAL(buf,pos)=((uint16)(val))
 155 #define SIVAL(buf,pos,val) IVAL(buf,pos)=((uint32)(val))
 156 #define SSVALS(buf,pos,val) SVALS(buf,pos)=((int16)(val))
 157 #define SIVALS(buf,pos,val) IVALS(buf,pos)=((int32)(val))
 158 
 159 #endif /* CAREFUL_ALIGNMENT */
 160 
 161 /* macros for reading / writing arrays */
 162 
 163 #define SMBMACRO(macro,buf,pos,val,len,size) \
 164 { int l; for (l = 0; l < (len); l++) (val)[l] = macro((buf), (pos) + (size)*l); }
 165 
 166 #define SSMBMACRO(macro,buf,pos,val,len,size) \
 167 { int l; for (l = 0; l < (len); l++) macro((buf), (pos) + (size)*l, (val)[l]); }
 168 
 169 /* reads multiple data from an SMB buffer */
 170 #define PCVAL(buf,pos,val,len) SMBMACRO(CVAL,buf,pos,val,len,1)
 171 #define PSVAL(buf,pos,val,len) SMBMACRO(SVAL,buf,pos,val,len,2)
 172 #define PIVAL(buf,pos,val,len) SMBMACRO(IVAL,buf,pos,val,len,4)
 173 #define PCVALS(buf,pos,val,len) SMBMACRO(CVALS,buf,pos,val,len,1)
 174 #define PSVALS(buf,pos,val,len) SMBMACRO(SVALS,buf,pos,val,len,2)
 175 #define PIVALS(buf,pos,val,len) SMBMACRO(IVALS,buf,pos,val,len,4)
 176 
 177 /* stores multiple data in an SMB buffer */
 178 #define PSCVAL(buf,pos,val,len) SSMBMACRO(SCVAL,buf,pos,val,len,1)
 179 #define PSSVAL(buf,pos,val,len) SSMBMACRO(SSVAL,buf,pos,val,len,2)
 180 #define PSIVAL(buf,pos,val,len) SSMBMACRO(SIVAL,buf,pos,val,len,4)
 181 #define PSCVALS(buf,pos,val,len) SSMBMACRO(SCVALS,buf,pos,val,len,1)
 182 #define PSSVALS(buf,pos,val,len) SSMBMACRO(SSVALS,buf,pos,val,len,2)
 183 #define PSIVALS(buf,pos,val,len) SSMBMACRO(SIVALS,buf,pos,val,len,4)
 184 
 185 
 186 /* now the reverse routines - these are used in nmb packets (mostly) */
 187 #define SREV(x) ((((x)&0xFF)<<8) | (((x)>>8)&0xFF))
 188 #define IREV(x) ((SREV(x)<<16) | (SREV((x)>>16)))
 189 
 190 #define RSVAL(buf,pos) SREV(SVAL(buf,pos))
 191 #define RSVALS(buf,pos) SREV(SVALS(buf,pos))
 192 #define RIVAL(buf,pos) IREV(IVAL(buf,pos))
 193 #define RIVALS(buf,pos) IREV(IVALS(buf,pos))
 194 #define RSSVAL(buf,pos,val) SSVAL(buf,pos,SREV(val))
 195 #define RSSVALS(buf,pos,val) SSVALS(buf,pos,SREV(val))
 196 #define RSIVAL(buf,pos,val) SIVAL(buf,pos,IREV(val))
 197 #define RSIVALS(buf,pos,val) SIVALS(buf,pos,IREV(val))
 198 
 199 /* reads multiple data from an SMB buffer (big-endian) */
 200 #define RPSVAL(buf,pos,val,len) SMBMACRO(RSVAL,buf,pos,val,len,2)
 201 #define RPIVAL(buf,pos,val,len) SMBMACRO(RIVAL,buf,pos,val,len,4)
 202 #define RPSVALS(buf,pos,val,len) SMBMACRO(RSVALS,buf,pos,val,len,2)
 203 #define RPIVALS(buf,pos,val,len) SMBMACRO(RIVALS,buf,pos,val,len,4)
 204 
 205 /* stores multiple data in an SMB buffer (big-endian) */
 206 #define RPSSVAL(buf,pos,val,len) SSMBMACRO(RSSVAL,buf,pos,val,len,2)
 207 #define RPSIVAL(buf,pos,val,len) SSMBMACRO(RSIVAL,buf,pos,val,len,4)
 208 #define RPSSVALS(buf,pos,val,len) SSMBMACRO(RSSVALS,buf,pos,val,len,2)
 209 #define RPSIVALS(buf,pos,val,len) SSMBMACRO(RSIVALS,buf,pos,val,len,4)
 210 
 211 #endif /* _BYTEORDER_H */

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