mdw@git.distorted.org.uk Git - mLib/blob - bits.h

   1 /* -*-c-*-
   2  *
   3  * $Id: bits.h,v 1.2 1999/06/17 00:12:46 mdw Exp $
   4  *
   5  * Portable bit-level manipulation macros
   6  *
   7  * (c) 1998 Straylight/Edgeware
   8  */
   9
  10 /*----- Licensing notice --------------------------------------------------*
  11  *
  12  * This file is part of the mLib utilities library.
  13  *
  14  * mLib is free software; you can redistribute it and/or modify
  15  * it under the terms of the GNU Library General Public License as
  16  * published by the Free Software Foundation; either version 2 of the
  17  * License, or (at your option) any later version.
  18  *
  19  * mLib is distributed in the hope that it will be useful,
  20  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  21  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  22  * GNU Library General Public License for more details.
  23  *
  24  * You should have received a copy of the GNU Library General Public
  25  * License along with mLib; if not, write to the Free
  26  * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
  27  * MA 02111-1307, USA.
  28  */
  29
  30 /*----- Revision history --------------------------------------------------*
  31  *
  32  * $Log: bits.h,v $
  33  * Revision 1.2  1999/06/17 00:12:46  mdw
  34  * Improve portability for shift and rotate macros.
  35  *
  36  * Revision 1.1  1999/06/01 09:46:19  mdw
  37  * New addition: bit manipulation macros.
  38  *
  39  */
  40
  41 #ifndef BITS_H
  42 #define BITS_H
  43
  44 #ifdef __cplusplus
  45   extern "C" {
  46 #endif
  47
  48 /*----- Header files ------------------------------------------------------*/
  49
  50 #include <limits.h>
  51 #include <stddef.h>
  52
  53 /*----- Decide on some types ----------------------------------------------*/
  54
  55 /* --- Decide on a 32-bit type --- *
  56  *
  57  * I want a type which is capable of expressing 32-bit numbers.  Because some
  58  * implementations have 64-bit @long@s (infinitely preferable to the abortion
  59  * that is @long long@), using @unsigned long@ regardless is wasteful.  So,
  60  * if @int@ appears to be good enough, then I'll go with that.
  61  */
  62
  63 #if UINT_MAX >= 0xffffffffu
  64   typedef unsigned int uint32;
  65 #else
  66   typedef unsigned long uint32;
  67 #endif
  68
  69 /* --- Decide on 16-bit and 8-bit types --- *
  70  *
  71  * This is more for brevity than anything else.
  72  */
  73
  74 typedef unsigned short uint16;
  75 typedef unsigned char octet;
  76
  77 /* --- WARNING! --- *
  78  *
  79  * Never lose sight of the fact that the above types may be wider than the
  80  * names suggest.  Some architectures have 32-bit @short@s for example.
  81  */
  82
  83 /*----- Macros ------------------------------------------------------------*/
  84
  85 /* --- Useful masks --- */
  86
  87 #define MASK8 0xffu
  88 #define MASK16 0xffffu
  89 #define MASK32 0xffffffffu
  90
  91 /* --- Type coercions --- */
  92
  93 #define U8(x) ((octet)((x) & MASK8))
  94 #define U16(x) ((uint16)((x) & MASK16))
  95 #define U32(x) ((uint32)((x) & MASK32))
  96
  97 /* --- Safe shifting macros --- */
  98
  99 #define LSL8(v, s) U8(U8(v) << ((s) & 7u))
 100 #define LSR8(v, s) U8(U8(v) >> ((s) & 7u))
 101 #define LSL16(v, s) U16(U16(v) << ((s) & 15u))
 102 #define LSR16(v, s) U16(U16(v) >> ((s) & 15u))
 103 #define LSL32(v, s) U32(U32(v) << ((s) & 31u))
 104 #define LSR32(v, s) U32(U32(v) >> ((s) & 31u))
 105
 106 /* --- Rotation macros --- */
 107
 108 #define ROL8(v, s) (LSL8((v), (s)) | (LSR8((v), 8u - (s))))
 109 #define ROR8(v, s) (LSR8((v), (s)) | (LSL8((v), 8u - (s))))
 110 #define ROL16(v, s) (LSL16((v), (s)) | (LSR16((v), 16u - (s))))
 111 #define ROR16(v, s) (LSR16((v), (s)) | (LSL16((v), 16u - (s))))
 112 #define ROL32(v, s) (LSL32((v), (s)) | (LSR32((v), 32u - (s))))
 113 #define ROR32(v, s) (LSR32((v), (s)) | (LSL32((v), 32u - (s))))
 114
 115 /* --- Storage and retrieval --- */
 116
 117 #define GETBYTE(p, o) (((octet *)(p))[o] & MASK8)
 118 #define PUTBYTE(p, o, v) (((octet *)(p))[o] = U8((v)))
 119
 120 #define LOAD8(p) (GETBYTE((p), 0))
 121 #define STORE8(p, v) (PUTBYTE((p), 0, (v)))
 122
 123 #define LOAD16_B(p) ((GETBYTE((p), 0) << 8) | GETBYTE((p), 1))
 124 #define LOAD16_L(p) (GETBYTE((p), 0) | (GETBYTE((p), 1) << 8))
 125 #define LOAD16(p) LOAD16_B((p))
 126
 127 #define STORE16_B(p, v) (PUTBYTE((p), 0, (v) >> 8), PUTBYTE((p), 1, (v)))
 128 #define STORE16_L(p, v) (PUTBYTE((p), 0, (v)), PUTBYTE((p), 1, (v) >> 8))
 129 #define STORE16(p, v) STORE16_B((p), (v))
 130
 131 #define LOAD32_B(p)                                                     \
 132   ((GETBYTE((p), 0) << 24) | (GETBYTE((p), 1) << 16) |                  \
 133    (GETBYTE((p), 2) <<  8) | (GETBYTE((p), 3) <<  0))
 134 #define LOAD32_L(p)                                                     \
 135   ((GETBYTE((p), 0) <<  0) | (GETBYTE((p), 1) <<  8) |                  \
 136    (GETBYTE((p), 2) << 16) | (GETBYTE((p), 3) << 24))
 137 #define LOAD32(p) LOAD32_B((p))
 138
 139 #define STORE32_B(p, v)                                                 \
 140   (PUTBYTE((p), 0, (v) >> 24), PUTBYTE((p), 1, (v) >> 16),              \
 141    PUTBYTE((p), 2, (v) >>  8), PUTBYTE((p), 3, (v) >>  0))
 142 #define STORE32_L(p, v)                                                 \
 143   (PUTBYTE((p), 0, (v) >>  0), PUTBYTE((p), 1, (v) >>  8),              \
 144    PUTBYTE((p), 2, (v) >> 16), PUTBYTE((p), 3, (v) >> 24))
 145 #define STORE32(p, v) STORE32_B((p), (v))
 146
 147 /*----- That's all, folks -------------------------------------------------*/
 148
 149 #ifdef __cplusplus
 150   }
 151 #endif
 152
 153 #endif