New addition: bit manipulation macros.

[mLib] / bits.h

/* -*-c-*-
 *
 * $Id: bits.h,v 1.1 1999/06/01 09:46:19 mdw Exp $
 *
 * Portable bit-level manipulation macros
 *
 * (c) 1998 Straylight/Edgeware
 */

/*----- Licensing notice --------------------------------------------------* 
 *
 * This file is part of the mLib utilities library.
 *
 * mLib is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Library General Public License as
 * published by the Free Software Foundation; either version 2 of the
 * License, or (at your option) any later version.
 * 
 * mLib is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Library General Public License for more details.
 * 
 * You should have received a copy of the GNU Library General Public
 * License along with mLib; if not, write to the Free
 * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
 * MA 02111-1307, USA.
 */

/*----- Revision history --------------------------------------------------* 
 *
 * $Log: bits.h,v $
 * Revision 1.1  1999/06/01 09:46:19  mdw
 * New addition: bit manipulation macros.
 *
 */

#ifndef BITS_H
#define BITS_H

#ifdef __cplusplus
  extern "C" {
#endif

/*----- Header files ------------------------------------------------------*/

#include <limits.h>
#include <stddef.h>

/*----- Decide on some types ----------------------------------------------*/

/* --- Decide on a 32-bit type --- *
 *
 * I want a type which is capable of expressing 32-bit numbers.  Because some
 * implementations have 64-bit @long@s (infinitely preferable to the abortion
 * that is @long long@), using @unsigned long@ regardless is wasteful.  So,
 * if @int@ appears to be good enough, then I'll go with that.
 */

#if UINT_MAX >= 0xffffffffu
  typedef unsigned int uint32;
#else
  typedef unsigned long uint32;
#endif

/* --- Decide on 16-bit and 8-bit types --- *
 *
 * This is more for brevity than anything else.
 */

typedef unsigned short uint16;
typedef unsigned char octet;

/* --- WARNING! --- *
 *
 * Never lose sight of the fact that the above types may be wider than the
 * names suggest.  Some architectures have 32-bit @short@s for example.
 */

/*----- Macros ------------------------------------------------------------*/

/* --- Useful masks --- */

#define MASK8 0xffu
#define MASK16 0xffffu
#define MASK32 0xffffffffu

/* --- Type coercions --- */

#define U8(x) ((octet)((x) & MASK8))
#define U16(x) ((uint16)((x) & MASK16))
#define U32(x) ((uint32)((x) & MASK32))

/* --- Safe shifting macros --- */

#define LSL8(v, s) (U8(v) << ((s) & 7u))
#define LSR8(v, s) (U8(v) >> ((s) & 7u))
#define LSL16(v, s) (U16(v) << ((s) & 15u))
#define LSR16(v, s) (U16(v) >> ((s) & 15u))
#define LSL32(v, s) (U32(v) << ((s) & 31u))
#define LSR32(v, s) (U32(v) >> ((s) & 31u))

/* --- Rotation macros --- */

#define ROL8(v, s) (LSL8((v), (s)) | (LSR8((v), 8 - (s))))
#define ROR8(v, s) (LSR8((v), (s)) | (LSL8((v), 8 - (s))))
#define ROL16(v, s) (LSL16((v), (s)) | (LSR16((v), 16 - (s))))
#define ROR16(v, s) (LSR16((v), (s)) | (LSL16((v), 16 - (s))))
#define ROL32(v, s) (LSL32((v), (s)) | (LSR32((v), 32 - (s))))
#define ROR32(v, s) (LSR32((v), (s)) | (LSL32((v), 32 - (s))))

/* --- Storage and retrieval --- */

#define GETBYTE(p, o) (((octet *)(p))[o] & MASK8)
#define PUTBYTE(p, o, v) (((octet *)(p))[o] = U8((v)))

#define LOAD8(p) (GETBYTE((p), 0))
#define STORE8(p, v) (PUTBYTE((p), 0, (v)))

#define LOAD16_B(p) ((GETBYTE((p), 0) << 8) | GETBYTE((p), 1))
#define LOAD16_L(p) (GETBYTE((p), 0) | (GETBYTE((p), 1) << 8))
#define LOAD16(p) LOAD16_B((p))

#define STORE16_B(p, v) (PUTBYTE((p), 0, (v) >> 8), PUTBYTE((p), 1, (v)))
#define STORE16_L(p, v) (PUTBYTE((p), 0, (v)), PUTBYTE((p), 1, (v) >> 8))
#define STORE16(p, v) STORE16_B((p), (v))

#define LOAD32_B(p)							\
  ((GETBYTE((p), 0) << 24) | (GETBYTE((p), 1) << 16) |			\
   (GETBYTE((p), 2) <<  8) | (GETBYTE((p), 3) <<  0))
#define LOAD32_L(p)							\
  ((GETBYTE((p), 0) <<  0) | (GETBYTE((p), 1) <<  8) |			\
   (GETBYTE((p), 2) << 16) | (GETBYTE((p), 3) << 24))
#define LOAD32(p) LOAD32_B((p))

#define STORE32_B(p, v)							\
  (PUTBYTE((p), 0, (v) >> 24), PUTBYTE((p), 1, (v) >> 16),		\
   PUTBYTE((p), 2, (v) >>  8), PUTBYTE((p), 3, (v) >>  0))
#define STORE32_L(p, v)							\
  (PUTBYTE((p), 0, (v) >>  0), PUTBYTE((p), 1, (v) >>  8),		\
   PUTBYTE((p), 2, (v) >> 16), PUTBYTE((p), 3, (v) >> 24))
#define STORE32(p, v) STORE32_B((p), (v))

/*----- That's all, folks -------------------------------------------------*/

#ifdef __cplusplus
  }
#endif

#endif