sys/ddb/db_access.c

   1 /*
   2  * Mach Operating System
   3  * Copyright (c) 1991,1990 Carnegie Mellon University
   4  * All Rights Reserved.
   5  *
   6  * Permission to use, copy, modify and distribute this software and its
   7  * documentation is hereby granted, provided that both the copyright
   8  * notice and this permission notice appear in all copies of the
   9  * software, derivative works or modified versions, and any portions
  10  * thereof, and that both notices appear in supporting documentation.
  11  *
  12  * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS
  13  * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
  14  * ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
  15  *
  16  * Carnegie Mellon requests users of this software to return to
  17  *
  18  *  Software Distribution Coordinator  or  Software.Distribution@CS.CMU.EDU
  19  *  School of Computer Science
  20  *  Carnegie Mellon University
  21  *  Pittsburgh PA 15213-3890
  22  *
  23  * any improvements or extensions that they make and grant Carnegie the
  24  * rights to redistribute these changes.
  25  *
  26  * $FreeBSD: src/sys/ddb/db_access.c,v 1.15 1999/08/28 00:41:04 peter Exp $
  27  * $DragonFly: src/sys/ddb/db_access.c,v 1.4 2005/12/23 21:35:44 swildner Exp $
  28  */
  29
  30 /*
  31  *      Author: David B. Golub, Carnegie Mellon University
  32  *      Date:   7/90
  33  */
  34 #include <sys/param.h>
  35
  36 #include <ddb/ddb.h>
  37 #include <ddb/db_access.h>
  38
  39 /*
  40  * Access unaligned data items on aligned (longword)
  41  * boundaries.
  42  */
  43
  44 static unsigned db_extend[] = { /* table for sign-extending */
  45         0,
  46         0xFFFFFF80U,
  47         0xFFFF8000U,
  48         0xFF800000U
  49 };
  50
  51 db_expr_t
  52 db_get_value(db_addr_t addr, int size, boolean_t is_signed)
  53 {
  54         char            data[sizeof(int)];
  55         db_expr_t       value;
  56         int     i;
  57
  58         db_read_bytes(addr, size, data);
  59
  60         value = 0;
  61 #if     BYTE_MSF
  62         for (i = 0; i < size; i++)
  63 #else   /* BYTE_LSF */
  64         for (i = size - 1; i >= 0; i--)
  65 #endif
  66         {
  67             value = (value << 8) + (data[i] & 0xFF);
  68         }
  69
  70         if (size < 4) {
  71             if (is_signed && (value & db_extend[size]) != 0)
  72                 value |= db_extend[size];
  73         }
  74         return (value);
  75 }
  76
  77 void
  78 db_put_value(db_addr_t addr, int size, db_expr_t value)
  79 {
  80         char            data[sizeof(int)];
  81         int             i;
  82
  83 #if     BYTE_MSF
  84         for (i = size - 1; i >= 0; i--)
  85 #else   /* BYTE_LSF */
  86         for (i = 0; i < size; i++)
  87 #endif
  88         {
  89             data[i] = value & 0xFF;
  90             value >>= 8;
  91         }
  92
  93         db_write_bytes(addr, size, data);
  94 }
  95