_ Git - BearSSL/blob - T0/TPointerExpr.cs

   1 /*
   2  * Copyright (c) 2016 Thomas Pornin <pornin@bolet.org>
   3  *
   4  * Permission is hereby granted, free of charge, to any person obtaining
   5  * a copy of this software and associated documentation files (the
   6  * "Software"), to deal in the Software without restriction, including
   7  * without limitation the rights to use, copy, modify, merge, publish,
   8  * distribute, sublicense, and/or sell copies of the Software, and to
   9  * permit persons to whom the Software is furnished to do so, subject to
  10  * the following conditions:
  11  *
  12  * The above copyright notice and this permission notice shall be
  13  * included in all copies or substantial portions of the Software.
  14  *
  15  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  16  * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  17  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  18  * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
  19  * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
  20  * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
  21  * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  22  * SOFTWARE.
  23  */
  24
  25 using System;
  26
  27 class TPointerExpr : TPointerBase {
  28
  29         string expr;
  30         int min, max;
  31
  32         internal TPointerExpr(string expr, int min, int max)
  33         {
  34                 this.expr = expr;
  35                 this.min = min;
  36                 this.max = max;
  37         }
  38
  39         internal override bool ToBool(TValue vp)
  40         {
  41                 throw new Exception("Cannot evaluate C-expr at compile time");
  42         }
  43
  44         internal override string ToString(TValue vp)
  45         {
  46                 return ToCExpr(vp.x);
  47         }
  48
  49         internal string ToCExpr(int off)
  50         {
  51                 if (off == 0) {
  52                         return expr;
  53                 } else if (off > 0) {
  54                         return String.Format(
  55                                 "(uint32_t)({0}) + {1}", expr, off);
  56                 } else {
  57                         return String.Format(
  58                                 "(uint32_t)({0}) - {1}", expr, -(long)off);
  59                 }
  60         }
  61
  62         internal int GetMaxBitLength(int off)
  63         {
  64                 long rmin = (long)min + off;
  65                 long rmax = (long)max + off;
  66                 int numBits = 1;
  67                 if (rmin < 0) {
  68                         numBits = Math.Max(numBits, BitLength(rmin));
  69                 }
  70                 if (rmax > 0) {
  71                         numBits = Math.Max(numBits, BitLength(rmax));
  72                 }
  73                 return Math.Min(numBits, 32);
  74         }
  75
  76         /*
  77          * Get the minimal bit length of a value. This is for a signed
  78          * representation: the length includes a sign bit. Thus, the
  79          * returned value will be at least 1.
  80          */
  81         static int BitLength(long v)
  82         {
  83                 int num = 1;
  84                 if (v < 0) {
  85                         while (v != -1) {
  86                                 num ++;
  87                                 v >>= 1;
  88                         }
  89                 } else {
  90                         while (v != 0) {
  91                                 num ++;
  92                                 v >>= 1;
  93                         }
  94                 }
  95                 return num;
  96         }
  97 }