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  }