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
25using System;
26
27class 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}
98