bitfield.hh revision 4257 
1/*
2 * Copyright (c) 2003-2005 The Regents of The University of Michigan
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions are
7 * met: redistributions of source code must retain the above copyright
8 * notice, this list of conditions and the following disclaimer;
9 * redistributions in binary form must reproduce the above copyright
10 * notice, this list of conditions and the following disclaimer in the
11 * documentation and/or other materials provided with the distribution;
12 * neither the name of the copyright holders nor the names of its
13 * contributors may be used to endorse or promote products derived from
14 * this software without specific prior written permission.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
17 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
18 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
19 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
20 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
21 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
22 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
23 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
24 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
26 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27 *
28 * Authors: Steve Reinhardt
29 *          Nathan Binkert
30 */
31
32#ifndef __BASE_BITFIELD_HH__
33#define __BASE_BITFIELD_HH__
34
35#include <inttypes.h>
36//#include "base/misc.hh"
37
38/**
39 * Generate a 64-bit mask of 'nbits' 1s, right justified.
40 */
41inline uint64_t
42mask(int nbits)
43{
44    return (nbits == 64) ? (uint64_t)-1LL : (1ULL << nbits) - 1;
45}
46
47
48
49/**
50 * Extract the bitfield from position 'first' to 'last' (inclusive)
51 * from 'val' and right justify it.  MSB is numbered 63, LSB is 0.
52 */
53template <class T>
54inline
55T
56bits(T val, int first, int last)
57{
58    int nbits = first - last + 1;
59    return (val >> last) & mask(nbits);
60}
61
62/**
63 * Mask off the given bits in place like bits() but without shifting.
64 * msb = 63, lsb = 0
65 */
66template <class T>
67inline
68T
69mbits(T val, int first, int last)
70{
71    return val & (mask(first+1) & ~mask(last));
72}
73
74inline uint64_t
75mask(int first, int last)
76{
77    return mbits((uint64_t)-1LL, first, last);
78}
79
80/**
81 * Sign-extend an N-bit value to 64 bits.
82 */
83template <int N>
84inline
85int64_t
86sext(uint64_t val)
87{
88    int sign_bit = bits(val, N-1, N-1);
89    return sign_bit ? (val | ~mask(N)) : val;
90}
91
92/**
93 * Return val with bits first to last set to bit_val
94 */
95template <class T, class B>
96inline
97T
98insertBits(T val, int first, int last, B bit_val)
99{
100    T bmask = mask(first - last + 1) << last;
101    return ((bit_val << last) & bmask) | (val & ~bmask);
102}
103
104/**
105 * A convenience function to replace bits first to last of val with bit_val
106 * in place.
107 */
108template <class T, class B>
109inline
110void
111replaceBits(T& val, int first, int last, B bit_val)
112{
113    val = insertBits(val, first, last, bit_val);
114}
115
116/**
117 * Returns the bit position of the MSB that is set in the input
118 */
119inline
120int
121findMsbSet(uint64_t val) {
122    int msb = 0;
123    if (!val)
124        return 0;
125    if (bits(val, 63,32)) { msb += 32; val >>= 32; }
126    if (bits(val, 31,16)) { msb += 16; val >>= 16; }
127    if (bits(val, 15,8))  { msb += 8;  val >>= 8;  }
128    if (bits(val, 7,4))   { msb += 4;  val >>= 4;  }
129    if (bits(val, 3,2))   { msb += 2;  val >>= 2;  }
130    if (bits(val, 1,1))   { msb += 1; }
131    return msb;
132}
133
134template<class Data, int first, int last=first>
135class BitfieldBase
136{
137  protected:
138    uint8_t __data[sizeof(Data)];
139
140    //These are defined here so it can be specialized for Data, but can be
141    //hidden by RO and WO variants.
142    inline uint64_t getBits(int _first, int _last)
143    {
144        //build up the right bits from the byte array "data"
145        //panic("Not yet implemented.\n");
146        return 0;
147    }
148
149    inline void setBits(int _first, int _last, uint64_t val)
150    {
151        //Set the right bits from the byte array "data"
152        //panic("Not yet implemented.\n");
153    }
154};
155
156template<class Data, int first, int last=first>
157class BitfieldNativeBase
158{
159  protected:
160    Data __data;
161
162    inline uint64_t getBits(int _first, int _last)
163    {
164        return bits(__data, first, last);
165    }
166
167    inline void setBits(int _first, int _last, uint64_t val)
168    {
169        replaceBits(__data, first, last, val);
170    }
171};
172
173template <int first>
174class BitfieldBase<uint64_t, first, first> :
175        public BitfieldNativeBase<uint64_t, first, first>
176{};
177
178template <int first, int last>
179class BitfieldBase<uint64_t, first, last> :
180        public BitfieldNativeBase<uint64_t, first, last>
181{};
182
183template <int first>
184class BitfieldBase<uint32_t, first, first> :
185        public BitfieldNativeBase<uint32_t, first, first>
186{};
187
188template <int first, int last>
189class BitfieldBase<uint32_t, first, last> :
190        public BitfieldNativeBase<uint32_t, first, last>
191{};
192
193template <int first>
194class BitfieldBase<uint16_t, first, first> :
195        public BitfieldNativeBase<uint16_t, first, first>
196{};
197
198template <int first, int last>
199class BitfieldBase<uint16_t, first, last> :
200        public BitfieldNativeBase<uint16_t, first, last>
201{};
202
203template <int first>
204class BitfieldBase<uint8_t, first, first> :
205        public BitfieldNativeBase<uint8_t, first, first>
206{};
207
208template <int first, int last>
209class BitfieldBase<uint8_t, first, last> :
210        public BitfieldNativeBase<uint8_t, first, last>
211{};
212
213template<class Data, int first, int last=first>
214class _BitfieldRO : public BitfieldBase<Data, first, last>
215{
216  public:
217    operator const Data & ()
218    {
219        return this->getBits(first, last);
220    }
221};
222
223template<class Data, int first, int last=first>
224class _BitfieldWO : public BitfieldBase<Data, first, last>
225{
226  public:
227    const Data & operator = (const Data & _data)
228    {
229        this->setBits(first, last, _data);
230        return *this;
231    }
232};
233
234template<class Data, int first, int last=first>
235class _BitfieldRW : public BitfieldBase<Data, first, last>
236{
237  public:
238    operator const Data ()
239    {
240        return this->getBits(first, last);
241    }
242
243    const Data operator = (const Data & _data)
244    {
245        this->setBits(first, last, _data);
246        return *this;
247    }
248};
249
250template <class Type, class Base>
251class BitUnionOperators : public Base
252{
253  public:
254    operator const Type ()
255    {
256        return Base::__data;
257    }
258
259    const Type operator = (const Type & _data)
260    {
261        Base::__data = _data;
262    }
263
264    bool operator < (const Base & base)
265    {
266        return Base::__data < base.__data;
267    }
268
269    bool operator == (const Base & base)
270    {
271        return Base::__data == base.__data;
272    }
273};
274
275#define __BitUnion(type, name) \
276    class __##name { \
277      public: \
278        typedef type __DataType; \
279        union { \
280            type __data;\
281
282#define EndBitUnion(name) \
283        }; \
284    }; \
285    typedef BitUnionOperators<__##name::__DataType, __##name> name;
286
287#define __SubBitUnion(type, name) \
288        union { \
289            type __data; \
290            inline operator const __DataType () \
291            { return __data; } \
292            \
293            inline const __DataType operator = (const __DataType & _data) \
294            { __data = _data; }
295
296#define EndSubBitUnion(name) } name;
297
298//Regular read/write bitfields
299#define BitfieldRW(first, last) _BitfieldRW<__DataType, first, last>
300#define SubBitUnionRW(name, first, last) \
301        __SubBitUnion(BitfieldRW(first, last), name)
302#define Bitfield(first, last) BitfieldRW(first, last)
303#define SubBitUnion(name, first, last) SubBitUnionRW(name, first, last)
304
305//Read only bitfields
306#define BitfieldRO(first, last) _BitfieldRO<__DataType, first, last>
307#define SubBitUnionRO(name, first, last) \
308        __SubBitUnion(BitfieldRO(first, last), name)
309
310//Write only bitfields
311#define BitfieldWO(first, last) _BitfieldWO<__DataType, first, last>
312#define SubBitUnionWO(name, first, last) \
313        __SubBitUnion(BitfieldWO(first, last), name)
314
315#define BitUnion(type, name) __BitUnion(type, name)
316
317#define BitUnion64(name) __BitUnion(uint64_t, name)
318#define BitUnion32(name) __BitUnion(uint32_t, name)
319#define BitUnion16(name) __BitUnion(uint16_t, name)
320#define BitUnion8(name) __BitUnion(uint8_t, name)
321
322#endif // __BASE_BITFIELD_HH__
323