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1 siliconforks 332 /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
2     /* ***** BEGIN LICENSE BLOCK *****
3     * Version: MPL 1.1/GPL 2.0/LGPL 2.1
4     *
5     * The contents of this file are subject to the Mozilla Public License Version
6     * 1.1 (the "License"); you may not use this file except in compliance with
7     * the License. You may obtain a copy of the License at
8     * http://www.mozilla.org/MPL/
9     *
10     * Software distributed under the License is distributed on an "AS IS" basis,
11     * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
12     * for the specific language governing rights and limitations under the
13     * License.
14     *
15     * The Original Code is Mozilla Communicator client code, released
16     * March 31, 1998.
17     *
18     * The Initial Developer of the Original Code is
19     * Netscape Communications Corporation.
20     * Portions created by the Initial Developer are Copyright (C) 1998
21     * the Initial Developer. All Rights Reserved.
22     *
23     * Contributor(s):
24     *
25     * Alternatively, the contents of this file may be used under the terms of
26     * either of the GNU General Public License Version 2 or later (the "GPL"),
27     * or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
28     * in which case the provisions of the GPL or the LGPL are applicable instead
29     * of those above. If you wish to allow use of your version of this file only
30     * under the terms of either the GPL or the LGPL, and not to allow others to
31     * use your version of this file under the terms of the MPL, indicate your
32     * decision by deleting the provisions above and replace them with the notice
33     * and other provisions required by the GPL or the LGPL. If you do not delete
34     * the provisions above, a recipient may use your version of this file under
35     * the terms of any one of the MPL, the GPL or the LGPL.
36     *
37     * ***** END LICENSE BLOCK ***** */
38    
39     #ifndef jsbit_h___
40     #define jsbit_h___
41    
42     #include "jstypes.h"
43     #include "jsutil.h"
44    
45     JS_BEGIN_EXTERN_C
46    
47     /*
48     ** A jsbitmap_t is a long integer that can be used for bitmaps
49     */
50     typedef JSUword jsbitmap_t; /* NSPR name, a la Unix system types */
51     typedef jsbitmap_t jsbitmap; /* JS-style scalar typedef name */
52    
53     #define JS_BITMAP_SIZE(bits) (JS_HOWMANY(bits, JS_BITS_PER_WORD) * \
54     sizeof(jsbitmap))
55    
56     #define JS_TEST_BIT(_map,_bit) ((_map)[(_bit)>>JS_BITS_PER_WORD_LOG2] & \
57     ((jsbitmap)1<<((_bit)&(JS_BITS_PER_WORD-1))))
58     #define JS_SET_BIT(_map,_bit) ((_map)[(_bit)>>JS_BITS_PER_WORD_LOG2] |= \
59     ((jsbitmap)1<<((_bit)&(JS_BITS_PER_WORD-1))))
60     #define JS_CLEAR_BIT(_map,_bit) ((_map)[(_bit)>>JS_BITS_PER_WORD_LOG2] &= \
61     ~((jsbitmap)1<<((_bit)&(JS_BITS_PER_WORD-1))))
62    
63     /*
64     ** Compute the log of the least power of 2 greater than or equal to n
65     */
66     extern JS_PUBLIC_API(JSIntn) JS_CeilingLog2(JSUint32 i);
67    
68     /*
69     ** Compute the log of the greatest power of 2 less than or equal to n
70     */
71     extern JS_PUBLIC_API(JSIntn) JS_FloorLog2(JSUint32 i);
72    
73     /*
74     * Replace bit-scanning code sequences with CPU-specific instructions to
75     * speedup calculations of ceiling/floor log2.
76     *
77     * With GCC 3.4 or later we can use __builtin_clz for that, see bug 327129.
78     *
79     * SWS: Added MSVC intrinsic bitscan support. See bugs 349364 and 356856.
80     */
81     #if defined(_WIN32) && (_MSC_VER >= 1300) && defined(_M_IX86)
82    
83     unsigned char _BitScanForward(unsigned long * Index, unsigned long Mask);
84     unsigned char _BitScanReverse(unsigned long * Index, unsigned long Mask);
85     # pragma intrinsic(_BitScanForward,_BitScanReverse)
86    
87     __forceinline static int
88     __BitScanForward32(unsigned int val)
89     {
90     unsigned long idx;
91    
92     _BitScanForward(&idx, (unsigned long)val);
93     return (int)idx;
94     }
95     __forceinline static int
96     __BitScanReverse32(unsigned int val)
97     {
98     unsigned long idx;
99    
100     _BitScanReverse(&idx, (unsigned long)val);
101     return (int)(31-idx);
102     }
103     # define js_bitscan_ctz32(val) __BitScanForward32(val)
104     # define js_bitscan_clz32(val) __BitScanReverse32(val)
105     # define JS_HAS_BUILTIN_BITSCAN32
106    
107     #elif (__GNUC__ >= 4) || (__GNUC__ == 3 && __GNUC_MINOR__ >= 4)
108    
109     # define js_bitscan_ctz32(val) __builtin_ctz(val)
110     # define js_bitscan_clz32(val) __builtin_clz(val)
111     # define JS_HAS_BUILTIN_BITSCAN32
112     # if (JS_BYTES_PER_WORD == 8)
113     # define js_bitscan_ctz64(val) __builtin_ctzll(val)
114     # define js_bitscan_clz64(val) __builtin_clzll(val)
115     # define JS_HAS_BUILTIN_BITSCAN64
116     # endif
117    
118     #endif
119    
120     /*
121     ** Macro version of JS_CeilingLog2: Compute the log of the least power of
122     ** 2 greater than or equal to _n. The result is returned in _log2.
123     */
124     #ifdef JS_HAS_BUILTIN_BITSCAN32
125     /*
126     * Use intrinsic function or count-leading-zeros to calculate ceil(log2(_n)).
127     * The macro checks for "n <= 1" and not "n != 0" as js_bitscan_clz32(0) is
128     * undefined.
129     */
130     # define JS_CEILING_LOG2(_log2,_n) \
131     JS_BEGIN_MACRO \
132     unsigned int j_ = (unsigned int)(_n); \
133     (_log2) = (j_ <= 1 ? 0 : 32 - js_bitscan_clz32(j_ - 1)); \
134     JS_END_MACRO
135     #else
136     # define JS_CEILING_LOG2(_log2,_n) \
137     JS_BEGIN_MACRO \
138     JSUint32 j_ = (JSUint32)(_n); \
139     (_log2) = 0; \
140     if ((j_) & ((j_)-1)) \
141     (_log2) += 1; \
142     if ((j_) >> 16) \
143     (_log2) += 16, (j_) >>= 16; \
144     if ((j_) >> 8) \
145     (_log2) += 8, (j_) >>= 8; \
146     if ((j_) >> 4) \
147     (_log2) += 4, (j_) >>= 4; \
148     if ((j_) >> 2) \
149     (_log2) += 2, (j_) >>= 2; \
150     if ((j_) >> 1) \
151     (_log2) += 1; \
152     JS_END_MACRO
153     #endif
154    
155     /*
156     ** Macro version of JS_FloorLog2: Compute the log of the greatest power of
157     ** 2 less than or equal to _n. The result is returned in _log2.
158     **
159     ** This is equivalent to finding the highest set bit in the word.
160     */
161     #ifdef JS_HAS_BUILTIN_BITSCAN32
162     /*
163     * Use js_bitscan_clz32 or count-leading-zeros to calculate floor(log2(_n)).
164     * Since js_bitscan_clz32(0) is undefined, the macro set the loweset bit to 1
165     * to ensure 0 result when _n == 0.
166     */
167     # define JS_FLOOR_LOG2(_log2,_n) \
168     JS_BEGIN_MACRO \
169     (_log2) = 31 - js_bitscan_clz32(((unsigned int)(_n)) | 1); \
170     JS_END_MACRO
171     #else
172     # define JS_FLOOR_LOG2(_log2,_n) \
173     JS_BEGIN_MACRO \
174     JSUint32 j_ = (JSUint32)(_n); \
175     (_log2) = 0; \
176     if ((j_) >> 16) \
177     (_log2) += 16, (j_) >>= 16; \
178     if ((j_) >> 8) \
179     (_log2) += 8, (j_) >>= 8; \
180     if ((j_) >> 4) \
181     (_log2) += 4, (j_) >>= 4; \
182     if ((j_) >> 2) \
183     (_log2) += 2, (j_) >>= 2; \
184     if ((j_) >> 1) \
185     (_log2) += 1; \
186     JS_END_MACRO
187     #endif
188    
189     /*
190     * Internal function.
191     * Compute the log of the least power of 2 greater than or equal to n.
192     * This is a version of JS_CeilingLog2 that operates on jsuword with
193     * CPU-dependant size.
194     */
195     #define JS_CEILING_LOG2W(n) ((n) <= 1 ? 0 : 1 + JS_FLOOR_LOG2W((n) - 1))
196    
197     /*
198     * Internal function.
199     * Compute the log of the greatest power of 2 less than or equal to n.
200     * This is a version of JS_FloorLog2 that operates on jsuword with
201     * CPU-dependant size and requires that n != 0.
202     */
203     #define JS_FLOOR_LOG2W(n) (JS_ASSERT((n) != 0), js_FloorLog2wImpl(n))
204    
205     #if JS_BYTES_PER_WORD == 4
206    
207     # ifdef JS_HAS_BUILTIN_BITSCAN32
208     # define js_FloorLog2wImpl(n) \
209     ((JSUword)(JS_BITS_PER_WORD - 1 - js_bitscan_clz32(n)))
210     # else
211     # define js_FloorLog2wImpl(n) ((JSUword)JS_FloorLog2(n))
212     #endif
213    
214     #elif JS_BYTES_PER_WORD == 8
215    
216     # ifdef JS_HAS_BUILTIN_BITSCAN64
217     # define js_FloorLog2wImpl(n) \
218     ((JSUword)(JS_BITS_PER_WORD - 1 - js_bitscan_clz64(n)))
219     # else
220     extern JSUword js_FloorLog2wImpl(JSUword n);
221     # endif
222    
223     #else
224    
225     # error "NOT SUPPORTED"
226    
227     #endif
228    
229     /*
230     * Macros for rotate left. There is no rotate operation in the C Language so
231     * the construct (a << 4) | (a >> 28) is used instead. Most compilers convert
232     * this to a rotate instruction but some versions of MSVC don't without a
233     * little help. To get MSVC to generate a rotate instruction, we have to use
234     * the _rotl intrinsic and use a pragma to make _rotl inline.
235     *
236     * MSVC in VS2005 will do an inline rotate instruction on the above construct.
237     */
238    
239     #if defined(_MSC_VER) && (defined(_M_IX86) || defined(_M_AMD64) || \
240     defined(_M_X64))
241     #include <stdlib.h>
242     #pragma intrinsic(_rotl)
243     #define JS_ROTATE_LEFT32(a, bits) _rotl(a, bits)
244     #else
245     #define JS_ROTATE_LEFT32(a, bits) (((a) << (bits)) | ((a) >> (32 - (bits))))
246     #endif
247    
248     JS_END_EXTERN_C
249     #endif /* jsbit_h___ */

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