My Project
SDL_bits.h
Go to the documentation of this file.
1
/*
2
Simple DirectMedia Layer
3
Copyright (C) 1997-2018 Sam Lantinga <slouken@libsdl.org>
4
5
This software is provided 'as-is', without any express or implied
6
warranty. In no event will the authors be held liable for any damages
7
arising from the use of this software.
8
9
Permission is granted to anyone to use this software for any purpose,
10
including commercial applications, and to alter it and redistribute it
11
freely, subject to the following restrictions:
12
13
1. The origin of this software must not be misrepresented; you must not
14
claim that you wrote the original software. If you use this software
15
in a product, an acknowledgment in the product documentation would be
16
appreciated but is not required.
17
2. Altered source versions must be plainly marked as such, and must not be
18
misrepresented as being the original software.
19
3. This notice may not be removed or altered from any source distribution.
20
*/
21
28
#ifndef SDL_bits_h_
29
#define SDL_bits_h_
30
31
#include "
SDL_stdinc.h
"
32
33
#include "
begin_code.h
"
34
/* Set up for C function definitions, even when using C++ */
35
#ifdef __cplusplus
36
extern
"C"
{
37
#endif
38
50
#if defined(__WATCOMC__) && defined(__386__)
51
extern
_inline
int
_SDL_clz_watcom (Uint32);
52
#pragma aux _SDL_clz_watcom = \
53
"bsr eax, eax" \
54
"xor eax, 31" \
55
parm [eax] nomemory \
56
value [eax] \
57
modify exact [eax] nomemory;
58
#endif
59
60
SDL_FORCE_INLINE
int
61
SDL_MostSignificantBitIndex32
(Uint32 x)
62
{
63
#if defined(__GNUC__) && (__GNUC__ >= 4 || (__GNUC__ == 3 && __GNUC_MINOR__ >= 4))
64
/* Count Leading Zeroes builtin in GCC.
65
* http://gcc.gnu.org/onlinedocs/gcc-4.3.4/gcc/Other-Builtins.html
66
*/
67
if
(x == 0) {
68
return
-1;
69
}
70
return
31 - __builtin_clz(x);
71
#elif defined(__WATCOMC__) && defined(__386__)
72
if
(x == 0) {
73
return
-1;
74
}
75
return
31 - _SDL_clz_watcom(x);
76
#else
77
/* Based off of Bit Twiddling Hacks by Sean Eron Anderson
78
* <seander@cs.stanford.edu>, released in the public domain.
79
* http://graphics.stanford.edu/~seander/bithacks.html#IntegerLog
80
*/
81
const
Uint32 b[] = {0x2, 0xC, 0xF0, 0xFF00, 0xFFFF0000};
82
const
int
S[] = {1, 2, 4, 8, 16};
83
84
int
msbIndex = 0;
85
int
i;
86
87
if
(x == 0) {
88
return
-1;
89
}
90
91
for
(i = 4; i >= 0; i--)
92
{
93
if
(x & b[i])
94
{
95
x >>= S[i];
96
msbIndex |= S[i];
97
}
98
}
99
100
return
msbIndex;
101
#endif
102
}
103
104
/* Ends C function definitions when using C++ */
105
#ifdef __cplusplus
106
}
107
#endif
108
#include "
close_code.h
"
109
110
#endif
/* SDL_bits_h_ */
111
112
/* vi: set ts=4 sw=4 expandtab: */
begin_code.h
SDL_stdinc.h
close_code.h
SDL_MostSignificantBitIndex32
SDL_FORCE_INLINE int SDL_MostSignificantBitIndex32(Uint32 x)
Definition:
SDL_bits.h:61
Generated by
1.8.13