54 lines
730 B
C
54 lines
730 B
C
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#ifndef _SDL_bits_h
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#define _SDL_bits_h
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#include "SDL_stdinc.h"
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#include "begin_code.h"
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#ifdef __cplusplus
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extern "C" {
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#endif
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SDL_FORCE_INLINE int
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SDL_MostSignificantBitIndex32(Uint32 x)
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{
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#if defined(__GNUC__) && __GNUC__ >= 4
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if (x == 0) {
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return -1;
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}
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return 31 - __builtin_clz(x);
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#else
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const Uint32 b[] = {0x2, 0xC, 0xF0, 0xFF00, 0xFFFF0000};
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const int S[] = {1, 2, 4, 8, 16};
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int msbIndex = 0;
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int i;
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if (x == 0) {
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return -1;
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}
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for (i = 4; i >= 0; i--)
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{
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if (x & b[i])
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{
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x >>= S[i];
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msbIndex |= S[i];
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}
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}
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return msbIndex;
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#endif
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}
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#ifdef __cplusplus
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}
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#endif
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#include "close_code.h"
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#endif
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