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Added bsr.h.

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This commit is contained in:
Lasse Collin 2008-01-15 13:32:13 +02:00
parent f3c88e8b8d
commit 10437b5b56
2 changed files with 62 additions and 0 deletions
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1
src/liblzma/common/Makefile.am
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@ -24,6 +24,7 @@ libcommon_la_CPPFLAGS = \
libcommon_la_SOURCES = \
common.h \
sysdefs.h \
bsr.h \
allocator.c \
block_private.h \
extra.c \

61
src/liblzma/common/bsr.h Normal file
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@ -0,0 +1,61 @@
///////////////////////////////////////////////////////////////////////////////
//
/// \file bsr.h
/// \brief Bit scan reverse
//
// This code has been put into the public domain.
//
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
//
///////////////////////////////////////////////////////////////////////////////
#ifndef LZMA_BSR_H
#define LZMA_BSR_H
// NOTE: Both input and output variables for lzma_bsr must be uint32_t.
#if defined(__GNUC__) && (defined (HAVE_ASM_X86) || defined(HAVE_ASM_X86_64))
# define lzma_bsr(dest, n) \
__asm__("bsrl %1, %0" : "=r" (dest) : "rm" (n))
#else
# define lzma_bsr(dest, n) dest = lzma_bsr_helper(n)
static inline uint32_t
lzma_bsr_helper(uint32_t n)
{
assert(n != 0);
uint32_t i = 31;
if ((n & UINT32_C(0xFFFF0000)) == 0) {
n <<= 16;
i = 15;
}
if ((n & UINT32_C(0xFF000000)) == 0) {
n <<= 8;
i -= 8;
}
if ((n & UINT32_C(0xF0000000)) == 0) {
n <<= 4;
i -= 4;
}
if ((n & UINT32_C(0xC0000000)) == 0) {
n <<= 2;
i -= 2;
}
if ((n & UINT32_C(0x80000000)) == 0)
--i;
return i;
}
#endif
#endif