| /////////////////////////////////////////////////////////////////////////////// |
| // |
| /// \file bsr.h |
| /// \brief Bit scan reverse |
| // |
| // Author: Lasse Collin |
| // |
| // This file has been put into the public domain. |
| // You can do whatever you want with this file. |
| // |
| /////////////////////////////////////////////////////////////////////////////// |
| |
| #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 |
