Botan  1.11.15
src/lib/pubkey/mce/code_based_util.h
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00001 /**
00002  * (C) Copyright Projet SECRET, INRIA, Rocquencourt
00003  * (C) Bhaskar Biswas and  Nicolas Sendrier
00004  *
00005  * (C) 2014 cryptosource GmbH
00006  * (C) 2014 Falko Strenzke fstrenzke@cryptosource.de
00007  *
00008  * Botan is released under the Simplified BSD License (see license.txt)
00009  *
00010  */
00011 
00012 #ifndef BOTAN_CODE_BASED_UTIL_H__
00013 #define BOTAN_CODE_BASED_UTIL_H__
00014 
00015 #include <botan/gf2m_small_m.h>
00016 
00017 namespace Botan {
00018 
00019 /**
00020 * Expand an input to a bit mask depending on it being being zero or non-zero
00021 * @ param tst the input
00022 * @return the mask 0xFFFF if tst is non-zero and 0 otherwise
00023 */
00024 template<typename T>
00025 u16bit expand_mask_16bit(T tst)
00026    {
00027    const u16bit result = (tst != 0);
00028    return ~(result - 1);
00029    }
00030 
00031 inline gf2m_small_m::gf2m gray_to_lex(gf2m_small_m::gf2m gray)
00032    {
00033    gf2m_small_m::gf2m result = gray ^ (gray>>8);
00034    result ^= (result >> 4);
00035    result ^= (result >> 2);
00036    result ^= (result >> 1);
00037    return result;
00038    }
00039 
00040 inline gf2m_small_m::gf2m lex_to_gray(gf2m_small_m::gf2m lex)
00041    {
00042    return (lex>>1) ^ lex;
00043    }
00044 
00045 inline u32bit bit_size_to_byte_size(u32bit bit_size)
00046    {
00047    return (bit_size - 1) / 8 + 1;
00048    }
00049 
00050 inline u32bit bit_size_to_32bit_size(u32bit bit_size)
00051    {
00052    return (bit_size - 1) / 32 + 1;
00053    }
00054 
00055 }
00056 
00057 #endif