www.pudn.com > CiperLib_release_by_csk.rar > IntHelper.cpp

/* 
    Helper func for Integer Class 
    BY CSK(³ÂÊ¿¿­) 
    CSK@live.com 
    www.csksoft.net 
*/ 
 
#include "CiperLib.h" 
#include "inner_support.h" 
 
 
 
//random seeds number 
#define R_M_RND_SEEDS_NUM 37 
#define R_M_RND_SEEDS_F 14 
 
unsigned int IntHelper::rnd_seeds[R_M_RND_SEEDS_NUM]; 
unsigned int IntHelper::rnd_carry_flag = 0; 
int IntHelper::rnd_pos = 0; 
 
int IntHelper::logb2(const Integer& src) 
{ 
    int ans; 
    unsigned int top; 
     
    if (src.isZero()) return 0; 
     
    ans=32*(src.m_acutual_len-1); 
    top=src.m_p_data_arr[src.m_acutual_len-1]; 
    while (top>=1) 
    { 
        ans++; 
        top = top >> 1; 
    } 
    return ans; 
} 
 
 
int IntHelper::testbit(const Integer& x,unsigned int n) 
{ 
 
    if ((x.m_p_data_arr[n>>5] & ((unsigned int)1<<(n%32)))) return 1; 
 
    return 0; 
} 
 
int IntHelper::sliding_window(const Integer& x,int i,int *nbs,int * nzs,int window_size ) 
{ 
    int j,r,w; 
    w=window_size; 
/* check for leading 0 bit */ 
 
    *nbs=1; 
    *nzs=0; 
    if (!testbit(x,(unsigned int)i)) return 0; 
 
/* adjust window size if not enough bits left */ 
    
    if (i-w+1<0) w=i+1; 
 
    r=1; 
    for (j=i-1;j>i-w;j--) 
    { /* accumulate bits. Abort if two 0's in a row */ 
        (*nbs)++; 
        r*=2; 
        if (testbit( x,(unsigned int)j)) r+=1; 
        if (r%4==0) 
        { /* oops - too many zeros - shorten window */ 
            r/=4; 
            *nbs-=2; 
            *nzs=2; 
            break; 
        } 
    } 
    if (r%2==0) 
    { /* remove trailing 0 */ 
        r/=2; 
        *nzs=1; 
        (*nbs)--; 
    } 
    return r; 
 
} 
void IntHelper::MZ_seed(unsigned int seed) 
{ 
    int i,in; 
    unsigned int t,m=1L; 
    rnd_carry_flag=0; 
    rnd_pos=0; 
    rnd_seeds[0]^=seed; 
 
    for (i=1;it) rnd_carry_flag=1; 
        rnd_seeds[i]=pdiff;  
    } 
    return rnd_seeds[0]; 
 
 
}