标签：int double ePath ++ bit dbSt IEEE iMantissaLen iMark

编写软件vscode+gcc,英文名字乱起的,但每一步都对应着标准来着

#include <iostream> 
#include <math.h>

using namespace std;
struct DoubleBinary64{
 int iExponentLen = 11, iMantissaLen = 52, iDoubleBinLen = iMantissaLen+iExponentLen+1,iExponentsRange=(1<<(iExponentLen-1))-1;
};
typedef long long HASH;
void GetDoubleBin(char *binArr, double dbNum, DoubleBinary64& dbSt);
int GetMantissaBit(char *cArr, double dNum,int iMantissaLen);
void GetDecBit(char *ret, int num, int loop);
void GetDoubleBin(char *binArr, double dbNum,
    DoubleBinary64& dbSt)
{ 
    if (dbNum == 0)
    {
        for (int i = 0; i < dbSt.iDoubleBinLen; i++)
        {
            binArr[i] = '0';
        }
        return;
    }
    int ePath = (int)dbNum, iCount = 0, iMark = 0, iExponentLen = dbSt.iExponentLen
    , iMantissaLen = dbSt.iMantissaLen, iDoubleBinLen = dbSt.iDoubleBinLen,iExponentsRange=dbSt.iExponentsRange;
    char *fArr, *finArr;
    char fExponentArr[iExponentLen+1] = {0}, fMantissa[iMantissaLen+1] = {0}, finMantissa[iMantissaLen+1] = {0};
    //循环不能break; 否则无法输出string.函数不能返回指针,否则会被系统回收指针内的内容
    if (ePath > 0)
    {
        while (true)
        {
            if (ePath < 1)
            {
                break;
            }
            ePath = ePath >> 1;
            ++iCount;
        }
        if (iCount != 0)
        {
            char fArr2[iCount + 1] = {0};
            fArr = fArr2;
            ePath = (int)dbNum;
            for (int i = 0; i <= iCount; i++)
            {
                if (ePath <= 0)
                {
                    fArr[i] = '0';
                    continue;
                }
                int dnum = 1 << (iCount - i);
                if (dnum > ePath)
                {
                    fArr[i] = '0';
                }
                else
                {
                    if (iMark == 0)
                    {
                        iMark = iCount - i;
                    }
                    fArr[i] = '1';
                    ePath = ePath - dnum;
                }
            }
            iMark = iExponentsRange + iMark;
            GetDecBit(fExponentArr, iMark, iExponentLen);
            GetMantissaBit(fMantissa, dbNum,iMantissaLen);
            iMark = iMark - iExponentsRange;
            for (int i = 0; i < iMark; i++)
            {
                finMantissa[i] = fArr[iCount - iMark + i + 1];
            }
            for (int i = 0; i < iMantissaLen; i++)
            {
                if (iMark + i >= iMantissaLen)
                {
                    break;
                }
                finMantissa[iMark + i] = fMantissa[i];
            }
        }
    }
    else
    {
        iMark = GetMantissaBit(fMantissa, dbNum,iMantissaLen);
        iMark = iExponentsRange - iMark;
        GetDecBit(fExponentArr, iMark, iExponentLen);
        iMark = iExponentsRange - iMark;
        for (int i = 0; i < iMantissaLen; i++)
        {
            if (iMark + i >= iMantissaLen)
            {
                finMantissa[i] = '0';
            }
            else
            {
                finMantissa[i] = fMantissa[iMark + i];
            }
        }
    }
    if (dbNum > 0)
    {
        binArr[0] = '0';
    }
    else
    {
        binArr[0] = '1';
    }
    for (int i = 0; i < iExponentLen; i++)
    {
        binArr[1 + i] = fExponentArr[i];
    }
    for (int i = 0; i < iMantissaLen; i++)
    {
        binArr[12 + i] = finMantissa[i];
    }
}
HASH GetDoubleHashByBin(char *binArr,DoubleBinary64& dbSt)
{
    //正向输出string,反向计算数值
    HASH dbHash = 0;
    for (int i = dbSt.iDoubleBinLen-1; i != 0; i--)
    {
        char c = binArr[i];
        if (c == '1')
        {
            dbHash += (1LL << (63 - i));
        }
    } 
    return dbHash;
}
//获取十进制bit,loop表示bit位数,decNum过大时loop位数会溢出
void GetDecBit(char *ret, int decNum, int loop)
{
    for (int i = 0; i < loop; i++)
    {
        if (decNum <= 0)
        {
            ret[i] = '0';
            continue;
        }
        int iSub = 1 << (loop - 1 - i);
        if (iSub > decNum)
        {
            ret[i] = '0';
        }
        else
        {
            ret[i] = '1';
            decNum = decNum - iSub;
        }
    }
}
//获取double在IEEE中规定的尾数bit,返回值为fraction标记
int GetMantissaBit(char *cArr, double dNum,int iMantissaLen)
{
    double dd = dNum - (int)dNum;
    int iMark = 0;
    for (int i = 0; i < iMantissaLen; i++)
    {
        if (dd <= 0)
        {
            cArr[i] = '0';
            continue;
        }
        double dbpow = pow(2, -(i + 1));
        if (dbpow > dd)
        { 
            cArr[i] = '0';
        }
        else
        {
            if (iMark == 0)
            {
                iMark = i + 1;
                if (iMark >= 52)
                {
                    iMark = 51;
                }
            }
            cArr[i] = '1';
            dd = dd - dbpow;
        }
    } 
    if (dNum > 1)
    {
        return 0;
    }
    return iMark;
}
int main()
{
    double dbTest=55.68756;
    DoubleBinary64 dbSt;
    char dbBinArr[dbSt.iDoubleBinLen+1] = {0};
    GetDoubleBin(dbBinArr, dbTest,dbSt);
    HASH dbBin2Hash = GetDoubleHashByBin(dbBinArr,dbSt); 
    cout << dbBin2Hash << endl;
}

　　输出:4633034144636536021

　　计算机内存中的值:4633034144636536021

　　string输出:0100000001001011110110000000000111110111010100010000010011010101

　　计算器输出:‭0100000001001011110110000000000111110111010100010000010011010101‬

　　如果可以简化代码,请大佬教下,谢谢

标签：int,double,ePath,++,bit,dbSt,IEEE,iMantissaLen,iMark
来源： https://www.cnblogs.com/phlq123/p/15757187.html

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