Converting double to BYTE array

[ba5h33r]

Hi All, i am intending to save double array values to blob fiels in MySql database. So i need to convert double value in to BYTE array. Can anyone help me to convert a double value (8byte) to BYTE array and vice versa. Thanks in advance Basheer

[toxcct]

double d = /*...*/;
char tab[8];
tab[0] = ((d >> 0) & 0xFF);
tab[1] = ((d >> 8) & 0xFF);
tab[2] = ((d >> 16) & 0xFF);
tab[3] = ((d >> 24) & 0xFF);
tab[4] = ((d >> 32) & 0xFF);
tab[5] = ((d >> 40) & 0xFF);
tab[6] = ((d >> 48) & 0xFF);
tab[7] = ((d >> 56) & 0xFF);

---

TOXCCT >>> GEII power
[toxcct][VisualCalc 2.20][VisualCalc 3.0]

[kakan]

unsigned char bArray[sizeof(double)]; double d; memcpy(bArray,&d, sizeof(double)); reverse: memcpy(&d, bArray, sizeof(double));

[toxcct]

kakan wrote:

unsigned char bArray[sizeof(double)];

won't compile. you have to do it this way :

unsigned char* bArray = new unsigned char[sizeof(double)];

which is why i directly put [8] to ease the code (standard C++ tell that the size of a double is fixed to 8 bytes, so doesn't vary).

---

TOXCCT >>> GEII power
[toxcct][VisualCalc 2.20][VisualCalc 3.0]

[kakan]

Hello. You are right (of course). But the memcpy is neat, isn't it? :laugh:

[toxcct]

yes, very good idea... but as i don't use it that much, it went off my thinking... :doh: well done

---

TOXCCT >>> GEII power
[toxcct][VisualCalc 2.20][VisualCalc 3.0]

[kakan]

Thanks.:)

[nde_plume]

Obviously the best wat to do this is to not do it, viz: union MyConvert { double d; BYTE bytes[sizeof(double)]; }; Thus for some function storeBytes(BYTE*p, size_t size) to get a double called myVal stored do this: MyConvert mc; mc.d = myVal; storeBytes(mc.bytes, sizeof(myVal); or if you want to go nuts and save the copy: storeBytes(((MyConvert*)(&myVal))->bytes, sizeof(myVal)); Though that might not work if the alignment requirements are different between double and unions.

[nde_plume]

Actually you are incorrect. sizeof(double) is a compile time constant, and so it will compile. (Just to double check, I tried and it did.)