Struct initialisation with large integer

Question

So I have the following struct:

typedef struct int64 {
    unsigned char value[8];
} int64;

Which I an using to represent a 64 bit integer (I know this exists in stdint.h but I thought it could be a good exercise to try and write it myself, and I plan to use this format for much larger integers). My question is there any way that I could initialize this struct with a binary string or an overlarge integer, something like:

int64 number = 0b1000000000000000000000000000000000000000000000000000000000011001

// Or

int64 number = 1231823812738123878;  // Or something larger than 2^32

Thanks for any help you can give me :)

Answer 1

You'd have to break it up byte by byte, since the struct contains an array of bytes:

int64 number = { { 0b10000000, 0b00000000, 0b00000000, 0b00000000, 
                   0b00000000, 0b00000000, 0b00000000, 0b00011001 } };

You can compress this using hex constants instead of binary constants:

int64 number = { { 0x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x19 } };