int my_test_int = 1337;
int * p_my_test_int = &my_test_int;
char * binarydata = ??
void * binarydata = ??
variable to binary data, how is this done?[SOLVED]
Author
[SOLVED] SOLUTION IN LAST POST
Ok some code:
#include <stdio.h>union U{ int i; unsigned __int8 b[4];};void main(){ int i=1337; // First way! U u; u.i=i; printf("%d %d %d %d\n",u.b[0],u.b[1],u.b[2],u.b[3]); // Second way! unsigned __int8 *p; p=(unsigned __int8 *)&i; printf("%d %d %d %d\n",p[0],p[1],p[2],p[3]);}
That depends on how portable you want to be :) If you want your binary file to be readable on all architectures, you're going to need something like:
If you don't care, just do:
Or something similar.
int value = whatever;char data[4];data[0] = (char)value;data[1] = (char)(value >> 8);data[2] = (char)(value >> 16);data[3] = (char)(value >> 24);std::fstream stream("myfile.bin");stream.write(data, 4);If you don't care, just do:
int value = whatever;std::fstream stream("myfile.bin");stream.write(reinterpret_cast<char*>(&value), sizeof(int));Or something similar.
Author
Thx both of you i prefer the method ZQJ uses, but how do i get the int back from that data[4] block?
Thx
Thx
#include <stdio.h>union U{ int i; unsigned __int8 b[4];};void main(){ // 1 { U u; u.b[0]=57; u.b[1]=5; u.b[2]=0; u.b[3]=0; printf("%d\n",u.i); } // 2 { int i; i=0; i|=0;i<<=8; i|=0;i<<=8; i|=5;i<<=8; i|=57; printf("%d\n",i); } //3 { int i; unsigned __int8 *p;//You can use char* too. p=(unsigned __int8*)&i; p[0]=57;p[1]=5;p[2]=0;p[3]=0; printf("%d\n",i); }}Output:
1337
1337
1337
Or in my version
value = data[0] + (data[1] << 8) + (data[2] << 16) + (data[3] << 24);
IIRC you don't need to cast data[0..3] to int because char is automatically widened to int for arithmetic operations. I'm not entirely sure about that though.
value = data[0] + (data[1] << 8) + (data[2] << 16) + (data[3] << 24);
IIRC you don't need to cast data[0..3] to int because char is automatically widened to int for arithmetic operations. I'm not entirely sure about that though.
Author
Thx both of you, i rated++ both of you:
Just for future reference this is what i used:
Just for future reference this is what i used:
int value = 1337;char data[4];data[0] = (char)value;data[1] = (char)(value >> 8);data[2] = (char)(value >> 16);data[3] = (char)(value >> 24);printf("binary content of data: |%x|%x|%x|%x|",data[0],data[1],data[2],data[3]);int i;i=0;i|=data[3];i<<=8;i|=data[2];i<<=8;i|=data[1];i<<=8;i|=data[0];printf("value of i = %d",i);
There is something you should know:
1.
(I think)The Union method should be much faster than the others because it does not involve any mathematical operations.
2.
You can write the integer data directly to a file. As long as you use the same types (specially if you want to write a cross platform application) to write and read the data, you should not have any problems.
I prefer to use __int32 instead of int because I do not know how different compilers on different PCs(16bit,32bit,64bit) are going to interpret "int".
1.
(I think)The Union method should be much faster than the others because it does not involve any mathematical operations.
2.
You can write the integer data directly to a file. As long as you use the same types (specially if you want to write a cross platform application) to write and read the data, you should not have any problems.
I prefer to use __int32 instead of int because I do not know how different compilers on different PCs(16bit,32bit,64bit) are going to interpret "int".
This topic is closed to new replies.
Advertisement
Popular Topics
Advertisement
