I am trying to use std::vector as a memmory buffer:
int main( )
{
int i = 0x01020304;
size_t size = sizeof(int);
std::vector<char> data;
data.insert( data.end(), (char*)&i, (char*)(&i + size) );
for ( int i = 0; i < data.size(); ++i){
std::cout << int(data[i]) << std::endl;
}
return 0;
}
I am expecting output 4 3 2 1
But I got
4
3
2
1
51
73
-107
81
-9
127
0
0
36
-7
84
-50
Can some one explaing what I am doing wrong?
size is in bytes, so you need to increase the char*, not int*.
data.insert( data.end(), (char*)&i, (char*)(&i)+size );
Just to add to other questions, when you avoid code duplicate and make it more readable you also avoid some mistakes:
int i = 0x01020304;
std::vector<char> data;
char *begin = reinterpret_cast<char *>( &i );
data.insert( data.end(), begin, begin + sizeof(i) ) );
you probably would need to work with different types:
template<typename T>
void insertData( std::vector<char> &data, T value )
{
char *begin = reinterpret_cast<char *>( &value );
data.insert( data.end(), begin, begin + sizeof(value) ) );
}
With (char*)(&i + size) you increase a pointer to int instead of a pointer to char. Since size seems to be 4 in your case you find yourself adding the data of 4 ints instead of 4 chars.
auto cp = reinterpret_cast<char*>(&i);
data.insert( data.end(), cp, cp + size );
