Union and entity without htonl / ntohl
I want to parse the header of my TCP packet that I am receiving.
Let's assume this is a header structure:
(2 bytes for commands) + (2 bytes for token) + (4 bytes for data length)
Example of package: 0x01 0x02 0x12 0x34 0x00 0x00 0x00 0x05
There 0x0102 is command, 0x1234 is token and 0x000005 is data length.
I want to parse this header efficiently on Windows platform. I made the following union for this header:
typedef union
{
struct
{
uint16_t command;
uint16_t token;
uint32_t data_length;
} field;
char bytes[8];
} MyHeader_t;
MyHeader_t bar;
read_8_bytes(bar.bytes);
std::cout << bar.fields.token << std::endl;
Then I tried to copy the package above to my array bytes
. But the network packet is in a big encyclopedia, and the PC tries to read the fields as minimal. As a result, my field token
is equal 0x3412
(not 0x1234).
How could I avoid this problem with individual endiannes?
source to share
Boost provides a library dedicated to endianess:
http://www.boost.org/doc/libs/1_61_0/libs/endian/doc/index.html
For example:
boost::endian::big_to_native_inplace(bar.field.command);
or AndyG:
std::cout << boost::endian::endian_reverse(bar.field.token) << std::endl;
Note. This library has three ways to deal with content, you need to spend time on what is right for your case.
source to share