What is the most efficient way to convert a short string into a 32 bit integer?

For many purposes, short strings/char arrays packed into an unsigned 32-bit integer are pretty useful, since they can be compared at one go with a simple integer comparison and be used in switch statements, while still maintaining a bit of human readability.

The most common way to convert these short strings to 32-bit integers is to shift/or:

#include <stdint.h>

uint32_t quadchar( const char* _str ) 
{

    uint32_t result = 0;

    for( size_t i=0; i<4; i++ )
    {
        if( _str[i] == 0 )
           return result;
        result = (result << 8) | _str[i];
    }

    return result;
}

(Another common way is using an union of a uint32_t and a char[4] - basically the same procedure.)

Strings, which are too long, are truncated.

So far so good, but this has to be done on runtime, which costs a bit of time. Would it be also possible to do this on compile time?