x86 convert to lower case assembly

Question

This program is to convert a char pointer into lower case. I\'m using Visual Studio 2010.

This is from another question, but much simpler to read and mo

Answer 1

I would load the data into a register, manipulate it there, then store the result back to memory.

int make_lower(char* token) {
    __asm {
        mov edi, token
        jmp short start_loop
    top_loop:   
        or al, 20h
        mov [edi], al
        inc edi
    start_loop:
        mov al, [edi]
        test al, al
        jnz top_loop
    }       
}

Note, however, that your conversion to upper-case is somewhat flawed. For example, if the input contains any control characters, it will change them to something else -- but they aren't upper case, and what it converts them to won't be lower case.