Question

I just read the whole documentation of Templates in the D programming language but cant seem to find a way for my very simple task, for functions I need 3 assembler instructions to be inserted at the beginning of each function, I would like to automate this through a macro so I dont have to manually write it each time.

__gshared void jump()
{
    asm{db START_KEY;}

    //bla bla bla

    asm{mov EBX, ip;add ip,4;jmp dword ptr [EBX];db END_KEY;}
}

something like this should get replaced with

__gshared void jump()
{
    mixin starttemplate();

    //bla bla bla

    mixin endtemplate();
}

In C I would have done something like this

#define STARTASM() asm{.......}

but if I try something like this

template endtemplate()
{
    asm{mov EBX, ip;add ip,4;jmp dword ptr [EBX];db END_KEY;}
}

it will throw an error saying that I have to declare a variable at a template (which I dont want to, since performance is absolutely needed here).

Answer 1

How about saving the asm command as a string, and using a mixin?

immutable string ASM_START=q{
    asm{db START_KEY;}
}
immutable string ASM_END=q{
    asm{mov EBX, ip;add ip,4;jmp dword ptr [EBX];db END_KEY;}
}

__gshared void jump()
{
    mixin(ASM_START);
    //bla bla bla
    mixin(ASM_END);
}

Another option is to use the mixing to create the entire function, and pass it’s signature and content(=body) as arguments:

string functionWithAsm(string signature,string content)(){
    return Format!(q{
        %s
        {
            asm{db START_KEY;}
            %s
            asm{mov EBX, ip;add ip,4;jmp dword ptr [EBX];db END_KEY;}
        }
        },signature,content);
}

mixin(functionWithAsm!("__gshared void jump()",q{
            /*some actual code*/
            })());