On Wednesday, 9 August 2017 at 02:11:13 UTC, Johnson Jones wrote:
I like to create code that automates much of the manual labor that we, as programmers, are generally forced to do. D generally makes much of this work automatable. For example, I have created the following code which makes loading dlls similar to libs:




/* Import DLL functions in to type T. The following example shows methodology
struct DLLImports
{
        @("DLLImport") public static extern(Windows)
        {
                @("libgdk-3-0.dll")
                {
void* function(GdkWindow *window) gdk_win32_window_get_handle;
                }
        }
}

// Fixes static functions and function pointers to point to their specified DLL's
DllImport!DLLImports;
*/
void DLLImport(alias T)()
{
        version(Windows)
        {
import core.sys.windows.windows, std.conv, std.meta, std.traits;
                HINSTANCE[string] DLLs;
        
                foreach(fname; __traits(allMembers, T))
                {       
                        mixin("enum isf = isFunction!(T."~fname~");");
                        mixin("enum isfp = isFunctionPointer!(T."~fname~");");
mixin("enum attrs = __traits(getAttributes, T."~fname~");");

static if ((isf || isfp) && attrs.length == 2 && attrs[0] == "DLLImport")
                        {
                                auto dllName = attrs[1];
                                if (dllName !in DLLs)
                                        DLLs[dllName] = 
LoadLibrary(to!wstring(dllName~"\0").ptr);

                                auto dll = DLLs[dllName];
                                if (dll == null)
                                        assert(0, "Cannot load DLL 
`"~dllName~"'");

                                auto func = GetProcAddress(dll, fname);

                                if (isf)
mixin("auto p = cast(void**)&"~T.stringof~"."~fname~"; *p = cast(typeof(p))func;");
                                else            
mixin(""~T.stringof~"."~fname~" = cast(typeof("~T.stringof~"."~fname~"))func;");
                        }
                
                }
        }



But this got me thinking that we don't even need to have to specify the function in D, hell, they already exist in the lib and we are just duplicating work.

What if, at compile time, D could get all the functions and their type information and build a class for them for us? We could then just write something like

struct DLLImports
{
        @("DLLImport") string libgdk = "libgdk-3-0.dll";
}


and have some ctfe meta functions extract all the function from libgdk and insert them in to the struct.

There are two problems with this, one easy and one hard/impossible(which would be easy if people were intelligent enough to have foresight):


1. Get the dll function by name from the dll at compile time. This would probably require manually reading the dll file and scanning for the function.

2. Get the type information to build a declaration. This is probably impossible since dll's do not contain the type information about their parameters and return type(or do they?). If they did, it would be easy. I would suggest that all dll's generated by D include this information somewhere and an easy way to extract it for future programmers so such things could be implemented.

Alternatively, maybe a master database could be queried for such information by using the function names and dll name? I don't know if D has network capabilities at compile time though.

Alternatively, completely scrap the lethargic way things are done in the name of backwards compatibility and $$$ and do things right(learn from the past, stop repeating same mistakes, etc). Sure it's a lot of work, but in the end is far less than one thinks considering the increased productivity... but I guess the we gotta keep buying the kids christmas presents.



And while we are at it, here is a set of meta functions that make using glade files easier:

// Loads the glade interface element id's and types directly from the glade interface file so we do not have to declare them manually // Use: @("Glade") { mixin(DeclareGladeInterfaceElements!gladeFile); } where ever variables will be defined and InstantiateGladeInterfaceElements( to initalize them
public string DeclareGladeInterfaceElements(string filename)()
{
        auto token1 = "<object class=\"";
        auto token2 = " id=\"";
        string res = "";
        import std.file;
        auto data = import(filename);
        for(int i = 0; i < data.length; i++)
        {
// Matched class/object type, get name actual type then get id if it has one. if (i+token1.length < data.length && data[i..i+token1.length] == token1)
                {
                        i += token1.length;
                        auto pos = i;
                        while(i < data.length && data[i] != '"') i++;
                        auto type = cast(string)data[pos..i];

                        // Match id if it has one.
while(i+token2.length < data.length && data[i] != '>' && data[i] != '<' && data[i] != '"' && data[i..i+token2.length] != token2) i++;
                        i++;

                        if (data[i] == '>') { continue; }
                        i += token2.length;
                        pos = i;
                        if (data[i] == '>') { continue; }
                        while(i+1 < data.length && data[i] != '"') i++;
res ~= "public gtk."~type[3..$] ~ " " ~ data[pos..i] ~ ";\n";
                }

                if (i > data.length - 7130)
                {
                        continue;
                }
        }
        return res;
}

public void InstantiateGladeInterfaceElements(T)(Builder builder, T t)
{
        import std.meta;                
        foreach(m; __traits(allMembers, T))
        {
                mixin("enum w = __traits(getAttributes, T."~m~");");            
    
                static if (w.length > 0 && w[0] == "Glade")
                {
mixin("t."~m~" = (cast(typeof(T."~m~"))builder.getObject(`"~m~"`));"); mixin("if (t."~m~" is null) { error(\"Error: `"~m~"` not found, User Interface Corrupted, Cannot continue!\"); }");
                }
        }
}

They automatically extract objects that have ID's with them, add/declare them in D and instantiate them. This means one doesn't have to duplicate code.

(DeclareGladeInterfaceElements could probably be optimized using proper D code but I just hacked something other)

Mainly posted for posterity and it might be useful to a few others, but is in line with using D's meta capabilities to generate D code at compile time from external sources so less keystrokes are required.




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