implemented interfaces in Spin2

Author: totalspectrum

Changelog.txt

@@ -4,6 +4,7 @@ Version 7.3.0
 - Make Spin2 structs actually packed
 - Fix parsing of `[++]` and `[--]` as pre operators
 - Fixed error reporting around __builtin_printf
+- Implemented `%interface` for Spin2
 - Updated __builtin_printf to handle %X
 
 Version 7.2.1

doc/spin.md

@@ -394,7 +394,7 @@ waits until CNT reaches "newcnt", and returns "newcnt + incr".
 
 Note that unlike most Spin blocks, the `asm` block has to end with `endasm`. This is because indentation is not significant inside the assembly code. For example, labels typically start at the leftmost margin.
 
-### Spin2 style inline assembly (org/end)
+#### Spin2 style inline assembly (org/end)
 
 flexspin also accepts Spin2 style inline assembly, marked with `org` and `end` instead of `asm` and `endasm`. So the above example could be written as:
 ```
@@ -422,6 +422,28 @@ Unlike the "official" Spin2 compiler, flexspin does not accept an address for th
 
 (4) In PNut/PropTool only the first 16 local variables may be accessed in inline assembly; flexspin has this restriction only for bytecode output. For assembly output other locals may be accessed as well.
 
+### Interfaces
+
+Flexspin supports pointers to interfaces. An interface is like a struct, but instead of having only member variables it has only public functions (no variables are allowed). Any object which implements all of the methods declared in the interface may be passed to an interface pointer.
+
+Interfaces are declared with the `%interface` keyword.
+
+For example, if an object has a declaration like:
+```
+con
+  %interface MyIface (
+    pub getval(): r
+    pub incr()
+  )
+
+pub myfunc(^MyIface i): ret
+  i.incr()
+  ret := i.getval()
+```
+Then any object having `incr` and `getval` methods may be passed
+as the parameter to `myfunc`, and it will first call the `incr`
+method for that object and then return the result of `getval`.
+
 ### Method pointers
 
 Pointers to methods may be created with `@` and called using the normal calling syntax. For example:

frontends/spin/spin.y

@@ -342,6 +342,50 @@ SpinDeclareStruct(AST *ident, AST *defs)
     PopCurrentModule();
 }
 
+// declare a Spin structure
+static void
+SpinDeclareInterface(AST *ident, AST *defs)
+{
+    const char *classname = GetUserIdentifierName(ident);
+    Module *P = NewModule(classname, current->curLanguage);
+    AST *newobj = NewAbstractObject(ident, NULL, 0);
+    newobj->d.ptr = P;
+    P->isInterface = 1;
+    
+    AddSymbol(currentTypes, classname, SYM_TYPEDEF, newobj, NULL);
+    
+    if (P != current) {
+        P->Lptr = current->Lptr;
+        P->subclasses = current->subclasses;
+        current->subclasses = P;
+        P->superclass = current;
+        P->fullname = current->fullname; // for finding "class using"
+         newobj->d.ptr = (void *)P;
+        P->isPacked = 1;
+
+        /* import parent's symbols into P */
+        P->objsyms.next = &current->objsyms;
+        AddSymbol(&current->objsyms, classname, SYM_TYPEDEF, newobj, NULL);
+    }
+
+    PushCurrentModule();
+    current = P;
+    AST *item;
+    /* declare abstract methods */
+    while (defs) {
+        AST *rettype;
+        AST *body = NULL;
+        item = defs->left;
+        defs = defs->right;
+        while (item && item->kind == AST_COMMENTEDNODE) {
+            item = item->left;
+        }
+        rettype = SpinRetType(item);
+        DeclareFunction(current, rettype, 1, item, body, NULL, NULL);
+    }
+    PopCurrentModule();
+}
+
 #define YYERROR_VERBOSE 1
 %}
 
@@ -1180,6 +1224,14 @@ conline:
         SpinDeclareStruct(name, defs);
         $$ = NULL;
     }
+  | SP_INTERFACE SP_IDENTIFIER '(' ifacelist ')' SP_EOLN
+    {
+        /* basically an inline object definition */
+        AST *defs = $4;
+        AST *name = $2;
+        SpinDeclareInterface(name, defs);
+        $$ = NULL;
+    }
   | SP_STRUCT SP_IDENTIFIER '(' structlist ')' SP_EOLN
     {
         /* basically an inline object definition */
@@ -1256,6 +1308,20 @@ structitem:
   }
 ;
 
+ifacelist:
+  ifaceitem
+    { $$ = CommentedListHolder($1); }
+  | ifacelist ifaceitem
+    { $$ = AddToList($1, CommentedListHolder($2)); }
+;
+
+ifaceitem:
+  SP_EOLN /* empty */
+    { $$ = NULL; }
+  | SP_PUB funcdef funcdef_end
+    { $$ = $2; }
+;
+
 enumlist:
   enumitem
     { $$ = CommentedListHolder($1); }