[Xen-devel] [PATCH v4 03/27] libxl: ocaml: support for KeyedUnion in the bindings generator.

[Rob Hoes <rob.hoes@xxxxxxxxxx>]

A KeyedUnion consists of two fields in the containing struct. First an
enum field ("e") used as a descriminator and second a union ("u")
containing potentially anonymous structs associated with each enum
value.

We map the anonymous structs to structs named after the descriminator
field ("e") and the specific enum values. We then declare an ocaml
variant type name e__union mapping each enum value to its associated
struct.

So given IDL:

foo = Enumeration("foo", [
    (0, "BAR"),
    (1, "BAZ"),
])
s = Struct("s", [
    ("u", KeyedUnion(none, foo, "blargle", [
        ("bar", Struct(...xxx...)),
        ("baz", Struct(...yyy...)),
    ])),
])

We generate C:

enum foo { BAR, BAZ };
struct s {
    enum foo blargle;
    union {
        struct { ...xxx... } bar;
        struct { ...yyy... } baz;
    } u;
}

and map this to ocaml

type foo = BAR | BAZ;

module S = struct

    type blargle_bar = ...xxx...;

    type blargle_baz = ...yyy...;

    type blargle__union = Bar of blargle_bar | Baz of blargle_baz;

    type t =
    {
        blargle : blargle__union;
    }
end

These type names are OK because they are already within the namespace
associated with the struct "s".

If the struct associated with bar is empty then we don't bother with
blargle_bar of "of blargle_bar".

No actually change in the generated code since we don't generate any
KeyedUnions yet.

The actual implementation was inspired by
http://www.linux-nantes.org/~fmonnier/ocaml/ocaml-wrapping-c.php#ref_constvrnt

Signed-off-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
Signed-off-by: Rob Hoes <rob.hoes@xxxxxxxxxx>
Acked-by: David Scott <dave.scott@xxxxxxxxxxxxx>
---
 tools/libxl/idl.py             |    3 +
 tools/ocaml/libs/xl/genwrap.py |  162 +++++++++++++++++++++++++++++++++++-----
 2 files changed, 147 insertions(+), 18 deletions(-)

diff --git a/tools/libxl/idl.py b/tools/libxl/idl.py
index 7d95e3f..f4908dd 100644
--- a/tools/libxl/idl.py
+++ b/tools/libxl/idl.py
@@ -216,6 +216,9 @@ class Struct(Aggregate):
         kwargs.setdefault('passby', PASS_BY_REFERENCE)
         Aggregate.__init__(self, "struct", name, fields, **kwargs)
 
+    def has_fields(self):
+        return len(self.fields) != 0
+
 class Union(Aggregate):
     def __init__(self, name, fields, **kwargs):
         # Generally speaking some intelligence is required to free a
diff --git a/tools/ocaml/libs/xl/genwrap.py b/tools/ocaml/libs/xl/genwrap.py
index bdac6e9..f98d686 100644
--- a/tools/ocaml/libs/xl/genwrap.py
+++ b/tools/ocaml/libs/xl/genwrap.py
@@ -65,6 +65,8 @@ def ocaml_type_of(ty):
         if not typename:
             raise NotImplementedError("No typename for Builtin %s (%s)" % 
(ty.typename, type(ty)))
         return typename
+    elif isinstance(ty,idl.KeyedUnion):
+        return ty.union_name
     elif isinstance(ty,idl.Aggregate):
         return ty.rawname.capitalize() + ".t"
     else:
@@ -83,8 +85,67 @@ def munge_name(name):
     else:
         return name
 
-def ocaml_instance_of(type, name):
-    return "%s : %s" % (munge_name(name), ocaml_type_of(type))
+def ocaml_instance_of_field(f):
+    if isinstance(f.type, idl.KeyedUnion):
+        name = f.type.keyvar.name
+    else:
+        name = f.name
+    return "%s : %s" % (munge_name(name), ocaml_type_of(f.type))
+
+def gen_struct(ty):
+    s = ""
+    for f in ty.fields:
+        if f.type.private:
+            continue
+        x = ocaml_instance_of_field(f)
+        x = x.replace("\n", "\n\t\t")
+        s += "\t\t" + x + ";\n"
+    return s
+
+def gen_ocaml_keyedunions(ty, interface, indent, parent = None):
+    s = ""
+    
+    if ty.rawname is not None:
+        # Non-anonymous types need no special handling
+        pass
+    elif isinstance(ty, idl.KeyedUnion):
+        if parent is None:
+            nparent = ty.keyvar.name
+        else:
+            nparent = parent + "_" + ty.keyvar.name
+
+        for f in ty.fields:
+            if f.type is None: continue
+            if f.type.rawname is not None: continue
+            if isinstance(f.type, idl.Struct) and not f.type.has_fields(): 
continue
+            s += "\ntype %s_%s =\n" % (nparent,f.name)
+            s += "{\n"
+            s += gen_struct(f.type)
+            s += "}\n"
+
+        name = "%s__union" % ty.keyvar.name
+        s += "\n"
+        s += "type %s = " % name
+        u = []
+        for f in ty.fields:
+            if f.type is None:
+                u.append("%s" % (f.name.capitalize()))
+            elif isinstance(f.type, idl.Struct):
+                if f.type.rawname is not None:
+                    u.append("%s of %s" % (f.name.capitalize(), 
f.type.rawname.capitalize()))
+                elif f.type.has_fields():
+                    u.append("%s of %s_%s" % (f.name.capitalize(), nparent, 
f.name))
+                else:
+                    u.append("%s" % (f.name.capitalize()))
+            else:
+                raise NotImplementedError("Cannot handle KeyedUnion fields 
which are not Structs")
+            
+        s += " | ".join(u) + "\n"
+        ty.union_name = name
+
+    if s == "":
+        return None
+    return s.replace("\n", "\n%s" % indent)
 
 def gen_ocaml_ml(ty, interface, indent=""):
 
@@ -110,16 +171,17 @@ def gen_ocaml_ml(ty, interface, indent=""):
                 s += "module %s : sig\n" % module_name
             else:
                 s += "module %s = struct\n" % module_name
-            s += "\ttype t =\n"
-            s += "\t{\n"
-            
+                
+        # Handle KeyedUnions...
         for f in ty.fields:
-            if f.type.private:
-                continue
-            x = ocaml_instance_of(f.type, f.name)
-            x = x.replace("\n", "\n\t\t")
-            s += "\t\t" + x + ";\n"
-
+            ku = gen_ocaml_keyedunions(f.type, interface, "\t")
+            if ku is not None:
+                s += ku
+                s += "\n"
+
+        s += "\ttype t =\n"
+        s += "\t{\n"
+        s += gen_struct(ty)
         s += "\t}\n"
         
         if functions.has_key(ty.rawname):
@@ -172,12 +234,43 @@ def c_val(ty, c, o, indent="", parent = None):
             n += 1
         s += "    default: failwith_xl(\"cannot convert value to %s\", lg); 
break;\n" % ty.typename
         s += "}"
-    elif isinstance(ty, idl.Aggregate) and (parent is None):
+    elif isinstance(ty, idl.KeyedUnion):
+        s += "{\n"
+        s += "\tif(Is_long(%s)) {\n" % o
+        n = 0
+        s += "\t\tswitch(Int_val(%s)) {\n" % o
+        for f in ty.fields:
+            if f.type is None or not f.type.has_fields():
+                s += "\t\t    case %d: %s = %s; break;\n" % (n,
+                                                    parent + ty.keyvar.name,
+                                                    f.enumname)
+                n += 1
+        s += "\t\t    default: failwith_xl(\"variant handling bug %s%s 
(long)\", lg); break;\n" % (parent, ty.keyvar.name)        
+        s += "\t\t}\n"
+        s += "\t} else {\n"
+        s += "\t\t/* Is block... */\n"
+        s += "\t\tswitch(Tag_val(%s)) {\n" % o
+        n = 0
+        for f in ty.fields:
+            if f.type is not None and f.type.has_fields():
+                if f.type.private:
+                    continue
+                s += "\t\t    case %d:\n" % (n)
+                s += "\t\t        %s = %s;\n" % (parent + ty.keyvar.name, 
f.enumname)
+                (nparent,fexpr) = ty.member(c, f, False)
+                s += "%s" % c_val(f.type, fexpr, "Field(%s, 0)" % o, 
indent=indent+"\t\t        ")
+                s += "break;\n"
+                n += 1
+        s += "\t\t    default: failwith_xl(\"variant handling bug %s%s 
(block)\", lg); break;\n" % (parent, ty.keyvar.name)
+        s += "\t\t}\n"
+        s += "\t}\n"
+        s += "}"
+    elif isinstance(ty, idl.Aggregate) and (parent is None or ty.rawname is 
None):
         n = 0
         for f in ty.fields:
             if f.type.private:
                 continue
-            (nparent,fexpr) = ty.member(c, f, parent is None)
+            (nparent,fexpr) = ty.member(c, f, ty.rawname is not None)
             s += "%s\n" % c_val(f.type, fexpr, "Field(%s, %d)" % (o,n), 
parent=nparent)
             n = n + 1
     else:
@@ -199,7 +292,7 @@ def gen_c_val(ty, indent=""):
     s += "}\n"
     
     return s.replace("\n", "\n%s" % indent)
-
+    
 def ocaml_Val(ty, o, c, indent="", parent = None):
     s = indent
     if isinstance(ty,idl.UInt):
@@ -239,9 +332,42 @@ def ocaml_Val(ty, o, c, indent="", parent = None):
             n += 1
         s += "    default: failwith_xl(\"cannot convert value from %s\", lg); 
break;\n" % ty.typename
         s += "}"
-    elif isinstance(ty,idl.Aggregate) and (parent is None):
+    elif isinstance(ty, idl.KeyedUnion):
+        n = 0
+        m = 0
+        s += "switch(%s) {\n" % (parent + ty.keyvar.name)
+        for f in ty.fields:
+            s += "\t    case %s:\n" % f.enumname
+            if f.type is None:
+                s += "\t        /* %d: None */\n" % n
+                s += "\t        %s = Val_long(%d);\n" % (o,n)
+                n += 1
+            elif not f.type.has_fields():
+                s += "\t        /* %d: Long */\n" % n
+                s += "\t        %s = Val_long(%d);\n" % (o,n)
+                n += 1
+            else:
+                s += "\t        /* %d: Block */\n" % m
+                (nparent,fexpr) = ty.member(c, f, parent is None)
+                s += "\t        {\n"
+                s += "\t\t        CAMLlocal1(tmp);\n"
+                s += "\t\t        %s = caml_alloc(%d,%d);\n" % (o, 1, m)
+                s += ocaml_Val(f.type, 'tmp', fexpr, indent="\t\t        ", 
parent=nparent)
+                s += "\n"
+                s += "\t\t        Store_field(%s, 0, tmp);\n" % o
+                s += "\t        }\n"
+                m += 1
+                #s += "\t        %s = caml_alloc(%d,%d);\n" % 
(o,len(f.type.fields),n)
+            s += "\t        break;\n"
+        s += "\t    default: failwith_xl(\"cannot convert value from %s\", 
lg); break;\n" % ty.typename
+        s += "\t}"
+    elif isinstance(ty,idl.Aggregate) and (parent is None or ty.rawname is 
None):
         s += "{\n"
-        s += "\tvalue %s_field;\n" % ty.rawname
+        if ty.rawname is None:
+            fn = "anon_field"
+        else:
+            fn = "%s_field" % ty.rawname
+        s += "\tvalue %s;\n" % fn
         s += "\n"
         s += "\t%s = caml_alloc_tuple(%d);\n" % (o, len(ty.fields))
         
@@ -253,8 +379,8 @@ def ocaml_Val(ty, o, c, indent="", parent = None):
             (nparent,fexpr) = ty.member(c, f, parent is None)
 
             s += "\n"
-            s += "\t%s\n" % ocaml_Val(f.type, "%s_field" % ty.rawname, 
ty.pass_arg(fexpr, c), parent=nparent)
-            s += "\tStore_field(%s, %d, %s);\n" % (o, n, "%s_field" % 
ty.rawname)
+            s += "\t%s\n" % ocaml_Val(f.type, fn, ty.pass_arg(fexpr, c), 
parent=nparent)
+            s += "\tStore_field(%s, %d, %s);\n" % (o, n, fn)
             n = n + 1
         s += "}"
     else:
-- 
1.7.10.4


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