[PATCH] alsaseq: fix constant objects in Python 3

[PATCH] alsaseq: fix constant objects in Python 3

[Hector Martin]

In Py3 everything is a long, so we can't get away with duplicating the
integer object layout any more. Properly subclass PyLong_Type instead,
with a bit of a hack to add an extra name field after the variable-sized
data section.

Also get rid of the enum type stuff, which seems to be unused cruft, and
the numprotocol stuff, because the base type can take care of that (and
we can't map arbitrary arithmetic results back to constants anyway).

Signed-off-by: Hector Martin <marcan@marcan.st>
---
 pyalsa/alsaseq.c | 149 +++++++++++++++++------------------------------
 1 file changed, 52 insertions(+), 97 deletions(-)

diff --git a/pyalsa/alsaseq.c b/pyalsa/alsaseq.c
index 0e7cc35..9d9b1a9 100644
--- a/pyalsa/alsaseq.c
+++ b/pyalsa/alsaseq.c
@@ -51,9 +51,6 @@
 /* the C variable of a constant dict */
 #define TDICT(subtype) _dictPYALSASEQ_CONST_##subtype
 
-/* the C enumeration of a constant dict */
-#define TTYPE(subtype) PYALSASEQ_CONST_##subtype
-
 /* defines constant dict by type */
 #define TCONSTDICT(subtype)			\
   static PyObject * TDICT(subtype);
@@ -71,7 +68,7 @@
 /* creates a typed constant and add it to the module and dictionary */
 #define TCONSTADD(module, subtype, name) {				\
     PyObject *tmp =							\
-      Constant_create(#name, SND_##name, TTYPE(subtype));		\
+      Constant_create(#name, SND_##name);		\
     if (tmp == NULL) {							\
       return MOD_ERROR_VAL;						\
     }									\
@@ -109,46 +106,6 @@
     }							\
   }
 
-
-/* num protocol support for binary Constant operations */
-#define NUMPROTOCOL2(name, oper)				\
-  static PyObject *						\
-  Constant_##name (PyObject *v, PyObject *w) {			\
-    int type = 0;						\
-    long val1, val2, val;					\
-    if (get_long1(v, &val1) || get_long1(w, &val2)) {		\
-      Py_INCREF(Py_NotImplemented);				\
-      return Py_NotImplemented;					\
-    }								\
-    val = val1 oper val2;					\
-    /* always asume left will be the type */			\
-    if (PyObject_TypeCheck(v, &ConstantType)) {			\
-      type = ((ConstantObject *) v)->type;			\
-    } else if (PyObject_TypeCheck(w, &ConstantType)) {		\
-      type = ((ConstantObject *) w)->type;			\
-    }								\
-    PyObject *self = Constant_create(#oper, val, type);		\
-    return self;						\
-  }
-
-/* num protocol support for unary Constant operations */
-#define NUMPROTOCOL1(name, oper)			\
-  static PyObject *					\
-  Constant_##name (PyObject *v) {			\
-    int type = 0;					\
-    long val1, val;					\
-    if (get_long1(v, &val1)) {				\
-      Py_INCREF(Py_NotImplemented);			\
-      return Py_NotImplemented;				\
-    }							\
-    val = oper val1;					\
-    if (PyObject_TypeCheck(v, &ConstantType)) {		\
-      type = ((ConstantObject *) v)->type;		\
-    }							\
-    PyObject *self = Constant_create(#oper, val, type); \
-    return self;					\
-  }
-
 /* sets the object into the dict */
 #define SETDICTOBJ(name, object)		\
   PyDict_SetItemString(dict, name, object)
@@ -328,21 +285,6 @@
 // alsaseq.Constant implementation
 //////////////////////////////////////////////////////////////////////////////
 
-/* alsaseq.Constant->type enumeration */
-enum {
-  PYALSASEQ_CONST_STREAMS,
-  PYALSASEQ_CONST_MODE,
-  PYALSASEQ_CONST_QUEUE,
-  PYALSASEQ_CONST_CLIENT_TYPE,
-  PYALSASEQ_CONST_PORT_CAP,
-  PYALSASEQ_CONST_PORT_TYPE,
-  PYALSASEQ_CONST_EVENT_TYPE,
-  PYALSASEQ_CONST_EVENT_TIMESTAMP,
-  PYALSASEQ_CONST_EVENT_TIMEMODE,
-  PYALSASEQ_CONST_ADDR_CLIENT,
-  PYALSASEQ_CONST_ADDR_PORT,
-};
-
 // constants dictionaries
 
 TCONSTDICT(STREAMS);
@@ -390,34 +332,66 @@ PyDoc_STRVAR(Constant__doc__,
   "Python number protocol."
 );
 
-/** alsaseq.Constant object structure type */
+/** alsaseq.Constant additional fields */
+/* This follows the variable length portion of the Long type */
 typedef struct {
-  PyObject_HEAD
-  ;
-
-  /* value of constant */
-  unsigned long int value;
   /* name of constant */
   const char *name;
-  /* type of constant */
-  int type;
+} ConstantExtraFields;
+
+/** alsaseq.Constant object structure type */
+typedef struct {
+#if PY_MAJOR_VERSION < 3
+  PyIntObject base;
+#else
+  /* NOTE: this only works if the value fits in one digit */
+  PyLongObject base;
+#endif
+  /* This field is actually offset by the base type's variable size portion */
+  ConstantExtraFields extra;
 } ConstantObject;
 
+#if PY_MAJOR_VERSION < 3
+/* PyInt is fixed size in Python 2 */
+# define CONST_VALUE(x) PyInt_AsLong((PyObject *)x)
+# define CONST_EXTRA(x) (&(x->extra))
+#else
+/* PyLong is variable size in Python 3 */
+# define CONST_VALUE(x) PyLong_AsLong((PyObject *)x)
+# define CONST_EXTRA(x) \
+    ((ConstantExtraFields *)( \
+        ((intptr_t)(&x->extra)) \
+        + abs(Py_SIZE(&x->base)) * Py_TYPE(x)->tp_itemsize \
+    ))
+#endif
+
 /** alsaseq.Constant type (initialized later...) */
 static PyTypeObject ConstantType;
 
 /** alsaseq.Constant internal create */
 static PyObject *
-Constant_create(const char *name, long value, int type) {
-  ConstantObject *self = PyObject_New(ConstantObject, &ConstantType);
+Constant_create(const char *name, long value) {
+#if PY_MAJOR_VERSION < 3
+  PyObject *val = PyInt_FromLong(value);
+#else
+  PyObject *val = PyLong_FromLong(value);
+#endif
+
+  PyObject *args = PyTuple_Pack(1, val);
+  Py_DECREF(val);
+  
+#if PY_MAJOR_VERSION < 3
+  ConstantObject *self = (ConstantObject *)PyInt_Type.tp_new(&ConstantType, args, NULL);
+#else
+  ConstantObject *self = (ConstantObject *)PyLong_Type.tp_new(&ConstantType, args, NULL);
+#endif
+  Py_DECREF(args);
 
   if (self == NULL) {
     return NULL;
   }
 
-  self->value = value;
-  self->name = name;
-  self->type = type;
+  CONST_EXTRA(self)->name = name;
 
   return (PyObject *)self;
 }
@@ -426,34 +400,16 @@ Constant_create(const char *name, long value, int type) {
 static PyObject *
 Constant_repr(ConstantObject *self) {
   return PyUnicode_FromFormat("%s(0x%x)",
-			     self->name,
-			     (unsigned int)self->value);
+			     CONST_EXTRA(self)->name,
+			     (unsigned int)CONST_VALUE(self));
 }
 
 /** alsaseq.Constant tp_str */
 static PyObject *
 Constant_str(ConstantObject *self) {
   return PyUnicode_FromFormat("%s",
-			     self->name);
-}
-
-/** alsaseq.Constant Number protocol support (note: not all ops supported) */
-NUMPROTOCOL2(Add, +)
-NUMPROTOCOL2(Subtract, -)
-NUMPROTOCOL2(Xor, ^)
-NUMPROTOCOL2(Or, |)
-NUMPROTOCOL2(And, &)
-NUMPROTOCOL1(Invert, ~)
-
-/** alsaseq.Constant number protocol methods */
-static PyNumberMethods Constant_as_number = {
- nb_add: (binaryfunc)Constant_Add,
- nb_subtract: (binaryfunc)Constant_Subtract,
- nb_xor: (binaryfunc)Constant_Xor,
- nb_or: (binaryfunc)Constant_Or,
- nb_and: (binaryfunc)Constant_And,
- nb_invert: (unaryfunc)Constant_Invert
-};
+			     CONST_EXTRA(self)->name);
+}
 
 /** alsaseq.Constant type */
 static PyTypeObject ConstantType = {
@@ -464,7 +420,7 @@ static PyTypeObject ConstantType = {
 #else
   tp_base: &PyLong_Type,
 #endif
-  tp_basicsize: sizeof(ConstantObject),
+  tp_basicsize: sizeof(ConstantObject) + sizeof(ConstantExtraFields),
   tp_flags:
 #if PY_MAJOR_VERSION < 3
   Py_TPFLAGS_HAVE_GETCHARBUFFER
@@ -474,7 +430,6 @@ static PyTypeObject ConstantType = {
   0,
 #endif
   tp_doc: Constant__doc__,
-  tp_as_number: &Constant_as_number,
   tp_free: PyObject_Del,
   tp_str: (reprfunc)Constant_str,
   tp_repr: (reprfunc)Constant_repr
@@ -1730,7 +1685,7 @@ SeqEvent_repr(SeqEventObject *self) {
   unsigned int ntime = 0;
   Py_DECREF(key);
   if (constObject != NULL) {
-    typestr = constObject->name;
+    typestr = constObject->extra.name;
   }
 
   if (snd_seq_ev_is_real(self->event)) {
-- 
2.27.0

Re: [PATCH] alsaseq: fix constant objects in Python 3

[Takashi Iwai]

On Wed, 05 Aug 2020 17:42:43 +0200,
Hector Martin wrote:
> 
> In Py3 everything is a long, so we can't get away with duplicating the
> integer object layout any more. Properly subclass PyLong_Type instead,
> with a bit of a hack to add an extra name field after the variable-sized
> data section.
> 
> Also get rid of the enum type stuff, which seems to be unused cruft, and
> the numprotocol stuff, because the base type can take care of that (and
> we can't map arbitrary arithmetic results back to constants anyway).
> 
> Signed-off-by: Hector Martin <marcan@marcan.st>

Applied now.  Thanks.


Takashi