abstract.h

#ifndef Py_ABSTRACTOBJECT_H
#define Py_ABSTRACTOBJECT_H
#ifdef __cplusplus
extern "C" {
#endif

/***********************************************************
Copyright 1991-1995 by Stichting Mathematisch Centrum, Amsterdam,
The Netherlands.

                        All Rights Reserved

Permission to use, copy, modify, and distribute this software and its 
documentation for any purpose and without fee is hereby granted, 
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OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

******************************************************************/

/* Abstract Object Interface (many thanks to Jim Fulton) */

/*
   PROPOSAL: A Generic Python Object Interface for Python C Modules

Problem

  Python modules written in C that must access Python objects must do
  so through routines whose interfaces are described by a set of
  include files.  Unfortunately, these routines vary according to the
  object accessed.  To use these routines, the C programmer must check
  the type of the object being used and must call a routine based on
  the object type.  For example, to access an element of a sequence,
  the programmer must determine whether the sequence is a list or a
  tuple:

    if(is_tupleobject(o))
      e=gettupleitem(o,i)
    else if(is_listitem(o))
      e=getlistitem(o,i)

  If the programmer wants to get an item from another type of object
  that provides sequence behavior, there is no clear way to do it
  correctly.  

  The persistent programmer may peruse object.h and find that the
  _typeobject structure provides a means of invoking up to (currently
  about) 41 special operators.  So, for example, a routine can get an
  item from any object that provides sequence behavior. However, to
  use this mechanism, the programmer must make their code dependent on
  the current Python implementation.

  Also, certain semantics, especially memory management semantics, may
  differ by the type of object being used.  Unfortunately, these
  semantics are not clearly described in the current include files.
  An abstract interface providing more consistent semantics is needed. 

Proposal

  I propose the creation of a standard interface (with an associated
  library of routines and/or macros) for generically obtaining the
  services of Python objects.  This proposal can be viewed as one
  components of a Python C interface consisting of several components.

  From the viewpoint of of C access to Python services, we have (as
  suggested by Guido in off-line discussions):

  - "Very high level layer": two or three functions that let you exec or
    eval arbitrary Python code given as a string in a module whose name is
    given, passing C values in and getting C values out using
    mkvalue/getargs style format strings.  This does not require the user
    to declare any variables of type "PyObject *".  This should be enough
    to write a simple application that gets Python code from the user,
    execs it, and returns the output or errors.  (Error handling must also
    be part of this API.)

  - "Abstract objects layer": which is the subject of this proposal.
    It has many functions operating on objects, and lest you do many
    things from C that you can also write in Python, without going
    through the Python parser.

  - "Concrete objects layer": This is the public type-dependent
    interface provided by the standard built-in types, such as floats,
    strings, and lists.  This interface exists and is currently
    documented by the collection of include files provides with the
    Python distributions.

  From the point of view of Python accessing services provided by C
  modules: 

  - "Python module interface": this interface consist of the basic
    routines used to define modules and their members.  Most of the
    current extensions-writing guide deals with this interface.

  - "Built-in object interface": this is the interface that a new
    built-in type must provide and the mechanisms and rules that a
    developer of a new built-in type must use and follow.

  This proposal is a "first-cut" that is intended to spur
  discussion. See especially the lists of notes.

  The Python C object interface will provide four protocols: object,
  numeric, sequence, and mapping.  Each protocol consists of a
  collection of related operations.  If an operation that is not
  provided by a particular type is invoked, then a standard exception,
  NotImplementedError is raised with a operation name as an argument.
  In addition, for convenience this interface defines a set of
  constructors for building objects of built-in types.  This is needed
  so new objects can be returned from C functions that otherwise treat
  objects generically.

Memory Management

  For all of the functions described in this proposal, if a function
  retains a reference to a Python object passed as an argument, then the
  function will increase the reference count of the object.  It is
  unnecessary for the caller to increase the reference count of an
  argument in anticipation of the object's retention.

  All Python objects returned from functions should be treated as new
  objects.  Functions that return objects assume that the caller will
  retain a reference and the reference count of the object has already
  been incremented to account for this fact.  A caller that does not
  retain a reference to an object that is returned from a function
  must decrement the reference count of the object (using
  DECREF(object)) to prevent memory leaks.

  Note that the behavior mentioned here is different from the current
  behavior for some objects (e.g. lists and tuples) when certain
  type-specific routines are called directly (e.g. setlistitem).  The
  proposed abstraction layer will provide a consistent memory
  management interface, correcting for inconsistent behavior for some
  built-in types.

Protocols

xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx*/

/*  Object Protocol: */

     /* Implemented elsewhere:

     int PyObject_Print(PyObject *o, FILE *fp, int flags);

         Print an object, o, on file, fp.  Returns -1 on
	 error.  The flags argument is used to enable certain printing
	 options. The only option currently supported is Py_Print_RAW. 

         (What should be said about Py_Print_RAW?)	

       */

     /* Implemented elsewhere:

     int PyObject_HasAttrString(PyObject *o, char *attr_name);

         Returns 1 if o has the attribute attr_name, and 0 otherwise.
	 This is equivalent to the Python expression:
	 hasattr(o,attr_name). 

	 This function always succeeds.

       */

     /* Implemented elsewhere:

     PyObject* PyObject_GetAttrString(PyObject *o, char *attr_name);

	 Retrieve an attributed named attr_name form object o.
	 Returns the attribute value on success, or NULL on failure.
	 This is the equivalent of the Python expression: o.attr_name.

       */

     /* Implemented elsewhere:

     int PyObject_HasAttr(PyObject *o, PyObject *attr_name);

         Returns 1 if o has the attribute attr_name, and 0 otherwise.
	 This is equivalent to the Python expression:
	 hasattr(o,attr_name). 

	 This function always succeeds.

       */

     /* Implemented elsewhere:

     PyObject* PyObject_GetAttr(PyObject *o, PyObject *attr_name);

	 Retrieve an attributed named attr_name form object o.
	 Returns the attribute value on success, or NULL on failure.
	 This is the equivalent of the Python expression: o.attr_name.

       */


     /* Implemented elsewhere:

     int PyObject_SetAttrString(PyObject *o, char *attr_name, PyObject *v);

	 Set the value of the attribute named attr_name, for object o,
	 to the value, v. Returns -1 on failure.  This is
	 the equivalent of the Python statement: o.attr_name=v.

       */

     /* Implemented elsewhere:

     int PyObject_SetAttr(PyObject *o, PyObject *attr_name, PyObject *v);

	 Set the value of the attribute named attr_name, for object o,
	 to the value, v. Returns -1 on failure.  This is
	 the equivalent of the Python statement: o.attr_name=v.

       */

     /* implemented as a macro:

     int PyObject_DelAttrString(PyObject *o, char *attr_name);

	 Delete attribute named attr_name, for object o. Returns
	 -1 on failure.  This is the equivalent of the Python
	 statement: del o.attr_name.

       */
#define  PyObject_DelAttrString(O,A) PyObject_SetAttrString((O),(A),NULL)

     /* implemented as a macro:

     int PyObject_DelAttr(PyObject *o, PyObject *attr_name);

	 Delete attribute named attr_name, for object o. Returns -1
	 on failure.  This is the equivalent of the Python
	 statement: del o.attr_name.

       */
#define  PyObject_DelAttr(O,A) PyObject_SetAttr((O),(A),NULL)

     int PyObject_Cmp Py_PROTO((PyObject *o1, PyObject *o2, int *result));

       /*
	 Compare the values of o1 and o2 using a routine provided by
	 o1, if one exists, otherwise with a routine provided by o2.
	 The result of the comparison is returned in result.  Returns
	 -1 on failure.  This is the equivalent of the Python
	 statement: result=cmp(o1,o2).

       */

     /* Implemented elsewhere:

     int PyObject_Compare(PyObject *o1, PyObject *o2);

	 Compare the values of o1 and o2 using a routine provided by
	 o1, if one exists, otherwise with a routine provided by o2.
	 Returns the result of the comparison on success.  On error,
	 the value returned is undefined. This is equivalent to the
	 Python expression: cmp(o1,o2).

       */

     /* Implemented elsewhere:

     PyObject *PyObject_Repr(PyObject *o);

	 Compute the string representation of object, o.  Returns the
	 string representation on success, NULL on failure.  This is
	 the equivalent of the Python expression: repr(o).

	 Called by the repr() built-in function and by reverse quotes.

       */

     /* Implemented elsewhere:

     PyObject *PyObject_Str(PyObject *o);

	 Compute the string representation of object, o.  Returns the
	 string representation on success, NULL on failure.  This is
	 the equivalent of the Python expression: str(o).)

	 Called by the str() built-in function and by the print
	 statement.

       */

     int PyCallable_Check Py_PROTO((PyObject *o));

       /*
	 Determine if the object, o, is callable.  Return 1 if the
	 object is callable and 0 otherwise.

	 This function always succeeds.

       */


     
     PyObject *PyObject_CallObject Py_PROTO((PyObject *callable_object,
					     PyObject *args));

       /*

	 Call a callable Python object, callable_object, with
	 arguments given by the tuple, args.  If no arguments are
	 needed, then args may be NULL.  Returns the result of the
	 call on success, or NULL on failure.  This is the equivalent
	 of the Python expression: apply(o,args).

       */

     PyObject *PyObject_CallFunction Py_PROTO((PyObject *callable_object,
					       char *format, ...));

       /*
	 Call a callable Python object, callable_object, with a
	 variable number of C arguments. The C arguments are described
	 using a mkvalue-style format string. The format may be NULL,
	 indicating that no arguments are provided.  Returns the
	 result of the call on success, or NULL on failure.  This is
	 the equivalent of the Python expression: apply(o,args).

       */


     PyObject *PyObject_CallMethod Py_PROTO((PyObject *o, char *m,
					     char *format, ...));

       /*
	 Call the method named m of object o with a variable number of
	 C arguments.  The C arguments are described by a mkvalue
	 format string.  The format may be NULL, indicating that no
	 arguments are provided. Returns the result of the call on
	 success, or NULL on failure.  This is the equivalent of the
	 Python expression: o.method(args).

         Note that Special method names, such as "__add__",
	 "__getitem__", and so on are not supported. The specific
	 abstract-object routines for these must be used.

       */


     /* Implemented elsewhere:

     long PyObject_Hash(PyObject *o);

         Compute and return the hash, hash_value, of an object, o.  On
	 failure, return -1.  This is the equivalent of the Python
	 expression: hash(o).

       */


     /* Implemented elsewhere:

     int PyObject_IsTrue(PyObject *o);

	 Returns 1 if the object, o, is considered to be true, and
	 0 otherwise. This is equivalent to the Python expression:
	 not not o

	 This function always succeeds.
	 
       */

     PyObject *PyObject_Type Py_PROTO((PyObject *o));

       /*
	 On success, returns a type object corresponding to the object
	 type of object o. On failure, returns NULL.  This is
	 equivalent to the Python expression: type(o).
       */

     int PyObject_Length Py_PROTO((PyObject *o));

       /*
         Return the length of object o.  If the object, o, provides
	 both sequence and mapping protocols, the sequence length is
	 returned. On error, -1 is returned.  This is the equivalent
	 to the Python expression: len(o).

       */

     PyObject *PyObject_GetItem Py_PROTO((PyObject *o, PyObject *key));

       /*
	 Return element of o corresponding to the object, key, or NULL
	 on failure. This is the equivalent of the Python expression:
	 o[key].

       */

     int PyObject_SetItem Py_PROTO((PyObject *o, PyObject *key, PyObject *v));

       /*
	 Map the object, key, to the value, v.  Returns
	 -1 on failure.  This is the equivalent of the Python
	 statement: o[key]=v.
       */


/*  Number Protocol:*/

     int PyNumber_Check Py_PROTO((PyObject *o));

       /*
         Returns 1 if the object, o, provides numeric protocols, and
	 false otherwise. 

	 This function always succeeds.

       */

     PyObject *PyNumber_Add Py_PROTO((PyObject *o1, PyObject *o2));

       /*
	 Returns the result of adding o1 and o2, or null on failure.
	 This is the equivalent of the Python expression: o1+o2.


       */

     PyObject *PyNumber_Subtract Py_PROTO((PyObject *o1, PyObject *o2));

       /*
	 Returns the result of subtracting o2 from o1, or null on
	 failure.  This is the equivalent of the Python expression:
	 o1-o2.

       */

     PyObject *PyNumber_Multiply Py_PROTO((PyObject *o1, PyObject *o2));

       /*
	 Returns the result of multiplying o1 and o2, or null on
	 failure.  This is the equivalent of the Python expression:
	 o1*o2.


       */

     PyObject *PyNumber_Divide Py_PROTO((PyObject *o1, PyObject *o2));

       /*
	 Returns the result of dividing o1 by o2, or null on failure.
	 This is the equivalent of the Python expression: o1/o2.


       */

     PyObject *PyNumber_Remainder Py_PROTO((PyObject *o1, PyObject *o2));

       /*
	 Returns the remainder of dividing o1 by o2, or null on
	 failure.  This is the equivalent of the Python expression:
	 o1%o2.


       */

     PyObject *PyNumber_Divmod Py_PROTO((PyObject *o1, PyObject *o2));

       /*
	 See the built-in function divmod.  Returns NULL on failure.
	 This is the equivalent of the Python expression:
	 divmod(o1,o2).


       */

     PyObject *PyNumber_Power Py_PROTO((PyObject *o1, PyObject *o2, PyObject *o3));

       /*
	 See the built-in function pow.  Returns NULL on failure.
	 This is the equivalent of the Python expression:
	 pow(o1,o2,o3), where o3 is optional.

       */

     PyObject *PyNumber_Negative Py_PROTO((PyObject *o));

       /*
	 Returns the negation of o on success, or null on failure.
	 This is the equivalent of the Python expression: -o.

       */

     PyObject *PyNumber_Positive Py_PROTO((PyObject *o));

       /*
         Returns the (what?) of o on success, or NULL on failure.
	 This is the equivalent of the Python expression: +o.

       */

     PyObject *PyNumber_Absolute Py_PROTO((PyObject *o));

       /*
	 Returns the absolute value of o, or null on failure.  This is
	 the equivalent of the Python expression: abs(o).

       */

     PyObject *PyNumber_Invert Py_PROTO((PyObject *o));

       /*
	 Returns the bitwise negation of o on success, or NULL on
	 failure.  This is the equivalent of the Python expression:
	 ~o.


       */

     PyObject *PyNumber_Lshift Py_PROTO((PyObject *o1, PyObject *o2));

       /*
	 Returns the result of left shifting o1 by o2 on success, or
	 NULL on failure.  This is the equivalent of the Python
	 expression: o1 << o2.


       */

     PyObject *PyNumber_Rshift Py_PROTO((PyObject *o1, PyObject *o2));

       /*
	 Returns the result of right shifting o1 by o2 on success, or
	 NULL on failure.  This is the equivalent of the Python
	 expression: o1 >> o2.

       */

     PyObject *PyNumber_And Py_PROTO((PyObject *o1, PyObject *o2));

       /*
	 Returns the result of "anding" o2 and o2 on success and NULL
	 on failure. This is the equivalent of the Python
	 expression: o1 and o2.


       */

     PyObject *PyNumber_Xor Py_PROTO((PyObject *o1, PyObject *o2));

       /*
	 Returns the bitwise exclusive or of o1 by o2 on success, or
	 NULL on failure.  This is the equivalent of the Python
	 expression: o1^o2.


       */

     PyObject *PyNumber_Or Py_PROTO((PyObject *o1, PyObject *o2));

       /*
	 Returns the result or o1 and o2 on success, or NULL on
	 failure.  This is the equivalent of the Python expression: 
	 o1 or o2.

       */

     /* Implemented elsewhere:

     int PyNumber_Coerce(PyObject *o1, PyObject *o2);

         On success, returns a tuple containing o1 and o2 converted to
	 a common numeric type, or None if no conversion is possible.
	 Returns -1 on failure. This is equivalent to the Python
	 expression: coerce(o1,o2).

       */

     PyObject *PyNumber_Int Py_PROTO((PyObject *o));

       /*
	 Returns the o converted to an integer object on success, or
	 NULL on failure.  This is the equivalent of the Python
	 expression: int(o).

       */

     PyObject *PyNumber_Long Py_PROTO((PyObject *o));

       /*
	 Returns the o converted to a long integer object on success,
	 or NULL on failure.  This is the equivalent of the Python
	 expression: long(o).

       */

     PyObject *PyNumber_Float Py_PROTO((PyObject *o));

       /*
	 Returns the o converted to a float object on success, or NULL
	 on failure.  This is the equivalent of the Python expression:
	 float(o).
       */
	 

/*  Sequence protocol:*/

     int PySequence_Check Py_PROTO((PyObject *o));

       /*
         Return 1 if the object provides sequence protocol, and zero
	 otherwise.  

	 This function always succeeds.

       */

     int PySequence_Lenth Py_PROTO((PyObject *o));

       /*
         Return the length of sequence object o, or -1 on failure.

       */

     PyObject *PySequence_Concat Py_PROTO((PyObject *o1, PyObject *o2));

       /*
	 Return the concatination of o1 and o2 on success, and NULL on
	 failure.   This is the equivalent of the Python
	 expression: o1+o2.

       */

     PyObject *PySequence_Repeat Py_PROTO((PyObject *o, int count));

       /*
	 Return the result of repeating sequence object o count times,
	 or NULL on failure.  This is the equivalent of the Python
	 expression: o1*count.

       */

     PyObject *PySequence_GetItem Py_PROTO((PyObject *o, int i));

       /*
	 Return the ith element of o, or NULL on failure. This is the
	 equivalent of the Python expression: o[i].

       */

     PyObject *PySequence_GetSlice Py_PROTO((PyObject *o, int i1, int i2));

       /*
	 Return the slice of sequence object o between i1 and i2, or
	 NULL on failure. This is the equivalent of the Python
	 expression: o[i1:i2].

       */

     int PySequence_SetItem Py_PROTO((PyObject *o, int i, PyObject *v));

       /*
	 Assign object v to the ith element of o.  Returns
	 -1 on failure.  This is the equivalent of the Python
	 statement: o[i]=v.

       */

     int PySequence_SetSlice Py_PROTO((PyObject *o, int i1, int i2, PyObject *v));

       /*
         Assign the sequence object, v, to the slice in sequence
	 object, o, from i1 to i2.  Returns -1 on failure. This is the
	 equivalent of the Python statement: o[i1:i2]=v.
       */

     PyObject *PySequence_Tuple Py_PROTO((PyObject *o));

       /*
	 Returns the o as a tuple on success, and NULL on failure.
	 This is equivalent to the Python expression: tuple(o)
       */

     int PySequence_Count Py_PROTO((PyObject *o, PyObject *value));

       /*
         Return the number of occurrences on value on o, that is,
	 return the number of keys for which o[key]==value.  On
	 failure, return -1.  This is equivalent to the Python
	 expression: o.count(value).
       */

     int PySequence_In Py_PROTO((PyObject *o, PyObject *value));

       /*
	 Determine if o contains value.  If an item in o is equal to
	 X, return 1, otherwise return 0.  On error, return -1.  This
	 is equivalent to the Python expression: value in o.
       */

     int PySequence_Index Py_PROTO((PyObject *o, PyObject *value));

       /*
	 Return the first index for which o[i]=value.  On error,
	 return -1.    This is equivalent to the Python
	 expression: o.index(value).
       */

/*  Mapping protocol:*/

     int PyMapping_Check Py_PROTO((PyObject *o));

       /*
         Return 1 if the object provides mapping protocol, and zero
	 otherwise.  

	 This function always succeeds.
       */

     int PyMapping_Length Py_PROTO((PyObject *o));

       /*
         Returns the number of keys in object o on success, and -1 on
	 failure.  For objects that do not provide sequence protocol,
	 this is equivalent to the Python expression: len(o).
       */

     int PyMapping_DelItemString Py_PROTO((PyObject *o, char *key));

       /*
	 Remove the mapping for object, key, from the object *o.
	 Returns -1 on failure.  This is equivalent to
	 the Python statement: del o[key].
       */

     int PyMapping_DelItem Py_PROTO((PyObject *o, PyObject *key));

       /*
	 Remove the mapping for object, key, from the object *o.
	 Returns -1 on failure.  This is equivalent to
	 the Python statement: del o[key].
       */

     int PyMapping_HasKeyString Py_PROTO((PyObject *o, char *key));

       /*
	 On success, return 1 if the mapping object has the key, key,
	 and 0 otherwise.  This is equivalent to the Python expression:
	 o.has_key(key). 

	 This function always succeeds.
       */

     int PyMapping_HasKey Py_PROTO((PyObject *o, PyObject *key));

       /*
	 Return 1 if the mapping object has the key, key,
	 and 0 otherwise.  This is equivalent to the Python expression:
	 o.has_key(key). 

	 This function always succeeds.

       */

     /* Implemented as macro:

     PyObject *PyMapping_Keys(PyObject *o);

         On success, return a list of the keys in object o.  On
	 failure, return NULL. This is equivalent to the Python
	 expression: o.keys().
       */
#define PyMapping_Keys(O) PyObject_CallMethod(O,"keys",NULL)

     /* Implemented as macro:

     PyObject *PyMapping_Values(PyObject *o);

         On success, return a list of the values in object o.  On
	 failure, return NULL. This is equivalent to the Python
	 expression: o.values().
       */
#define PyMapping_Values(O) PyObject_CallMethod(O,"values",NULL)

     /* Implemented as macro:

     PyObject *PyMapping_Items(PyObject *o);

         On success, return a list of the items in object o, where
	 each item is a tuple containing a key-value pair.  On
	 failure, return NULL. This is equivalent to the Python
	 expression: o.items().

       */
#define PyMapping_Items(O) PyObject_CallMethod(O,"items",NULL)

     PyObject *PyMapping_GetItemString Py_PROTO((PyObject *o, char *key));

       /*
	 Return element of o corresponding to the object, key, or NULL
	 on failure. This is the equivalent of the Python expression:
	 o[key].
       */

     int PyMapping_SetItemString Py_PROTO((PyObject *o, char *key,
					   PyObject *value));

       /*
	 Map the object, key, to the value, v.  Returns 
	 -1 on failure.  This is the equivalent of the Python
	 statement: o[key]=v.
      */


#ifdef __cplusplus
}
#endif
#endif /* Py_ABSTRACTOBJECT_H */