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+/* Object and type object interface */
+
+/*
+123456789-123456789-123456789-123456789-123456789-123456789-123456789-12
+
+Objects are structures allocated on the heap. Special rules apply to
+the use of objects to ensure they are properly garbage-collected.
+Objects are never allocated statically or on the stack; they must be
+accessed through special macros and functions only. (Type objects are
+exceptions to the first rule; the standard types are represented by
+statically initialized type objects.)
+
+An object has a 'reference count' that is increased or decreased when a
+pointer to the object is copied or deleted; when the reference count
+reaches zero there are no references to the object left and it can be
+removed from the heap.
+
+An object has a 'type' that determines what it represents and what kind
+of data it contains. An object's type is fixed when it is created.
+Types themselves are represented as objects; an object contains a
+pointer to the corresponding type object. The type itself has a type
+pointer pointing to the object representing the type 'type', which
+contains a pointer to itself!).
+
+Objects do not float around in memory; once allocated an object keeps
+the same size and address. Objects that must hold variable-size data
+can contain pointers to variable-size parts of the object. Not all
+objects of the same type have the same size; but the size cannot change
+after allocation. (These restrictions are made so a reference to an
+object can be simply a pointer -- moving an object would require
+updating all the pointers, and changing an object's size would require
+moving it if there was another object right next to it.)
+
+Objects are always accessed through pointers of the type 'object *'.
+The type 'object' is a structure that only contains the reference count
+and the type pointer. The actual memory allocated for an object
+contains other data that can only be accessed after casting the pointer
+to a pointer to a longer structure type. This longer type must start
+with the reference count and type fields; the macro OB_HEAD should be
+used for this (to accomodate for future changes). The implementation
+of a particular object type can cast the object pointer to the proper
+type and back.
+
+A standard interface exists for objects that contain an array of items
+whose size is determined when the object is allocated.
+
+123456789-123456789-123456789-123456789-123456789-123456789-123456789-12
+*/
+
+#ifdef THINK_C
+/* Debugging options for THINK_C (which has no -D compiler option): */
+/*#define TRACE_REFS*/
+/*#define REF_DEBUG*/
+#endif
+
+#ifdef TRACE_REFS
+#define OB_HEAD \
+ struct _object *_ob_next, *_ob_prev; \
+ unsigned int ob_refcnt; \
+ struct _typeobject *ob_type;
+#define OB_HEAD_INIT(type) 0, 0, 1, type,
+#else
+#define OB_HEAD \
+ unsigned int ob_refcnt; \
+ struct _typeobject *ob_type;
+#define OB_HEAD_INIT(type) 1, type,
+#endif
+
+#define OB_VARHEAD \
+ OB_HEAD \
+ unsigned int ob_size; /* Number of items in variable part */
+
+typedef struct _object {
+ OB_HEAD
+} object;
+
+typedef struct {
+ OB_VARHEAD
+} varobject;
+
+
+/*
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+
+Type objects contain a string containing the type name (to help somewhat
+in debugging), the allocation parameters (see newobj() and newvarobj()),
+and methods for accessing objects of the type. Methods are optional,a
+nil pointer meaning that particular kind of access is not available for
+this type. The DECREF() macro uses the tp_dealloc method without
+checking for a nil pointer; it should always be implemented except if
+the implementation can guarantee that the reference count will never
+reach zero (e.g., for type objects).
+
+NB: the methods for certain type groups are now contained in separate
+method blocks.
+*/
+
+typedef struct {
+ object *(*nb_add) FPROTO((object *, object *));
+ object *(*nb_subtract) FPROTO((object *, object *));
+ object *(*nb_multiply) FPROTO((object *, object *));
+ object *(*nb_divide) FPROTO((object *, object *));
+ object *(*nb_remainder) FPROTO((object *, object *));
+ object *(*nb_power) FPROTO((object *, object *));
+ object *(*nb_negative) FPROTO((object *));
+ object *(*nb_positive) FPROTO((object *));
+} number_methods;
+
+typedef struct {
+ int (*sq_length) FPROTO((object *));
+ object *(*sq_concat) FPROTO((object *, object *));
+ object *(*sq_repeat) FPROTO((object *, int));
+ object *(*sq_item) FPROTO((object *, int));
+ object *(*sq_slice) FPROTO((object *, int, int));
+ int (*sq_ass_item) FPROTO((object *, int, object *));
+ int (*sq_ass_slice) FPROTO((object *, int, int, object *));
+} sequence_methods;
+
+typedef struct {
+ int (*mp_length) FPROTO((object *));
+ object *(*mp_subscript) FPROTO((object *, object *));
+ int (*mp_ass_subscript) FPROTO((object *, object *, object *));
+} mapping_methods;
+
+typedef struct _typeobject {
+ OB_VARHEAD
+ char *tp_name; /* For printing */
+ unsigned int tp_basicsize, tp_itemsize; /* For allocation */
+
+ /* Methods to implement standard operations */
+
+ void (*tp_dealloc) FPROTO((object *));
+ void (*tp_print) FPROTO((object *, FILE *, int));
+ object *(*tp_getattr) FPROTO((object *, char *));
+ int (*tp_setattr) FPROTO((object *, char *, object *));
+ int (*tp_compare) FPROTO((object *, object *));
+ object *(*tp_repr) FPROTO((object *));
+
+ /* Method suites for standard classes */
+
+ number_methods *tp_as_number;
+ sequence_methods *tp_as_sequence;
+ mapping_methods *tp_as_mapping;
+} typeobject;
+
+extern typeobject Typetype; /* The type of type objects */
+
+#define is_typeobject(op) ((op)->ob_type == &Typetype)
+
+extern void printobject PROTO((object *, FILE *, int));
+extern object * reprobject PROTO((object *));
+extern int cmpobject PROTO((object *, object *));
+
+/* Flag bits for printing: */
+#define PRINT_RAW 1 /* No string quotes etc. */
+
+/*
+123456789-123456789-123456789-123456789-123456789-123456789-123456789-12
+
+The macros INCREF(op) and DECREF(op) are used to increment or decrement
+reference counts. DECREF calls the object's deallocator function; for
+objects that don't contain references to other objects or heap memory
+this can be the standard function free(). Both macros can be used
+whereever a void expression is allowed. The argument shouldn't be a
+NIL pointer. The macro NEWREF(op) is used only to initialize reference
+counts to 1; it is defined here for convenience.
+
+We assume that the reference count field can never overflow; this can
+be proven when the size of the field is the same as the pointer size
+but even with a 16-bit reference count field it is pretty unlikely so
+we ignore the possibility. (If you are paranoid, make it a long.)
+
+Type objects should never be deallocated; the type pointer in an object
+is not considered to be a reference to the type object, to save
+complications in the deallocation function. (This is actually a
+decision that's up to the implementer of each new type so if you want,
+you can count such references to the type object.)
+
+*** WARNING*** The DECREF macro must have a side-effect-free argument
+since it may evaluate its argument multiple times. (The alternative
+would be to mace it a proper function or assign it to a global temporary
+variable first, both of which are slower; and in a multi-threaded
+environment the global variable trick is not safe.)
+*/
+
+#ifdef TRACE_REFS
+#ifndef REF_DEBUG
+#define REF_DEBUG
+#endif
+#endif
+
+#ifndef TRACE_REFS
+#define DELREF(op) (*(op)->ob_type->tp_dealloc)((object *)(op))
+#endif
+
+#ifdef REF_DEBUG
+extern long ref_total;
+#ifndef TRACE_REFS
+#define NEWREF(op) (ref_total++, (op)->ob_refcnt = 1)
+#endif
+#define INCREF(op) (ref_total++, (op)->ob_refcnt++)
+#define DECREF(op) \
+ if (--ref_total, --(op)->ob_refcnt != 0) \
+ ; \
+ else \
+ DELREF(op)
+#else
+#define NEWREF(op) ((op)->ob_refcnt = 1)
+#define INCREF(op) ((op)->ob_refcnt++)
+#define DECREF(op) \
+ if (--(op)->ob_refcnt != 0) \
+ ; \
+ else \
+ DELREF(op)
+#endif
+
+
+/* Definition of NULL, so you don't have to include <stdio.h> */
+
+#ifndef NULL
+#define NULL 0
+#endif
+
+
+/*
+NoObject is an object of undefined type which can be used in contexts
+where NULL (nil) is not suitable (since NULL often means 'error').
+
+Don't forget to apply INCREF() when returning this value!!!
+*/
+
+extern object NoObject; /* Don't use this directly */
+
+#define None (&NoObject)
+
+
+/*
+123456789-123456789-123456789-123456789-123456789-123456789-123456789-12
+
+More conventions
+================
+
+Argument Checking
+-----------------
+
+Functions that take objects as arguments normally don't check for nil
+arguments, but they do check the type of the argument, and return an
+error if the function doesn't apply to the type.
+
+Failure Modes
+-------------
+
+Functions may fail for a variety of reasons, including running out of
+memory. This is communicated to the caller in two ways: 'errno' is set
+to indicate the error, and the function result differs: functions that
+normally return a pointer return nil for failure, functions returning
+an integer return -1 (which can be a legal return value too!), and
+other functions return 0 for success and the error number for failure.
+Callers should always check for errors before using the result. The
+following error codes are used:
+
+ EBADF bad object type (first argument only)
+ EINVAL bad argument type (second and further arguments)
+ ENOMEM no memory (malloc failed)
+ ENOENT key not found in dictionary
+ EDOM index out of range or division by zero
+ ERANGE result not representable
+
+ XXX any others?
+
+Reference Counts
+----------------
+
+It takes a while to get used to the proper usage of reference counts.
+
+Functions that create an object set the reference count to 1; such new
+objects must be stored somewhere or destroyed again with DECREF().
+Functions that 'store' objects such as settupleitem() and dictinsert()
+don't increment the reference count of the object, since the most
+frequent use is to store a fresh object. Functions that 'retrieve'
+objects such as gettupleitem() and dictlookup() also don't increment
+the reference count, since most frequently the object is only looked at
+quickly. Thus, to retrieve an object and store it again, the caller
+must call INCREF() explicitly.
+
+NOTE: functions that 'consume' a reference count like dictinsert() even
+consume the reference if the object wasn't stored, to simplify error
+handling.
+
+It seems attractive to make other functions that take an object as
+argument consume a reference count; however this may quickly get
+confusing (even the current practice is already confusing). Consider
+it carefully, it may safe lots of calls to INCREF() and DECREF() at
+times.
+
+123456789-123456789-123456789-123456789-123456789-123456789-123456789-12
+*/
+
+/* Error number interface */
+#include <errno.h>
+
+#ifndef errno
+extern int errno;
+#endif
+
+#ifdef THINK_C
+/* Lightspeed C doesn't define these in <errno.h> */
+#define EDOM 33
+#define ERANGE 34
+#endif