diff options
Diffstat (limited to 'src/object.h')
| -rw-r--r-- | src/object.h | 164 |
1 files changed, 82 insertions, 82 deletions
diff --git a/src/object.h b/src/object.h index f0266c4..9ea5260 100644 --- a/src/object.h +++ b/src/object.h @@ -2,12 +2,12 @@ Copyright 1991 by Stichting Mathematisch Centrum, Amsterdam, The Netherlands. - All Rights Reserved + All Rights Reserved -Permission to use, copy, modify, and distribute this software and its -documentation for any purpose and without fee is hereby granted, +Permission to use, copy, modify, and distribute this software and its +documentation for any purpose and without fee is hereby granted, provided that the above copyright notice appear in all copies and that -both that copyright notice and this permission notice appear in +both that copyright notice and this permission notice appear in supporting documentation, and that the names of Stichting Mathematisch Centrum or CWI not be used in advertising or publicity pertaining to distribution of the software without specific, written prior permission. @@ -28,10 +28,10 @@ OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. /* 123456789-123456789-123456789-123456789-123456789-123456789-123456789-12 -Objects are structures allocated on the heap. Special rules apply to +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 +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.) @@ -41,28 +41,28 @@ 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. +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 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 +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 +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 +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 +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 +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. @@ -84,27 +84,27 @@ whose size is determined when the object is allocated. #ifdef TRACE_REFS #define OB_HEAD \ - struct _object *_ob_next, *_ob_prev; \ - int ob_refcnt; \ - struct _typeobject *ob_type; + struct _object *_ob_next, *_ob_prev; \ + 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; + 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 */ - + OB_HEAD \ + unsigned int ob_size; /* Number of items in variable part */ + typedef struct _object { - OB_HEAD + OB_HEAD } object; typedef struct { - OB_VARHEAD + OB_VARHEAD } varobject; @@ -113,9 +113,9 @@ typedef struct { 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 +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 +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). @@ -125,51 +125,51 @@ 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 *)); + 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 *)); + 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 *)); + 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; + 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 */ @@ -184,32 +184,32 @@ extern object *getattr PROTO((object *, char *)); extern int setattr PROTO((object *, char *, object *)); /* Flag bits for printing: */ -#define PRINT_RAW 1 /* No string quotes etc. */ +#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 +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 +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.) +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 +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 +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.) @@ -233,18 +233,18 @@ extern long ref_total; #endif #define INCREF(op) (ref_total++, (op)->ob_refcnt++) #define DECREF(op) \ - if (--ref_total, --(op)->ob_refcnt > 0) \ - ; \ - else \ - DELREF(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) + if (--(op)->ob_refcnt > 0) \ + ; \ + else \ + DELREF(op) #endif /* Macros to use in case the object pointer may be NULL: */ @@ -288,7 +288,7 @@ Failure Modes ------------- Functions may fail for a variety of reasons, including running out of -memory. This is communicated to the caller in two ways: an error string +memory. This is communicated to the caller in two ways: an error string is set (see errors.h), and the function result differs: functions that normally return a pointer return NULL for failure, functions returning an integer return -1 (which could be a legal return value too!), and @@ -304,10 +304,10 @@ 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' +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 +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 @@ -316,7 +316,7 @@ 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 +confusing (even the current practice is already confusing). Consider it carefully, it may safe lots of calls to INCREF() and DECREF() at times. |