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563 lines
19 KiB
563 lines
19 KiB
// General object definitions: pointers, reference counting, garbage collection.
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#ifndef _CL_OBJECT_H
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#define _CL_OBJECT_H
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#include "cln/types.h"
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#include "cln/modules.h"
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#include <stdlib.h>
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namespace cln {
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// We don't have to deal with circular structures, so normal reference counting
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// is sufficient. Is also has the advantage of being mostly non-interrupting.
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// An object is either a pointer to heap allocated data
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// or immediate data.
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// It is possible to distinguish these because pointers are aligned.
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// cl_uint_alignment is the guaranteed alignment of a `void*' or `long'
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// in memory. Must be > 1.
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#if defined(__m68k__)
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#define cl_word_alignment 2
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#endif
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#if defined(__i386__) || defined(__mips__) || defined(__sparc__) || defined(__hppa__) || defined(__arm__) || defined(__rs6000__) || defined(__m88k__) || defined(__convex__) || defined(__s390__)
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#define cl_word_alignment 4
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#endif
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#if defined(__alpha__) || defined(__mips64__) || defined(__sparc64__) || defined(__ia64__) || defined(__x86_64__)
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#define cl_word_alignment 8
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#endif
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#if !defined(cl_word_alignment)
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#error "Define cl_word_alignment for your CPU!"
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#endif
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// Four basic classes are introduced:
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//
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// gcobject rcobject
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//
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// gcpointer rcpointer
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//
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// `gcobject' = garbage collectible object (pointer or immediate),
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// `gcpointer' = garbage collectible pointer,
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// `rcobject' = reference counted object (pointer or immediate),
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// `rcpointer' = reference counted pointer.
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//
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// "garbage collectible" means that a reference count is maintained, and
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// when the reference count drops to 0, the object is freed. This is useful
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// for all kind of short- or long-lived objects.
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// "reference counted" means that a reference count is maintained, which
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// cannot drop to 0. This is useful for objects which are registered in a
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// global cache table, in order to know which objects can be thrown away
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// when the cache is cleaned. (If the cache were never cleaned, its objects
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// would never be freed, and we could get away with normal C pointers.)
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//
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// It is permissible to treat a `rcobject' as a `gcobject', and a `rcpointer'
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// as a `gcpointer', but this just increases the destructor and copy-constructor
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// overhead.
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// It is also permissible to treat a `gcpointer' as a `gcobject', and a
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// `rcpointer' as a `rcobject', but this just increases the destructor and
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// copy-constructor overhead.
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// Immediate data is a word, as wide as a pointer.
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typedef sintP cl_sint;
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typedef uintP cl_uint; // This ought to be called `cl_word'.
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#define cl_pointer_size intPsize
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// NB: (cl_pointer_size==64) implies defined(HAVE_FAST_LONGLONG)
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#if (cl_pointer_size==64)
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#define CL_WIDE_POINTERS
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#endif
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// Distinguish immediate data from pointers.
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inline cl_boolean cl_pointer_p (cl_uint word)
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{
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return (cl_boolean)((word & (cl_word_alignment-1)) == 0);
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}
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inline cl_boolean cl_immediate_p (cl_uint word)
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{
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return (cl_boolean)((word & (cl_word_alignment-1)) != 0);
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}
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// Immediate data: Fixnum, Short Float, maybe Single Float.
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// They have type tags.
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// |...............................|......|
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// cl_value cl_tag
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// Number of bits reserved for tagging information:
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#if (cl_word_alignment <= 4)
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#define cl_tag_len 2
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#else
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#define cl_tag_len 3
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#endif
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#define cl_tag_shift 0
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#if (cl_pointer_size == 64)
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#define cl_value_shift 32
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#else
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#define cl_value_shift (cl_tag_len+cl_tag_shift)
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#endif
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#define cl_value_len (cl_pointer_size - cl_value_shift)
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#define cl_tag_mask (((1UL << cl_tag_len) - 1) << cl_tag_shift)
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#define cl_value_mask (((1UL << cl_value_len) - 1) << cl_value_shift)
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// Return the tag of a word.
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inline cl_uint cl_tag (cl_uint word)
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{
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return (word & cl_tag_mask) >> cl_tag_shift;
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}
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// Return the value (unsigned) of a word.
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inline cl_uint cl_value (cl_uint word)
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{
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// This assumes cl_value_shift + cl_value_len == cl_pointer_size.
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return word >> cl_value_shift;
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}
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// Return a word, combining a value and a tag.
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inline cl_uint cl_combine (cl_uint tag, cl_uint value)
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{
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return (value << cl_value_shift) + (tag << cl_tag_shift);
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}
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inline cl_uint cl_combine (cl_uint tag, cl_sint value)
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{
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// This assumes cl_value_shift + cl_value_len == cl_pointer_size.
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return (value << cl_value_shift) + (tag << cl_tag_shift);
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}
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// Keep the compiler happy.
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inline cl_uint cl_combine (cl_uint tag, unsigned int value)
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{ return cl_combine(tag, (cl_uint)value); }
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inline cl_uint cl_combine (cl_uint tag, int value)
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{ return cl_combine(tag, (cl_sint)value); }
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#ifdef HAVE_LONGLONG
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inline cl_uint cl_combine (cl_uint tag, unsigned long long value)
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{ return cl_combine(tag, (cl_uint)value); }
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inline cl_uint cl_combine (cl_uint tag, long long value)
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{ return cl_combine(tag, (cl_uint)value); }
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#endif
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// Definition of the tags.
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#if !defined(CL_WIDE_POINTERS)
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#if (cl_word_alignment == 2)
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#define cl_FN_tag 1
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#define cl_SF_tag 3 // must satisfy the cl_immediate_p predicate!
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#endif
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#if (cl_word_alignment == 4)
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#define cl_FN_tag 1
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#define cl_SF_tag 2
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#endif
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#else // CL_WIDE_POINTERS
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// Single Floats are immediate as well.
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#define cl_FN_tag 1
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#define cl_SF_tag 2
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#define cl_FF_tag 3
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#endif
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// Corresponding classes.
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extern const struct cl_class * cl_immediate_classes [1<<cl_tag_len];
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// Heap allocated data contains a header, for two purposes:
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// - dynamic typing,
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// - reference count (a portable alternative to garbage collection,
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// or the basis for a portable and interoperable garbage collection).
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struct cl_heap {
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int refcount; // reference count
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const struct cl_class * type; // type tag
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};
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// Function to destroy the contents of a heap object.
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typedef void (*cl_heap_destructor_function) (cl_heap* pointer);
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// Flags, to be ORed together.
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#define cl_class_flags_subclass_complex 1 // all instances belong to cl_N
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#define cl_class_flags_subclass_real 2 // all instances belong to cl_R
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#define cl_class_flags_subclass_float 4 // all instances belong to cl_F
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#define cl_class_flags_subclass_rational 8 // all instances belong to cl_RA
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#define cl_class_flags_number_ring 16 // all instances are rings whose
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// elements belong to cl_number
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// Function to print an object for debugging, to cerr.
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typedef void (*cl_heap_dprint_function) (cl_heap* pointer);
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struct cl_class {
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cl_heap_destructor_function destruct;
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int flags;
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cl_heap_dprint_function dprint;
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};
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// Free an object on heap.
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extern void cl_free_heap_object (cl_heap* pointer);
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// Debugging support for dynamic typing: Register a debugging print function.
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#define cl_register_type_printer(type,printer) \
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{ extern cl_class type; type.dprint = (printer); }
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// cl_private_thing: An immediate value or a pointer into the heap.
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// This must be as wide as a `cl_uint'.
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// (Actually, this ought to be a union { void*; cl_uint; }, but using
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// a pointer type generates better code.)
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// Never throw away a cl_private_thing, or reference counts will be wrong!
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typedef struct cl_anything * cl_private_thing;
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// Increment the reference count.
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inline void cl_inc_pointer_refcount (cl_heap* pointer)
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{
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pointer->refcount++;
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}
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// Decrement the reference count of a garbage collected pointer.
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inline void cl_gc_dec_pointer_refcount (cl_heap* pointer)
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{
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if (--pointer->refcount == 0)
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cl_free_heap_object(pointer);
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}
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// Decrement the reference count of a reference counted pointer.
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inline void cl_rc_dec_pointer_refcount (cl_heap* pointer)
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{
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--pointer->refcount;
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}
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// Increment the reference count.
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// This must be a macro, not an inline function, because pointer_p() and
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// inc_pointer_refcount() are non-virtual member functions, so that the
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// compiler can optimize it.
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#define cl_inc_refcount(x) \
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if ((x).pointer_p()) \
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(x).inc_pointer_refcount(); \
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// Decrement the reference count.
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// This must be a macro, not an inline function, because pointer_p() and
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// dec_pointer_refcount() are non-virtual member functions, so that the
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// compiler can optimize it.
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#define cl_dec_refcount(x) \
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if ((x).pointer_p()) \
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(x).dec_pointer_refcount(); \
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// The declaration of a copy constructor.
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// Restriction: The base class's default constructor must do nothing or
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// initialize `pointer' to a constant expression.
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#define CL_DEFINE_COPY_CONSTRUCTOR1(_class_) \
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_CL_DEFINE_COPY_CONSTRUCTOR1(_class_,_class_)
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#define _CL_DEFINE_COPY_CONSTRUCTOR1(_class_,_classname_) \
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inline _class_::_classname_ (const _class_& x) \
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{ \
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cl_uint x_word = x.word; \
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cl_inc_refcount(x); \
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this->word = x_word; \
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}
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// The declaration of a copy constructor.
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// Restriction: The base class must have the usual `cl_private_thing'
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// constructor. Drawback: The base class must be known here.
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#define CL_DEFINE_COPY_CONSTRUCTOR2(_class_,_baseclass_) \
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_CL_DEFINE_COPY_CONSTRUCTOR2(_class_,_class_,_baseclass_)
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#define _CL_DEFINE_COPY_CONSTRUCTOR2(_class_,_classname_,_baseclass_) \
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inline _class_::_classname_ (const _class_& x) \
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: _baseclass_ (as_cl_private_thing(x)) {}
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// The declaration of an assignment operator.
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#define CL_DEFINE_ASSIGNMENT_OPERATOR(dest_class,src_class) \
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inline dest_class& dest_class::operator= (const src_class& x) \
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{ \
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/* Be careful, we might be assigning x to itself. */ \
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cl_uint x_word = x.word; \
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cl_inc_refcount(x); \
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cl_dec_refcount(*this); \
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this->word = x_word; \
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return *this; \
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}
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// We have a small problem with destructors: The specialized destructor
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// of a leaf class such as `cl_SF' should be more efficient than the
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// general destructor for `cl_N'. Since (by C++ specs) destructing a cl_SF
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// would run the destructors for cl_SF, cl_F, cl_R, cl_N (in that order),
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// and in the last step the compiler does not know any more that the object
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// actually is a cl_SF, there is no way to optimize the destructor!
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// ("progn-reversed" method combination is evil.)
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// And if we define "mirror"/"shadow" classes with no destructors (such
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// that `cl_F' inherits from `cl_F_no_destructor' buts adds a destructor)
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// then we need to add explicit conversion operators cl_SF -> cl_F -> cl_R ...,
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// with the effect that calling an overloaded function like `as_cl_F'
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// (which has two signatures `as_cl_F(cl_number)' and `as_cl_F(cl_F)')
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// with a cl_SF argument gives an "call of overloaded function is ambiguous"
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// error.
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// There is no help: If we want overloaded functions to be callable in a way
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// that makes sense, `cl_SF' has to be a subclass of `cl_F', and then the
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// destructor of `cl_SF' will do at least as much computation as the `cl_F'
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// destructor. Praise C++ ! :-((
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// (Even making `pointer_p()' a virtual function would not help.)
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// This is obnoxious.
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template <class key1_type, class value_type> struct cl_htentry1;
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// The four concrete classes of all objects.
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class cl_gcobject {
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public: /* ugh */
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union {
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void* pointer;
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cl_heap* heappointer;
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cl_uint word;
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};
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public:
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// Default constructor. (Used for objects with no initializer.)
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cl_gcobject ();
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// Destructor. (Used when a variable goes out of scope.)
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~cl_gcobject ();
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// Copy constructor.
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cl_gcobject (const cl_gcobject&);
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// Assignment operator.
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cl_gcobject& operator= (const cl_gcobject&);
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// Distinguish immediate data from pointer.
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cl_boolean pointer_p() const
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{ return cl_pointer_p(word); }
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// Reference counting.
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void inc_pointer_refcount () const
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{ cl_inc_pointer_refcount(heappointer); }
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void dec_pointer_refcount () const
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{ cl_gc_dec_pointer_refcount(heappointer); }
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// Return the type tag of an immediate number.
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cl_uint nonpointer_tag () const
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{ return cl_tag(word); }
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// Return the type tag of a heap-allocated number.
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const cl_class * pointer_type () const
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{ return heappointer->type; }
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// Private pointer manipulations.
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cl_private_thing _as_cl_private_thing () const;
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// Private constructor.
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cl_gcobject (cl_private_thing p)
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#if !(defined(__alpha__) && !defined(__GNUC__))
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: pointer (p) {}
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#else
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{ pointer = p; }
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#endif
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// Debugging output.
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void debug_print () const;
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// Ability to place an object at a given address.
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void* operator new (size_t size, void* ptr) { (void)size; return ptr; }
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void* operator new (size_t size) { return ::operator new (size); }
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};
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inline cl_gcobject::cl_gcobject () {}
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inline cl_gcobject::~cl_gcobject () { cl_dec_refcount(*this); }
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CL_DEFINE_COPY_CONSTRUCTOR1(cl_gcobject)
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CL_DEFINE_ASSIGNMENT_OPERATOR(cl_gcobject,cl_gcobject)
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class cl_gcpointer {
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public: /* ugh */
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union {
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void* pointer;
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cl_heap* heappointer;
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cl_uint word;
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};
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public:
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// Default constructor. (Used for objects with no initializer.)
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cl_gcpointer ();
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// Destructor. (Used when a variable goes out of scope.)
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~cl_gcpointer ();
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// Copy constructor.
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cl_gcpointer (const cl_gcpointer&);
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// Assignment operator.
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cl_gcpointer& operator= (const cl_gcpointer&);
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// Distinguish immediate data from pointer.
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cl_boolean pointer_p() const
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{ return cl_true; }
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// Reference counting.
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void inc_pointer_refcount () const
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{ cl_inc_pointer_refcount(heappointer); }
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void dec_pointer_refcount () const
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{ cl_gc_dec_pointer_refcount(heappointer); }
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// Return the type tag of an immediate number.
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cl_uint nonpointer_tag () const
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{ return cl_tag(word); }
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// Return the type tag of a heap-allocated number.
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const cl_class * pointer_type () const
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{ return heappointer->type; }
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// Private pointer manipulations.
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cl_private_thing _as_cl_private_thing () const;
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// Private constructor.
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cl_gcpointer (cl_private_thing p)
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#if !(defined(__alpha__) && !defined(__GNUC__))
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: pointer (p) {}
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#else
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{ pointer = p; }
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#endif
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// Debugging output.
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void debug_print () const;
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// Ability to place an object at a given address.
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void* operator new (size_t size, void* ptr) { (void)size; return ptr; }
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void* operator new (size_t size) { return ::operator new (size); }
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};
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inline cl_gcpointer::cl_gcpointer () {}
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inline cl_gcpointer::~cl_gcpointer () { cl_dec_refcount(*this); }
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CL_DEFINE_COPY_CONSTRUCTOR1(cl_gcpointer)
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CL_DEFINE_ASSIGNMENT_OPERATOR(cl_gcpointer,cl_gcpointer)
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class cl_rcobject {
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public: /* ugh */
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union {
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void* pointer;
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cl_heap* heappointer;
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cl_uint word;
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};
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public:
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// Default constructor. (Used for objects with no initializer.)
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cl_rcobject ();
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// Destructor. (Used when a variable goes out of scope.)
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~cl_rcobject ();
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// Copy constructor.
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cl_rcobject (const cl_rcobject&);
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// Assignment operator.
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cl_rcobject& operator= (const cl_rcobject&);
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// Distinguish immediate data from pointer.
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cl_boolean pointer_p() const
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{ return cl_pointer_p(word); }
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// Reference counting.
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void inc_pointer_refcount () const
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{ cl_inc_pointer_refcount(heappointer); }
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void dec_pointer_refcount () const
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{ cl_rc_dec_pointer_refcount(heappointer); }
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// Return the type tag of an immediate number.
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cl_uint nonpointer_tag () const
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{ return cl_tag(word); }
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// Return the type tag of a heap-allocated number.
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const cl_class * pointer_type () const
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{ return heappointer->type; }
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// Private pointer manipulations.
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cl_private_thing _as_cl_private_thing () const;
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// Private constructor.
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cl_rcobject (cl_private_thing p)
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#if !(defined(__alpha__) && !defined(__GNUC__))
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: pointer (p) {}
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#else
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{ pointer = p; }
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#endif
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// Debugging output.
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void debug_print () const;
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// Ability to place an object at a given address.
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void* operator new (size_t size, void* ptr) { (void)size; return ptr; }
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void* operator new (size_t size) { return ::operator new (size); }
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};
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inline cl_rcobject::cl_rcobject () {}
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inline cl_rcobject::~cl_rcobject () { cl_dec_refcount(*this); }
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CL_DEFINE_COPY_CONSTRUCTOR1(cl_rcobject)
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CL_DEFINE_ASSIGNMENT_OPERATOR(cl_rcobject,cl_rcobject)
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class cl_rcpointer {
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public: /* ugh */
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union {
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void* pointer;
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cl_heap* heappointer;
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cl_uint word;
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};
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public:
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// Default constructor. (Used for objects with no initializer.)
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cl_rcpointer ();
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// Destructor. (Used when a variable goes out of scope.)
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~cl_rcpointer ();
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// Copy constructor.
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cl_rcpointer (const cl_rcpointer&);
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// Assignment operator.
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cl_rcpointer& operator= (const cl_rcpointer&);
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// Distinguish immediate data from pointer.
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cl_boolean pointer_p() const
|
|
{ return cl_true; }
|
|
// Reference counting.
|
|
void inc_pointer_refcount () const
|
|
{ cl_inc_pointer_refcount(heappointer); }
|
|
void dec_pointer_refcount () const
|
|
{ cl_rc_dec_pointer_refcount(heappointer); }
|
|
// Return the type tag of an immediate number.
|
|
cl_uint nonpointer_tag () const
|
|
{ return cl_tag(word); }
|
|
// Return the type tag of a heap-allocated number.
|
|
const cl_class * pointer_type () const
|
|
{ return heappointer->type; }
|
|
// Private pointer manipulations.
|
|
cl_private_thing _as_cl_private_thing () const;
|
|
// Private constructor.
|
|
cl_rcpointer (cl_private_thing p)
|
|
#if !(defined(__alpha__) && !defined(__GNUC__))
|
|
: pointer (p) {}
|
|
#else
|
|
{ pointer = p; }
|
|
#endif
|
|
// Debugging output.
|
|
void debug_print () const;
|
|
// Ability to place an object at a given address.
|
|
void* operator new (size_t size, void* ptr) { (void)size; return ptr; }
|
|
void* operator new (size_t size) { return ::operator new (size); }
|
|
};
|
|
inline cl_rcpointer::cl_rcpointer () {}
|
|
inline cl_rcpointer::~cl_rcpointer () { cl_dec_refcount(*this); }
|
|
CL_DEFINE_COPY_CONSTRUCTOR1(cl_rcpointer)
|
|
CL_DEFINE_ASSIGNMENT_OPERATOR(cl_rcpointer,cl_rcpointer)
|
|
|
|
// Private pointer manipulations.
|
|
|
|
inline cl_private_thing cl_gcobject::_as_cl_private_thing () const
|
|
{
|
|
cl_private_thing p = (cl_private_thing) pointer;
|
|
cl_inc_refcount(*this);
|
|
return p;
|
|
}
|
|
inline cl_private_thing as_cl_private_thing (const cl_gcobject& x)
|
|
{
|
|
return x._as_cl_private_thing();
|
|
}
|
|
|
|
inline cl_private_thing cl_gcpointer::_as_cl_private_thing () const
|
|
{
|
|
cl_private_thing p = (cl_private_thing) pointer;
|
|
cl_inc_refcount(*this);
|
|
return p;
|
|
}
|
|
inline cl_private_thing as_cl_private_thing (const cl_gcpointer& x)
|
|
{
|
|
return x._as_cl_private_thing();
|
|
}
|
|
|
|
inline cl_private_thing cl_rcobject::_as_cl_private_thing () const
|
|
{
|
|
cl_private_thing p = (cl_private_thing) pointer;
|
|
cl_inc_refcount(*this);
|
|
return p;
|
|
}
|
|
inline cl_private_thing as_cl_private_thing (const cl_rcobject& x)
|
|
{
|
|
return x._as_cl_private_thing();
|
|
}
|
|
|
|
inline cl_private_thing cl_rcpointer::_as_cl_private_thing () const
|
|
{
|
|
cl_private_thing p = (cl_private_thing) pointer;
|
|
cl_inc_refcount(*this);
|
|
return p;
|
|
}
|
|
inline cl_private_thing as_cl_private_thing (const cl_rcpointer& x)
|
|
{
|
|
return x._as_cl_private_thing();
|
|
}
|
|
|
|
// Note: When we define a function that returns a class object by value,
|
|
// we normally return it as const value. The declarations
|
|
// T func (...); (A)
|
|
// and
|
|
// const T func (...); (B)
|
|
// behave identically and generate identical code, except that the code
|
|
// func(...) = foo;
|
|
// compiles fine with (A) but is an error (and yields a warning) with (B).
|
|
// We want this warning.
|
|
|
|
// Define a conversion operator from one object to another object of the
|
|
// same size.
|
|
#define CL_DEFINE_CONVERTER(target_class) \
|
|
operator const target_class & () const \
|
|
{ \
|
|
if (sizeof(*this) != sizeof(target_class)) cl_abort(); \
|
|
return * (const target_class *) (void*) this; \
|
|
}
|
|
|
|
} // namespace cln
|
|
|
|
#endif /* _CL_OBJECT_H */
|