src/method-impl.lisp, etc.: Add a `readonly' message property.

[sod] / lib / sod-structs.3

diff --git a/lib/sod-structs.3 b/lib/sod-structs.3
index 5846079..161fc4e 100644 (file)
--- a/lib/sod-structs.3
+++ b/lib/sod-structs.3
@@ -7,21 +7,22 @@
 .
 .\"----- Licensing notice ---------------------------------------------------
 .\"
 .
 .\"----- Licensing notice ---------------------------------------------------
 .\"

-.\" This file is part of the Sensble Object Design, an object system for C.
+.\" This file is part of the Sensible Object Design, an object system for C.

 .\"
 .\" SOD is free software; you can redistribute it and/or modify
 .\"
 .\" SOD is free software; you can redistribute it and/or modify

-.\" it under the terms of the GNU General Public License as published by
-.\" the Free Software Foundation; either version 2 of the License, or
-.\" (at your option) any later version.
+.\" it under the terms of the GNU Library General Public License as
+.\" published by the Free Software Foundation; either version 2 of the
+.\" License, or (at your option) any later version.

 .\"
 .\" SOD is distributed in the hope that it will be useful,
 .\" but WITHOUT ANY WARRANTY; without even the implied warranty of
 .\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 .\"
 .\" SOD is distributed in the hope that it will be useful,
 .\" but WITHOUT ANY WARRANTY; without even the implied warranty of
 .\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

-.\" GNU General Public License for more details.
+.\" GNU Library General Public License for more details.

 .\"
 .\"

-.\" You should have received a copy of the GNU General Public License
-.\" along with SOD; if not, write to the Free Software Foundation,
-.\" Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+.\" You should have received a copy of the GNU Library General Public
+.\" License along with SOD; if not, write to the Free
+.\" Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
+.\" MA 02111-1307, USA.

 .
 .\" Highlight using terminal escapes, rather than overstriking.
 .\"\X'tty: sgr 1'
 .
 .\" Highlight using terminal escapes, rather than overstriking.
 .\"\X'tty: sgr 1'


@@ -68,6 +69,11 @@ struct sod_vtable {
 struct SodObject__vt_obj {
 \h'2n'const SodClass *_class;
 \h'2n'size_t _base;
 struct SodObject__vt_obj {
 \h'2n'const SodClass *_class;
 \h'2n'size_t _base;

+\h'2n'struct SodObject__vtmsgs_obj {
+\h'4n'void (*init)(SodObject *\fIme\fB, ...);
+\h'4n'void (*init__v)(SodObject *\fIme\fB, va_list);
+\h'4n'int (*teardown)(SodObject *\fIme\fB);
+\h'2n'} obj;

 };
 
 struct SodObject__ilayout {
 };
 
 struct SodObject__ilayout {


@@ -84,9 +90,14 @@ extern const struct SodClass__ilayout SodObject__classobj;
 struct SodClass__vt_obj {
 \h'2n'const SodClass *_class;
 \h'2n'size_t _base;
 struct SodClass__vt_obj {
 \h'2n'const SodClass *_class;
 \h'2n'size_t _base;

+\h'2n'struct SodClass__vtmsgs_obj {
+\h'4n'void (*init)(SodClass *\fIme\fB, ...);
+\h'4n'void (*init__v)(SodClass *\fIme\fB, va_list);
+\h'4n'int (*teardown)(SodClass *\fIme\fB);
+\h'2n'} obj;

 };
 
 };
 

-struct SodObject__ilayout {
+struct SodClass__ilayout {

 \h'2n'union {
 \h'4n'struct SodClass__ichain_obj {
 \h'6n'const struct SodClass__vt_obj *_vt;
 \h'2n'union {
 \h'4n'struct SodClass__ichain_obj {
 \h'6n'const struct SodClass__vt_obj *_vt;


@@ -94,8 +105,8 @@ struct SodObject__ilayout {
 \h'8n'const char *name;
 \h'8n'const char *nick;
 \h'8n'size_t initsz;
 \h'8n'const char *name;
 \h'8n'const char *nick;
 \h'8n'size_t initsz;

+\h'8n'size_t align;

 \h'8n'void *(*imprint)(void *\fIp\fB);
 \h'8n'void *(*imprint)(void *\fIp\fB);

-\h'8n'void *(*init)(void *\fIp\fB);

 \h'8n'size_t n_supers;
 \h'8n'const SodClass *const *supers;
 \h'8n'size_t n_cpl;
 \h'8n'size_t n_supers;
 \h'8n'const SodClass *const *supers;
 \h'8n'size_t n_cpl;


@@ -211,7 +222,7 @@ and not really to be recommended.
 .SS The SodObject class
 The
 .B SodObject
 .SS The SodObject class
 The
 .B SodObject

-class defines no slots or messages.
+class defines no slots.

 Because
 .B SodObject
 has no direct superclasses,
 Because
 .B SodObject
 has no direct superclasses,


@@ -219,8 +230,7 @@ there is only one chain,
 and no inherited slots or messages,
 so the single chain contains only a vtable pointer.
 .PP
 and no inherited slots or messages,
 so the single chain contains only a vtable pointer.
 .PP

-Since there are no messages,
-and
+Since

 .B SodClass
 also has only one chain,
 the vtable contains only the standard class pointer and offset-to-base
 .B SodClass
 also has only one chain,
 the vtable contains only the standard class pointer and offset-to-base


@@ -231,6 +241,79 @@ In an actual instance of
 the class pointer contains the address of
 .B SodObject__class
 and the offset is zero.
 the class pointer contains the address of
 .B SodObject__class
 and the offset is zero.

+.PP
+The
+.B init
+message is used to initialize a newly allocated instance.
+.PP
+This message uses a custom method combination
+which works like the standard method combination
+except that default behaviour
+specific to the receiver's direct class
+is invoked if no primary or around method overrides.
+This default behaviour may be invoked multiple times
+if some method calls on its
+.B next_method
+function more than once.
+.PP
+This default behaviour is to initialize the instance's slots
+using the defined slot initializers,
+and execute the initialization fragments.
+Each slot is initialized
+using the most specific applicable initializer,
+if any.
+Slots without an initializer
+are left uninitialized.
+.PP
+Slots are initialized and initialization fragments executed together,
+a superclass at a time:
+first, the superclass's slots are initialized (if any);
+then the superclass's initialization fragments (if any) are executed,
+starting with the least specific superclass first.
+Slots and initialization fragments defined by the same class
+are processed in the order in which they appear in the class definition.
+.PP
+There are no standard keyword arguments;
+methods on subclasses are free to
+introduce their own in the usual way.
+.PP
+It is usual to provide complex initialization behaviour as
+.B after
+methods.
+This ensures that slots have been initialized as necessary
+before the method executes.
+.PP
+The
+.B teardown
+message is used to tear down an instance which is no longer required.
+.PP
+The message returns an integer flag.
+A zero value means that the instance is safe to deallocate.
+A nonzero value means that the instance should not be deallocated,
+and that it is safe for the caller to simply forget about it.
+This simple protocol may be used, for example,
+to implement a reference-counting system.
+.PP
+This message uses a custom method combination
+which works like the standard method combination
+except that default behaviour is invoked if
+no primary or around method overrides.
+This default behaviour is to execute
+each superclass's teardown fragments,
+most specific first,
+and then return zero to indicate
+that the object is ready for deallocation.
+Teardown fragments defined by the same class
+are processed in the order in which they appear
+in the class definition.
+.PP
+It is usual to provide complex teardown behaviour as
+.B before
+methods.
+Logic to decide whether to allow deallocation
+is usually implemented as
+.B around
+methods.

 .
 .SS The SodClass class
 The
 .
 .SS The SodClass class
 The


@@ -252,6 +335,9 @@ A pointer to the class's nickname.
 .B size_t initsz;
 The size in bytes required to store an instance of the class.
 .TP
 .B size_t initsz;
 The size in bytes required to store an instance of the class.
 .TP

+.B size_t align;
+A sufficient alignment for the class's instance storage.
+.TP

 .BI "void *(*imprint)(void *" p );
 A pointer to a function:
 given a pointer
 .BI "void *(*imprint)(void *" p );
 A pointer to a function:
 given a pointer


@@ -266,20 +352,6 @@ but the slots are left untouched.
 The function returns its argument
 .IR p .
 .TP
 The function returns its argument
 .IR p .
 .TP

-.BI "void *(*init)(void *" p );
-A pointer to a function:
-given a pointer
-.I p
-to at least
-.I initsz
-bytes of appropriately aligned memory,
-initialize an instance of the class in it:
-all of the vtable and class pointers are initialized,
-as are slots for which initializers are defined.
-Other slots are left untouched.
-The function returns its argument
-.IR p .
-.TP

 .B size_t n_supers;
 The number of direct superclasses.
 (This is zero exactly in the case of
 .B size_t n_supers;
 The number of direct superclasses.
 (This is zero exactly in the case of


@@ -470,7 +542,7 @@ struct \fIC\fB__ilayout {
 \h'6n'} \fIc\fB;
 \h'4n'} \fIc\fB;
 \h'4n'\fR...\fB
 \h'6n'} \fIc\fB;
 \h'4n'} \fIc\fB;
 \h'4n'\fR...\fB

-\h'4n'struct \fIH\fB__ichain_\fIh\fB \fIh\fB;
+\h'4n'struct \fIA\fB__ichain_\fIh\fB \fIa\fB;

 \h'2n'} \fIh\fB;
 \h'2n'union \fIB\fB__ichainu_\fIi\fB \fIi\fB;
 \h'2n'\fR...\fB
 \h'2n'} \fIh\fB;
 \h'2n'union \fIB\fB__ichainu_\fIi\fB \fIi\fB;
 \h'2n'\fR...\fB


@@ -554,13 +626,9 @@ for each of
 superclasses
 .IR A
 in the same chain in some (unimportant) order.
 superclasses
 .IR A
 in the same chain in some (unimportant) order.

-A `pointer to
-.IR C '
-is always assumed
-(and, indeed, defined in C's type system)
-to be a pointer to the
-.B struct
-.IB C __ichain_ h \fR.
+The (somewhat obtuse) purpose of this union is to
+engage the `common initial sequence' rule of
+C99 (clause 6.5.2.3).

 .PP
 The
 .B ichain
 .PP
 The
 .B ichain


@@ -592,6 +660,14 @@ then the last member is
 .IB C __islots 
 .IB c ;
 .PP
 .IB C __islots 
 .IB c ;
 .PP

+A `pointer to
+.IR C '
+is always assumed
+(and, indeed, defined in C's type system)
+to be a pointer to the
+.B struct
+.IB C __ichain_ h \fR.
+.PP

 Finally, the
 .B islots
 structure simply contains one member for each slot defined by
 Finally, the
 .B islots
 structure simply contains one member for each slot defined by


@@ -616,7 +692,7 @@ will have
 .I different
 structures.
 .PP
 .I different
 structures.
 .PP

-The instance layout split neatly into disjoint chains.
+The instance layout splits neatly into disjoint chains.

 This is necessary because
 each
 .B ichain
 This is necessary because
 each
 .B ichain


@@ -629,7 +705,7 @@ it doesn't matter that there are
 multiple method entry pointers
 for the same effective method
 as long as they all work correctly.
 multiple method entry pointers
 for the same effective method
 as long as they all work correctly.

-Indeed, it's essential that they do,
+Indeed, it's essential that there are multiple entry pointers,

 because each chain's method entry function
 will need to apply a different offset to the receiver pointer
 before invoking the effective method.
 because each chain's method entry function
 will need to apply a different offset to the receiver pointer
 before invoking the effective method.


@@ -663,6 +739,12 @@ extern const union \fIC\fB__vtu_\fIh\fB \fIC\fB__vtable_\fIh\fB;
 .ft P
 .fi
 .PP
 .ft P
 .fi
 .PP

+In the following,
+let
+.I M
+be the metaclass of
+.IR C .
+.PP

 The outer layer is a
 .B union
 .IB C __vtu_ h
 The outer layer is a
 .B union
 .IB C __vtu_ h


@@ -787,8 +869,9 @@ be the most specific superclass of
 .I M
 in the same chain as
 .IR J .
 .I M
 in the same chain as
 .IR J .

-Then, if there is currently no class pointer of type
-.IR Q ,
+If there is currently no class pointer
+for the chain headed by
+.IR J ,

 then add a member
 .RS
 .IP
 then add a member
 .RS
 .IP


@@ -801,7 +884,13 @@ pointing to the appropriate
 .B islots
 structure within
 .IR M 's
 .B islots
 structure within
 .IR M 's

-class object.
+class object,
+where
+.I Q
+is the most specific superclass of
+.I M
+in the same chain as
+.IR J .

 .RE
 .hP \*o
 Examine the superclass chains of
 .RE
 .hP \*o
 Examine the superclass chains of


@@ -892,6 +981,27 @@ defined as
 .IB an , 
 .B ...);
 .PP
 .IB an , 
 .B ...);
 .PP

+or a standard message which takes keyword arguments,
+defined as
+.IP
+.I tr
+.IB m ( \c
+.I t1
+.IB a1 ,
+.RB ... ,
+.I tn
+.IB an ?\&
+.IR tn +1
+.IR kn +1
+.RB [ =
+.IR dn +1] \c
+.B ,
+.I tm
+.I km
+.RB [ =
+.IR dm ] \c
+);
+.PP

 two entry points are defined:
 the usual `main' entry point
 which accepts a variable number of
 two entry points are defined:
 the usual `main' entry point
 which accepts a variable number of


@@ -899,7 +1009,8 @@ arguments,
 and a `valist' entry point
 which accepts an argument of type
 .B va_list
 and a `valist' entry point
 which accepts an argument of type
 .B va_list

-in place of the variable portion of the argument list.
+in place of the variable portion of the argument list
+or keywords.

 .IP
 .I tr
 .BI (* m )( \c
 .IP
 .I tr
 .BI (* m )( \c


@@ -949,6 +1060,7 @@ somewhat less ugly.
 If
 .I m
 takes a variable number of arguments,
 If
 .I m
 takes a variable number of arguments,

+or keyword arguments,

 the macro is more complicated
 and is only available in compilers advertising C99 support,
 but the effect is the same.
 the macro is more complicated
 and is only available in compilers advertising C99 support,
 but the effect is the same.


@@ -1002,6 +1114,12 @@ Finally, the class object is defined as
 .B #define
 .IB C __class
 .BI (& C __classobj. j . r )
 .B #define
 .IB C __class
 .BI (& C __classobj. j . r )

+.br
+.B #define
+.IB C __cls_ k
+.BI (& C __classobj. k . n )
+.br
+\&...

 .PP
 The exported symbol
 .IB C __classobj
 .PP
 The exported symbol
 .IB C __classobj


@@ -1020,7 +1138,32 @@ is the root metaclass of
 i.e., the metaclass of the least specific superclass of
 .IR C ;
 usually this is
 i.e., the metaclass of the least specific superclass of
 .IR C ;
 usually this is

-.BR "const SodClass *" .
+.BR "const SodClass\ *" .
+For each chain of
+.IR C 's
+metaclass, a macro
+.IB C __cls_ k
+is defined, usable as a pointer of type
+.B const
+.IR N \ \c
+.BR * ,
+where
+.I K
+and
+.I N
+are the chain's head and tail classes
+(i.e., the least- and most-specific classes in the chain)
+respectively;
+this macro is
+.I omitted
+if
+.IR N "\ =\ " R ,
+i.e., in the common case where
+.IR C 's
+metaclass is precisely the root metaclass,
+since the existing
+.IB C __class
+macro is already sufficient.

 .
 .\"--------------------------------------------------------------------------
 .SH SEE ALSO
 .
 .\"--------------------------------------------------------------------------
 .SH SEE ALSO