| 1 | @c -*-texinfo-*- |
| 2 | @c This is part of the GNU Guile Reference Manual. |
| 3 | @c Copyright (C) 1996, 1997, 2000, 2001, 2002, 2003, 2004 |
| 4 | @c Free Software Foundation, Inc. |
| 5 | @c See the file guile.texi for copying conditions. |
| 6 | |
| 7 | @page |
| 8 | @node Smobs |
| 9 | @section Smobs |
| 10 | |
| 11 | This chapter contains reference information related to defining and |
| 12 | working with smobs. See @ref{Defining New Types (Smobs)} for a |
| 13 | tutorial-like introduction to smobs. |
| 14 | |
| 15 | @deftypefun scm_t_bits scm_make_smob_type (const char *name, size_t size) |
| 16 | This function adds a new smob type, named @var{name}, with instance size |
| 17 | @var{size}, to the system. The return value is a tag that is used in |
| 18 | creating instances of the type. |
| 19 | |
| 20 | If @var{size} is 0, the default @emph{free} function will do nothing. |
| 21 | |
| 22 | If @var{size} is not 0, the default @emph{free} function will |
| 23 | deallocate the memory block pointed to by @code{SCM_SMOB_DATA} with |
| 24 | @code{scm_gc_free}. The @var{WHAT} parameter in the call to |
| 25 | @code{scm_gc_free} will be @var{NAME}. |
| 26 | |
| 27 | Default values are provided for the @emph{mark}, @emph{free}, |
| 28 | @emph{print}, and @emph{equalp} functions, as described in |
| 29 | @ref{Defining New Types (Smobs)}. If you want to customize any of |
| 30 | these functions, the call to @code{scm_make_smob_type} should be |
| 31 | immediately followed by calls to one or several of |
| 32 | @code{scm_set_smob_mark}, @code{scm_set_smob_free}, |
| 33 | @code{scm_set_smob_print}, and/or @code{scm_set_smob_equalp}. |
| 34 | @end deftypefun |
| 35 | |
| 36 | @deftypefn {C Function} void scm_set_smob_mark (scm_t_bits tc, SCM (*mark) (SCM obj)) |
| 37 | This function sets the smob marking procedure for the smob type specified by |
| 38 | the tag @var{tc}. @var{tc} is the tag returned by @code{scm_make_smob_type}. |
| 39 | |
| 40 | The @var{mark} procedure must cause @code{scm_gc_mark} to be called |
| 41 | for every @code{SCM} value that is directly referenced by the smob |
| 42 | instance @var{obj}. One of these @code{SCM} values can be returned |
| 43 | from the procedure and Guile will call @code{scm_gc_mark} for it. |
| 44 | This can be used to avoid deep recursions for smob instances that form |
| 45 | a list. |
| 46 | |
| 47 | It must not call any libguile function or macro except |
| 48 | @code{scm_gc_mark}, @code{SCM_SMOB_FLAGS}, @code{SCM_SMOB_DATA}, |
| 49 | @code{SCM_SMOB_DATA_2}, and @code{SCM_SMOB_DATA_3}. |
| 50 | @end deftypefn |
| 51 | |
| 52 | @deftypefn {C Function} void scm_set_smob_free (scm_t_bits tc, size_t (*free) (SCM obj)) |
| 53 | This function sets the smob freeing procedure for the smob type |
| 54 | specified by the tag @var{tc}. @var{tc} is the tag returned by |
| 55 | @code{scm_make_smob_type}. |
| 56 | |
| 57 | The @var{free} procedure must deallocate all resources that are |
| 58 | directly associated with the smob instance @var{OBJ}. It must assume |
| 59 | that all @code{SCM} values that it references have already been freed |
| 60 | and are thus invalid. |
| 61 | |
| 62 | It must also not call any libguile function or macro except |
| 63 | @code{scm_gc_free}, @code{SCM_SMOB_FLAGS}, @code{SCM_SMOB_DATA}, |
| 64 | @code{SCM_SMOB_DATA_2}, and @code{SCM_SMOB_DATA_3}. |
| 65 | |
| 66 | The @var{free} procedure must return 0. |
| 67 | @end deftypefn |
| 68 | |
| 69 | @deftypefn {C Function} void scm_set_smob_print (scm_t_bits tc, int (*print) (SCM obj, SCM port, scm_print_state* pstate)) |
| 70 | This function sets the smob printing procedure for the smob type |
| 71 | specified by the tag @var{tc}. @var{tc} is the tag returned by |
| 72 | @code{scm_make_smob_type}. |
| 73 | |
| 74 | The @var{print} procedure should output a textual representation of |
| 75 | the smob instance @var{obj} to @var{port}, using information in |
| 76 | @var{pstate}. |
| 77 | |
| 78 | The textual representation should be of the form @code{#<name ...>}. |
| 79 | This ensures that @code{read} will not interpret it as some other |
| 80 | Scheme value. |
| 81 | |
| 82 | It is often best to ignore @var{pstate} and just print to @var{port} |
| 83 | with @code{scm_display}, @code{scm_write}, @code{scm_simple_format}, |
| 84 | and @code{scm_puts}. |
| 85 | @end deftypefn |
| 86 | |
| 87 | @deftypefn {C Function} void scm_set_smob_equalp (scm_t_bits tc, SCM (*equalp) (SCM obj1, SCM obj1)) |
| 88 | This function sets the smob equality-testing predicate for the smob |
| 89 | type specified by the tag @var{tc}. @var{tc} is the tag returned by |
| 90 | @code{scm_make_smob_type}. |
| 91 | |
| 92 | The @var{equalp} procedure should return @code{SCM_BOOL_T} when |
| 93 | @var{obj1} is @code{equal?} to @var{obj2}. Else it should return |
| 94 | @var{SCM_BOOL_F}. Both @var{obj1} and @var{obj2} are instances of the |
| 95 | smob type @var{tc}. |
| 96 | @end deftypefn |
| 97 | |
| 98 | @deftypefn {C Function} void scm_assert_smob_type (scm_t_bits tag, SCM val) |
| 99 | When @var{val} is a smob of the type indicated by @var{tag}, do nothing. |
| 100 | Else, signal an error. |
| 101 | @end deftypefn |
| 102 | |
| 103 | @deftypefn {C Macro} int SCM_SMOB_PREDICATE (scm_t_bits tag, SCM exp) |
| 104 | Return true iff @var{exp} is a smob instance of the type indicated by |
| 105 | @var{tag}. The expression @var{exp} can be evaluated more than once, |
| 106 | so it shouldn't contain any side effects. |
| 107 | @end deftypefn |
| 108 | |
| 109 | @deftypefn {C Macro} void SCM_NEWSMOB (SCM value, scm_t_bits tag, void *data) |
| 110 | @deftypefnx {C Macro} void SCM_NEWSMOB2 (SCM value, scm_t_bits tag, void *data, void *data2) |
| 111 | @deftypefnx {C Macro} void SCM_NEWSMOB3 (SCM value, scm_t_bits tag, void *data, void *data2, void *data3) |
| 112 | Make @var{value} contain a smob instance of the type with tag |
| 113 | @var{tag} and smob data @var{data}, @var{data2}, and @var{data3}, as |
| 114 | appropriate. |
| 115 | |
| 116 | The @var{tag} is what has been returned by @code{scm_make_smob_type}. |
| 117 | The initial values @var{data}, @var{data2}, and @var{data3} are of |
| 118 | type @code{scm_t_bits}; when you want to use them for @code{SCM} |
| 119 | values, these values need to be converted to a @code{scm_t_bits} first |
| 120 | by using @code{SCM_UNPACK}. |
| 121 | |
| 122 | The flags of the smob instance start out as zero. |
| 123 | @end deftypefn |
| 124 | |
| 125 | Since it is often the case (e.g., in smob constructors) that you will |
| 126 | create a smob instance and return it, there is also a slightly specialized |
| 127 | macro for this situation: |
| 128 | |
| 129 | @deftypefn {C Macro} {} SCM_RETURN_NEWSMOB (scm_t_bits tag, void *data) |
| 130 | @deftypefnx {C Macro} {} SCM_RETURN_NEWSMOB2 (scm_t_bits tag, void *data1, void *data2) |
| 131 | @deftypefnx {C Macro} {} SCM_RETURN_NEWSMOB3 (scm_t_bits tag, void *data1, void *data2, void *data3) |
| 132 | This macro expands to a block of code that creates a smob instance of |
| 133 | the type with tag @var{tag} and smob data @var{data}, @var{data2}, and |
| 134 | @var{data3}, as with @code{SCM_NEWSMOB}, etc., and causes the |
| 135 | surrounding function to return that @code{SCM} value. It should be |
| 136 | the last piece of code in a block. |
| 137 | @end deftypefn |
| 138 | |
| 139 | @deftypefn {C Macro} scm_t_bits SCM_SMOB_FLAGS (SCM obj) |
| 140 | Return the 16 extra bits of the smob @var{obj}. No meaning is |
| 141 | predefined for these bits, you can use them freely. |
| 142 | @end deftypefn |
| 143 | |
| 144 | @deftypefn {C Macro} scm_t_bits SCM_SET_SMOB_FLAGS (SCM obj, scm_t_bits flags) |
| 145 | Set the 16 extra bits of the smob @var{obj} to @var{flags}. No |
| 146 | meaning is predefined for these bits, you can use them freely. |
| 147 | @end deftypefn |
| 148 | |
| 149 | @deftypefn {C Macro} scm_t_bits SCM_SMOB_DATA (SCM obj) |
| 150 | @deftypefnx {C Macro} scm_t_bits SCM_SMOB_DATA_2 (SCM obj) |
| 151 | @deftypefnx {C Macro} scm_t_bits SCM_SMOB_DATA_3 (SCM obj) |
| 152 | Return the first (second, third) immediate word of the smob @var{obj} |
| 153 | as a @code{scm_t_bits} value. When the word contains a @code{SCM} |
| 154 | value, use @code{SCM_SMOB_OBJECT} (etc.) instead. |
| 155 | @end deftypefn |
| 156 | |
| 157 | @deftypefn {C Macro} void SCM_SET_SMOB_DATA (SCM obj, scm_t_bits val) |
| 158 | @deftypefnx {C Macro} void SCM_SET_SMOB_DATA_2 (SCM obj, scm_t_bits val) |
| 159 | @deftypefnx {C Macro} void SCM_SET_SMOB_DATA_3 (SCM obj, scm_t_bits val) |
| 160 | Set the first (second, third) immediate word of the smob @var{obj} to |
| 161 | @var{val}. When the word should be set to a @code{SCM} value, use |
| 162 | @code{SCM_SMOB_SET_OBJECT} (etc.) instead. |
| 163 | @end deftypefn |
| 164 | |
| 165 | @deftypefn {C Macro} SCM SCM_SMOB_OBJECT (SCM obj) |
| 166 | @deftypefnx {C Macro} SCM SCM_SMOB_OBJECT_2 (SCM obj) |
| 167 | @deftypefnx {C Macro} SCM SCM_SMOB_OBJECT_3 (SCM obj) |
| 168 | Return the first (second, third) immediate word of the smob @var{obj} |
| 169 | as a @code{SCM} value. When the word contains a @code{scm_t_bits} |
| 170 | value, use @code{SCM_SMOB_DATA} (etc.) instead. |
| 171 | @end deftypefn |
| 172 | |
| 173 | @deftypefn {C Macro} void SCM_SET_SMOB_OBJECT (SCM obj, SCM val) |
| 174 | @deftypefnx {C Macro} void SCM_SET_SMOB_OBJECT_2 (SCM obj, SCM val) |
| 175 | @deftypefnx {C Macro} void SCM_SET_SMOB_OBJECT_3 (SCM obj, SCM val) |
| 176 | Set the first (second, third) immediate word of the smob @var{obj} to |
| 177 | @var{val}. When the word should be set to a @code{scm_t_bits} value, use |
| 178 | @code{SCM_SMOB_SET_DATA} (etc.) instead. |
| 179 | @end deftypefn |
| 180 | |
| 181 | @deftypefn {C Macro} {SCM *} SCM_SMOB_OBJECT_LOC (SCM obj) |
| 182 | @deftypefnx {C Macro} {SCM *} SCM_SMOB_OBJECT_2_LOC (SCM obj) |
| 183 | @deftypefnx {C Macro} {SCM *} SCM_SMOB_OBJECT_3_LOC (SCM obj) |
| 184 | Return a pointer to the first (second, third) immediate word of the |
| 185 | smob @var{obj}. Note that this is a pointer to @code{SCM}. If you |
| 186 | need to work with @code{scm_t_bits} values, use @code{SCM_PACK} and |
| 187 | @code{SCM_UNPACK}, as appropriate. |
| 188 | @end deftypefn |
| 189 | |
| 190 | @deftypefun SCM scm_markcdr (SCM @var{x}) |
| 191 | Mark the references in the smob @var{x}, assuming that @var{x}'s first |
| 192 | data word contains an ordinary Scheme object, and @var{x} refers to no |
| 193 | other objects. This function simply returns @var{x}'s first data word. |
| 194 | @end deftypefun |
| 195 | |
| 196 | @c Local Variables: |
| 197 | @c TeX-master: "guile.texi" |
| 198 | @c End: |