/* Copyright (C) 1995, 1996, 1998, 2000, 2001, 2003, 2006, 2008, 2009, 2010, * 2011, 2012, 2014 Free Software Foundation, Inc. * * This library is free software; you can redistribute it and/or * modify it under the terms of the GNU Lesser General Public License * as published by the Free Software Foundation; either version 3 of * the License, or (at your option) any later version. * * This library 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 * Lesser General Public License for more details. * * You should have received a copy of the GNU Lesser General Public * License along with this library; if not, write to the Free Software * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA * 02110-1301 USA */ #ifdef HAVE_CONFIG_H # include #endif #include #include "libguile/_scm.h" #include "libguile/vectors.h" #include "libguile/hashtab.h" #include "libguile/validate.h" #include "libguile/weaks.h" #include "libguile/bdw-gc.h" #include /* Weak pairs for use in weak alist vectors and weak hash tables. We have weal-car pairs, weak-cdr pairs, and doubly weak pairs. In weak pairs, the weak component(s) are not scanned for pointers and are registered as disapperaring links; therefore, the weak component may be set to NULL by the garbage collector when no other reference to that word exist. Thus, users should only access weak pairs via the `SCM_WEAK_PAIR_C[AD]R ()' macros. See also `scm_fixup_weak_alist ()' in `hashtab.c'. */ /* Type descriptors for weak-c[ad]r pairs. */ static GC_descr wcar_pair_descr, wcdr_pair_descr; SCM scm_weak_car_pair (SCM car, SCM cdr) { scm_t_cell *cell; cell = (scm_t_cell *)GC_malloc_explicitly_typed (sizeof (*cell), wcar_pair_descr); cell->word_0 = car; cell->word_1 = cdr; if (SCM_NIMP (car)) /* Weak car cells make sense iff the car is non-immediate. */ SCM_I_REGISTER_DISAPPEARING_LINK ((void **) &cell->word_0, SCM2PTR (car)); return (SCM_PACK (cell)); } SCM scm_weak_cdr_pair (SCM car, SCM cdr) { scm_t_cell *cell; cell = (scm_t_cell *)GC_malloc_explicitly_typed (sizeof (*cell), wcdr_pair_descr); cell->word_0 = car; cell->word_1 = cdr; if (SCM_NIMP (cdr)) /* Weak cdr cells make sense iff the cdr is non-immediate. */ SCM_I_REGISTER_DISAPPEARING_LINK ((void **) &cell->word_1, SCM2PTR (cdr)); return (SCM_PACK (cell)); } SCM scm_doubly_weak_pair (SCM car, SCM cdr) { /* Doubly weak cells shall not be scanned at all for pointers. */ scm_t_cell *cell = (scm_t_cell *)scm_gc_malloc_pointerless (sizeof (*cell), "weak cell"); cell->word_0 = car; cell->word_1 = cdr; if (SCM_NIMP (car)) SCM_I_REGISTER_DISAPPEARING_LINK ((void **) &cell->word_0, SCM2PTR (car)); if (SCM_NIMP (cdr)) SCM_I_REGISTER_DISAPPEARING_LINK ((void **) &cell->word_1, SCM2PTR (cdr)); return (SCM_PACK (cell)); } /* 1. The current hash table implementation in hashtab.c uses weak alist * vectors (formerly called weak hash tables) internally. * * 2. All hash table operations still work on alist vectors. * * 3. The weak vector and alist vector Scheme API is accessed through * the module (ice-9 weak-vector). */ /* {Weak Vectors} */ #define SCM_VALIDATE_WEAK_VECTOR(pos, var) \ SCM_I_MAKE_VALIDATE_MSG2 (pos, var, SCM_I_WVECTP, "weak vector") SCM_DEFINE (scm_make_weak_vector, "make-weak-vector", 1, 1, 0, (SCM size, SCM fill), "Return a weak vector with @var{size} elements. If the optional\n" "argument @var{fill} is given, all entries in the vector will be\n" "set to @var{fill}. The default value for @var{fill} is the\n" "empty list.") #define FUNC_NAME s_scm_make_weak_vector { return scm_i_make_weak_vector (0, size, fill); } #undef FUNC_NAME SCM_REGISTER_PROC(s_list_to_weak_vector, "list->weak-vector", 1, 0, 0, scm_weak_vector); SCM_DEFINE (scm_weak_vector, "weak-vector", 0, 0, 1, (SCM l), "@deffnx {Scheme Procedure} list->weak-vector l\n" "Construct a weak vector from a list: @code{weak-vector} uses\n" "the list of its arguments while @code{list->weak-vector} uses\n" "its only argument @var{l} (a list) to construct a weak vector\n" "the same way @code{list->vector} would.") #define FUNC_NAME s_scm_weak_vector { return scm_i_make_weak_vector_from_list (0, l); } #undef FUNC_NAME SCM_DEFINE (scm_weak_vector_p, "weak-vector?", 1, 0, 0, (SCM obj), "Return @code{#t} if @var{obj} is a weak vector. Note that all\n" "weak hashes are also weak vectors.") #define FUNC_NAME s_scm_weak_vector_p { return scm_from_bool (scm_is_weak_vector (obj)); } #undef FUNC_NAME int scm_is_weak_vector (SCM obj) { return SCM_I_WVECTP (obj) && !SCM_IS_WHVEC (obj); } SCM_DEFINE (scm_weak_vector_length, "weak-vector-length", 1, 0, 0, (SCM wvect), "Returns the number of elements in @var{wvect} as an exact integer.") #define FUNC_NAME s_scm_weak_vector_length { return scm_from_size_t (scm_c_weak_vector_length (wvect)); } #undef FUNC_NAME size_t scm_c_weak_vector_length (SCM wvect) #define FUNC_NAME s_scm_weak_vector_length { SCM_VALIDATE_WEAK_VECTOR (1, wvect); return SCM_I_VECTOR_LENGTH (wvect); } #undef FUNC_NAME SCM_DEFINE (scm_weak_vector_ref, "weak-vector-ref", 2, 0, 0, (SCM wvect, SCM k), "Like @code{vector-ref}, but for weak vectors.") #define FUNC_NAME s_scm_weak_vector_ref { return scm_c_weak_vector_ref (wvect, scm_to_size_t (k)); } #undef FUNC_NAME SCM scm_c_weak_vector_ref (SCM wvect, size_t k) #define FUNC_NAME s_scm_weak_vector_ref { SCM elt; SCM_VALIDATE_WEAK_VECTOR (1, wvect); if (k >= SCM_I_VECTOR_LENGTH (wvect)) scm_out_of_range ("weak-vector-ref", scm_from_size_t (k)); elt = (SCM_I_VECTOR_ELTS(wvect))[k]; if (SCM_UNPACK (elt) == 0) /* ELT was a weak pointer and got nullified by the GC. */ return SCM_BOOL_F; return elt; } #undef FUNC_NAME SCM_DEFINE (scm_weak_vector_set_x, "weak-vector-set!", 3, 0, 0, (SCM wvect, SCM k, SCM elt), "Like @code{vector-set!}, but for weak vectors.") #define FUNC_NAME s_scm_weak_vector_set_x { scm_c_weak_vector_set_x (wvect, scm_to_size_t (k), elt); return SCM_UNSPECIFIED; } #undef FUNC_NAME void scm_c_weak_vector_set_x (SCM wvect, size_t k, SCM elt) #define FUNC_NAME s_scm_weak_vector_set_x { SCM *loc; SCM_VALIDATE_WEAK_VECTOR (1, wvect); if (k >= SCM_I_VECTOR_LENGTH (wvect)) scm_out_of_range ("weak-vector-set!", scm_from_size_t (k)); loc = & SCM_I_VECTOR_WELTS (wvect)[k]; *loc = elt; /* Make it a weak pointer. */ SCM_I_REGISTER_DISAPPEARING_LINK ((void **) loc, SCM2PTR (elt)); } #undef FUNC_NAME /* Weak alist vectors, i.e., vectors of alists. The alist vector themselves are _not_ weak. The `car' (or `cdr', or both) of the pairs within it are weak. See `hashtab.c' for details. */ /* FIXME: We used to have two implementations of weak hash tables: the one in here and the one in `hashtab.c'. The difference is that weak alist vectors could be used as vectors while (weak) hash tables can't. We need to unify that. */ SCM_DEFINE (scm_make_weak_key_alist_vector, "make-weak-key-alist-vector", 0, 1, 0, (SCM size), "@deffnx {Scheme Procedure} make-weak-value-alist-vector size\n" "@deffnx {Scheme Procedure} make-doubly-weak-alist-vector size\n" "Return a weak hash table with @var{size} buckets. As with any\n" "hash table, choosing a good size for the table requires some\n" "caution.\n" "\n" "You can modify weak hash tables in exactly the same way you\n" "would modify regular hash tables. (@pxref{Hash Tables})") #define FUNC_NAME s_scm_make_weak_key_alist_vector { return scm_make_weak_key_hash_table (size); } #undef FUNC_NAME SCM_DEFINE (scm_make_weak_value_alist_vector, "make-weak-value-alist-vector", 0, 1, 0, (SCM size), "Return a hash table with weak values with @var{size} buckets.\n" "(@pxref{Hash Tables})") #define FUNC_NAME s_scm_make_weak_value_alist_vector { return scm_make_weak_value_hash_table (size); } #undef FUNC_NAME SCM_DEFINE (scm_make_doubly_weak_alist_vector, "make-doubly-weak-alist-vector", 1, 0, 0, (SCM size), "Return a hash table with weak keys and values with @var{size}\n" "buckets. (@pxref{Hash Tables})") #define FUNC_NAME s_scm_make_doubly_weak_alist_vector { return scm_make_doubly_weak_hash_table (size); } #undef FUNC_NAME SCM_DEFINE (scm_weak_key_alist_vector_p, "weak-key-alist-vector?", 1, 0, 0, (SCM obj), "@deffnx {Scheme Procedure} weak-value-alist-vector? obj\n" "@deffnx {Scheme Procedure} doubly-weak-alist-vector? obj\n" "Return @code{#t} if @var{obj} is the specified weak hash\n" "table. Note that a doubly weak hash table is neither a weak key\n" "nor a weak value hash table.") #define FUNC_NAME s_scm_weak_key_alist_vector_p { return scm_from_bool (SCM_I_WVECTP (obj) && SCM_IS_WHVEC (obj)); } #undef FUNC_NAME SCM_DEFINE (scm_weak_value_alist_vector_p, "weak-value-alist-vector?", 1, 0, 0, (SCM obj), "Return @code{#t} if @var{obj} is a weak value hash table.") #define FUNC_NAME s_scm_weak_value_alist_vector_p { return scm_from_bool (SCM_I_WVECTP (obj) && SCM_IS_WHVEC_V (obj)); } #undef FUNC_NAME SCM_DEFINE (scm_doubly_weak_alist_vector_p, "doubly-weak-alist-vector?", 1, 0, 0, (SCM obj), "Return @code{#t} if @var{obj} is a doubly weak hash table.") #define FUNC_NAME s_scm_doubly_weak_alist_vector_p { return scm_from_bool (SCM_I_WVECTP (obj) && SCM_IS_WHVEC_B (obj)); } #undef FUNC_NAME SCM scm_init_weaks_builtins () { #include "libguile/weaks.x" return SCM_UNSPECIFIED; } void scm_weaks_prehistory () { /* Initialize weak pairs. */ GC_word wcar_pair_bitmap[GC_BITMAP_SIZE (scm_t_cell)] = { 0 }; GC_word wcdr_pair_bitmap[GC_BITMAP_SIZE (scm_t_cell)] = { 0 }; /* In a weak-car pair, only the second word must be scanned for pointers. */ GC_set_bit (wcar_pair_bitmap, GC_WORD_OFFSET (scm_t_cell, word_1)); wcar_pair_descr = GC_make_descriptor (wcar_pair_bitmap, GC_WORD_LEN (scm_t_cell)); /* Conversely, in a weak-cdr pair, only the first word must be scanned for pointers. */ GC_set_bit (wcdr_pair_bitmap, GC_WORD_OFFSET (scm_t_cell, word_0)); wcdr_pair_descr = GC_make_descriptor (wcdr_pair_bitmap, GC_WORD_LEN (scm_t_cell)); } void scm_init_weaks () { scm_c_define_gsubr ("%init-weaks-builtins", 0, 0, 0, scm_init_weaks_builtins); } /* Local Variables: c-file-style: "gnu" End: */