--- /dev/null
+/* Copyright (C) 1995,1996,1998,2000,2001,2004, 2006, 2008 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 2.1 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
+ */
+
+
+\f
+#ifdef HAVE_CONFIG_H
+# include <config.h>
+#endif
+
+#include "libguile/_scm.h"
+
+#include <string.h>
+#include <stdio.h>
+
+#include "libguile/async.h"
+#include "libguile/debug.h"
+#include "libguile/root.h"
+#include "libguile/stackchk.h"
+#include "libguile/smob.h"
+#include "libguile/ports.h"
+#include "libguile/dynwind.h"
+#include "libguile/values.h"
+#include "libguile/eval.h"
+
+#include "libguile/validate.h"
+#include "libguile/continuations.h"
+
+\f
+
+/* {Continuations}
+ */
+
+scm_t_bits scm_tc16_continuation;
+
+static SCM
+continuation_mark (SCM obj)
+{
+ scm_t_contregs *continuation = SCM_CONTREGS (obj);
+
+ scm_gc_mark (continuation->root);
+ scm_gc_mark (continuation->throw_value);
+ scm_mark_locations (continuation->stack, continuation->num_stack_items);
+#ifdef __ia64__
+ if (continuation->backing_store)
+ scm_mark_locations (continuation->backing_store,
+ continuation->backing_store_size /
+ sizeof (SCM_STACKITEM));
+#endif /* __ia64__ */
+ return continuation->dynenv;
+}
+
+static size_t
+continuation_free (SCM obj)
+{
+ scm_t_contregs *continuation = SCM_CONTREGS (obj);
+ /* stack array size is 1 if num_stack_items is 0. */
+ size_t extra_items = (continuation->num_stack_items > 0)
+ ? (continuation->num_stack_items - 1)
+ : 0;
+ size_t bytes_free = sizeof (scm_t_contregs)
+ + extra_items * sizeof (SCM_STACKITEM);
+
+#ifdef __ia64__
+ scm_gc_free (continuation->backing_store, continuation->backing_store_size,
+ "continuation backing store");
+#endif /* __ia64__ */
+ scm_gc_free (continuation, bytes_free, "continuation");
+ return 0;
+}
+
+static int
+continuation_print (SCM obj, SCM port, scm_print_state *state SCM_UNUSED)
+{
+ scm_t_contregs *continuation = SCM_CONTREGS (obj);
+
+ scm_puts ("#<continuation ", port);
+ scm_intprint (continuation->num_stack_items, 10, port);
+ scm_puts (" @ ", port);
+ scm_uintprint (SCM_CELL_WORD_1 (obj), 16, port);
+ scm_putc ('>', port);
+ return 1;
+}
+
+/* this may return more than once: the first time with the escape
+ procedure, then subsequently with the value to be passed to the
+ continuation. */
+#define FUNC_NAME "scm_make_continuation"
+SCM
+scm_make_continuation (int *first)
+{
+ scm_i_thread *thread = SCM_I_CURRENT_THREAD;
+ SCM cont;
+ scm_t_contregs *continuation;
+ long stack_size;
+ SCM_STACKITEM * src;
+
+ SCM_FLUSH_REGISTER_WINDOWS;
+ stack_size = scm_stack_size (thread->continuation_base);
+ continuation = scm_gc_malloc (sizeof (scm_t_contregs)
+ + (stack_size - 1) * sizeof (SCM_STACKITEM),
+ "continuation");
+ continuation->num_stack_items = stack_size;
+ continuation->dynenv = scm_i_dynwinds ();
+ continuation->throw_value = SCM_EOL;
+ continuation->root = thread->continuation_root;
+ continuation->dframe = scm_i_last_debug_frame ();
+ src = thread->continuation_base;
+ SCM_NEWSMOB (cont, scm_tc16_continuation, continuation);
+
+#if ! SCM_STACK_GROWS_UP
+ src -= stack_size;
+#endif
+ continuation->offset = continuation->stack - src;
+ memcpy (continuation->stack, src, sizeof (SCM_STACKITEM) * stack_size);
+
+ *first = !SCM_I_SETJMP (continuation->jmpbuf);
+ if (*first)
+ {
+#ifdef __ia64__
+ continuation->backing_store_size =
+ (char *) scm_ia64_ar_bsp(&continuation->jmpbuf.ctx)
+ -
+ (char *) thread->register_backing_store_base;
+ continuation->backing_store = NULL;
+ continuation->backing_store =
+ scm_gc_malloc (continuation->backing_store_size,
+ "continuation backing store");
+ memcpy (continuation->backing_store,
+ (void *) thread->register_backing_store_base,
+ continuation->backing_store_size);
+#endif /* __ia64__ */
+ return cont;
+ }
+ else
+ {
+ SCM ret = continuation->throw_value;
+ continuation->throw_value = SCM_BOOL_F;
+ return ret;
+ }
+}
+#undef FUNC_NAME
+
+
+/* Invoking a continuation proceeds as follows:
+ *
+ * - the stack is made large enough for the called continuation
+ * - the old windchain is unwound down to the branching point
+ * - the continuation stack is copied into place
+ * - the windchain is rewound up to the continuation's context
+ * - the continuation is invoked via longjmp (or setcontext)
+ *
+ * This order is important so that unwind and rewind handlers are run
+ * with their correct stack.
+ */
+
+static void scm_dynthrow (SCM, SCM);
+
+/* Grow the stack by a fixed amount to provide space to copy in the
+ * continuation. Possibly this function has to be called several times
+ * recursively before enough space is available. Make sure the compiler does
+ * not optimize the growth array away by storing it's address into a global
+ * variable.
+ */
+
+scm_t_bits scm_i_dummy;
+
+static void
+grow_stack (SCM cont, SCM val)
+{
+ scm_t_bits growth[100];
+
+ scm_i_dummy = (scm_t_bits) growth;
+ scm_dynthrow (cont, val);
+}
+
+
+/* Copy the continuation stack into the current stack. Calling functions from
+ * within this function is safe, since only stack frames below this function's
+ * own frame are overwritten. Thus, memcpy can be used for best performance.
+ */
+
+typedef struct {
+ scm_t_contregs *continuation;
+ SCM_STACKITEM *dst;
+} copy_stack_data;
+
+static void
+copy_stack (void *data)
+{
+ copy_stack_data *d = (copy_stack_data *)data;
+ memcpy (d->dst, d->continuation->stack,
+ sizeof (SCM_STACKITEM) * d->continuation->num_stack_items);
+#ifdef __ia64__
+ SCM_I_CURRENT_THREAD->pending_rbs_continuation = d->continuation;
+#endif
+}
+
+static void
+copy_stack_and_call (scm_t_contregs *continuation, SCM val,
+ SCM_STACKITEM * dst)
+{
+ long delta;
+ copy_stack_data data;
+
+ delta = scm_ilength (scm_i_dynwinds ()) - scm_ilength (continuation->dynenv);
+ data.continuation = continuation;
+ data.dst = dst;
+ scm_i_dowinds (continuation->dynenv, delta, copy_stack, &data);
+
+ scm_i_set_last_debug_frame (continuation->dframe);
+
+ continuation->throw_value = val;
+ SCM_I_LONGJMP (continuation->jmpbuf, 1);
+}
+
+#ifdef __ia64__
+void
+scm_ia64_longjmp (scm_i_jmp_buf *JB, int VAL)
+{
+ scm_i_thread *t = SCM_I_CURRENT_THREAD;
+
+ if (t->pending_rbs_continuation)
+ {
+ memcpy (t->register_backing_store_base,
+ t->pending_rbs_continuation->backing_store,
+ t->pending_rbs_continuation->backing_store_size);
+ t->pending_rbs_continuation = NULL;
+ }
+ setcontext (&JB->ctx);
+}
+#endif
+
+/* Call grow_stack until the stack space is large enough, then, as the current
+ * stack frame might get overwritten, let copy_stack_and_call perform the
+ * actual copying and continuation calling.
+ */
+static void
+scm_dynthrow (SCM cont, SCM val)
+{
+ scm_i_thread *thread = SCM_I_CURRENT_THREAD;
+ scm_t_contregs *continuation = SCM_CONTREGS (cont);
+ SCM_STACKITEM *dst = thread->continuation_base;
+ SCM_STACKITEM stack_top_element;
+
+ if (thread->critical_section_level)
+ {
+ fprintf (stderr, "continuation invoked from within critical section.\n");
+ abort ();
+ }
+
+#if SCM_STACK_GROWS_UP
+ if (dst + continuation->num_stack_items >= &stack_top_element)
+ grow_stack (cont, val);
+#else
+ dst -= continuation->num_stack_items;
+ if (dst <= &stack_top_element)
+ grow_stack (cont, val);
+#endif /* def SCM_STACK_GROWS_UP */
+
+ SCM_FLUSH_REGISTER_WINDOWS;
+ copy_stack_and_call (continuation, val, dst);
+}
+
+
+static SCM
+continuation_apply (SCM cont, SCM args)
+#define FUNC_NAME "continuation_apply"
+{
+ scm_i_thread *thread = SCM_I_CURRENT_THREAD;
+ scm_t_contregs *continuation = SCM_CONTREGS (cont);
+
+ if (continuation->root != thread->continuation_root)
+ {
+ SCM_MISC_ERROR
+ ("invoking continuation would cross continuation barrier: ~A",
+ scm_list_1 (cont));
+ }
+
+ scm_dynthrow (cont, scm_values (args));
+ return SCM_UNSPECIFIED; /* not reached */
+}
+#undef FUNC_NAME
+
+SCM
+scm_i_with_continuation_barrier (scm_t_catch_body body,
+ void *body_data,
+ scm_t_catch_handler handler,
+ void *handler_data,
+ scm_t_catch_handler pre_unwind_handler,
+ void *pre_unwind_handler_data)
+{
+ SCM_STACKITEM stack_item;
+ scm_i_thread *thread = SCM_I_CURRENT_THREAD;
+ SCM old_controot;
+ SCM_STACKITEM *old_contbase;
+ scm_t_debug_frame *old_lastframe;
+ SCM result;
+
+ /* Establish a fresh continuation root.
+ */
+ old_controot = thread->continuation_root;
+ old_contbase = thread->continuation_base;
+ old_lastframe = thread->last_debug_frame;
+ thread->continuation_root = scm_cons (thread->handle, old_controot);
+ thread->continuation_base = &stack_item;
+ thread->last_debug_frame = NULL;
+
+ /* Call FUNC inside a catch all. This is now guaranteed to return
+ directly and exactly once.
+ */
+ result = scm_c_catch (SCM_BOOL_T,
+ body, body_data,
+ handler, handler_data,
+ pre_unwind_handler, pre_unwind_handler_data);
+
+ /* Return to old continuation root.
+ */
+ thread->last_debug_frame = old_lastframe;
+ thread->continuation_base = old_contbase;
+ thread->continuation_root = old_controot;
+
+ return result;
+}
+
+struct c_data {
+ void *(*func) (void *);
+ void *data;
+ void *result;
+};
+
+static SCM
+c_body (void *d)
+{
+ struct c_data *data = (struct c_data *)d;
+ data->result = data->func (data->data);
+ return SCM_UNSPECIFIED;
+}
+
+static SCM
+c_handler (void *d, SCM tag, SCM args)
+{
+ struct c_data *data = (struct c_data *)d;
+ data->result = NULL;
+ return SCM_UNSPECIFIED;
+}
+
+void *
+scm_c_with_continuation_barrier (void *(*func) (void *), void *data)
+{
+ struct c_data c_data;
+ c_data.func = func;
+ c_data.data = data;
+ scm_i_with_continuation_barrier (c_body, &c_data,
+ c_handler, &c_data,
+ scm_handle_by_message_noexit, NULL);
+ return c_data.result;
+}
+
+struct scm_data {
+ SCM proc;
+};
+
+static SCM
+scm_body (void *d)
+{
+ struct scm_data *data = (struct scm_data *)d;
+ return scm_call_0 (data->proc);
+}
+
+static SCM
+scm_handler (void *d, SCM tag, SCM args)
+{
+ return SCM_BOOL_F;
+}
+
+SCM_DEFINE (scm_with_continuation_barrier, "with-continuation-barrier", 1,0,0,
+ (SCM proc),
+"Call @var{proc} and return its result. Do not allow the invocation of\n"
+"continuations that would leave or enter the dynamic extent of the call\n"
+"to @code{with-continuation-barrier}. Such an attempt causes an error\n"
+"to be signaled.\n"
+"\n"
+"Throws (such as errors) that are not caught from within @var{proc} are\n"
+"caught by @code{with-continuation-barrier}. In that case, a short\n"
+"message is printed to the current error port and @code{#f} is returned.\n"
+"\n"
+"Thus, @code{with-continuation-barrier} returns exactly once.\n")
+#define FUNC_NAME s_scm_with_continuation_barrier
+{
+ struct scm_data scm_data;
+ scm_data.proc = proc;
+ return scm_i_with_continuation_barrier (scm_body, &scm_data,
+ scm_handler, &scm_data,
+ scm_handle_by_message_noexit, NULL);
+}
+#undef FUNC_NAME
+
+void
+scm_init_continuations ()
+{
+ scm_tc16_continuation = scm_make_smob_type ("continuation", 0);
+ scm_set_smob_mark (scm_tc16_continuation, continuation_mark);
+ scm_set_smob_free (scm_tc16_continuation, continuation_free);
+ scm_set_smob_print (scm_tc16_continuation, continuation_print);
+ scm_set_smob_apply (scm_tc16_continuation, continuation_apply, 0, 0, 1);
+#include "libguile/continuations.x"
+}
+
+/*
+ Local Variables:
+ c-file-style: "gnu"
+ End:
+*/
projects / lilypond.git / blobdiff