factor/vm/contexts.cpp

193 lines
4.2 KiB
C++

#include "master.hpp"
factor::context *stack_chain;
namespace factor
{
cell ds_size, rs_size;
context *unused_contexts;
void reset_datastack()
{
ds = ds_bot - sizeof(cell);
}
void reset_retainstack()
{
rs = rs_bot - sizeof(cell);
}
static const cell stack_reserved = (64 * sizeof(cell));
void fix_stacks()
{
if(ds + sizeof(cell) < ds_bot || ds + stack_reserved >= ds_top) reset_datastack();
if(rs + sizeof(cell) < rs_bot || rs + stack_reserved >= rs_top) reset_retainstack();
}
/* called before entry into foreign C code. Note that ds and rs might
be stored in registers, so callbacks must save and restore the correct values */
void save_stacks()
{
if(stack_chain)
{
stack_chain->datastack = ds;
stack_chain->retainstack = rs;
}
}
context *alloc_context()
{
context *new_context;
if(unused_contexts)
{
new_context = unused_contexts;
unused_contexts = unused_contexts->next;
}
else
{
new_context = (context *)safe_malloc(sizeof(context));
new_context->datastack_region = alloc_segment(ds_size);
new_context->retainstack_region = alloc_segment(rs_size);
}
return new_context;
}
void dealloc_context(context *old_context)
{
old_context->next = unused_contexts;
unused_contexts = old_context;
}
/* called on entry into a compiled callback */
void nest_stacks()
{
context *new_context = alloc_context();
new_context->callstack_bottom = (stack_frame *)-1;
new_context->callstack_top = (stack_frame *)-1;
/* note that these register values are not necessarily valid stack
pointers. they are merely saved non-volatile registers, and are
restored in unnest_stacks(). consider this scenario:
- factor code calls C function
- C function saves ds/cs registers (since they're non-volatile)
- C function clobbers them
- C function calls Factor callback
- Factor callback returns
- C function restores registers
- C function returns to Factor code */
new_context->datastack_save = ds;
new_context->retainstack_save = rs;
/* save per-callback userenv */
new_context->current_callback_save = userenv[CURRENT_CALLBACK_ENV];
new_context->catchstack_save = userenv[CATCHSTACK_ENV];
new_context->next = stack_chain;
stack_chain = new_context;
reset_datastack();
reset_retainstack();
}
/* called when leaving a compiled callback */
void unnest_stacks()
{
ds = stack_chain->datastack_save;
rs = stack_chain->retainstack_save;
/* restore per-callback userenv */
userenv[CURRENT_CALLBACK_ENV] = stack_chain->current_callback_save;
userenv[CATCHSTACK_ENV] = stack_chain->catchstack_save;
context *old_stacks = stack_chain;
stack_chain = old_stacks->next;
dealloc_context(old_stacks);
}
/* called on startup */
void init_stacks(cell ds_size_, cell rs_size_)
{
ds_size = ds_size_;
rs_size = rs_size_;
stack_chain = NULL;
unused_contexts = NULL;
}
bool stack_to_array(cell bottom, cell top)
{
fixnum depth = (fixnum)(top - bottom + sizeof(cell));
if(depth < 0)
return false;
else
{
array *a = allot_array_internal<array>(depth / sizeof(cell));
memcpy(a + 1,(void*)bottom,depth);
dpush(tag<array>(a));
return true;
}
}
PRIMITIVE(datastack)
{
if(!stack_to_array(ds_bot,ds))
general_error(ERROR_DS_UNDERFLOW,F,F,NULL);
}
PRIMITIVE(retainstack)
{
if(!stack_to_array(rs_bot,rs))
general_error(ERROR_RS_UNDERFLOW,F,F,NULL);
}
/* returns pointer to top of stack */
cell array_to_stack(array *array, cell bottom)
{
cell depth = array_capacity(array) * sizeof(cell);
memcpy((void*)bottom,array + 1,depth);
return bottom + depth - sizeof(cell);
}
PRIMITIVE(set_datastack)
{
ds = array_to_stack(untag_check<array>(dpop()),ds_bot);
}
PRIMITIVE(set_retainstack)
{
rs = array_to_stack(untag_check<array>(dpop()),rs_bot);
}
/* Used to implement call( */
PRIMITIVE(check_datastack)
{
fixnum out = to_fixnum(dpop());
fixnum in = to_fixnum(dpop());
fixnum height = out - in;
array *saved_datastack = untag_check<array>(dpop());
fixnum saved_height = array_capacity(saved_datastack);
fixnum current_height = (ds - ds_bot + sizeof(cell)) / sizeof(cell);
if(current_height - height != saved_height)
dpush(F);
else
{
fixnum i;
for(i = 0; i < saved_height - in; i++)
{
if(((cell *)ds_bot)[i] != array_nth(saved_datastack,i))
{
dpush(F);
return;
}
}
dpush(T);
}
}
}