ruby/ext/fiddle/closure.c

#include <fiddle.h>
#include <stdbool.h>
#include <ruby/thread.h>

int ruby_thread_has_gvl_p(void); /* from internal.h */

VALUE cFiddleClosure;

typedef struct {
    void * code;
    ffi_closure *pcl;
    ffi_cif cif;
    int argc;
    ffi_type **argv;
} fiddle_closure;

#if defined(__OpenBSD__)
# define USE_FFI_CLOSURE_ALLOC 0
#endif

#if defined(USE_FFI_CLOSURE_ALLOC)
#elif !defined(HAVE_FFI_CLOSURE_ALLOC)
# define USE_FFI_CLOSURE_ALLOC 0
#else
# define USE_FFI_CLOSURE_ALLOC 1
#endif

static void
dealloc(void * ptr)
{
    fiddle_closure * cls = (fiddle_closure *)ptr;
#if USE_FFI_CLOSURE_ALLOC
    ffi_closure_free(cls->pcl);
#else
    munmap(cls->pcl, sizeof(*cls->pcl));
#endif
    if (cls->argv) xfree(cls->argv);
    xfree(cls);
}

static size_t
closure_memsize(const void * ptr)
{
    fiddle_closure * cls = (fiddle_closure *)ptr;
    size_t size = 0;

    size += sizeof(*cls);
#if !defined(FFI_NO_RAW_API) || !FFI_NO_RAW_API
    size += ffi_raw_size(&cls->cif);
#endif
    size += sizeof(*cls->argv);
    size += sizeof(ffi_closure);

    return size;
}

const rb_data_type_t closure_data_type = {
    .wrap_struct_name = "fiddle/closure",
    .function = {
        .dmark = 0,
        .dfree = dealloc,
        .dsize = closure_memsize
    },
    .flags = FIDDLE_DEFAULT_TYPED_DATA_FLAGS,
};

struct callback_args {
    ffi_cif *cif;
    void *resp;
    void **args;
    void *ctx;
};

static void *
with_gvl_callback(void *ptr)
{
    struct callback_args *x = ptr;

    VALUE self      = (VALUE)x->ctx;
    VALUE rbargs    = rb_iv_get(self, "@args");
    VALUE ctype     = rb_iv_get(self, "@ctype");
    int argc        = RARRAY_LENINT(rbargs);
    VALUE params    = rb_ary_tmp_new(argc);
    VALUE ret;
    VALUE cPointer;
    int i, type;

    cPointer = rb_const_get(mFiddle, rb_intern("Pointer"));

    for (i = 0; i < argc; i++) {
        type = NUM2INT(RARRAY_AREF(rbargs, i));
        switch (type) {
	  case TYPE_VOID:
	    argc = 0;
	    break;
	  case TYPE_INT:
	    rb_ary_push(params, INT2NUM(*(int *)x->args[i]));
	    break;
	  case TYPE_UINT:
	    rb_ary_push(params, UINT2NUM(*(unsigned int *)x->args[i]));
	    break;
	  case TYPE_VOIDP:
	    rb_ary_push(params,
			rb_funcall(cPointer, rb_intern("[]"), 1,
				   PTR2NUM(*(void **)x->args[i])));
	    break;
	  case TYPE_LONG:
	    rb_ary_push(params, LONG2NUM(*(long *)x->args[i]));
	    break;
	  case TYPE_ULONG:
	    rb_ary_push(params, ULONG2NUM(*(unsigned long *)x->args[i]));
	    break;
	  case TYPE_CHAR:
	    rb_ary_push(params, INT2NUM(*(signed char *)x->args[i]));
	    break;
	  case TYPE_UCHAR:
	    rb_ary_push(params, UINT2NUM(*(unsigned char *)x->args[i]));
	    break;
	  case TYPE_SHORT:
	    rb_ary_push(params, INT2NUM(*(signed short *)x->args[i]));
	    break;
	  case TYPE_USHORT:
	    rb_ary_push(params, UINT2NUM(*(unsigned short *)x->args[i]));
	    break;
	  case TYPE_DOUBLE:
	    rb_ary_push(params, rb_float_new(*(double *)x->args[i]));
	    break;
	  case TYPE_FLOAT:
	    rb_ary_push(params, rb_float_new(*(float *)x->args[i]));
	    break;
#if HAVE_LONG_LONG
	  case TYPE_LONG_LONG:
	    rb_ary_push(params, LL2NUM(*(LONG_LONG *)x->args[i]));
	    break;
	  case TYPE_ULONG_LONG:
	    rb_ary_push(params, ULL2NUM(*(unsigned LONG_LONG *)x->args[i]));
	    break;
#endif
	  case TYPE_CONST_STRING:
	    rb_ary_push(params,
                        rb_str_new_cstr(*((const char **)(x->args[i]))));
	    break;
	  case TYPE_BOOL:
            if (sizeof(bool) == sizeof(char)) {
                rb_ary_push(params, CBOOL2RBBOOL(*(unsigned char *)x->args[i]));
            } else if (sizeof(bool) == sizeof(short)) {
                rb_ary_push(params, CBOOL2RBBOOL(*(unsigned short *)x->args[i]));
            } else if (sizeof(bool) == sizeof(int)) {
                rb_ary_push(params, CBOOL2RBBOOL(*(unsigned int *)x->args[i]));
            } else if (sizeof(bool) == sizeof(long)) {
                rb_ary_push(params, CBOOL2RBBOOL(*(unsigned long *)x->args[i]));
            } else {
                rb_raise(rb_eNotImpError, "bool isn't supported: %u",
                         (unsigned int)sizeof(bool));
            }
	    break;
	  default:
	    rb_raise(rb_eRuntimeError, "closure args: %d", type);
        }
    }

    ret = rb_funcall2(self, rb_intern("call"), argc, RARRAY_CONST_PTR(params));
    RB_GC_GUARD(params);

    type = NUM2INT(ctype);
    switch (type) {
      case TYPE_VOID:
	break;
      case TYPE_LONG:
	*(long *)x->resp = NUM2LONG(ret);
	break;
      case TYPE_ULONG:
	*(unsigned long *)x->resp = NUM2ULONG(ret);
	break;
      case TYPE_CHAR:
      case TYPE_SHORT:
      case TYPE_INT:
	*(ffi_sarg *)x->resp = NUM2INT(ret);
	break;
      case TYPE_UCHAR:
      case TYPE_USHORT:
      case TYPE_UINT:
	*(ffi_arg *)x->resp = NUM2UINT(ret);
	break;
      case TYPE_VOIDP:
	*(void **)x->resp = NUM2PTR(ret);
	break;
      case TYPE_DOUBLE:
	*(double *)x->resp = NUM2DBL(ret);
	break;
      case TYPE_FLOAT:
	*(float *)x->resp = (float)NUM2DBL(ret);
	break;
#if HAVE_LONG_LONG
      case TYPE_LONG_LONG:
	*(LONG_LONG *)x->resp = NUM2LL(ret);
	break;
      case TYPE_ULONG_LONG:
	*(unsigned LONG_LONG *)x->resp = NUM2ULL(ret);
	break;
#endif
      case TYPE_CONST_STRING:
        /* Dangerous. Callback must keep reference of the String. */
        *((const char **)(x->resp)) = StringValueCStr(ret);
        break;
      case TYPE_BOOL:
        if (sizeof(bool) == sizeof(long)) {
            *(unsigned long *)x->resp = RB_TEST(ret);
        } else {
            *(ffi_arg *)x->resp = RB_TEST(ret);
        }
        break;
      default:
	rb_raise(rb_eRuntimeError, "closure retval: %d", type);
    }
    return 0;
}

static void
callback(ffi_cif *cif, void *resp, void **args, void *ctx)
{
    struct callback_args x;

    x.cif = cif;
    x.resp = resp;
    x.args = args;
    x.ctx = ctx;

    if (ruby_thread_has_gvl_p()) {
	(void)with_gvl_callback(&x);
    } else {
	(void)rb_thread_call_with_gvl(with_gvl_callback, &x);
    }
}

static VALUE
allocate(VALUE klass)
{
    fiddle_closure * closure;

    VALUE i = TypedData_Make_Struct(klass, fiddle_closure,
	    &closure_data_type, closure);

#if USE_FFI_CLOSURE_ALLOC
    closure->pcl = ffi_closure_alloc(sizeof(ffi_closure), &closure->code);
#else
    closure->pcl = mmap(NULL, sizeof(ffi_closure), PROT_READ | PROT_WRITE,
        MAP_ANON | MAP_PRIVATE, -1, 0);
#endif

    return i;
}

static fiddle_closure *
get_raw(VALUE self)
{
    fiddle_closure *closure;
    TypedData_Get_Struct(self, fiddle_closure, &closure_data_type, closure);
    if (!closure) {
        rb_raise(rb_eArgError, "already freed: %+"PRIsVALUE, self);
    }
    return closure;
}

typedef struct {
    VALUE self;
    int argc;
    VALUE *argv;
} initialize_data;

static VALUE
initialize_body(VALUE user_data)
{
    initialize_data *data = (initialize_data *)user_data;
    VALUE ret;
    VALUE args;
    VALUE normalized_args;
    VALUE abi;
    fiddle_closure * cl;
    ffi_cif * cif;
    ffi_closure *pcl;
    ffi_status result;
    int i, argc;

    if (2 == rb_scan_args(data->argc, data->argv, "21", &ret, &args, &abi))
        abi = INT2NUM(FFI_DEFAULT_ABI);

    Check_Type(args, T_ARRAY);

    argc = RARRAY_LENINT(args);

    TypedData_Get_Struct(data->self, fiddle_closure, &closure_data_type, cl);

    cl->argv = (ffi_type **)xcalloc(argc + 1, sizeof(ffi_type *));

    normalized_args = rb_ary_new_capa(argc);
    for (i = 0; i < argc; i++) {
        VALUE arg = rb_fiddle_type_ensure(RARRAY_AREF(args, i));
        rb_ary_push(normalized_args, arg);
        cl->argv[i] = rb_fiddle_int_to_ffi_type(NUM2INT(arg));
    }
    cl->argv[argc] = NULL;
    OBJ_FREEZE_RAW(normalized_args);

    ret = rb_fiddle_type_ensure(ret);
    rb_iv_set(data->self, "@ctype", ret);
    rb_iv_set(data->self, "@args", normalized_args);

    cif = &cl->cif;
    pcl = cl->pcl;

    result = ffi_prep_cif(cif,
                          NUM2INT(abi),
                          argc,
                          rb_fiddle_int_to_ffi_type(NUM2INT(ret)),
                          cl->argv);

    if (FFI_OK != result) {
        rb_raise(rb_eRuntimeError, "error prepping CIF %d", result);
    }

#if USE_FFI_CLOSURE_ALLOC
    result = ffi_prep_closure_loc(pcl, cif, callback,
                                  (void *)(data->self), cl->code);
#else
    result = ffi_prep_closure(pcl, cif, callback, (void *)(data->self));
    cl->code = (void *)pcl;
    i = mprotect(pcl, sizeof(*pcl), PROT_READ | PROT_EXEC);
    if (i) {
        rb_sys_fail("mprotect");
    }
#endif

    if (FFI_OK != result) {
        rb_raise(rb_eRuntimeError, "error prepping closure %d", result);
    }

    return data->self;
}

static VALUE
initialize_rescue(VALUE user_data, VALUE exception)
{
    initialize_data *data = (initialize_data *)user_data;
    dealloc(RTYPEDDATA_DATA(data->self));
    RTYPEDDATA_DATA(data->self) = NULL;
    rb_exc_raise(exception);
    return data->self;
}

static VALUE
initialize(int argc, VALUE *argv, VALUE self)
{
    initialize_data data;
    data.self = self;
    data.argc = argc;
    data.argv = argv;
    return rb_rescue(initialize_body, (VALUE)&data,
                     initialize_rescue, (VALUE)&data);
}

static VALUE
to_i(VALUE self)
{
    fiddle_closure *closure = get_raw(self);
    return PTR2NUM(closure->code);
}

static VALUE
closure_free(VALUE self)
{
    fiddle_closure *closure;
    TypedData_Get_Struct(self, fiddle_closure, &closure_data_type, closure);
    if (closure) {
        dealloc(closure);
        RTYPEDDATA_DATA(self) = NULL;
    }
    return RUBY_Qnil;
}

static VALUE
closure_freed_p(VALUE self)
{
    fiddle_closure *closure;
    TypedData_Get_Struct(self, fiddle_closure, &closure_data_type, closure);
    return closure ? RUBY_Qfalse : RUBY_Qtrue;
}

void
Init_fiddle_closure(void)
{
#if 0
    mFiddle = rb_define_module("Fiddle"); /* let rdoc know about mFiddle */
#endif

    /*
     * Document-class: Fiddle::Closure
     *
     * == Description
     *
     * An FFI closure wrapper, for handling callbacks.
     *
     * == Example
     *
     *   closure = Class.new(Fiddle::Closure) {
     *     def call
     *       10
     *     end
     *   }.new(Fiddle::TYPE_INT, [])
     *	    #=> #<#<Class:0x0000000150d308>:0x0000000150d240>
     *   func = Fiddle::Function.new(closure, [], Fiddle::TYPE_INT)
     *	    #=> #<Fiddle::Function:0x00000001516e58>
     *   func.call
     *	    #=> 10
     */
    cFiddleClosure = rb_define_class_under(mFiddle, "Closure", rb_cObject);

    rb_define_alloc_func(cFiddleClosure, allocate);

    /*
     * Document-method: new
     *
     * call-seq: new(ret, args, abi = Fiddle::DEFAULT)
     *
     * Construct a new Closure object.
     *
     * * +ret+ is the C type to be returned
     * * +args+ is an Array of arguments, passed to the callback function
     * * +abi+ is the abi of the closure
     *
     * If there is an error in preparing the ffi_cif or ffi_prep_closure,
     * then a RuntimeError will be raised.
     */
    rb_define_method(cFiddleClosure, "initialize", initialize, -1);

    /*
     * Document-method: to_i
     *
     * Returns the memory address for this closure.
     */
    rb_define_method(cFiddleClosure, "to_i", to_i, 0);

    /*
     * Document-method: free
     *
     * Free this closure explicitly. You can't use this closure anymore.
     *
     * If this closure is already freed, this does nothing.
     */
    rb_define_method(cFiddleClosure, "free", closure_free, 0);

    /*
     * Document-method: freed?
     *
     * Whether this closure was freed explicitly.
     */
    rb_define_method(cFiddleClosure, "freed?", closure_freed_p, 0);
}