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Add a "pinning" reference (#44)
* Add a "pinning" reference A `Fiddle::Pinned` objects will prevent the objects they point to from moving. This is useful in the case where you need to pass a reference to a C extension that keeps the address in a global and needs the address to be stable. For example: ```ruby class Foo A = "hi" # this is an embedded string some_c_function A # A might move! end ``` If `A` moves, then the underlying string buffer may also move. `Fiddle::Pinned` will prevent the object from moving: ```ruby class Foo A = "hi" # this is an embedded string A_pinner = Fiddle::Pinned.new(A) # :nodoc: some_c_function A # A can't move because of `Fiddle::Pinned` end ``` This is a similar strategy to what Graal uses: https://www.graalvm.org/sdk/javadoc/org/graalvm/nativeimage/PinnedObject.html#getObject-- * rename global to match exception name * Introduce generic Fiddle::Error and rearrange error classes Fiddle::Error is the generic exception base class for Fiddle exceptions. This commit introduces the class and rearranges Fiddle exceptions to inherit from it.
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7 files changed

+173
-12
lines changed

7 files changed

+173
-12
lines changed

‎ext/fiddle/fiddle.c

Lines changed: 11 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -1,9 +1,11 @@
11
#include <fiddle.h>
22

33
VALUE mFiddle;
4+
VALUE rb_eFiddleDLError;
45
VALUE rb_eFiddleError;
56

67
void Init_fiddle_pointer(void);
8+
void Init_fiddle_pinned(void);
79

810
/*
911
* call-seq: Fiddle.malloc(size)
@@ -132,12 +134,19 @@ Init_fiddle(void)
132134
*/
133135
mFiddle = rb_define_module("Fiddle");
134136

137+
/*
138+
* Document-class: Fiddle::Error
139+
*
140+
* Generic error class for Fiddle
141+
*/
142+
rb_eFiddleError = rb_define_class_under(mFiddle, "Error", rb_eStandardError);
143+
135144
/*
136145
* Document-class: Fiddle::DLError
137146
*
138147
* standard dynamic load exception
139148
*/
140-
rb_eFiddleError = rb_define_class_under(mFiddle, "DLError", rb_eStandardError);
149+
rb_eFiddleDLError = rb_define_class_under(mFiddle, "DLError", rb_eFiddleError);
141150

142151
/* Document-const: TYPE_VOID
143152
*
@@ -439,5 +448,6 @@ Init_fiddle(void)
439448
Init_fiddle_closure();
440449
Init_fiddle_handle();
441450
Init_fiddle_pointer();
451+
Init_fiddle_pinned();
442452
}
443453
/* vim: set noet sws=4 sw=4: */

‎ext/fiddle/fiddle.h

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -164,7 +164,7 @@
164164
#define ALIGN_DOUBLE ALIGN_OF(double)
165165

166166
extern VALUE mFiddle;
167-
extern VALUE rb_eFiddleError;
167+
extern VALUE rb_eFiddleDLError;
168168

169169
VALUE rb_fiddle_new_function(VALUE address, VALUE arg_types, VALUE ret_type);
170170

‎ext/fiddle/handle.c

Lines changed: 7 additions & 7 deletions
Original file line numberDiff line numberDiff line change
@@ -74,14 +74,14 @@ rb_fiddle_handle_close(VALUE self)
7474
/* Check dlclose for successful return value */
7575
if(ret) {
7676
#if defined(HAVE_DLERROR)
77-
rb_raise(rb_eFiddleError, "%s", dlerror());
77+
rb_raise(rb_eFiddleDLError, "%s", dlerror());
7878
#else
79-
rb_raise(rb_eFiddleError, "could not close handle");
79+
rb_raise(rb_eFiddleDLError, "could not close handle");
8080
#endif
8181
}
8282
return INT2NUM(ret);
8383
}
84-
rb_raise(rb_eFiddleError, "dlclose() called too many times");
84+
rb_raise(rb_eFiddleDLError, "dlclose() called too many times");
8585

8686
UNREACHABLE;
8787
}
@@ -177,12 +177,12 @@ rb_fiddle_handle_initialize(int argc, VALUE argv[], VALUE self)
177177
ptr = dlopen(clib, cflag);
178178
#if defined(HAVE_DLERROR)
179179
if( !ptr && (err = dlerror()) ){
180-
rb_raise(rb_eFiddleError, "%s", err);
180+
rb_raise(rb_eFiddleDLError, "%s", err);
181181
}
182182
#else
183183
if( !ptr ){
184184
err = dlerror();
185-
rb_raise(rb_eFiddleError, "%s", err);
185+
rb_raise(rb_eFiddleDLError, "%s", err);
186186
}
187187
#endif
188188
TypedData_Get_Struct(self, struct dl_handle, &fiddle_handle_data_type, fiddle_handle);
@@ -278,7 +278,7 @@ rb_fiddle_handle_sym(VALUE self, VALUE sym)
278278

279279
TypedData_Get_Struct(self, struct dl_handle, &fiddle_handle_data_type, fiddle_handle);
280280
if( ! fiddle_handle->open ){
281-
rb_raise(rb_eFiddleError, "closed handle");
281+
rb_raise(rb_eFiddleDLError, "closed handle");
282282
}
283283

284284
return fiddle_handle_sym(fiddle_handle->ptr, sym);
@@ -366,7 +366,7 @@ fiddle_handle_sym(void *handle, VALUE symbol)
366366
}
367367
#endif
368368
if( !func ){
369-
rb_raise(rb_eFiddleError, "unknown symbol \"%"PRIsVALUE"\"", symbol);
369+
rb_raise(rb_eFiddleDLError, "unknown symbol \"%"PRIsVALUE"\"", symbol);
370370
}
371371

372372
return PTR2NUM(func);

‎ext/fiddle/pinned.c

Lines changed: 123 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,123 @@
1+
#include <fiddle.h>
2+
3+
VALUE rb_cPinned;
4+
VALUE rb_eFiddleClearedReferenceError;
5+
6+
struct pinned_data {
7+
VALUE ptr;
8+
};
9+
10+
static void
11+
pinned_mark(void *ptr)
12+
{
13+
struct pinned_data *data = (struct pinned_data*)ptr;
14+
/* Ensure reference is pinned */
15+
if (data->ptr) {
16+
rb_gc_mark(data->ptr);
17+
}
18+
}
19+
20+
static size_t
21+
pinned_memsize(const void *ptr)
22+
{
23+
return sizeof(struct pinned_data);
24+
}
25+
26+
static const rb_data_type_t pinned_data_type = {
27+
"fiddle/pinned",
28+
{pinned_mark, xfree, pinned_memsize, },
29+
0, 0, RUBY_TYPED_FREE_IMMEDIATELY | RUBY_TYPED_WB_PROTECTED
30+
};
31+
32+
static VALUE
33+
allocate(VALUE klass)
34+
{
35+
struct pinned_data *data;
36+
VALUE obj = TypedData_Make_Struct(klass, struct pinned_data, &pinned_data_type, data);
37+
data->ptr = 0;
38+
return obj;
39+
}
40+
41+
/*
42+
* call-seq:
43+
* Fiddle::Pinned.new(object) => pinned_object
44+
*
45+
* Create a new pinned object reference. The Fiddle::Pinned instance will
46+
* prevent the GC from moving +object+.
47+
*/
48+
static VALUE
49+
initialize(VALUE self, VALUE ref)
50+
{
51+
struct pinned_data *data;
52+
TypedData_Get_Struct(self, struct pinned_data, &pinned_data_type, data);
53+
RB_OBJ_WRITE(self, &data->ptr, ref);
54+
return self;
55+
}
56+
57+
/*
58+
* call-seq: ref
59+
*
60+
* Return the object that this pinned instance references.
61+
*/
62+
static VALUE
63+
ref(VALUE self)
64+
{
65+
struct pinned_data *data;
66+
TypedData_Get_Struct(self, struct pinned_data, &pinned_data_type, data);
67+
if (data->ptr) {
68+
return data->ptr;
69+
} else {
70+
rb_raise(rb_eFiddleClearedReferenceError, "`ref` called on a cleared object");
71+
}
72+
}
73+
74+
/*
75+
* call-seq: clear
76+
*
77+
* Clear the reference to the object this is pinning.
78+
*/
79+
static VALUE
80+
clear(VALUE self)
81+
{
82+
struct pinned_data *data;
83+
TypedData_Get_Struct(self, struct pinned_data, &pinned_data_type, data);
84+
data->ptr = 0;
85+
return self;
86+
}
87+
88+
/*
89+
* call-seq: cleared?
90+
*
91+
* Returns true if the reference has been cleared, otherwise returns false.
92+
*/
93+
static VALUE
94+
cleared_p(VALUE self)
95+
{
96+
struct pinned_data *data;
97+
TypedData_Get_Struct(self, struct pinned_data, &pinned_data_type, data);
98+
if (data->ptr) {
99+
return Qfalse;
100+
} else {
101+
return Qtrue;
102+
}
103+
}
104+
105+
extern VALUE rb_eFiddleError;
106+
107+
void
108+
Init_fiddle_pinned(void)
109+
{
110+
rb_cPinned = rb_define_class_under(mFiddle, "Pinned", rb_cObject);
111+
rb_define_alloc_func(rb_cPinned, allocate);
112+
rb_define_method(rb_cPinned, "initialize", initialize, 1);
113+
rb_define_method(rb_cPinned, "ref", ref, 0);
114+
rb_define_method(rb_cPinned, "clear", clear, 0);
115+
rb_define_method(rb_cPinned, "cleared?", cleared_p, 0);
116+
117+
/*
118+
* Document-class: Fiddle::ClearedReferenceError
119+
*
120+
* Cleared reference exception
121+
*/
122+
rb_eFiddleClearedReferenceError = rb_define_class_under(mFiddle, "ClearedReferenceError", rb_eFiddleError);
123+
}

‎ext/fiddle/pointer.c

Lines changed: 3 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -622,7 +622,7 @@ rb_fiddle_ptr_aref(int argc, VALUE argv[], VALUE self)
622622
struct ptr_data *data;
623623

624624
TypedData_Get_Struct(self, struct ptr_data, &fiddle_ptr_data_type, data);
625-
if (!data->ptr) rb_raise(rb_eFiddleError, "NULL pointer dereference");
625+
if (!data->ptr) rb_raise(rb_eFiddleDLError, "NULL pointer dereference");
626626
switch( rb_scan_args(argc, argv, "11", &arg0, &arg1) ){
627627
case 1:
628628
offset = NUM2ULONG(arg0);
@@ -660,7 +660,7 @@ rb_fiddle_ptr_aset(int argc, VALUE argv[], VALUE self)
660660
struct ptr_data *data;
661661

662662
TypedData_Get_Struct(self, struct ptr_data, &fiddle_ptr_data_type, data);
663-
if (!data->ptr) rb_raise(rb_eFiddleError, "NULL pointer dereference");
663+
if (!data->ptr) rb_raise(rb_eFiddleDLError, "NULL pointer dereference");
664664
switch( rb_scan_args(argc, argv, "21", &arg0, &arg1, &arg2) ){
665665
case 2:
666666
offset = NUM2ULONG(arg0);
@@ -741,7 +741,7 @@ rb_fiddle_ptr_s_to_ptr(VALUE self, VALUE val)
741741
wrap = 0;
742742
}
743743
else{
744-
rb_raise(rb_eFiddleError, "to_ptr should return a Fiddle::Pointer object");
744+
rb_raise(rb_eFiddleDLError, "to_ptr should return a Fiddle::Pointer object");
745745
}
746746
}
747747
else{

‎fiddle.gemspec

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -34,6 +34,7 @@ Gem::Specification.new do |spec|
3434
"ext/fiddle/function.c",
3535
"ext/fiddle/function.h",
3636
"ext/fiddle/handle.c",
37+
"ext/fiddle/pinned.c",
3738
"ext/fiddle/pointer.c",
3839
"ext/fiddle/win32/fficonfig.h",
3940
"ext/fiddle/win32/libffi-3.2.1-mswin.patch",

‎test/fiddle/test_pinned.rb

Lines changed: 27 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,27 @@
1+
# frozen_string_literal: true
2+
begin
3+
require_relative 'helper'
4+
rescue LoadError
5+
end
6+
7+
module Fiddle
8+
class TestPinned < Fiddle::TestCase
9+
def test_pin_object
10+
x = Object.new
11+
pinner = Pinned.new x
12+
assert_same x, pinner.ref
13+
end
14+
15+
def test_clear
16+
pinner = Pinned.new Object.new
17+
refute pinner.cleared?
18+
pinner.clear
19+
assert pinner.cleared?
20+
ex = assert_raise(Fiddle::ClearedReferenceError) do
21+
pinner.ref
22+
end
23+
assert_match "called on", ex.message
24+
end
25+
end
26+
end
27+

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