Re: [racket-dev] ffi vectors
When you run this program on a 32-bit machine:
#include stdio.h
void go(float a[4])
{
printf(in go: %d\n, sizeof(a));
}
int main() {
float a[4];
printf(in main: %d\n, sizeof(a));
go(a);
}
you'll see in main: 16 and in go: 4.
As far as I know, the 4 in void go(float a[4]) is ignored. It's
really the same as void go(float a[]) or void go(float *a). Unless
the declaration of an array variable is allocating the variable, the
variable is really a pointer, and sizeof() reflects that.
Along the same lines, a `_cvector' in the FFI always has a pointer
size, because it's always like a pointer.
A `(_cvector o _float 4)' or `(_f32vector o 4)' is probably
what you want, if the function you'll calling fills in the vector. A
`_float4-pointer' (not `_float4'!) if you allocate it yourself or
`(_pointer o _float4)' is also fine.
At Thu, 30 Sep 2010 16:41:29 -0600, Jay McCarthy wrote:
I'd like to be able to define ctypes like I would make a typedef in C like
typedef float float4[4];
But it doesn't seem like this works in the FFI. See the program below
with its awkward work-around:
#lang racket
(require ffi/unsafe
ffi/unsafe/cvector
ffi/vector
tests/eli-tester)
(test
(ctype-sizeof _float) = 4
(ctype-sizeof _cvector) = 4
(ctype-sizeof (_cvector i _float)) = 4
(ctype-sizeof (_cvector o _float 4)) = (* 4 4)
(ctype-sizeof (_cvector io _float 4)) = (* 4 4)
(ctype-sizeof _f32vector) = 4
(ctype-sizeof (_f32vector i)) = 4
(ctype-sizeof (_f32vector o 4)) = (* 4 4)
(ctype-sizeof (_f32vector io 4)) = (* 4 4)
(local [(define-cstruct _float4
([f0 _float]
[f1 _float]
[f2 _float]
[f3 _float]))]
(test
(ctype-sizeof _float4) = 16)))
Output is:
test: 5/11 test failures:
unsaved-editor4119:11:1: test failure in (ctype-sizeof (_cvector i _float))
expected: 4
got: error: expand: unbound identifier in module
unsaved-editor4119:12:1: test failure in (ctype-sizeof (_cvector o _float 4))
expected: 16
got: 4
unsaved-editor4119:13:1: test failure in (ctype-sizeof (_cvector io _float 4))
expected: 16
got: error: expand: unbound identifier in module
unsaved-editor4119:17:1: test failure in (ctype-sizeof (_f32vector o 4))
expected: 16
got: 4
unsaved-editor4119:18:1: test failure in (ctype-sizeof (_f32vector io 4))
expected: 16
got: error: expand: unbound identifier in module
Normally I would just go do this, but I don't really understand the
FFI. If someone can point me appropriately, I'll go do it.
Jay
--
Jay McCarthy j...@cs.byu.edu
Assistant Professor / Brigham Young University
http://teammccarthy.org/jay
The glory of God is Intelligence - DC 93
_
For list-related administrative tasks:
http://lists.racket-lang.org/listinfo/dev
_
For list-related administrative tasks:
http://lists.racket-lang.org/listinfo/dev
Re: [racket-dev] ffi vectors
I guess I misunderstood what you were looking for.
It would be nice to have a compact ctype that adapts like the C array
type to different contexts. For my FFI tasks, I've gotten by with
structure types like `_float4'; I manually choose between `_float4' or
`_float4-pointer' as needed in different contexts (the former for
`malloc' or a struct member, the latter for a function argument or
result). That strategy was was particularly awkward for a struct that
contained an array of 32 bytes, though.
At Thu, 30 Sep 2010 17:19:43 -0600, Jay McCarthy wrote:
Yes, but this program:
typedef float float4[4];
typedef struct {
float4 a;
float b;
} astruct;
void go(float4 a, astruct b)
{
printf(in go: %d\n, sizeof(a));
printf(in go: %d\n, sizeof(float4));
printf(in go: %d\n, sizeof(b));
printf(in go: %d\n, sizeof(astruct));
}
int main() {
float4 a;
astruct b;
printf(in main: %d\n, sizeof(a));
printf(in main: %d\n, sizeof(float4));
printf(in main: %d\n, sizeof(b));
printf(in main: %d\n, sizeof(astruct));
go(a, b);
}
produces
in main: 16
in main: 16
in main: 20
in main: 20
in go: 8
in go: 16
in go: 20
in go: 20
The FFI is not just used for making function calls, it is also used
for specify structures and malloc-ing on behalf of the functions you
want to call. It is very awkward to make cstructs that are the correct
size and malloc the right amount without similar functionality to C in
this regard.
Jay
On Thu, Sep 30, 2010 at 4:51 PM, Matthew Flatt mfl...@cs.utah.edu wrote:
When you run this program on a 32-bit machine:
#include stdio.h
void go(float a[4])
{
printf(in go: %d\n, sizeof(a));
}
int main() {
float a[4];
printf(in main: %d\n, sizeof(a));
go(a);
}
you'll see in main: 16 and in go: 4.
As far as I know, the 4 in void go(float a[4]) is ignored. It's
really the same as void go(float a[]) or void go(float *a). Unless
the declaration of an array variable is allocating the variable, the
variable is really a pointer, and sizeof() reflects that.
Along the same lines, a `_cvector' in the FFI always has a pointer
size, because it's always like a pointer.
A `(_cvector o _float 4)' or `(_f32vector o 4)' is probably
what you want, if the function you'll calling fills in the vector. A
`_float4-pointer' (not `_float4'!) if you allocate it yourself or
`(_pointer o _float4)' is also fine.
At Thu, 30 Sep 2010 16:41:29 -0600, Jay McCarthy wrote:
I'd like to be able to define ctypes like I would make a typedef in C like
typedef float float4[4];
But it doesn't seem like this works in the FFI. See the program below
with its awkward work-around:
#lang racket
(require ffi/unsafe
ffi/unsafe/cvector
ffi/vector
tests/eli-tester)
(test
(ctype-sizeof _float) = 4
(ctype-sizeof _cvector) = 4
(ctype-sizeof (_cvector i _float)) = 4
(ctype-sizeof (_cvector o _float 4)) = (* 4 4)
(ctype-sizeof (_cvector io _float 4)) = (* 4 4)
(ctype-sizeof _f32vector) = 4
(ctype-sizeof (_f32vector i)) = 4
(ctype-sizeof (_f32vector o 4)) = (* 4 4)
(ctype-sizeof (_f32vector io 4)) = (* 4 4)
(local [(define-cstruct _float4
([f0 _float]
[f1 _float]
[f2 _float]
[f3 _float]))]
(test
(ctype-sizeof _float4) = 16)))
Output is:
test: 5/11 test failures:
unsaved-editor4119:11:1: test failure in (ctype-sizeof (_cvector i _float))
expected: 4
got: error: expand: unbound identifier in module
unsaved-editor4119:12:1: test failure in (ctype-sizeof (_cvector o _float
4))
expected: 16
got: 4
unsaved-editor4119:13:1: test failure in (ctype-sizeof (_cvector io _float
4))
expected: 16
got: error: expand: unbound identifier in module
unsaved-editor4119:17:1: test failure in (ctype-sizeof (_f32vector o 4))
expected: 16
got: 4
unsaved-editor4119:18:1: test failure in (ctype-sizeof (_f32vector io 4))
expected: 16
got: error: expand: unbound identifier in module
Normally I would just go do this, but I don't really understand the
FFI. If someone can point me appropriately, I'll go do it.
Jay
--
Jay McCarthy j...@cs.byu.edu
Assistant Professor / Brigham Young University
http://teammccarthy.org/jay
The glory of God is Intelligence - DC 93
_
For list-related administrative tasks:
http://lists.racket-lang.org/listinfo/dev
--
Jay McCarthy j...@cs.byu.edu
Assistant Professor / Brigham Young University
http://teammccarthy.org/jay
The glory of God is Intelligence - DC 93
_
For list-related administrative tasks:
http://lists.racket-lang.org/listinfo/dev
Re: [racket-dev] ffi vectors
Okay. I'm kind of glad that I came up with the normal thing.
I'll put it on my infinitely long list of TODO items to come back and
extend the ctypes so that they can specify both aspects of their size.
Jay
On Thu, Sep 30, 2010 at 7:25 PM, Matthew Flatt mfl...@cs.utah.edu wrote:
I guess I misunderstood what you were looking for.
It would be nice to have a compact ctype that adapts like the C array
type to different contexts. For my FFI tasks, I've gotten by with
structure types like `_float4'; I manually choose between `_float4' or
`_float4-pointer' as needed in different contexts (the former for
`malloc' or a struct member, the latter for a function argument or
result). That strategy was was particularly awkward for a struct that
contained an array of 32 bytes, though.
At Thu, 30 Sep 2010 17:19:43 -0600, Jay McCarthy wrote:
Yes, but this program:
typedef float float4[4];
typedef struct {
float4 a;
float b;
} astruct;
void go(float4 a, astruct b)
{
printf(in go: %d\n, sizeof(a));
printf(in go: %d\n, sizeof(float4));
printf(in go: %d\n, sizeof(b));
printf(in go: %d\n, sizeof(astruct));
}
int main() {
float4 a;
astruct b;
printf(in main: %d\n, sizeof(a));
printf(in main: %d\n, sizeof(float4));
printf(in main: %d\n, sizeof(b));
printf(in main: %d\n, sizeof(astruct));
go(a, b);
}
produces
in main: 16
in main: 16
in main: 20
in main: 20
in go: 8
in go: 16
in go: 20
in go: 20
The FFI is not just used for making function calls, it is also used
for specify structures and malloc-ing on behalf of the functions you
want to call. It is very awkward to make cstructs that are the correct
size and malloc the right amount without similar functionality to C in
this regard.
Jay
On Thu, Sep 30, 2010 at 4:51 PM, Matthew Flatt mfl...@cs.utah.edu wrote:
When you run this program on a 32-bit machine:
#include stdio.h
void go(float a[4])
{
printf(in go: %d\n, sizeof(a));
}
int main() {
float a[4];
printf(in main: %d\n, sizeof(a));
go(a);
}
you'll see in main: 16 and in go: 4.
As far as I know, the 4 in void go(float a[4]) is ignored. It's
really the same as void go(float a[]) or void go(float *a). Unless
the declaration of an array variable is allocating the variable, the
variable is really a pointer, and sizeof() reflects that.
Along the same lines, a `_cvector' in the FFI always has a pointer
size, because it's always like a pointer.
A `(_cvector o _float 4)' or `(_f32vector o 4)' is probably
what you want, if the function you'll calling fills in the vector. A
`_float4-pointer' (not `_float4'!) if you allocate it yourself or
`(_pointer o _float4)' is also fine.
At Thu, 30 Sep 2010 16:41:29 -0600, Jay McCarthy wrote:
I'd like to be able to define ctypes like I would make a typedef in C like
typedef float float4[4];
But it doesn't seem like this works in the FFI. See the program below
with its awkward work-around:
#lang racket
(require ffi/unsafe
ffi/unsafe/cvector
ffi/vector
tests/eli-tester)
(test
(ctype-sizeof _float) = 4
(ctype-sizeof _cvector) = 4
(ctype-sizeof (_cvector i _float)) = 4
(ctype-sizeof (_cvector o _float 4)) = (* 4 4)
(ctype-sizeof (_cvector io _float 4)) = (* 4 4)
(ctype-sizeof _f32vector) = 4
(ctype-sizeof (_f32vector i)) = 4
(ctype-sizeof (_f32vector o 4)) = (* 4 4)
(ctype-sizeof (_f32vector io 4)) = (* 4 4)
(local [(define-cstruct _float4
([f0 _float]
[f1 _float]
[f2 _float]
[f3 _float]))]
(test
(ctype-sizeof _float4) = 16)))
Output is:
test: 5/11 test failures:
unsaved-editor4119:11:1: test failure in (ctype-sizeof (_cvector i
_float))
expected: 4
got: error: expand: unbound identifier in module
unsaved-editor4119:12:1: test failure in (ctype-sizeof (_cvector o _float
4))
expected: 16
got: 4
unsaved-editor4119:13:1: test failure in (ctype-sizeof (_cvector io _float
4))
expected: 16
got: error: expand: unbound identifier in module
unsaved-editor4119:17:1: test failure in (ctype-sizeof (_f32vector o 4))
expected: 16
got: 4
unsaved-editor4119:18:1: test failure in (ctype-sizeof (_f32vector io 4))
expected: 16
got: error: expand: unbound identifier in module
Normally I would just go do this, but I don't really understand the
FFI. If someone can point me appropriately, I'll go do it.
Jay
--
Jay McCarthy j...@cs.byu.edu
Assistant Professor / Brigham Young University
http://teammccarthy.org/jay
The glory of God is Intelligence - DC 93
_
For list-related administrative tasks:
http://lists.racket-lang.org/listinfo/dev
--
Jay McCarthy j...@cs.byu.edu
Assistant Professor / Brigham Young University
