Alignment in ctypes struct field
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I have a library with structs like this:
#define __aligned_u64 __u64 __attribute__((aligned(8)))
struct my_struct {
uint32_t a;
uint32_t b;
uint8_t c[8];
uint32_t d;
uint32_t e;
__aligned_u64 f;
__aligned_u64 g;
uint64_t h;
...
} __attribute__((aligned(8)));
I want to parse it with a ctypes Structure. I think the structure alignment attribute (at the end) is not important for the Python Structure (not to be confused with packed).
But I suspect that the alignment of the fields f and g (the same __aligned_u64 used in the Linux kernel) may mess with the arrangement of the bytes, adding some potential padding after field e. I didn't see any option in Structure to define this.
Any ideas? Alternatives? I would like it to be portable...
python struct ctypes memory-alignment
asked Nov 12 at 16:28
oarcas
1185
add a comment |
up vote
0
down vote
favorite
I have a library with structs like this:
#define __aligned_u64 __u64 __attribute__((aligned(8)))
struct my_struct {
uint32_t a;
uint32_t b;
uint8_t c[8];
uint32_t d;
uint32_t e;
__aligned_u64 f;
__aligned_u64 g;
uint64_t h;
...
} __attribute__((aligned(8)));
I want to parse it with a ctypes Structure. I think the structure alignment attribute (at the end) is not important for the Python Structure (not to be confused with packed).
But I suspect that the alignment of the fields f and g (the same __aligned_u64 used in the Linux kernel) may mess with the arrangement of the bytes, adding some potential padding after field e. I didn't see any option in Structure to define this.
Any ideas? Alternatives? I would like it to be portable...
python struct ctypes memory-alignment
asked Nov 12 at 16:28
oarcas
1185
PD: I verified that the first fields, such a and b are correct, but I have doubts about the rest...
– oarcas
Nov 12 at 16:32
Couldn't find the answer, but since fields a + b + c + d + e take 24 bytes, f and g are already aligned to 8 bytes, so no extra alignment is needed.
– oarcas
Nov 14 at 16:52
add a comment |
up vote
0
down vote
favorite
up vote
0
down vote
favorite
I have a library with structs like this:
#define __aligned_u64 __u64 __attribute__((aligned(8)))
struct my_struct {
uint32_t a;
uint32_t b;
uint8_t c[8];
uint32_t d;
uint32_t e;
__aligned_u64 f;
__aligned_u64 g;
uint64_t h;
...
} __attribute__((aligned(8)));
I want to parse it with a ctypes Structure. I think the structure alignment attribute (at the end) is not important for the Python Structure (not to be confused with packed).
But I suspect that the alignment of the fields f and g (the same __aligned_u64 used in the Linux kernel) may mess with the arrangement of the bytes, adding some potential padding after field e. I didn't see any option in Structure to define this.
Any ideas? Alternatives? I would like it to be portable...
python struct ctypes memory-alignment
asked Nov 12 at 16:28
oarcas
1185
I have a library with structs like this:
#define __aligned_u64 __u64 __attribute__((aligned(8)))
struct my_struct {
uint32_t a;
uint32_t b;
uint8_t c[8];
uint32_t d;
uint32_t e;
__aligned_u64 f;
__aligned_u64 g;
uint64_t h;
...
} __attribute__((aligned(8)));
I want to parse it with a ctypes Structure. I think the structure alignment attribute (at the end) is not important for the Python Structure (not to be confused with packed).
But I suspect that the alignment of the fields f and g (the same __aligned_u64 used in the Linux kernel) may mess with the arrangement of the bytes, adding some potential padding after field e. I didn't see any option in Structure to define this.
Any ideas? Alternatives? I would like it to be portable...
python struct ctypes memory-alignment
python struct ctypes memory-alignment
asked Nov 12 at 16:28
oarcas
1185
asked Nov 12 at 16:28
oarcas
1185
asked Nov 12 at 16:28
oarcas
1185
asked Nov 12 at 16:28
oarcas
1185
asked Nov 12 at 16:28
oarcas
1185
1185
PD: I verified that the first fields, such a and b are correct, but I have doubts about the rest...
– oarcas
Nov 12 at 16:32
Couldn't find the answer, but since fields a + b + c + d + e take 24 bytes, f and g are already aligned to 8 bytes, so no extra alignment is needed.
– oarcas
Nov 14 at 16:52
add a comment |
PD: I verified that the first fields, such a and b are correct, but I have doubts about the rest...
– oarcas
Nov 12 at 16:32
Couldn't find the answer, but since fields a + b + c + d + e take 24 bytes, f and g are already aligned to 8 bytes, so no extra alignment is needed.
– oarcas
Nov 14 at 16:52
PD: I verified that the first fields, such a and b are correct, but I have doubts about the rest...
– oarcas
Nov 12 at 16:32
PD: I verified that the first fields, such a and b are correct, but I have doubts about the rest...
– oarcas
Nov 12 at 16:32
Couldn't find the answer, but since fields a + b + c + d + e take 24 bytes, f and g are already aligned to 8 bytes, so no extra alignment is needed.
– oarcas
Nov 14 at 16:52
Couldn't find the answer, but since fields a + b + c + d + e take 24 bytes, f and g are already aligned to 8 bytes, so no extra alignment is needed.
– oarcas
Nov 14 at 16:52
add a comment |
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PD: I verified that the first fields, such a and b are correct, but I have doubts about the rest...
– oarcas
Nov 12 at 16:32
Couldn't find the answer, but since fields a + b + c + d + e take 24 bytes, f and g are already aligned to 8 bytes, so no extra alignment is needed.
– oarcas
Nov 14 at 16:52