How to correctly copy Boost arrays in ROS callbacks?
I am relatively new to C++ (I am experienced in C and embedded C), some C++ concepts are still difficult to wrap my head around.
I am trying to copy boost array from a ROS callback. For those who are not familiar with ROS, the callback in my program (node) passes a reference to an object from the ROS messaging system.
The callback's declaration is: void callback(const boost::shared_ptr<std_msgs::uint8_t>&);
Let's say I have two references that I want to copy from the callback, one of bool foo and another one boost::array<uint8_t, 8UL> bar.
Now, this is how I can copy the bool type:
bool x;
void callback(const boost::shared_ptr<std_msgs::uint8_t>& msg) {
x = msg->foo;
}
This works fine, copies the value into another variable before the object is destructed.
Now, I am not familiar with Boost at all. Boost's array public construct/copy/destruct is this (reference):
template<typename U> array& operator=(const array<U, N>& other);
Effects:
std::copy(rhs.begin(),rhs.end(), begin())
Here's how I am trying to do to copy bar variable:
boost::array<uint8_t, 8UL> y;
void callback(const boost::shared_ptr<std_msgs::uint8_t>& msg) {
std::copy(msg->bar.begin(), msg->bar.end() + 8, y.begin());
}
This again works fine, however is that the correct way of doing it? As far as I know std::copy function uses iterators, I don't exactly understand how this works (and if it's correct). I am familiar with memcpy(), could I use that instead, and if so, what would be the advantages?
EDIT: Also, if I did something like this:
boost::array<uint8_t, 8UL> y;
void callback(const boost::shared_ptr<std_msgs::uint8_t>& msg) {
y = msg->bar;
}
Would that be copied or referenced?
c++ arrays boost callback ros
add a comment |
I am relatively new to C++ (I am experienced in C and embedded C), some C++ concepts are still difficult to wrap my head around.
I am trying to copy boost array from a ROS callback. For those who are not familiar with ROS, the callback in my program (node) passes a reference to an object from the ROS messaging system.
The callback's declaration is: void callback(const boost::shared_ptr<std_msgs::uint8_t>&);
Let's say I have two references that I want to copy from the callback, one of bool foo and another one boost::array<uint8_t, 8UL> bar.
Now, this is how I can copy the bool type:
bool x;
void callback(const boost::shared_ptr<std_msgs::uint8_t>& msg) {
x = msg->foo;
}
This works fine, copies the value into another variable before the object is destructed.
Now, I am not familiar with Boost at all. Boost's array public construct/copy/destruct is this (reference):
template<typename U> array& operator=(const array<U, N>& other);
Effects:
std::copy(rhs.begin(),rhs.end(), begin())
Here's how I am trying to do to copy bar variable:
boost::array<uint8_t, 8UL> y;
void callback(const boost::shared_ptr<std_msgs::uint8_t>& msg) {
std::copy(msg->bar.begin(), msg->bar.end() + 8, y.begin());
}
This again works fine, however is that the correct way of doing it? As far as I know std::copy function uses iterators, I don't exactly understand how this works (and if it's correct). I am familiar with memcpy(), could I use that instead, and if so, what would be the advantages?
EDIT: Also, if I did something like this:
boost::array<uint8_t, 8UL> y;
void callback(const boost::shared_ptr<std_msgs::uint8_t>& msg) {
y = msg->bar;
}
Would that be copied or referenced?
c++ arrays boost callback ros
1
'Would that be copied or referenced?' Copied. It calls the assigment operator for the boost array which copies the elements. Note there is no way in C++ to copy a reference. Maybe that helps.
– john
Jan 20 at 14:47
@john, thank you, that's really helpful. What about the correct way of copying?
– user10940762
Jan 20 at 14:50
1
Using the assignment operator is the correct way (in this case). Usingstd::copycomes to the same thing but is less idiomatic.
– john
Jan 20 at 14:51
@john, after looking at that reference link I can now see what you mean (even though I am not very familiar with templates and OOP). If you put this in an answer I will give it a star, thank you!
– user10940762
Jan 20 at 15:10
add a comment |
I am relatively new to C++ (I am experienced in C and embedded C), some C++ concepts are still difficult to wrap my head around.
I am trying to copy boost array from a ROS callback. For those who are not familiar with ROS, the callback in my program (node) passes a reference to an object from the ROS messaging system.
The callback's declaration is: void callback(const boost::shared_ptr<std_msgs::uint8_t>&);
Let's say I have two references that I want to copy from the callback, one of bool foo and another one boost::array<uint8_t, 8UL> bar.
Now, this is how I can copy the bool type:
bool x;
void callback(const boost::shared_ptr<std_msgs::uint8_t>& msg) {
x = msg->foo;
}
This works fine, copies the value into another variable before the object is destructed.
Now, I am not familiar with Boost at all. Boost's array public construct/copy/destruct is this (reference):
template<typename U> array& operator=(const array<U, N>& other);
Effects:
std::copy(rhs.begin(),rhs.end(), begin())
Here's how I am trying to do to copy bar variable:
boost::array<uint8_t, 8UL> y;
void callback(const boost::shared_ptr<std_msgs::uint8_t>& msg) {
std::copy(msg->bar.begin(), msg->bar.end() + 8, y.begin());
}
This again works fine, however is that the correct way of doing it? As far as I know std::copy function uses iterators, I don't exactly understand how this works (and if it's correct). I am familiar with memcpy(), could I use that instead, and if so, what would be the advantages?
EDIT: Also, if I did something like this:
boost::array<uint8_t, 8UL> y;
void callback(const boost::shared_ptr<std_msgs::uint8_t>& msg) {
y = msg->bar;
}
Would that be copied or referenced?
c++ arrays boost callback ros
I am relatively new to C++ (I am experienced in C and embedded C), some C++ concepts are still difficult to wrap my head around.
I am trying to copy boost array from a ROS callback. For those who are not familiar with ROS, the callback in my program (node) passes a reference to an object from the ROS messaging system.
The callback's declaration is: void callback(const boost::shared_ptr<std_msgs::uint8_t>&);
Let's say I have two references that I want to copy from the callback, one of bool foo and another one boost::array<uint8_t, 8UL> bar.
Now, this is how I can copy the bool type:
bool x;
void callback(const boost::shared_ptr<std_msgs::uint8_t>& msg) {
x = msg->foo;
}
This works fine, copies the value into another variable before the object is destructed.
Now, I am not familiar with Boost at all. Boost's array public construct/copy/destruct is this (reference):
template<typename U> array& operator=(const array<U, N>& other);
Effects:
std::copy(rhs.begin(),rhs.end(), begin())
Here's how I am trying to do to copy bar variable:
boost::array<uint8_t, 8UL> y;
void callback(const boost::shared_ptr<std_msgs::uint8_t>& msg) {
std::copy(msg->bar.begin(), msg->bar.end() + 8, y.begin());
}
This again works fine, however is that the correct way of doing it? As far as I know std::copy function uses iterators, I don't exactly understand how this works (and if it's correct). I am familiar with memcpy(), could I use that instead, and if so, what would be the advantages?
EDIT: Also, if I did something like this:
boost::array<uint8_t, 8UL> y;
void callback(const boost::shared_ptr<std_msgs::uint8_t>& msg) {
y = msg->bar;
}
Would that be copied or referenced?
c++ arrays boost callback ros
c++ arrays boost callback ros
edited Jan 20 at 14:49
asked Jan 20 at 14:15
user10940762
1
'Would that be copied or referenced?' Copied. It calls the assigment operator for the boost array which copies the elements. Note there is no way in C++ to copy a reference. Maybe that helps.
– john
Jan 20 at 14:47
@john, thank you, that's really helpful. What about the correct way of copying?
– user10940762
Jan 20 at 14:50
1
Using the assignment operator is the correct way (in this case). Usingstd::copycomes to the same thing but is less idiomatic.
– john
Jan 20 at 14:51
@john, after looking at that reference link I can now see what you mean (even though I am not very familiar with templates and OOP). If you put this in an answer I will give it a star, thank you!
– user10940762
Jan 20 at 15:10
add a comment |
1
'Would that be copied or referenced?' Copied. It calls the assigment operator for the boost array which copies the elements. Note there is no way in C++ to copy a reference. Maybe that helps.
– john
Jan 20 at 14:47
@john, thank you, that's really helpful. What about the correct way of copying?
– user10940762
Jan 20 at 14:50
1
Using the assignment operator is the correct way (in this case). Usingstd::copycomes to the same thing but is less idiomatic.
– john
Jan 20 at 14:51
@john, after looking at that reference link I can now see what you mean (even though I am not very familiar with templates and OOP). If you put this in an answer I will give it a star, thank you!
– user10940762
Jan 20 at 15:10
1
1
'Would that be copied or referenced?' Copied. It calls the assigment operator for the boost array which copies the elements. Note there is no way in C++ to copy a reference. Maybe that helps.
– john
Jan 20 at 14:47
'Would that be copied or referenced?' Copied. It calls the assigment operator for the boost array which copies the elements. Note there is no way in C++ to copy a reference. Maybe that helps.
– john
Jan 20 at 14:47
@john, thank you, that's really helpful. What about the correct way of copying?
– user10940762
Jan 20 at 14:50
@john, thank you, that's really helpful. What about the correct way of copying?
– user10940762
Jan 20 at 14:50
1
1
Using the assignment operator is the correct way (in this case). Using
std::copy comes to the same thing but is less idiomatic.– john
Jan 20 at 14:51
Using the assignment operator is the correct way (in this case). Using
std::copy comes to the same thing but is less idiomatic.– john
Jan 20 at 14:51
@john, after looking at that reference link I can now see what you mean (even though I am not very familiar with templates and OOP). If you put this in an answer I will give it a star, thank you!
– user10940762
Jan 20 at 15:10
@john, after looking at that reference link I can now see what you mean (even though I am not very familiar with templates and OOP). If you put this in an answer I will give it a star, thank you!
– user10940762
Jan 20 at 15:10
add a comment |
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1
'Would that be copied or referenced?' Copied. It calls the assigment operator for the boost array which copies the elements. Note there is no way in C++ to copy a reference. Maybe that helps.
– john
Jan 20 at 14:47
@john, thank you, that's really helpful. What about the correct way of copying?
– user10940762
Jan 20 at 14:50
1
Using the assignment operator is the correct way (in this case). Using
std::copycomes to the same thing but is less idiomatic.– john
Jan 20 at 14:51
@john, after looking at that reference link I can now see what you mean (even though I am not very familiar with templates and OOP). If you put this in an answer I will give it a star, thank you!
– user10940762
Jan 20 at 15:10