uint8_t* data = reinterpret_cast<uint8_t*>(buffer.get());
时间: 2024-04-11 09:25:32 浏览: 16
`uint8_t* data = reinterpret_cast<uint8_t*>(buffer.get());` 这行代码是将一个指针 `buffer` 转换为 `uint8_t*` 类型的指针 `data`。
`reinterpret_cast` 是 C++ 中的一种类型转换操作符,它可以将一个指针或引用转换为另一种类型的指针或引用,而不进行类型检查。在这个例子中,`reinterpret_cast<uint8_t*>` 将 `buffer.get()` 的返回值转换为 `uint8_t*` 类型。
`buffer.get()` 是一个智能指针 `buffer` 的成员函数,它返回指向所管理对象的原始指针。
所以,这行代码的作用是将智能指针 `buffer` 所管理对象的原始指针转换为 `uint8_t*` 类型的指针 `data`。
相关问题
写出这段函数的调用方法:int16_t SdFile::read(void* buf, uint16_t nbyte) { uint8_t* dst = reinterpret_cast<uint8_t*>(buf); // error if not open or write only if (!isOpen() || !(flags_ & F_READ)) return -1; // max bytes left in file if (nbyte > (fileSize_ - curPosition_)) nbyte = fileSize_ - curPosition_; // amount left to read uint16_t toRead = nbyte; while (toRead > 0) { uint32_t block; // raw device block number uint16_t offset = curPosition_ & 0X1FF; // offset in block if (type_ == FAT_FILE_TYPE_ROOT16) { block = vol_->rootDirStart() + (curPosition_ >> 9); } else { uint8_t blockOfCluster = vol_->blockOfCluster(curPosition_); if (offset == 0 && blockOfCluster == 0) { // start of new cluster if (curPosition_ == 0) { // use first cluster in file curCluster_ = firstCluster_; } else { // get next cluster from FAT if (!vol_->fatGet(curCluster_, &curCluster_)) return -1; } } block = vol_->clusterStartBlock(curCluster_) + blockOfCluster; } uint16_t n = toRead; // amount to be read from current block if (n > (512 - offset)) n = 512 - offset; // no buffering needed if n == 512 or user requests no buffering if ((unbufferedRead() || n == 512) && block != SdVolume::cacheBlockNumber_) { if (!vol_->readData(block, offset, n, dst)) return -1; dst += n; } else { // read block to cache and copy data to caller if (!SdVolume::cacheRawBlock(block, SdVolume::CACHE_FOR_READ)) return -1; uint8_t* src = SdVolume::cacheBuffer_.data + offset; uint8_t* end = src + n; while (src != end) *dst++ = *src++; } curPosition_ += n; toRead -= n; } return nbyte; }
假设已经创建了一个SdFile对象,名为myFile,要读取其中的数据并存储到一个名为data的缓冲区中,可以调用如下代码:
```
char data[100]; // 缓冲区,用于存储读取的数据
int16_t bytesRead = myFile.read(data, sizeof(data)); // 调用read()方法读取数据
if (bytesRead > 0) {
// 成功读取数据
// 处理读取的数据,例如打印出来
Serial.print("Read data: ");
Serial.println(data);
} else {
// 读取失败
Serial.println("Failed to read data!");
}
```
write a C++ example shows how to do force or torque control in offboard mode from a ROS 2 node with XRCE-DDS
Here's an example of how to do force control in offboard mode using C++ and XRCE-DDS:
```cpp
#include <iostream>
#include <chrono>
#include <thread>
#include "rclcpp/rclcpp.hpp"
#include "geometry_msgs/msg/wrench_stamped.hpp"
#include "std_msgs/msg/float64_multi_array.hpp"
#include "rosidl_runtime_cpp/message_type_support_decl.hpp"
#include "rosidl_typesupport_cpp/message_type_support.hpp"
#include "rmw_fastrtps_cpp/get_participant.hpp"
#include "rmw_fastrtps_cpp/get_publisher.hpp"
#include "rmw_fastrtps_cpp/get_subscriber.hpp"
#include "rmw_uros/options.h"
#include "uxr/client/client.h"
#include "sensor_msgs/msg/joint_state.hpp"
using namespace std::chrono_literals;
#define DEFAULT_TIMEOUT 1000
void set_wrench(float fx, float fy, float fz, float tx, float ty, float tz, geometry_msgs::msg::WrenchStamped& wrench)
{
wrench.wrench.force.x = fx;
wrench.wrench.force.y = fy;
wrench.wrench.force.z = fz;
wrench.wrench.torque.x = tx;
wrench.wrench.torque.y = ty;
wrench.wrench.torque.z = tz;
}
class ForceControlNode : public rclcpp::Node
{
public:
ForceControlNode() : Node("force_control_node")
{
joint_state_sub_ = this->create_subscription<sensor_msgs::msg::JointState>("joint_states", 10,
std::bind(&ForceControlNode::joint_state_callback, this, std::placeholders::_1));
wrench_pub_ = this->create_publisher<geometry_msgs::msg::WrenchStamped>("wrench", 10);
setup_dds();
}
private:
void setup_dds()
{
auto domain_id = 0;
uxr_set_custom_transport(uxr::Transport::CUSTOM);
rmw_uros_options_t custom_transport_options = rmw_get_zero_initialized_uros_options();
uxr_init_custom_transport(&custom_transport_options, uxr_common_tcp_platform);
const char* participant_name = "force_control_participant";
const char* topic_name = "force_control_topic";
// Create participant
uxr_init_options_t init_options = uxr_init_options_create();
uxr_set_custom_transport_callbacks(
&init_options,
uxr_common_tcp_platform,
custom_transport_open_cb,
custom_transport_close_cb,
custom_transport_write_cb,
custom_transport_read_cb,
reinterpret_cast<void*>(this));
participant_ = rmw_fastrtps_cpp::get_participant(
this->get_node_base_interface(),
this->get_node_topics_interface(),
domain_id,
participant_name,
"", // empty node namespace
std::vector<std::string>());
// Register ROS message type with XRCE-DDS
const rosidl_message_type_support_t* type_support =
rosidl_typesupport_cpp::get_message_type_support_handle<geometry_msgs::msg::WrenchStamped>();
uxr_register_topic_xml(
&session_,
participant_->impl_->participant,
topic_name,
type_support->typesupport_identifier,
"<dds>"
"<topic>"
"<name>force_control_topic</name>"
"<dataType>geometry_msgs::msg::WrenchStamped_</dataType>"
"</topic>"
"</dds>");
// Create publisher
publisher_ = rmw_fastrtps_cpp::get_publisher(
this->get_node_base_interface(),
this->get_node_topics_interface(),
participant_,
type_support,
topic_name,
"",
&rmw_qos_profile_default);
// Create subscriber
subscriber_ = rmw_fastrtps_cpp::get_subscriber(
this->get_node_base_interface(),
this->get_node_topics_interface(),
participant_,
type_support,
topic_name,
"",
&rmw_qos_profile_default,
false);
// Create session
uxr_init_session_xml(&init_options, &session_, participant_->impl_->participant, domain_id);
UXR_AGENT_LOG_INFO(
&session_.info,
UXR_CREATE_ENTITIES_FROM_REF_RESOURCE,
reinterpret_cast<uint64_t>(participant_->impl_->participant),
session_.last_requested_resource);
// Get publisher and subscriber handles
publisher_handle_ = static_cast<uxrObjectId>(publisher_->publisher_->id_);
subscriber_handle_ = static_cast<uxrObjectId>(subscriber_->subscriber_->id_);
}
void joint_state_callback(const sensor_msgs::msg::JointState::SharedPtr msg)
{
// Compute force and torque based on joint positions and publish to topic
float fx = 0.0;
float fy = 0.0;
float fz = 0.0;
float tx = 0.0;
float ty = 0.0;
float tz = 0.0;
// Compute desired force and torque values here, based on joint positions and other sensor data
geometry_msgs::msg::WrenchStamped wrench;
set_wrench(fx, fy, fz, tx, ty, tz, wrench);
wrench_pub_->publish(wrench);
// Send desired force and torque values to robot using XRCE-DDS
uint8_t buffer[1024];
uint32_t length = 0;
const uint16_t writer_id = 0x01;
const uint16_t reader_id = 0x02;
// Serialize message
ucdrBuffer ub;
ucdr_init_buffer(&ub, buffer, sizeof(buffer));
length = serialize_wrench(msg, &ub);
// Write message to DDS network
uxrStreamId output_stream = uxr_create_output_stream(&session_, UXR_RELIABLE_STREAM);
uxr_prepare_output_stream(&session_, output_stream, publisher_handle_, writer_id, buffer, length);
uxr_run_session_until_timeout(&session_, DEFAULT_TIMEOUT);
uxr_delete_output_stream(&session_, output_stream);
}
uint32_t serialize_wrench(const geometry_msgs::msg::WrenchStamped::SharedPtr msg, ucdrBuffer* ub)
{
uint32_t length = 0;
length += ucdr_serialize_uint32_t(ub, msg->header.stamp.sec);
length += ucdr_serialize_uint32_t(ub, msg->header.stamp.nanosec);
length += ucdr_serialize_float(ub, msg->wrench.force.x);
length += ucdr_serialize_float(ub, msg->wrench.force.y);
length += ucdr_serialize_float(ub, msg->wrench.force.z);
length += ucdr_serialize_float(ub, msg->wrench.torque.x);
length += ucdr_serialize_float(ub, msg->wrench.torque.y);
length += ucdr_serialize_float(ub, msg->wrench.torque.z);
return length;
}
static bool custom_transport_open_cb(void* args, const char* ip, uint16_t port)
{
return true;
}
static bool custom_transport_close_cb(void* args)
{
return true;
}
static size_t custom_transport_write_cb(
void* args,
const uint8_t* buf,
size_t len,
uint8_t* errcode)
{
auto* node = reinterpret_cast<ForceControlNode*>(args);
return node->write_cb(buf, len, errcode);
}
static size_t custom_transport_read_cb(void* args, uint8_t* buf, size_t len, int timeout, uint8_t* errcode)
{
auto* node = reinterpret_cast<ForceControlNode*>(args);
return node->read_cb(buf, len, timeout, errcode);
}
size_t write_cb(const uint8_t* buf, size_t len, uint8_t* errcode)
{
// Write data to ROS topic
geometry_msgs::msg::WrenchStamped wrench;
ucdrBuffer ub;
ucdr_init_buffer(&ub, const_cast<uint8_t*>(buf), len);
deserialize_wrench(&ub, wrench);
wrench_pub_->publish(wrench);
return len;
}
size_t read_cb(uint8_t* buf, size_t len, int timeout, uint8_t* errcode)
{
// Read data from ROS topic
geometry_msgs::msg::WrenchStamped wrench;
if (subscriber_->take(&wrench, nullptr, nullptr) == RMW_RET_OK) {
ucdrBuffer ub;
ucdr_init_buffer(&ub, buf, len);
serialize_wrench(wrench, &ub);
return ub.iterator - ub.init;
}
return 0;
}
void deserialize_wrench(ucdrBuffer* ub, geometry_msgs::msg::WrenchStamped& wrench)
{
wrench.header.stamp.sec = ucdr_deserialize_uint32_t(ub);
wrench.header.stamp.nanosec = ucdr_deserialize_uint32_t(ub);
wrench.wrench.force.x = ucdr_deserialize_float(ub);
wrench.wrench.force.y = ucdr_deserialize_float(ub);
wrench.wrench.force.z = ucdr_deserialize_float(ub);
wrench.wrench.torque.x = ucdr_deserialize_float(ub);
wrench.wrench.torque.y = ucdr_deserialize_float(ub);
wrench.wrench.torque.z = ucdr_deserialize_float(ub);
}
rclcpp::Subscription<sensor_msgs::msg::JointState>::SharedPtr joint_state_sub_;
rclcpp::Publisher<geometry_msgs::msg::WrenchStamped>::SharedPtr wrench_pub_;
rmw_fastrtps_cpp::Participant* participant_;
rmw_fastrtps_cpp::Publisher* publisher_;
rmw_fastrtps_cpp::Subscriber* subscriber_;
uxrSession session_;
uxrObjectId publisher_handle_;
uxrObjectId subscriber_handle_;
};
int main(int argc, char** argv)
{
rclcpp::init(argc, argv);
rclcpp::spin(std::make_shared<ForceControlNode>());
rclcpp::shutdown();
return 0;
}
```
This example subscribes to joint state data and computes the desired force and torque values based on the current joint positions. It then publishes these values to a ROS topic and sends them to the robot using XRCE-DDS. The robot can then use these values to apply the desired force and torque using a force/torque controller.