C++ 字符串数组在 20 字节后拆分

Question

我有这个代码示例，用于制作最终将通过 BLE 发送的 20 字节大小的数据包。我想更改代码，以便输入数据数组（加速度计读数）。

我的数据：

float ax, ay, az, gx, gy, gz, mx, my, mz, yaw, pitch, roll;
char myConcatenation[80];
sprintf(myConcatenation, "%3.2f,%3.2f,%3.2f,%3.2f,%3.2f,%3.2f,%3.2f,%3.2f,%3.2f,%3.2f,%3.2f,%3.2f", ax,  ay, az, gx, gy, gz, mx, my, mz, yaw, pitch, roll);

函数定义：

std::vector<std::string> buildPackets(std::string data, size_t packetSize) {
  // split up the packet
  size_t partialPacketSize = packetSize - 4;

  // calculate how many packets
  size_t packetCount = data.length() / partialPacketSize;
  packetCount = data.length() % partialPacketSize == 0 ? packetCount : packetCount + 1;

  std::vector<std::string> packets;
  // construct each packet
  for (int i = 0; i < packetCount; i++) {
    // start of packet
    std::string packet = "##";
    packet += (char)packetCount;
    packet += (char)(i + 1);
    std::string part = i == packetCount - 1 ? data.substr(i * partialPacketSize) : data.substr(i * partialPacketSize, partialPacketSize);
    packet.append(part);

    // add to vector of packets
    packets.push_back(packet);
  }

函数调用：变量 data 这里是字符串，我只需要把我的 myConcatenation[]

放在那里

我应该对代码进行哪些更改才能使其正常工作？

   std::string data = "averylongstringofdatathatislargerthantwentycharacters";
size_t chars = data.length();
size_t packetSize = 20;

// assume I have this characteristic already setup
if (chars > packetSize) {
  auto packets = buildPackets(data, packetSize);
  for (auto packet : packets) {
    txCharacteristic->setValue(packet);
    txCharacteristic->notify();
  }
}
else {
  txCharacteristic->setValue(data);
  txCharacteristic->notify();
}

感谢您的帮助。

编辑：

this is what I have now: 

std::vector<std::string> buildPackets(std::string data, size_t packetSize) {
  // split up the packet
  size_t partialPacketSize = packetSize - 4;

  // calculate how many packets
  size_t packetCount = data.length() / partialPacketSize;
  packetCount = data.length() % partialPacketSize == 0 ? packetCount : packetCount + 1;

  std::vector<std::string> packets;
  // construct each packet
  for (int i = 0; i < packetCount; i++) {
    // start of packet
    std::string packet = "@";
    packet += (char)packetCount;
    packet += (char)(i + 1);
    std::string part = i == packetCount - 1 ? data.substr(i * partialPacketSize) : data.substr(i * partialPacketSize, partialPacketSize);
    packet.append(part);

    // add to vector of packets
    packets.push_back(packet);
  }

  return packets;
}


--------
**call function**

sprintf(myConcatenation, "#%3.2f,%3.2f,%3.2f,#%3.2f,%3.2f,%3.2f,#%3.2f,%3.2f,%3.2f,#%3.2f,%3.2f,%3.2f", ax,  ay, az, gx, gy, gz, mx, my, mz, yaw, pitch, roll);

size_t packetSize = 20;

auto packets = buildPackets(myConcatenation, packetSize);
  for (auto packet : packets) {
    pCharacteristic->setValue(packet);
    pCharacteristic->notify();
  }

  Serial.println(myConcatenation);

可以问一下收货方吗？我的字符串在每个不同的传感器读数（#ax、ay、az、#gx、gy ...）的开头都有 #，在每个数据包的开头都有 @。你知道接收方应该如何实现吗（我在 MITAppInventor 中这样做，但我想不出如何按顺序连接 packetst 并将它们附加到 .csv 文件中。（每列 = 不同的数据）。

谢谢！

Answer 1

String class 提供了一个接受输入 const char* 的构造函数，因此您可以使用它来将您的变量命名数据（隐式或显式）转换为 std::string.

所以最后，把它传递给函数

float ax, ay, az, gx, gy, gz, mx, my, mz, yaw, pitch, roll; char myConcatenation[80]; sprintf(myConcatenation, "%3.2f,%3.2f,%3.2f,%3.2f,%3.2f,%3.2f,%3.2f,%3.2f,%3.2f,%3.2f,%3.2f,%3.2f", ax, ay, az, gx, gy, gz, mx, my, mz, yaw, pitch, roll); auto packets = buildPackets(myConcatenation, packetSize);

就这些了。

快速补充建议：

把sprintf换成sprintf_s，更安全

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