I get a compile error, additionally I cannot boost::asio::read buf without giving it array elements.

std::string eport::read_data (void)
{
    io_service io;  // create the I/O service that talks to the serial device
    serial_port port (io, PORT);    // create the serial device, note it takes the io service and the port name
    error_code ec;  // address used for error checking
    std::string buf [100];  // data with crc on end

    try
    {
        read (port, buffer (buf), ec);
        std::cout << "eport::read: result: " << buf << std::endl;
    }
    catch (error_code &ec)
    {
        std::cout << "eport::read: ERROR: " << ec << std::endl; 
        return "error";
    }

    std::cout << "eport::read: SUCCESS" << std::endl;

    return buf;

The error:

eport.cc:83:9: error: could not convert ‘(std::string*)(& buf)’ from ‘std::string* {aka std::basic_string<char>*}’ to ‘std::string {aka std::basic_string<char>}’

Does the function need to be cast as const char* ? I am not sure what is wrong. Any help is appreciated, thank you.

UPDATED CODE

This is my code. I hope it can help someone because asio lacks good examples on the web. I know my write function could be written better, and this code has not been tested so I'm not sure if I'm doing this right or not. Thanks.

#include "../include/main.H"
#include <boost/asio.hpp>   // asynchronous input/output
#include <boost/crc.hpp>    // cyclic redundancy code (for data checking)

using namespace::boost::system;
using namespace::boost::asio;

const char *PORT = "/dev/ttyS0";

// serial port communication setup
serial_port_base::baud_rate BAUD (9600);    // what baud rate do we communicate at (default is 9600)
serial_port_base::character_size C_SIZE (8);    // how big is each "packet" of data (default is 8 bits)
serial_port_base::flow_control FLOW (serial_port_base::flow_control::none); // what flow control is used (default is none)
serial_port_base::parity PARITY (serial_port_base::parity::none);   // what parity is used (default is none)
serial_port_base::stop_bits STOP (serial_port_base::stop_bits::one);    // how many stop bits are used (default is one)

int eport::initialize (void)
{
    io_service io;  // create the I/O service that talks to the serial device
    serial_port port (io, PORT);    // create the serial device, note it takes the io service and the port name

    // set serial port options
    port.set_option (BAUD);
    port.set_option (C_SIZE);
    port.set_option (FLOW);
    port.set_option (PARITY);
    port.set_option (STOP);

    return 0;
}

int eport::write_data (std::string data)
{
    io_service io;  // create the I/O service that talks to the serial device
    serial_port port (io, PORT);    // create the serial device, note it takes the io service and the port name
    error_code ec;  // address used for error checking
    boost::crc_32_type crcresult;   // used for communication checking
    char buf [1024];    // buffer to hold data
    int crc;    // holds crc value
    std::ostringstream convert; // used to convert int to string
    std::string data_crc;   // data with crc on end
    std::stringstream ss;   // used to add strings

    strncpy (buf, data.c_str(), sizeof(buf));   // put data into buffer
    buf [sizeof(buf) - 1] = 0;  // make sure the last element has a null

    crcresult.process_bytes (buf, sizeof(buf)); // get crc value from buffer contents
    crc = crcresult.checksum(); // put crc value into integer
    convert << crc; // convert integer to string
    ss << data << convert.str ();   // add crc string to data string
    data_crc = ss.str ();   // data string with crc appended to be used in reading / writing
    std::cout << "eport::write: data with crc: " << data_crc << std::endl; 

    std::cout << "eport::write: writing: " << data_crc << std::endl; 
    write (port, buffer (data_crc, sizeof(data_crc)), ec);  // write data with crc to serial device

    if (ec) // if error code is true, print and return
    {
        std::cout << "eport::write: ERROR: " << ec << std::endl; 
        return -1;
    }

    std::cout << "eport::write: SUCCESS" << std::endl;

    return crc;
}

std::string eport::read_data (void)
{
    io_service io;  // create the I/O service that talks to the serial device
    serial_port port (io, PORT);    // create the serial device, note it takes the io service and the port name
    error_code ec;  // address used for error checking
    streambuf sb;   // asio stream buffer to hold read data
    std::string buf;    // read buffer will be put into this string

    size_t transferred = read (port, sb, ec);   // read data from serial device
    buf.resize (transferred);   // resize the string to the read data size
    sb.sgetn (&buf[0], buf.size ());    // stores characters from the stream to the array
    std::cout << "eport::read: result: " << buf << std::endl;

    if (ec)
    {
        std::cout << "eport::read: ERROR: " << ec << std::endl; 
        return "error";
    }

    std::cout << "eport::read: SUCCESS" << std::endl;

    return buf;
}