Uli Köhler

Just add the

-fdiagnostics-color=always

compiler flag

The following encoder can be used to encode frames into a byte stream. It operates on complete buffers (i.e. this is not a streaming encoder) but is fast and easy to use.

/*
 * Author: Uli Köhler - techoverflow.net
 * License: CC0 1.0 Universal
 *
 * Description:
 * This is a C++ implementation of a buffer-based SLIP encoder.
 * It can be used to encode frames unambiguously into a stream of bytes.
 * The encoder does not use any memory allocation, but instead requires
 * the caller to provide a buffer for the encoded data - hence being
 * ideally suited for use in embedded systems
 */
#pragma once
#include <cstdint>
#include <cstddef>

#define SLIP_END             ((uint8_t)0300)   // SLIP end of packet character
#define SLIP_ESC             ((uint8_t)0333)   // SLIP escape character
#define SLIP_ESCEND         ((uint8_t)0334)    // Escaped END data byte
#define SLIP_ESCESC         ((uint8_t)0335)    // Escaped ESC data byte

// Return value of slip_encode_packet if the output buffer is not large enough
#define SLIP_ENCODE_ERROR SIZE_MAX // Maximum value of size_t

/**
 * Determine the packet length when sending the given buffer [p] using SLIP.
 * This DOES NOT ENCODE ANYTHING, it just determines the length
 * which an encoded version of the data would have
 * @return The number of bytes a SLIP encoded version of [in] would consume
 */
size_t slip_packet_length(const uint8_t* in, size_t inlen);

/**
 * Encode given input data using SLIP, saving it into the given output buffer.
 * WARNING! The output buffer MUST have a length of at least the return value of
 *    slip_packet_len(in, inlen)
 * In case the output buffer is not large enough, this function will return SLIP_ENCODE_ERROR and
 * the output buffer will be left in an undefined space.
 * Take special care that the input data does not change between the calls to
 * slip_packet_len() and slip_encode_packet()
 * @return The number of bytes in [out], or SLIP_ENCODE_ERROR
 */
size_t slip_encode_packet(const uint8_t* in, size_t inlen, uint8_t* out, size_t outlen);

/*
 * Author: Uli Köhler - techoverflow.net
 * License: CC0 1.0 Universal
 *
 * Description:
 * This is a C++ implementation of a buffer-based SLIP encoder.
 * It can be used to encode frames unambiguously into a stream of bytes.
 * The encoder does not use any memory allocation, but instead requires
 * the caller to provide a buffer for the encoded data - hence being
 * ideally suited for use in embedded systems
 */
#include "SLIPEncoder.hpp"

size_t slip_packet_length(const uint8_t* in, size_t inlen) {
    // This variable contains the length of the data
    size_t outlen = 0;
    const uint8_t* inend = in + inlen; // First character AFTER the
    for (; in < inend ; in++) {
        switch (*in) {
        case SLIP_END: // Need to escape END character to avoid RX seeing end of frame
            // Same as "case SLIP_ESC" so just continue.
        case SLIP_ESC: // Need to escape ESC character, we'll send
            outlen += 2; // Will send ESC + ESCESC
            break;
        default: // Any other character => will just copy
            outlen++; // Will only send the given character
        }
    }
    // + 1: SLIP END bytes
    return outlen + 1;
}

size_t slip_encode_packet(const uint8_t* in, size_t inlen, uint8_t* out, size_t outlen) {
    // This variable contains the length of the data
    uint8_t* out_start = out; // We will increment [out], hence copy the original value.

    // Output buffer must be AT LEAST as long as input data (sanity check)
    if(outlen < inlen) {
        return SLIP_ENCODE_ERROR;
    }

    uint8_t* outend = out + outlen; // First character AFTER the
    const uint8_t* inend = in + inlen; // First character AFTER the
    for (; in < inend ; in++) {
        switch (*in) {
        case SLIP_END: // Need to escape END character to avoid RX seeing end of frame
            // Check out of bounds memory acces
            if(out + 2 >= outend) {
                return SLIP_ENCODE_ERROR;
            }
            // Copy escaped END character
            *out++ = SLIP_ESC;
            *out++ = SLIP_ESCEND;
            break;
        case SLIP_ESC: // Need to escape ESC character, we'll send
            // Check out of bounds memory access
            if(out + 2 >= outend) {
                return SLIP_ENCODE_ERROR;
            }
            // Copy escaped END character
            *out++ = SLIP_ESC;
            *out++ = SLIP_ESCESC;
            break;
        default: // Any other character => just copy the character
            if(out + 1 >= outend) {
                return SLIP_ENCODE_ERROR;
            }
            *out++ = *in;
        }
    }
    // Check out of bounds access for END byte
    if(out + 1 > outend) { // NOTE: > instead of >= since there is only ONE character to be written
        return SLIP_ENCODE_ERROR;
    }
    // Insert END byte
    *out++ = SLIP_END;
    // Return number of bytes
    return (out - out_start);
}

Problem:

You want to generate a filename, e.g., for datalogging, that contains the current date and time in C++ – for example:

2023-04-22_19-38-34.csv

Solution:

To generate a filename with the current date and time in C++, you can use the chrono library to get the current time and format it as a string. Here’s a code snippet that shows how to do this:

#include <chrono>
#include <iomanip>
#include <sstream>

std::string GetFilenameByCurrentDate(const char* extension=".bin") {
    // Get the current time
    auto now = std::chrono::system_clock::now();

    // Convert to local time
    auto localTime = std::chrono::system_clock::to_time_t(now);

    // Format the timestamp as a string
    std::stringstream ss;
    ss << std::put_time(std::localtime(&localTime), "%F_%H-%M-%S") << extension;
    return ss.str();
}

This function takes an optional extension parameter that specifies the file extension to use (by default, “.bin”). It uses the chrono library to get the current time (now), convert it to local time (localTime), and format it as a string (ss). The put_time function is used to format the time as a string in the format “%F_%H-%M-%S”, which represents the date and time in ISO 8601 format (e.g., 2023-04-23_19-13-22).

This will produce a filename such as 2023-04-23_19-13-22.bin, which can be used to create a new file or to store data in an existing file. By including a timestamp in the filename, you can easily keep track of when the file was created and quickly identify files that were created at a particular time.