Helper Class Reference

Static helper class that includes some functionalities used in multiple places throughout the library, especially the ThingsBoardHttp and ThingsBoard implementations. More...

#include <Helper.h>

Static Public Member Functions
template<typename... Args>
static size_t	Calculate_Print_Size (char const *format, Args const &... args)
	Returns the total amount of bytes needed to store the formatted string with null termination, that will be created if the given format string and the arguments are passed to snprintf. More...
static size_t	Calculate_Symbol_Occurences (uint8_t const *bytes, char symbol, uint32_t length)
	Returns the amount of occurences of the given smybol in the given byte payload. More...
static bool	String_IsNull_Or_Empty (char const *str)
	Returns wheter the given string is either a nullptr or is an empty string, meaning it only contains a null terminator and no other characters. More...
static size_t	Split_Topic_Into_Request_ID (char const *received_topic, size_t const &end_position)
	Splits the topic at the given position and extracts the request id parameter from the remaining string. More...
template<typename TSource >
static size_t	Measure_Json (TSource const &source)
	Calculates the total size of the string the serializeJson method would produce including the null end terminator. More...
template<typename InputIterator >
static size_t	distance (InputIterator const &first, InputIterator const &last)
	Calculates the distance between two iterators. More...

Detailed Description

Static helper class that includes some functionalities used in multiple places throughout the library, especially the ThingsBoardHttp and ThingsBoard implementations.

Member Function Documentation

Calculate_Print_Size()

template<typename... Args>

static size_t Helper::Calculate_Print_Size ( char const *  format, Args const &...  args  )

inlinestatic

Returns the total amount of bytes needed to store the formatted string with null termination, that will be created if the given format string and the arguments are passed to snprintf.

Note

This is achieved by using the snprintf without a buffer that the string should be copied into and with the buffer size of 0. This works because the result returned by snprintf is what would have been written if the passed buffer would have been large enough not counting null character, or if an error occured while creating the string a negative number is returned instead. This value is then simply incremented by 1 and returned. Additionally to ensure no negative number is ever returned even if an error occured an assert is called beforehand to ensure the size value is bigger than 0

Template Parameters

...Args

Holds the multiple arguments that will simply be forwarded to the snprintf method, allowing any arbitrary amount of combinations without having to rely on va_list

Parameters

format	Non owning pointer to the formatting message that the given arguments will be inserted into. Does not need to be kept alive, because the formatting message is only used for the scope of the method itself
...args	Arguments that will be forwarded into the snprintf method see https://cplusplus.com/reference/cstdio/snprintf/ for more information

Returns

Amount of bytes in characters, needed for the formatted string with the given arguments inserted, to be displayed completly including null termination

Calculate_Symbol_Occurences()

size_t Helper::Calculate_Symbol_Occurences ( uint8_t const *  bytes, char  symbol, uint32_t  length  )

static

Returns the amount of occurences of the given smybol in the given byte payload.

Parameters

bytes	Non owning pointer to the byte payload that we want to check the symbol for. Does not need to be kept alive, because the byte payload is only used for the scope of the method itself
symbol	Symbol we want to search for
length	Length of the byte payload, meaning if we reach the given length and have not found any occurence of the symbol we return 0. Ensure to never pass a length that is longer than the actualy payload, because this will cause this method to read outside of the bounds of the buffer

Returns

Amount of occurences of the given symbol

distance()

template<typename InputIterator >

static size_t Helper::distance ( InputIterator const &  first, InputIterator const &  last  )

inlinestatic

Calculates the distance between two iterators.

Template Parameters

InputIterator

Class that allows for forward incrementable access to data of the given data container, allows for using / passing either std::vector or std::array. See https://en.cppreference.com/w/cpp/iterator/input_iterator for more information on the requirements of the iterator

Parameters

first	Iterator pointing to the first element in the data container
last	Iterator pointing to the end of the data container (last element + 1)

Returns

Distance between the two iterators

Measure_Json()

template<typename TSource >

static size_t Helper::Measure_Json ( TSource const &  source )

inlinestatic

Calculates the total size of the string the serializeJson method would produce including the null end terminator.

Note

Be aware that null terminator will later not be serialized in the serializeJson method, meaning the returned written amount of bytes is the return value of this method - 1. See https://arduinojson.org/v6/api/json/measurejson/ for more information on the underlying method used

Template Parameters

TSource

Source class that should be used to serialize the json that is sent to the server

Parameters

source

Source containing our json key-value pairs that we want to measure the resulting size of the serializeJson call for

Returns

Total size required for the string that would be produced by serializeJson + 1 byte for the string null terminator

Split_Topic_Into_Request_ID()

size_t Helper::Split_Topic_Into_Request_ID ( char const *  received_topic, size_t const &  end_position  )

static

Splits the topic at the given position and extracts the request id parameter from the remaining string.

Note

Should contain the request id that the original request was sent with. Is used to know which received response is connected to which inital request, so that the correct request can be informed that a response has been received. To achieve this the function removes the not needed part of the received topic string, which is everything before the request id and then simply call the atoi function on the remaning topic string.

Parameters

received_topic	Non owning pointer to the received topic that contains the base topic as well as the request id parameter (v1/devices/me/rpc/response/$request_id). Does not need to be kept alive, because the received topic is only used for the scope of the method itself
end_position	Number indicating the amount of characters that have to be incremented to reach the position where the $request_id lies in the received topic. Most of the time it can simply be the value returned by calling strlen() on the base version of the topic. So for example on (v1/devices/me/rpc/response/) instead of the received topic (v1/devices/me/rpc/response/42)

Returns

Converted integral request id if possible or 0 if parsing as an integer failed

String_IsNull_Or_Empty()

bool Helper::String_IsNull_Or_Empty ( char const *  str )

static

Returns wheter the given string is either a nullptr or is an empty string, meaning it only contains a null terminator and no other characters.

Parameters

str	Non owning poitner to the string that we want to check for emptiness

Returns

Wheter the given string is a nullptr or empty

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The documentation for this class was generated from the following files:

• src/Helper.h
• src/Helper.cpp