README.md

Eclipse iceoryx hoofs overview

The iceoryx hoofs (Handy Objects Optimised For Safety) are our basic building blocks - the foundation of iceoryx. There are a wide variety of building blocks grouped together in modules, depending on where or how they are used.

Modules

The following sections have a column labeled internal to indicate that the API is not stable and can change anytime. You should never rely on it and there is no support if it is used and breaks your code after an update.

Some modules contain STL constructs which are not part of the C++17 standard as well as convenience constructs like the NewType. Since the classes re-implements some STL constructs, the C++ STL coding guidelines are used for all files in this module, to help the user to have a painless transition from the official STL types to ours. The API should also be identical to the corresponding STL types but we have to make exceptions here. For instance, we do not throw exceptions, try to avoid undefined behavior and we do not use dynamic memory. In these cases we adjusted the API to our use case.

Most of the headers are providing some example code on how the class should be used.

The module structure is a logical grouping. It is replicated for concurrent and posix implementations.

Memory & lifetime management (memory)

class	internal	description
unique_ptr		Provides a heap-less unique_ptr implementation, unlike the STL
RelativePointer		Pointer which can be stored in shared memory
relocatable_ptr
static_storage	i	Untyped aligned static storage.
ScopeGuard		This is an abstraction of the C++ RAII idiom. Sometimes you have constructs where you would like to perform a certain task on creation and then again when they are getting out of scope, this is where ScopeGuard comes in. It is like a std::lock_guard or a std::shared_ptr but more generic.
scoped_static		Helper function to limit lifetime of static or global variables to a scope
BumpAllocator		Implementation of a bump allocator

Container (container)

class	internal	description
vector		Heap and exception free implementation of std::vector
forward_list		Heap and exception free, relocatable implementation of std::forward_list
list		Heap and exception free, relocatable implementation of std::list
FixedPositionContainer		A fixed-position container is similar to a list but is optimized for iterating over its elements without the back-and-forth jumping that can occur during iteration in a list.
UninitializedArray		Wrapper class for an uninitialized C-style array which can be zeroed via a template parameter

Vocabulary types (vocabulary)

class	internal	description
not_null		Runtime check wrapper to make sure a pointer is not nullptr
optional		Implementation of std::optional
variant		Implementation of std::variant
expected		Our base class used in error handling. Every function which can fail should return an expected. With this the user knows that this function can fail and that they have to do some kind of error handling. We got inspired by the C++ expected proposal and by the rust error handling concept.
string		Heap and exception free implementation of std::string. Attention, since the string is stack based, std::string or char array which are assigned to this string will be truncated and zero-terminated if they exceed the string capacity.
span		Implementation of std::span

Filesystem (filesystem)

class	internal	description
filesystem		Implementation of C++17 filesystem features for instance iox::access_rights and iox::perms to abstract file permissions
PosixAcl	i	Interface for Access Control Lists (ACL).
FileLock		File lock C++ wrapping class.
FileReader		Wrapper for opening files and reading them.

Functional (functional)

class	internal	description
storable_function	i	A std::function alternative with configurable backend for memory storage.
function		A stack-based std::function replacement based on storable_function
function_ref		Implementation of std::function_ref see function_ref proposal. It behaves like std::function but does not own the callable.

Utility (utility)

class	internal	description
system_configuration	i	Collection of free functions which acquire system information like the page-size.
UniqueId	i	Monotonic increasing IDs within a process.
convert	i	Converting a number into a string is easy, converting it back can be hard. You can use functions like strtoll, but you still have to handle errors like under- and overflow, or converting invalid strings into number. Here we abstract all the error handling so that you can convert strings into numbers safely.
into	i
Scheduler	i	Supported schedulers and functions to get their priority range are contained here.
serialization	i	Implements a simple serialization concept for classes based on the idea presented here ISOCPP serialization.

Primitives (primitives)

class	internal	description
type_traits		Extended support for evaluating types on compile-time.
types		Declares essential building block types like byte.
attributes		C++20 and C++23 attributes are sometimes available through compiler extensions. The attribute macros defined in here make sure that we are able to use them if the compiler supports it.
algorithm		Implements min and max for an arbitrary number of values of the same type. For instance min(1,2,3,4,5);
size		Helper functions to determine the size in generic ways

Buffer (buffer)

class	internal	description
SpscFifo	i	Single producer, single consumer lock-free FiFo
MpmcLockfreeQueue		Multi producer, multi consumer lock-free FiFo with ringbuffer like overflow handling
MpmcLoFFLi	i	Lock-free LIFO based index manager (lock-free free list). One building block of our memory manager. After construction it contains the indices {0 ... n} which you can acquire and release.
SpscSofi	i	Single producer, single consumer lock-free safely overflowing FiFo (SpscSofi).
MpmcResizeableLockFreeQueue		Resizeable variant of the MpmcLockfreeQueue
stack		Stack implementation with simple push/pop interface.

Attribute overview of the available buffers

Data Structure	Shared Memory usable	Thread-Safe	Lock-Free	Concurrent Producers : Consumers	Bounded Capacity	Data Type Restriction	Use Case
SpscFifo	Yes	Yes	Yes	1:1	Yes	Copyable	FIFO Data transfer
MpmcLockfreeQueue	Yes	Yes	Yes	n:m	Yes	Copyable or Movable	lock-free transfer of arbitrary data between multiple contexts in FIFO order with overflow handling (ringbuffer)
MpmcLoFFLi	Yes	Yes	Yes	n:m	Yes	int32	manage memory access, LIFO order
SpscSofi	Yes	Yes	Yes	1:1	Yes	Trivially Copyable	lock-free transfer of small data (e.g. pointers) between two contexts in FIFO order with overflow handling (ringbuffer)
MpmcResizeableLockFreeQueue	Yes	Yes	Yes	n:m	Yes	Copyable or Movable	Resizeable variant of the MpmcLockfreeQueue
stack	Yes	No	-	-	Yes	None	Stack for a single-threaded application

Inter-process communication (ipc)

class	internal	description
UnixDomainSocket		Interface for unix domain sockets.
MessageQueue	Interface for Message Queues, see ManPage mq_overview.
NamedPipe	Shared memory based IPC channel. Mainly a UnixDomainSocket replacement on Windows.
PosixSharedMemoryObject		Creates and maps existing shared memory into the application.
PosixMemoryMap	i	Abstraction of mmap, munmap and helper class for the PosixSharedMemoryObject.
PosixSharedMemory	i	Abstraction of shared memory, see ManPage shm_overview and helper class for the PosixSharedMemoryObject.

Threads & sychronisation (sync)

class	internal	description
PeriodicTask	i	Periodically executes a callable specified by the template parameter in a configurable time interval.
smart_lock		Creates arbitrary thread-safe constructs which then can be used like smart pointers. If some STL type should be thread safe use the smart_lock to create the thread safe version in one line. Based on some ideas presented in Wrapping C++ Member Function Calls
mutex	i	Mutex interface, see ManPage pthread_mutex_lock.
UnnamedSemaphore		Unamed semaphore interface, see ManPage sem_overview
NamedSemaphore		Named semaphore interface, see ManPage sem_overview
thread		Heap-less replacement for std::thread.
SignalGuard		Helper class for signal handler registration.
SignalWatcher		Batteries included signal handling with polling and optional blocking wait for SIGINT and SIGTERM.

Generalized design patterns & abstractions (design)

class	internal	description
Builder		Macro which generates a setter method useful for a builder pattern.
IOX_POSIX_CALL		Wrapper around C and POSIX function calls which performs a full error handling. Additionally, this wrapper makes sure that EINTR handling is performed correctly by repeating the system call.
functional_interface		Constructs to easily add functional interfaces like and_then to object container.
NewType<T, Policies>		Implementation of Haskells NewType-pattern.
StaticLifetimeGuard		Static instance manager which solves the singleton lifetime problem.
PolymorphicHandler		Singleton handler with a default instance that can be changed at runtime.

Reporting (reporting)

The error handler is a central instance for collecting all errors and react to them. The error-handling.hpp contains a list of all error enum values. The error handler has different error levels, for more information see error-handling.md For information about how to use the logger API see error-handling.md.

class	internal	description
errorHandler		Free function to call the error handler with a defined error and an error level, see header file for practical example.
ErrorHandler	i	error handler class only for testing purposes, should not be used directly
logger
requires		Base for IOX_EXPECTS/IOX_ENSURES from the C++ Core Guideline

Time (time)

Never use physical properties like speed or time directly as integer or float in your code. Otherwise you encounter problems like this function void setTimeout(int timeout). What is the unit of the argument, seconds? minutes? If you use Duration you see it directly in the code.

void setTimeout(const Duration & timeout);

setTimeout(11_s); // 11 seconds
setTimeout(5_ms); // 5 milliseconds

class	internal	description
Duration	i	Represents the unit time, is convertible to timespec and timeval. User defined literals are available for convenience and readability.
`deadline_timer		Polling based timer to check for an elapsed deadline.
adaptive_wait	i	Building block to realize busy waiting loops with low CPU load.

Authentication (auth)

class	internal	description
posix_group		Access to user information.
posix_user		Access to group information.

Comand line interface (cli)

component	internal	description
cli_definition		Classes and macros to create command line interfaces.

[Check out iceoryx_hoofs on GitHub :fontawesome-brands-github:](https://github.com/eclipse-iceoryx/iceoryx/tree/main/iceoryx_hoofs/){ .md-button }