# merrno

## Chapter 1: About

This is **merrno**, copied from **fancyt** (which is a copy of **merrno** from **parg** in **yabuilder/c_port**).

But this is a *"for the work with one thread optimized"* version.
Reasons for that see at Chapter 3: **Why Single Threaded**.
Maintainers can be found at [MAINTAINERS.md](MAINTAINERS.md) for the specific versions.
You can use merrno in your programs to have a *lightweigth*, *fast* implementation of error codes. It's developed for *ease* and as a *portable* error code system.

**Current Version**: 1.0.2

## Chapter 2: How to use

You can use `set_merrno(ec)` to set the global merrno error code.
**Examples**:

Set error code to invalid arg:

```c
set_merrno(MERRNO_EC_INV_ARG)
```

Set error code to out of range:

```c
set_merrno(MERRNO_EC_OUT_OF_RANGE)
```

You can use `get_merrno()` to get the global merrno error code.

**A not realistic example:**

Set error code to the actual error code, but with inverted value:

```c
set_merrno(~get_merrno())
```

## Chapter 3: Why Single Threaded

This version of merrno is used by the internal and public API error handling things in the h2ot3 core.
It's *single-threaded* because it's most used by the UI changing functions (and UI can only changed by the main thread) and to *increase the speed* and to *reduce the complexity*.