<!-- SPDX-FileCopyrightText: 2017 Adriaan de Groot <groot@kde.org>
     SPDX-FileCopyrightText: 2017-2020 Andrius Štikonas <andrius@stikonas.eu>
     SPDX-License-Identifier: CC-BY-4.0
-->

# KPMcore

> KPMcore, the KDE Partition Manager core, is a library for examining
> and modifying partitions, disk devices, and filesystems on a
> Linux system. It provides a unified programming interface over
> top of (external) system-manipulation tools.

KPMcore is a library for examining and manipulating all facets
of storage devices on a system:
* raw disk devices
* partition tables on a device
* filesystems within a partition

There are multiple backends so that KPMcore can support different
operating systems, although the only functional backend is the
one for Linux systems:
* sfdisk backend (Linux)
* null backend

## Using KPMcore

Most of the usage information on KPMcore is included in the API
documentation; this section contains only high-level usage information.

### Finding KPMcore with CMake

KPMcore supports CMake as (meta-)build system and installs suitable
CMake support files. Typical use of of KPMcore in a `CMakeLists.txt`
looks like this:

```cmake
    find_package( KPMcore 3.2 REQUIRED )
    target_link_libraries( target kpmcore )
```

There are no imported targets defined for KPMcore.

### Initialization

An application must initialize the library and load a suitable
backend before using KPMcore functions. By convention, the
environment variable `KPMCORE_BACKEND` names a backend,
and typical initialization code will look like this (or use the
class `KPMCoreInitializer` from `test/helpers.h`):

```cpp
    #include <backend/corebackendmanager.h>
    #include <QDebug>

    bool initKPMcore()
    {
        static bool inited = false;
        if ( inited ) return true;

        QByteArray env = qgetenv( "KPMCORE_BACKEND" );
        auto backendName = env.isEmpty() ? CoreBackendManager::defaultBackendName() : env;
        if ( !CoreBackendManager::self()->load( backendName ) )
        {
            qWarning() << "Failed to load backend plugin" << backendName;
            return false;
        }
        inited = true;
        return true;
    }
```

This code uses the environment variable if set, and otherwise falls
back to a default backend suitable for the current platform.

Calling KPMcore functions before the library is initialized will
result in undefined behavior.

### Devices

After the backend is initialized you can scan for available devices.
If you only want devices from the loaded backend you can call

```cpp
    QList<Device*> devices = backend->scanDevices( excludeReadOnly );
```

where `bool` option `excludeReadOnly` specifies whether to exclude
read only devices.

#### KPMcore device scanner

Alternatively, you can use KPMcore device scanner

```cpp
    #include <core/device.h>
    #include <core/devicescanner.h>
    #include <core/operationstack.h>

    // First create operationStack with another QObject as parent, we will use nullptr here.
    OperationStack *operationStack = new OperationStack(nullptr);
    DeviceScanner *deviceScanner = new DeviceScanner(nullptr, *operationStack);
    deviceScanner->scan(); // use start() for scanning in the background thread
    QList<Device*> devices = operationStack->previewDevices();
```

Then `deviceScanner` scans for the devices in a background thread. After
scanning is complete `DeviceScanner::finished()` signal will be emitted.
Then the devices can accessed using `operationStack->previewDevices()`.
