nod/README.md

### NOD

**NOD** is a library and utility (`nodtool`) for traversing, dumping, and authoring
*GameCube* and *Wii* optical disc images.

#### Library

The primary motivation of NOD is to supply a *uniform C++11 API* for accessing data
from image files directly. `nod::DiscBase` provides a common interface for traversing partitions
and individual files. Files may be individually streamed, or the whole partition may be extracted
to the user's filesystem. Raw *ISO* and *WBFS* images are supported read sources.

```cpp
bool isWii; /* Set by reference next line */
std::unique_ptr<nod::DiscBase> disc = nod::OpenDiscFromImage(path, isWii);
if (!disc)
    return FAILURE;

/* Access first data-partition on Wii, or full GameCube disc */
nod::Partition* dataPart = disc->getDataPartition();
if (!dataPart)
    return FAILURE;

/* One-shot extraction to filesystem */
if (!dataPart->extractToDirectory(outDir, ctx))
    return FAILURE;

return SUCCESS;
```

*Image authoring* is always done from the user's filesystem and may be integrated into
a content pipeline using the `nod::DiscBuilderBase` interface.

```cpp
/* Sample logging lambda for progress feedback */
size_t lastIdx = -1;
auto progFunc = [&](size_t idx, const nod::SystemString& name, size_t bytes)
{
    if (idx != lastIdx)
    {
        lastIdx = idx;
        /* NOD provides I/O wrappers using wchar_t on Windows;
         * _S() conditionally makes string-literals wide */
        fmt::print(_S("\n"));
    }
    if (bytes != -1)
        fmt::print(_S("\r{} {} B"), name, bytes);
    else
        fmt::print(_S("\r{}"), name);
    fflush(stdout);
};

/* Making a GCN image */
nod::DiscBuilderGCN b(isoOutPath, progFunc);
ret = b.buildFromDirectory(fsRootDirPath);

/* Making a Wii image */
nod::DiscBuilderWii b(isoOutPath, dualLayer, progFunc);
ret = b.buildFromDirectory(fsRootDirPath);
```

Wii images are fakesigned using a commonly-applied [signing bug](http://wiibrew.org/wiki/Signing_bug).

Additionally, any `*.dol` files added to the disc are patched to bypass the #001 error caused by invalid signature checks.
This allows games with multiple .dols to inter-boot without extensive loader-patching.

#### Tool

The library usage mentioned above is provided by a command-line tool called `nodtool`.

An extract/repack works like so:

```sh
>$ nodtool extract <image-in> [<dir-out>]
>$ cd <dir-out>

# Then one of:
>$ nodtool makegcn fsroot [<image-out>]
>$ nodtool makewii fsroot [<image-out>]
```