Aliphaticus.KrakenDecoder 0.1.0

Aliphaticus.KrakenDecoder

Aliphaticus.KrakenDecoder is an MIT-licensed, managed, dependency-free decoder for Oodle Kraken payloads. It is intended for tools that need to read FromSoftware DCX_KRAK files without distributing or loading oo2core.

The package decodes the payload after the DCX header; it does not replace a general DCX parser or write DCX files.

<PackageReference Include="Aliphaticus.KrakenDecoder" Version="0.1.0" />

using Aliphaticus.KrakenDecoder;

byte[] dcx = File.ReadAllBytes("input.dcx");
KrakenDcxInfo header = KrakenDcxHeader.Parse(dcx);

var decoder = new ManagedKrakenDecoder();
byte[] decompressed = decoder.Decompress(
    dcx.AsSpan(KrakenDcxHeader.PayloadOffset, checked((int)header.CompressedSize)),
    header.UncompressedSize);

Releasing

To produce NuGet artifacts run the following

dotnet pack KrakenDecoder.csproj --configuration Release --output ./artifacts

Supported scope

• Oodle decoder type 6 (Kraken) payloads, including Elden Ring's independently reset 0x40000-byte seek chunks.
• Strict validation of decoded size, consumed input, and malformed payloads.

The package deliberately does not support compression, general Oodle decoding, or non-Kraken codecs. In particular, LZHLW, Mermaid, Leviathan, BitKnit, LZNA, and any other decoder type are rejected. Callers that scan heterogeneous game archives should catch the error, log the path and codec, and skip unsupported files according to their own policy.

EldenRing DCX contract

SoulsFormats.DCX.DecompressDCXKRAK consumes this fixed big-endian layout:

The package's KrakenDcxHeader validates those boundaries before handing the payload to the decoder. It is deliberately not a replacement for SoulsFormats' DCX parser.

Corpus verification

Do not add game assets to this repository or NuGet package. Local/CI corpus tests obtain paths from KRAKEN_CORPUS_PATH and hashes/sizes from a separate, non-versioned manifest. A skipped corpus test is not compatibility evidence.

Corpus test protocol

No game asset belongs in this repository, its test output, or its NuGet package. Keep a local, ignored manifest next to an externally supplied corpus. Set KRAKEN_CORPUS_PATH to the corpus root and KRAKEN_CORPUS_MANIFEST to the manifest file, then invoke the test only on a machine that owns the files. The test is dynamically skipped if either variable is absent. You may instead copy .env.template to the ignored repository-root .env; the test imports those two values only when the corresponding process environment variable is unset. For several corpora with different roots, use one or more KRAKEN_CORPUS_SUITE_nn=ROOT|MANIFEST values instead.

The manifest may be a single entry, an array of entries, or an object with a files array (case-insensitive). It must list at least one multi-block DCX_KRAK file; each entry contains:

{
  "path": "map/mapstudio/example.msb.dcx",
  "uncompressedSize": 1234567,
  "sha256": "lowercase SHA-256 of the independently decoded payload"
}

fileName may be used instead of path when KRAKEN_CORPUS_PATH already points at the directory containing the files. Optional compressedSize and containerSize values validate the DCX header and complete container length. Uppercase SHA-256 is accepted for compatibility with native Convert.ToHexString output, although lowercase remains preferred. Elden Ring files may include up to 15 trailing zero alignment bytes after the declared compressed payload; the decoder receives only the declared compressed bytes.

The test must parse the DCX header, require uncompressedSize > 0x40000, decode the payload using the managed library with no native Oodle library available, and compare the complete SHA-256. Re-run it after truncating one byte, adding one byte, and changing each declared size; all four must fail.

Scope and licensing

The implementation is a clean C# port informed by MIT-licensed oozextract v0.5.5. See NOTICE for attribution and provenance.