ktav — .NET bindings

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.NET bindings for the Ktav configuration format. Thin wrapper around the reference Rust parser, loaded at runtime through P/Invoke — no native build on the consumer side, plain dotnet add package just works.

Targets net8.0 (with AOT-ready LibraryImport) and netstandard2.0 (DllImport, no NativeLibrary resolver — use NuGet's runtimes/ layout or KTAV_LIB_PATH).

Install

dotnet add package Ktav

Quick start

Parse — pull typed fields out of a document

using Ktav;

const string src = """
                   service: web
                   port:i 8080
                   ratio:f 0.75
                   tls: true
                   tags: [
                       prod
                       eu-west-1
                   ]
                   db.host: primary.internal
                   db.timeout:i 30
                   """;

var top = (KtavObject)Ktav.Loads(src);

string  service = ((KtavString)  top.TryGet("service")!).Value;
long    port    = ((KtavInteger) top.TryGet("port")!).ToInt64();
double  ratio   = ((KtavFloat)   top.TryGet("ratio")!).ToDouble();
bool    tls     = ((KtavBool)    top.TryGet("tls")!).Value;

var db = (KtavObject) top.TryGet("db")!;
string dbHost   = ((KtavString)  db.TryGet("host")!).Value;
long   dbTimeout = ((KtavInteger) db.TryGet("timeout")!).ToInt64();

Walk — pattern-match on the sealed KtavValue hierarchy

foreach (var entry in top.Entries)
{
    string kind = entry.Value switch
    {
        KtavNull        => "null",
        KtavBool b      => $"bool={b.Value}",
        KtavInteger i   => $"int={i.Text}",
        KtavFloat f     => $"float={f.Text}",
        KtavString s    => $"str=\"{s.Value}\"",
        KtavArray a     => $"array({a.Items.Count})",
        KtavObject o    => $"object({o.Entries.Count})",
        _               => throw new InvalidOperationException(),
    };
    Console.WriteLine($"{entry.Key} -> {kind}");
}

Build & render — construct a document in code

using System.Collections.Generic;

KtavObject Upstream(string host, long port) => new(new[]
{
    new KeyValuePair<string, KtavValue>("host", new KtavString(host)),
    new KeyValuePair<string, KtavValue>("port", KtavInteger.Of(port)),
});

var doc = new KtavObject(new[]
{
    new KeyValuePair<string, KtavValue>("name",      new KtavString("frontend")),
    new KeyValuePair<string, KtavValue>("port",      KtavInteger.Of(8443)),
    new KeyValuePair<string, KtavValue>("tls",       KtavBool.True),
    new KeyValuePair<string, KtavValue>("ratio",     KtavFloat.Of(0.95)),
    new KeyValuePair<string, KtavValue>("upstreams", new KtavArray(new KtavValue[]
    {
        Upstream("a.example", 1080),
        Upstream("b.example", 1080),
    })),
    new KeyValuePair<string, KtavValue>("notes",     KtavNull.Instance),
});

string text = Ktav.Dumps(doc);

A complete runnable version lives in examples/Basic.

API

Member	Purpose
Ktav.Loads(string) -> KtavValue	Parse a Ktav document into the KtavValue tree.
Ktav.Dumps(KtavValue) -> string	Render a KtavValue back as Ktav text. Top-level must be KtavObject.
Ktav.NativeVersion()	Version string reported by the loaded ktav_cabi.
Ktav.ExpectedNativeVersion	Version this build was compiled against.

KtavException is thrown on any parse / render failure; the message is the UTF-8 string produced by the native parser.

Type mapping

Mirrors the Rust crate's Value enum — one record per Ktav primitive, no lossy coercions:

Ktav	KtavValue variant
null	KtavNull.Instance
true / false	KtavBool
:i <digits>	KtavInteger (text form — ToBigInteger() / ToInt64())
:f <number>	KtavFloat (text form — ToDouble())
bare scalar	KtavString
[ ... ]	KtavArray (IReadOnlyList<KtavValue>)
{ ... }	KtavObject (key insertion order preserved)

Typed integers and floats are held as text so arbitrary precision (digits beyond long) and exact decimal round-trip are preserved byte for byte across parse / render cycles.

How the native library is resolved

On net8.0, NativeLoader registers a NativeLibrary.SetDllImportResolver callback. Resolution order:

1. $KTAV_LIB_PATH — absolute path to a local build. Most useful for development and air-gapped CI.
2. NuGet runtimes/<rid>/native/ layout — picked up automatically by .NET's default loader when consumed via Ktav.nupkg.
3. User cache — <userCache>/ktav-dotnet/v<version>/…, downloaded on a previous call.
4. GitHub Release download — fetched once from github.com/ktav-lang/csharp/releases/download/v<version>/<asset> and cached under (3). Requires network on first call after install.

<userCache> is %LOCALAPPDATA% on Windows, ~/Library/Caches on macOS, $XDG_CACHE_HOME or ~/.cache on Linux.

On netstandard2.0 only step (2) applies — the NativeLibrary API does not exist there.

Runtime support

• net8.0 (AOT-friendly via LibraryImport) and netstandard2.0 (Mono / Unity / .NET Framework 4.7.2+).
• Prebuilt binaries for: linux-x64, linux-arm64, osx-x64, osx-arm64, win-x64, win-arm64.
• Linux distros must use glibc 2.17+ (zigbuild baseline). Alpine (musl) support is planned.

License

MIT — see LICENSE.

Other Ktav implementations

• spec — specification + conformance suite
• rust — reference Rust crate (cargo add ktav)
• golang — Go (go get github.com/ktav-lang/golang)
• java — Java / JVM (io.github.ktav-lang:ktav on Maven Central)
• js — JS / TS (npm install @ktav-lang/ktav)
• php — PHP (composer require ktav-lang/ktav)
• python — Python (pip install ktav)