c-kzg-zig

Zig build packaging for c-kzg-4844.

This package exports:

• the c_kzg C library artifact
• the c-kzg public headers, installed on that artifact
• a trusted_setup Zig module with decoded byte slices for load_trusted_setup
• trusted_setup.txt as a named lazy path

This package does not export a full handwritten Zig wrapper over the C API. Consumers are still expected to add their own wrapper, and to add blst.zig separately for final linking.

Requirements

• Zig 0.16.0-dev

Public Surface

From a dependency handle:

• dep.artifact("c_kzg")
• dep.module("trusted_setup")
• dep.namedLazyPath("trusted_setup")

The c_kzg artifact installs:

• the full c-kzg public header tree
• blst.h and related installed headers forwarded from blst.zig

That means a consumer wrapper module can @cImport("ckzg.h") after linking against dep.artifact("c_kzg").

Usage

Add dependencies to build.zig.zon:

.dependencies = .{
    .c_kzg = .{
        .url = "https://github.com/ChainSafe/c-kzg-zig/archive/refs/tags/v0.1.0.tar.gz",
        .hash = "<hash>",
    },
    .blst = .{
        .url = "git+https://github.com/lodekeeper-z/blst.zig.git#254f2869b9c72b7f70900b41ec90213807c7a675",
        .hash = "blst_zig-0.0.0-cnAxzg4LAACIXTmj0X4unkf0FCYcFTZVzDdWE32PZl_A",
    },
},

That blst ref is the head commit of ChainSafe/blst.zig PR #4, which contains the Zig 0.16 build updates.

In build.zig:

const c_kzg_dep = b.dependency("c_kzg", .{
    .target = target,
    .optimize = optimize,
});
const blst_dep = b.dependency("blst", .{
    .target = target,
    .optimize = optimize,
});

const kzg_wrapper = b.addModule("kzg_wrapper", .{
    .root_source_file = b.path("src/kzg_wrapper.zig"),
    .target = target,
    .optimize = optimize,
});
kzg_wrapper.linkLibrary(c_kzg_dep.artifact("c_kzg"));

exe.root_module.addImport("trusted_setup", c_kzg_dep.module("trusted_setup"));
exe.root_module.addImport("kzg_wrapper", kzg_wrapper);
exe.root_module.linkLibrary(blst_dep.artifact("blst"));

const install_setup = b.addInstallFile(
    c_kzg_dep.namedLazyPath("trusted_setup"),
    "trusted_setup.txt",
);
b.getInstallStep().dependOn(&install_setup.step);

In your wrapper module:

pub const c = @cImport({
    @cInclude("ckzg.h");
});

The exported trusted_setup module contains the decoded buffers expected by load_trusted_setup:

const c = @import("kzg_wrapper").c;
const trusted_setup = @import("trusted_setup");

var settings: c.KZGSettings = undefined;
try expectOk(c.load_trusted_setup(
    &settings,
    trusted_setup.g1_monomial_bytes.ptr,
    trusted_setup.g1_monomial_bytes.len,
    trusted_setup.g1_lagrange_bytes.ptr,
    trusted_setup.g1_lagrange_bytes.len,
    trusted_setup.g2_monomial_bytes.ptr,
    trusted_setup.g2_monomial_bytes.len,
    0,
));
defer c.free_trusted_setup(&settings);

If you want the original upstream text file at runtime instead, keep using dep.namedLazyPath("trusted_setup").

Build Options

Option	Default	Description
-Dportable	false	Passed through to the package's build-time blst.zig dependency
-Dfield_elements_per_blob	4096	Override for non-mainnet

Tests

zig build test runs compile-time and C-API smoke tests against the exported embedded trusted setup module.

License

Apache 2.0.