md4zig

A Zig wrapper around md4c for parsing Markdown. Fork of fjebaker/md4zig, maintained for fizzy's markdown plugin.

What this fork changes

• Builds for wasm32-freestanding. md4c is vendored under vendor/md4c and compiled with shim headers (include/freestanding) plus a small libc subset (src/libc.zig), since that target ships no libc — not even headers. zig build check-wasm compiles and links it.
• Tag values match the vendored md4c. Upstream predates MD_SPAN_INS, which shifted every span type after code by one, and lacks the footnote, admonition and blank block types.
• Flag bits match MD_FLAG_*. md4c leaves bit 7 unused; upstream's packed struct did not, so everything from tables on was off by one bit.
• Flags.github — the GFM feature set, so callers don't hand-assemble it.
• entity.decode — resolves & and friends over md4c's own HTML5 table, which md4c compiles but does not use (it reports entities verbatim).
• Zig 0.16; md4c_flag_t is now pub const Flags.

Usage

const md4zig = @import("md4zig");

const Impl = struct {
    pub fn enterBlock(_: *Impl, block: md4zig.BlockInfo) !void { _ = block; }
    pub fn leaveBlock(_: *Impl, block: md4zig.BlockInfo) !void { _ = block; }
    pub fn enterSpan(_: *Impl, span: md4zig.SpanInfo) !void { _ = span; }
    pub fn leaveSpan(_: *Impl, span: md4zig.SpanInfo) !void { _ = span; }
    pub fn textCallback(_: *Impl, text: md4zig.Text) !void { _ = text; }
};

var impl: Impl = .{};
var parser = md4zig.MD4CParser(Impl).init(.{ .flags = .github });
try parser.parse(&impl, "# Hello World\nHow are *you*!");

md4c is a push parser: it reports the document as a stream of block/span enter+leave pairs and text runs. It does not report source line or column positions — derive them from Text.text, whose pointer for .normal runs falls inside the input buffer.

Including in a project

zig fetch --save=md4zig https://github.com/fizzyedit/md4zig/archive/main.tar.gz

const md4zig = b.dependency("md4zig", .{
    .optimize = optimize,
    .target = target,
}).module("md4zig");

exe.root_module.addImport("md4zig", md4zig);

The module carries md4c's C source and include paths, so nothing else is needed.

Vendored md4c

vendor/md4c is pinned to md4c 61f5ce76, which is ahead of release 0.5.3: footnotes, admonitions, MD_SPAN_INS and MD_SPAN_MARK are all unreleased upstream, and footnotes in particular are needed for GFM parity. Bumping it means re-checking the enums — zig build test pins every ordinal this wrapper depends on against the vendored header.

Licence

MIT, as upstream. Vendored md4c is MIT — see vendor/md4c/LICENSE.md.