YAML Ain’t Markup — parsed at library speed

YAML, parsed at
library speed.

yeptris is the YAML counterpart of libleptris: a YAML 1.2 parser, writer and streamer in pure C11 — zero required dependencies, a stable C ABI, opaque handles — with a Psych-compatible Ruby gem and a PyYAML-compatible Python package shaped like the incumbents.

Get started See the race

Speed with a referee — every figure comes from the open benchmark lane: interleaved runs, pinned competitors, medians, a performance ledger kept in the repository.
Conformance first — 395/395 on the yaml-test-suite, the libyaml emission goldens with zero divergences, ASan/UBSan/TSan suites, and a nightly libFuzzer lane.
One core, three surfaces — the same C11 engine from C, Ruby, and Python; bindings version in lockstep with the engine.

the fourth hare joins the chase

0/395yaml-test-suite

0×scalar-heavy vs libyaml, dev hardware

0libyaml emission goldens, zero divergences

0prebuilt platform gems, lockstep releases

zerorequired runtime dependencies

What it is

An engine built like a ledger, not a claim

yeptris is YAML 1.2 first — with a libyaml/Psych-compatible YAML 1.1 lenient mode for the real world. The yaml-test-suite is the conformance bar; every divergence is documented; every performance statement reproduces from the benchmark harness and the ledger (benchmarks/PERF-LEDGER.md).

up to 3.36× / libyaml, per shape

The race, in the open

Same-binary, min-of-N against libyaml: scalar-heavy 3.36×, block-nested ~2.3×, wide mappings ~2.4×, anchor-heavy ~1.8×. The interleaved head-to-head against rapidyaml runs in CI on every push — nine document shapes across DOM, pull, recorder and emit.

395/395 yaml-test-suite

Conformant where it counts

The full verification matrix: yaml-test-suite pinned atda267a5, psych-pure’s 67 corpus files, JSONTestSuite 95/95 accept and 188/188 reject in strict mode, 405-input libyaml parse differential with full-record equality, 1091 fuzz inputs across chunkings.

1 C call per document free

Beyond the DOM

Three consumption models over one engine: pull events (StAX-style, zero C→host callbacks — the FFI-friendly form), libyaml-compatible push events, and a packed record tape for bulk drains. Plans and schemas walk documents into typed columns with no intermediate tree. Zero-copy value views in C.

14 prebuilt gem rows · abi3 wheels

Packaging that installs

Ruby: fat platform gems (no C extension — FFI), every major OS×arch tier, lockstep-released with the engine. Python: self-contained wheels over ctypes, zero compilation at install. C: cmake --install with pkg-config.

The surface

Shaped like the incumbents

Ruby mirrors Psych (its YAML 1.1 implicit typing is the default; schema: :core_12 switches to the 1.2 core schema), and drops in beside it — including the error names. Python mirrors PyYAML’s safe surface.

#include <yeptris/yeptris.h>

YeptrisStatus st;
YeptrisDocument doc = yeptris_parse(data, len, &st);
if (!doc) {
    uint32_t line, col;
    const char *msg = yeptris_last_error(&line, &col);  /* 1-based */
}
size_t n = yeptris_document_count(doc);
YeptrisNode root = yeptris_document_root(doc, 0);
YeptrisNode port = yeptris_node_map_get(root, "port", 4);

char *out = NULL; size_t out_len = 0;
out = yeptris_serialize(doc, &out_len);      /* canonical YAML */
yeptris_document_free(doc);                  /* one free for everything */

require "yeptris"

Yeptris::YAML.load("name: yeptris\nrating: 10\n")
# => {"name" => "yeptris", "rating" => 10}   Psych's 1.1 typing

Yeptris::YAML.load(src, schema: :core_12)    # YAML 1.2 core semantics
Yeptris::YAML.dump({"name" => "yeptris", "tags" => [:yaml, :fast]})

Yeptris::JSON.load('{"a": [1, 2], "b": null}')   # strict RFC 8259

doc = Yeptris::Document.parse(config_yaml)
doc.root["server"]["port"].to_i
doc.serialize

import yeptris
from yeptris import yaml   # the PyYAML-compatible surface

yaml.safe_load("name: yeptris\nrating: 10\n")
# {'name': 'yeptris', 'rating': 10}

yaml.safe_load_all("--- 1\n--- two\n")     # [1, 'two']
yaml.safe_dump({"b": 2, "a": [1, "x"]})     # 'a:\n  - 1\n  - x\nb: 2\n'

yeptris.load("k: v")       # the neutral surface
yeptris.dump({"k": [1, 2]})

The chase begins

Install, three ways

surface	command	what you get
Ruby	`gem install yeptris`	a prebuilt platform gem where one exists — FFI over the shared library, zero compilation at install
Python	`pip install yeptris`	a self-contained wheel — ctypes FFI over libyeptris, PyYAML-compatible semantics
C	`cmake -B build -S . && cmake --build build`	LTO on by default; `cmake --install` carries headers and pkg-config

The yeptris docs — C, Ruby and Python guides →

Fast as hares.
Parsed at library speed.

yeptris v0.6.22 — libyeptris v0.6.22, the yeptris gem v0.6.22.1, the yeptris package v0.6.22.1. Repos canonical: yeptris, yeptris-ruby, yeptris-py.

YAML, parsed atlibrary speed.