C reference parsing library for Eno
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4.2 KiB


Eno parsing library for C

Getting started

#include <eno.h>
#include <string.h>

int main()
    char *content = "Who to greet: World";
    ENOIterator iterator;

    if (eno_parse_memory(&iterator, content, strlen(content))) {
        char *ptr;
        size_t size;

        eno_iterate_next(&iterator); /* advance to first element */

        if (eno_get_value(&iterator, &ptr, &size)) {
          printf("Hello %.*s!", (int)size, ptr);
    } else {


    return 0;

Development status

libeno already implements the full Eno specification. Some parts are still interim implementations, expect occassional full-on crashs for certain input or usage patterns (please do report those, happy to resolve them).

The API is partially documented through doc comments, please be aware that there are not yet any stability guarantees at this point.

In addition to the basic parser stuff you'd expect there is also some functionality for printing back the AST that libeno constructs during parsing, annotated with line numbers, both in plain text and with terminal coloring.

String encoding

Eno is always encoded in UTF-8, and so is the resulting content of all string buffers extracted from the document and provided to library consumers after parsing. The UTF-8 Everywhere Manifesto formulates a good rationale for this if you're curious about some of the reasoning for this design decision.

Building from source


You need to install icu4c (the ICU library for C), including its headers.

On linux this can be done through the package manager (e.g. libicu-dev on Ubuntu).

meson build
cd build
meson compile

After building you can optionally install libeno's shared library and header files to your system by running (inside build/):

meson install

Using CMake

mkdir build
cd build
cmake ..

There is no install target configured in the CMake build manifest yet.


Parsing correctness test suite

Inside build/ run:


This scans through the .eno files in test/examples/ and for each of them, after parsing, creates serializations of both the internally and externally accessible representation of the abstract syntax tree of the document, which are then stored in a directory named after the example but postfixed with .spec instead of .eno. These files are tracked with git and on consecutive runs the serializations are re-generated and compared to the previously generated snapshots, with any mismatches triggering errors and printing a diff for the affected line. These specs serve to ensure that the parser behaves according to specification and that regressions are quickly noticed during development. Furthermore this serves as an examplified version of the specification because more complex behavior can easily be studied by looking at the .eno files and their respective .spec directory counterparts, which reveal how documents are tokenized, continuations are assembled, etc.

To force an update of all specs you can run:

UPDATE_SPECS=yeah ./test_examples

Parsing a document, printing the AST

Inside build/ create a test document and run:

./test_parse your_document_path.eno

This debug-prints the document's abstract syntax tree and reports errors in the document if it encounters one.

Parsing a document, obtaining a value by key

Inside build/ create a test document and run:

./test_get your_document_path.eno "some key"

This parses the document and prints the value of a field at the root level of the document that matches the supplied key.

Building the Documentation

The documentation uses Doxygen, which can be installed from package manager on most linux distributions.

When doxygen is installed go to the root of the repository and run:


This generates the folder docs/ which contains html documentation which you can view in your browser.


libeno is licensed under the LGPLv3+.