https://github.com/rnpgp/sexpp

C++ Library for SEXP (S-expressions)
https://github.com/rnpgp/sexpp
Last synced: 4 months ago
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C++ Library for SEXP (S-expressions)
Host: GitHub
URL: https://github.com/rnpgp/sexpp
Owner: rnpgp
License: other
Created: 2022-09-07T12:34:17.000Z (almost 4 years ago)
Default Branch: main
Last Pushed: 2025-03-22T20:33:28.000Z (about 1 year ago)
Last Synced: 2025-10-22T02:51:35.111Z (8 months ago)
Language: C++
Homepage:
Size: 254 KB
Stars: 9
Watchers: 9
Forks: 5
Open Issues: 4
Metadata Files:
- Readme: README.adoc
- License: LICENSE.md
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README

          = S-Expressions parser and generator library in C\++ (SEXP in C++)

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== Purpose

This is a C++ library for working with S-Expressions.

This implementation is derived from the reference SEXP C library developed by

Prof. Ronald Rivest and Prof. Butler Lampson of MIT LCS (now CSAIL).

This library differs from the original C implementation in the following ways:

* It aims to be reusable in C++ implementations and is importable via CMake.

* It includes a test suite for correctness testing and tests against malformed

  S-Expressions.

* It supports, and is tested against, all major platforms, including:

** Ubuntu, Debian, Fedora, CentOS, NixOS

** macOS

** Windows native

** Windows MSys

* It implements additional interface to work with S-Expressions wrapped by GnuPG

  2.3+ extended format

== Background

S-Expressions are a data structure for representing complex data as a variation

on https://en.wikipedia.org/wiki/Lisp_(programming_language)[LISP] S-Expressions.

S-Expressions were originally adopted for use in

https://wikipedia.org/wiki/Simple_public-key_infrastructure[SPKI and SDSI].

SDSI has been developed by Prof.

https://people.csail.mit.edu/rivest/index.html[Ronald L. Rivest] and

Prof. Butler Lampson of

http://www.lcs.mit.edu/[MIT's Laboratory for Computer Science],

members of LCS's Cryptography and Information Security

research group.

NOTE: SDSI research has been supported by DARPA contract DABT63-96-C-0018,

"Security for Distributed Computer Systems".

NOTE: SPKI has been developed by Carl Ellison and others in the IETF SPKI

working group.

== S-Expressions specification

* https://datatracker.ietf.org/doc/draft-rivest-sexp/

== Code

The library is a deep rework to C++ of the original SEXP library that maintains full

support of original specification.

While most applications will not need anything but the simple canonical and

transport formats; however, the code here is considerably more complex because

it also supports the advanced format, both for input and for output.

== Building and installation

[source,sh]

----

$ mkdir build

$ cd build

$ cmake ..

$ cmake --build .

$ ctest

$ cmake --install .

----

== CMake script options

`BUILD_SHARED_LIBS:BOOL`::

(default: `OFF`)

build shared library

`WITH_SEXP_TESTS:BOOL`::

(default: `ON`)

build tests

`DOWNLOAD_GTEST`::

(default: `ON`)

if tests are built, automatically download googletest from GitHub;

when set to `OFF`, the googletest binary package needs to be available for SEXP

tests.

`WITH_SEXP_CLI:BOOL`::

(default: `ON`) build the `sexp` command-line utility

`WITH_SANITIZERS:BOOL`::

(default: `OFF`)

build with address and other sanitizers (requires clang compiler)

== SEXPP command-line utility

The `sexpp` command-line utility is reference parser and generator of

S-Expressions. It can read, parse and print out SEXP in all defined formats.

=== Switches

.`sexpp` switches

[options="header"]

|===

| Switch          | Description                                    | Default

3+| Input

| `-i ` | input file name                                | read input from console (stdin)

| `-p`            | prompt input if reading from console           | disabled

| `-s`            | treat input as a single SEXP string            | disabled, input is treated as an S-Expression

3+| Output

| `-o ` | output file name:                              | write output to console (stdout)

| `-a`            | generate advanced transport format             | enabled if no format is specified

| `-b`            | generate base-64 transport format              | disabled

| `-c`            | generate canonical format                      | disabled

| `-l`            | suppress linefeeds after output                | disabled

| `-w `    | set output line width (0 implies no constraint)| 75

3+| Miscellaneous

| `-x`            | execute repeatedly until EOF                   | process single S-Expression then exit

| `-h`            | print help message and exit                    |

|===

Running without switches implies: `-p -a -b -c -x`.

=== Usage examples

Prompt for S-Expressions input from console, parse and output it to

`certificate.dat` in base64 transport format.

[source]

----

$ sexpp -o certificate.dat -p -b

> Input:

> (aa bb (cc dd))

>

> Writing base64 (of canonical) output to 'certificate.dat'

----

Parse all S-Expressions from `certificate.dat`, output them to console in

advanced transport format with no prompts:

[source,sh]

----

$ sexpp -i certificate.dat -x

> (2:aa2:bb(2:cc2:dd))

----

Parse S-Expressions from `certificate.dat`, output it to console in canonical,

base64 and advanced format with prompts and no width limitation:

[source,sh]

----

$ sexpp -i certificate.dat -a -b -c -p -w 0

> Reading input from certificate.dat

>

> Canonical output:

> (2:aa2:bb(2:cc2:dd))

> Base64 (of canonical) output:

> {KDI6YWEyOmJiKDI6Y2MyOmRkKSk=}

> Advanced transport output:

> (aa bb (cc dd))

----

Repeatedly prompt for S-Expressions input from console, parse and output it

console in advanced, base64 and canonical formats:

[source,sh]

----

$ sexpp -p -a -b -c -x

----

or just

[source,sh]

----

$ sexpp

> Input:

> (abc def (ghi jkl))

>

> Canonical output:

> (3:abc3:def(3:ghi3:jkl))

> Base64 (of canonical) output:

> {KDM6YWJjMzpkZWYoMzpnaGkzOmprbCkp}

> Advanced transport output:

> (abc def (ghi jkl))

>

> Input:

> ^C

----

== License

Copyright Ribose.

The code is made available as open-source software under the MIT License.
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