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:
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It aims to be reusable in C implementations and is importable via CMake.
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It includes a test suite for correctness testing and tests against malformed S-Expressions.
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It supports, and is tested against, all major platforms, including:
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Ubuntu, Debian, Fedora, CentOS, NixOS
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macOS
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Windows
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msys
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It implements additional interface to work with S-Expressions wrapped by GnuPG 2.3 extended format (specification).
The original C library was available at (but no longer accessible):
S-Expressions are a data structure for representing complex data as a variation on LISP S-Expressions.
SDSI has been developed by Prof. Ronald L. Rivest and Prof. Butler Lampson of MIT’s Laboratory for Computer Science, members of LCS’s Cryptography and Information Security research group.
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Note
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SDSI research has been supported by DARPA contract DABT63-96-C-0018, "Security for Distributed Computer Systems". |
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Note
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SPKI has been developed by Carl Ellison and others in the IETF SPKI working group. |
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Note
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The "SEXP 1.0 guide" used to be at https://people.csail.mit.edu/rivest/Sexp.txt. |
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.
$ mkdir build
$ cd build
$ cmake ..
$ cmake --build .
$ ctest
$ cmake --install .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 toOFF, the googletest binary package needs to be available for SEXP tests. WITH_SEXP_CLI:BOOL-
(default:
ON) build thesexpcommand-line utility WITH_SANITIZERS:BOOL-
(default:
OFF) build with address and other sanitizers (requires clang compiler)
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.
sexpp switches
| Switch | Description | Default |
|---|---|---|
Input |
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input file name |
read input from console (stdin) |
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prompt input if reading from console |
disabled |
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treat input as a single SEXP string |
disabled, input is treated as an S-Expression |
Output |
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output file name: |
write output to console (stdout) |
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generate advanced transport format |
enabled if no format is specified |
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generate base-64 transport format |
disabled |
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generate canonical format |
disabled |
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suppress linefeeds after output |
disabled |
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set output line width (0 implies no constraint) |
75 |
Miscellaneous |
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execute repeatedly until EOF |
process single S-Expression then exit |
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print help message and exit |
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Running without switches implies: -p -a -b -c -x.
Prompt for S-Expressions input from console, parse and output it to
certificate.dat in base64 transport format.
$ 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:
$ 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:
$ 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:
$ sexpp -p -a -b -c -xor just
$ 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