Package {janssonr}

Type:	Package
Title:	Strict JSON Encoding and Decoding via the 'Jansson' C Library
Version:	0.1.2
Date:	2026-09-01
Copyright:	cornball.ai, except the bundled Jansson sources under src/jansson, whose per-file copyright holders and license statements are listed in inst/COPYRIGHTS.
Description:	An R-safe profile of RFC 8259 JSON: parsing and generation backed by the 'Jansson' C library, linked as a system library where one is available and compiled from the bundled sources otherwise. The parser rejects, with classed conditions carrying line, column, and byte position: malformed or truncated input, trailing content, duplicate object keys at any depth, invalid UTF-8, escapes encoding a null character, reals overflowing double, and integer literals whose magnitude exceeds 2^53, the range within which a double represents every integer exactly. Number literals with a fraction or exponent convert by ordinary correctly rounded IEEE 754 double conversion. Objects decode to named lists in key order, arrays to unnamed lists, and scalars to length-one vectors. The encoder maps named lists to objects in insertion order, unnamed lists to arrays, guarantees that every finite double, signed zero included, round-trips to the exact same value (whole-number doubles are written as integers), and refuses values with no faithful JSON representation (NA, NaN, infinities, named atomic vectors, classed objects) instead of guessing. No R package dependencies.
License:	MIT + file LICENSE
Depends:	R (≥ 4.4.0)
URL:	https://github.com/cornball-ai/janssonr
BugReports:	https://github.com/cornball-ai/janssonr/issues
SystemRequirements:	jansson (>= 2.11) is linked when present: libjansson-dev (deb), jansson-devel (rpm), jansson (brew). When it is absent, and always on Windows, the bundled Jansson 2.15.1 is compiled into the package.
Suggests:	tinytest
Encoding:	UTF-8
NeedsCompilation:	yes
Packaged:	2026-09-01 14:36:13 UTC; troy
Author:	Troy Hernandez [aut, cre], cornball.ai [cph], Petri Lehtinen [ctb, cph] (Author of the Jansson C library, bundled under src/jansson), Basile Starynkevitch [ctb, cph] (Jansson: src/jansson/memory.c), Graeme Smecher [ctb, cph] (Jansson: src/jansson/pack_unpack.c), Sean Bright [ctb, cph] (Jansson: src/jansson/version.c), David M. Gay [ctb] (Author of dtoa.c, bundled by Jansson as src/jansson/dtoa.c), Lucent Technologies [cph] (src/jansson/dtoa.c), Bob Jenkins [ctb] (Author of lookup3.c (public domain), bundled by Jansson as src/jansson/lookup3.h)
Maintainer:	Troy Hernandez <troy@cornball.ai>
Repository:	CRAN
Date/Publication:	2026-09-12 09:00:02 UTC

Parse JSON strictly

Description

Parses one JSON document under janssonr's R-safe profile of RFC 8259. The parser refuses, with a classed condition: malformed or truncated input, trailing content, duplicate object keys at any depth, invalid UTF-8, embedded NUL escapes, numbers overflowing double, and integer literals whose magnitude exceeds 2^53. The exactness guarantee is for integer literals only: number literals with a fraction or exponent (1.5, 9007199254740993.0, 1e-999) convert by ordinary correctly rounded IEEE 754 double conversion.

Usage

from_json(x)

Arguments

Details

Mapping: a JSON object becomes a named list in key order (an empty object keeps a character(0) names attribute, distinguishing it from an empty array); an array becomes an unnamed list, never an atomic vector; a string becomes character(1); an integer fitting R's integer range becomes integer(1) (except -2147483648, R's NA sentinel, which becomes double); any other number becomes double(1); true/false become logical(1); null becomes NULL. Nesting beyond 1024 containers refuses.

Character input is translated to UTF-8; raw input is taken byte for byte and must already be valid UTF-8.

Errors have class c("janssonr_parse_error", "janssonr_error", "error", "condition") and carry line, column, position (byte offset) for lexical errors, plus code, a stable string such as "duplicate_key" or "invalid_utf8". The "integer_precision" code covers every integer-form refusal: literals beyond 2^53 detected after parsing carry NA coordinates plus path, an RFC 6901 JSON Pointer to the offending value, while literals so large the lexer itself refuses them carry source coordinates and an NA path (no parse tree exists to point into). "numeric_overflow" is real-form overflow such as 1e999; "depth_limit" carries NA coordinates.

Value

The corresponding R value; see the mapping above.

Examples

from_json('{"a": 1, "b": [true, null]}')
from_json("[1, 2, 3]")

Serialize to JSON strictly

Description

Serializes an R value to one compact UTF-8 JSON document (no whitespace, no trailing newline). Values with no faithful JSON representation refuse with a classed condition instead of being coerced.

Usage

to_json(x)

Arguments

Details

Mapping: a list with a names attribute becomes an object in insertion order ("" is a valid key, so unnamed slots of a partially-named list encode as ""; duplicate keys refuse); an unnamed list becomes an array (a length-1 list stays a 1-element array); a length-1 unnamed atomic becomes a bare scalar; any other atomic becomes an array; NULL becomes null. Integral doubles with magnitude at most 2^53 are written as integers (1, not 1.0), except -0, which stays a real (-0.0) so its sign bit survives; other doubles are written with 17 significant digits. Every finite double, signed zero included, round-trips to the exact same value. The lexical spelling of non-integral doubles is not guaranteed byte-stable across Jansson versions.

Refused: NA of any type, NaN, infinities, named atomic vectors, atomics or lists with other attributes, classed objects, duplicate or NA keys, raw, complex, functions, environments, and nesting beyond 1024 containers. Errors have class c("janssonr_encode_error", "janssonr_error", "error", "condition").

Value

A length-1 UTF-8 character vector holding the JSON document.

Examples

to_json(list(a = 1L, b = list(TRUE, NULL)))
to_json(list())
to_json(structure(list(), names = character(0)))