JSON::Fast
A naive imperative JSON parser in pure Raku (but with direct access to nqp::
ops), to evaluate performance against JSON::Tiny
. It is a drop-in replacement for JSON::Tiny
’s from-json and to-json subs, but it offers a few extra features.
Currently it seems to be about 4x faster and uses up about a quarter of the RAM JSON::Tiny would use.
This module also includes a very fast to-json function that tony-o created and lizmat later completely refactored.
Exported subroutines
to-json
my $*JSON_NAN_INF_SUPPORT = 1; # allow NaN, Inf, and -Inf to be serialized.
say to-json [<my Raku data structure>];
say to-json [<my Raku data structure>], :!pretty;
say to-json [<my Raku data structure>], :spacing(4);
enum Blerp <Hello Goodbye>;
say to-json [Hello, Goodbye]; # ["Hello", "Goodbye"]
say to-json [Hello, Goodbye], :enums-as-value; # [0, 1]
Encode a Raku data structure into JSON. Takes one positional argument, which is a thing you want to encode into JSON. Takes these optional named arguments:
pretty
Bool
. Defaults to True
. Specifies whether the output should be "pretty", human-readable JSON. When set to false, will output json in a single line.
spacing
Int
. Defaults to 2
. Applies only when pretty
is True
. Controls how much spacing there is between each nested level of the output.
sorted-keys
Bool
, defaults to False
. Specifies whether keys from objects should be sorted before serializing them to a string or if $obj.keys
is good enough.
enum-as-value
Bool
, defaults to False
. Specifies whether enum
s should be json-ified as their underlying values, instead of as the name of the enum
.
from-json
my $x = from-json '["foo", "bar", {"ber": "bor"}]';
say $x.perl;
# outputs: $["foo", "bar", {:ber("bor")}]
Takes one positional argument that is coerced into a Str
type and represents a JSON text to decode. Returns a Raku datastructure representing that JSON.
immutable
Bool
. Defaults to False
. Specifies whether Hash
es and Array
s should be rendered as immutable datastructures instead (as Map
/ List
. Creating an immutable data structures is mostly saving on memory usage, and a little bit on CPU (typically around 5%).
This also has the side effect that elements from the returned structure can now be iterated over directly because they are not containerized.
my %hash := from-json "META6.json".IO.slurp, :immutable;
say "Provides:";
.say for %hash<provides>;
Additional features
Adapting defaults of "from-json"
In the use
statement, you can add the string "immutable"
to make the default of the immutable
parameter to the from-json
subroutine True
, rather than False.
use JSON::Fast <immutable>; # create immutable data structures by default
Adapting defaults of "to-json"
In the use
statement, you can add the strings "!pretty"
, "sorted-keys"
and/or "enums-as-value"
to change the associated defaults of the to-json
subroutine.
use JSON::FAST <!pretty sorted-keys enums-as-value>;
Strings containing multiple json pieces
When the document contains additional non-whitespace after the first successfully parsed JSON object, JSON::Fast will throw the exception X::JSON::AdditionalContent
. If you expect multiple objects, you can catch that exception, retrieve the parse result from its parsed
attribute, and remove the first rest-position
characters off of the string and restart parsing from there.