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JSON::Fast cpan:TIMOTIMO last updated on 2021-05-29


Build Status


a naive imperative json parser in pure perl6 (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


    my $*JSON_NAN_INF_SUPPORT = 1; # allow NaN, Inf, and -Inf to be serialized.
    say to-json [<my Perl data structure>];
    say to-json [<my Perl data structure>], :!pretty;
    say to-json [<my Perl 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 Perl data structure into JSON. Takes one positional argument, which is a thing you want to encode into JSON. Takes these optional named arguments:


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.


Int. Defaults to 2. Applies only when pretty is True. Controls how much spacing there is between each nested level of the output.


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.


    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 Perl datastructure representing that JSON.

Additional features

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.