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https://github.com/timo/json_fast

a naive imperative json parser in perl6, to evaluate performance against JSON::Tiny
https://github.com/timo/json_fast

json perl6

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a naive imperative json parser in perl6, to evaluate performance against JSON::Tiny

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[![Build Status](https://travis-ci.org/timo/json_fast.svg?branch=master)](https://travis-ci.org/timo/json_fast)



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.



SYNOPSIS

--------



        use JSON::Fast;

        my $storage-path = $*SPEC.tmpdir.child("json-fast-example-$*PID.json");

        say "using path $storage-path for example";

        for  -> $word {

            say "- loading json file";

            my $current-data = from-json ($storage-path.IO.slurp // "\{}");

            # $current-data now contains a Hash object populated with what was in the file

            # (or an empty hash in the very first step when the file didn't exsit yet)



            say "- adding entry for $word";

            $current-data{$word}{"length"} = $word.chars;

            $current-data{$word}{"first letter"} = $word.substr(0,1);



            say "- saving json file";

            $storage-path.IO.spurt(to-json $current-data);

            # to-json gives us a regular string, so we can plop that

            # into the file with the spurt method



            say "json file is now $storage-path.IO.s() bytes big";

            say "===";

        }

        say "here is the entire contents of the json file:";

        say "====";

        say $storage-path.IO.slurp();

        say "====";

        say "deleting storage file ...";

        $storage-path.IO.unlink;



Exported subroutines

--------------------



### to-json



        my $*JSON_NAN_INF_SUPPORT = 1; # allow NaN, Inf, and -Inf to be serialized.

        say to-json [];

        say to-json [], :!pretty;

        say to-json [], :spacing(4);



        enum Blerp ;

        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



Specifies whether keys from objects should be sorted before serializing them to a string or if `$obj.keys` is good enough. Defaults to `False`. Can also be specified as a `Callable` with the same type of argument that the `.sort` method accepts to provide alternate sorting methods.



#### 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;



#### allow-jsonc



`Bool`. Defaults to `False`. Specifies whether commmands adhering to the [JSONC standard](https://changelog.com/news/jsonc-is-a-superset-of-json-which-supports-comments-6LwR) are allowed.



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 ;  # 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 ;



### 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.