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1.1 |
=head1 NAME |
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JSON::XS - JSON serialising/deserialising, done correctly and fast |
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=head1 SYNOPSIS |
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use JSON::XS; |
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1.22 |
# exported functions, they croak on error |
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# and expect/generate UTF-8 |
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1.12 |
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$utf8_encoded_json_text = to_json $perl_hash_or_arrayref; |
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$perl_hash_or_arrayref = from_json $utf8_encoded_json_text; |
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1.22 |
# objToJson and jsonToObj aliases to to_json and from_json |
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# are exported for compatibility to the JSON module, |
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# but should not be used in new code. |
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1.21 |
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1.22 |
# OO-interface |
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1.12 |
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$coder = JSON::XS->new->ascii->pretty->allow_nonref; |
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$pretty_printed_unencoded = $coder->encode ($perl_scalar); |
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$perl_scalar = $coder->decode ($unicode_json_text); |
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1.1 |
=head1 DESCRIPTION |
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1.2 |
This module converts Perl data structures to JSON and vice versa. Its |
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primary goal is to be I<correct> and its secondary goal is to be |
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I<fast>. To reach the latter goal it was written in C. |
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As this is the n-th-something JSON module on CPAN, what was the reason |
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to write yet another JSON module? While it seems there are many JSON |
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modules, none of them correctly handle all corner cases, and in most cases |
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their maintainers are unresponsive, gone missing, or not listening to bug |
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reports for other reasons. |
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See COMPARISON, below, for a comparison to some other JSON modules. |
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1.10 |
See MAPPING, below, on how JSON::XS maps perl values to JSON values and |
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vice versa. |
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1.2 |
=head2 FEATURES |
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1.1 |
=over 4 |
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1.21 |
=item * correct unicode handling |
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1.2 |
|
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1.10 |
This module knows how to handle Unicode, and even documents how and when |
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it does so. |
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1.2 |
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=item * round-trip integrity |
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When you serialise a perl data structure using only datatypes supported |
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by JSON, the deserialised data structure is identical on the Perl level. |
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1.21 |
(e.g. the string "2.0" doesn't suddenly become "2" just because it looks |
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like a number). |
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1.2 |
|
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=item * strict checking of JSON correctness |
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1.16 |
There is no guessing, no generating of illegal JSON texts by default, |
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1.10 |
and only JSON is accepted as input by default (the latter is a security |
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feature). |
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1.2 |
|
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=item * fast |
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1.10 |
Compared to other JSON modules, this module compares favourably in terms |
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of speed, too. |
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1.2 |
|
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=item * simple to use |
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This module has both a simple functional interface as well as an OO |
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interface. |
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=item * reasonably versatile output formats |
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1.10 |
You can choose between the most compact guarenteed single-line format |
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1.21 |
possible (nice for simple line-based protocols), a pure-ascii format |
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(for when your transport is not 8-bit clean, still supports the whole |
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unicode range), or a pretty-printed format (for when you want to read that |
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stuff). Or you can combine those features in whatever way you like. |
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1.2 |
|
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=back |
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1.1 |
=cut |
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package JSON::XS; |
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1.20 |
use strict; |
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1.1 |
BEGIN { |
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1.21 |
our $VERSION = '0.8'; |
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1.20 |
our @ISA = qw(Exporter); |
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1.1 |
|
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1.21 |
our @EXPORT = qw(to_json from_json objToJson jsonToObj); |
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1.1 |
require Exporter; |
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require XSLoader; |
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XSLoader::load JSON::XS::, $VERSION; |
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} |
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1.2 |
=head1 FUNCTIONAL INTERFACE |
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The following convinience methods are provided by this module. They are |
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exported by default: |
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=over 4 |
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1.16 |
=item $json_text = to_json $perl_scalar |
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1.2 |
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Converts the given Perl data structure (a simple scalar or a reference to |
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a hash or array) to a UTF-8 encoded, binary string (that is, the string contains |
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octets only). Croaks on error. |
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1.16 |
This function call is functionally identical to: |
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1.2 |
|
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1.16 |
$json_text = JSON::XS->new->utf8->encode ($perl_scalar) |
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except being faster. |
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=item $perl_scalar = from_json $json_text |
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1.2 |
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The opposite of C<to_json>: expects an UTF-8 (binary) string and tries to |
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1.16 |
parse that as an UTF-8 encoded JSON text, returning the resulting simple |
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1.2 |
scalar or reference. Croaks on error. |
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1.16 |
This function call is functionally identical to: |
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$perl_scalar = JSON::XS->new->utf8->decode ($json_text) |
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except being faster. |
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1.2 |
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=back |
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1.23 |
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1.2 |
=head1 OBJECT-ORIENTED INTERFACE |
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The object oriented interface lets you configure your own encoding or |
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decoding style, within the limits of supported formats. |
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=over 4 |
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=item $json = new JSON::XS |
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Creates a new JSON::XS object that can be used to de/encode JSON |
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strings. All boolean flags described below are by default I<disabled>. |
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1.1 |
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1.2 |
The mutators for flags all return the JSON object again and thus calls can |
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be chained: |
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1.16 |
my $json = JSON::XS->new->utf8->space_after->encode ({a => [1,2]}) |
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1.3 |
=> {"a": [1, 2]} |
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1.2 |
|
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1.7 |
=item $json = $json->ascii ([$enable]) |
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1.2 |
|
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1.16 |
If C<$enable> is true (or missing), then the C<encode> method will not |
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generate characters outside the code range C<0..127> (which is ASCII). Any |
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unicode characters outside that range will be escaped using either a |
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single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence, |
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as per RFC4627. |
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1.2 |
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If C<$enable> is false, then the C<encode> method will not escape Unicode |
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1.16 |
characters unless required by the JSON syntax. This results in a faster |
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and more compact format. |
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1.2 |
|
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1.16 |
JSON::XS->new->ascii (1)->encode ([chr 0x10401]) |
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=> ["\ud801\udc01"] |
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1.3 |
|
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1.7 |
=item $json = $json->utf8 ([$enable]) |
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1.2 |
|
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1.7 |
If C<$enable> is true (or missing), then the C<encode> method will encode |
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1.16 |
the JSON result into UTF-8, as required by many protocols, while the |
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1.7 |
C<decode> method expects to be handled an UTF-8-encoded string. Please |
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note that UTF-8-encoded strings do not contain any characters outside the |
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1.16 |
range C<0..255>, they are thus useful for bytewise/binary I/O. In future |
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versions, enabling this option might enable autodetection of the UTF-16 |
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and UTF-32 encoding families, as described in RFC4627. |
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1.2 |
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If C<$enable> is false, then the C<encode> method will return the JSON |
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string as a (non-encoded) unicode string, while C<decode> expects thus a |
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unicode string. Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs |
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to be done yourself, e.g. using the Encode module. |
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1.16 |
Example, output UTF-16BE-encoded JSON: |
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use Encode; |
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$jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object); |
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Example, decode UTF-32LE-encoded JSON: |
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use Encode; |
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$object = JSON::XS->new->decode (decode "UTF-32LE", $jsontext); |
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1.12 |
|
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1.7 |
=item $json = $json->pretty ([$enable]) |
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1.2 |
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This enables (or disables) all of the C<indent>, C<space_before> and |
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1.3 |
C<space_after> (and in the future possibly more) flags in one call to |
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1.2 |
generate the most readable (or most compact) form possible. |
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1.12 |
Example, pretty-print some simple structure: |
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1.3 |
my $json = JSON::XS->new->pretty(1)->encode ({a => [1,2]}) |
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=> |
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{ |
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"a" : [ |
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1, |
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2 |
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] |
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} |
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1.7 |
=item $json = $json->indent ([$enable]) |
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1.2 |
|
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1.7 |
If C<$enable> is true (or missing), then the C<encode> method will use a multiline |
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1.2 |
format as output, putting every array member or object/hash key-value pair |
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into its own line, identing them properly. |
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If C<$enable> is false, no newlines or indenting will be produced, and the |
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1.16 |
resulting JSON text is guarenteed not to contain any C<newlines>. |
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1.2 |
|
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1.16 |
This setting has no effect when decoding JSON texts. |
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1.2 |
|
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1.7 |
=item $json = $json->space_before ([$enable]) |
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1.2 |
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1.7 |
If C<$enable> is true (or missing), then the C<encode> method will add an extra |
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1.2 |
optional space before the C<:> separating keys from values in JSON objects. |
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If C<$enable> is false, then the C<encode> method will not add any extra |
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space at those places. |
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1.16 |
This setting has no effect when decoding JSON texts. You will also |
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most likely combine this setting with C<space_after>. |
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1.2 |
|
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1.12 |
Example, space_before enabled, space_after and indent disabled: |
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{"key" :"value"} |
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1.7 |
=item $json = $json->space_after ([$enable]) |
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1.2 |
|
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1.7 |
If C<$enable> is true (or missing), then the C<encode> method will add an extra |
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1.2 |
optional space after the C<:> separating keys from values in JSON objects |
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and extra whitespace after the C<,> separating key-value pairs and array |
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members. |
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If C<$enable> is false, then the C<encode> method will not add any extra |
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space at those places. |
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1.16 |
This setting has no effect when decoding JSON texts. |
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1.2 |
|
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1.12 |
Example, space_before and indent disabled, space_after enabled: |
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{"key": "value"} |
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1.7 |
=item $json = $json->canonical ([$enable]) |
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1.2 |
|
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1.7 |
If C<$enable> is true (or missing), then the C<encode> method will output JSON objects |
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1.2 |
by sorting their keys. This is adding a comparatively high overhead. |
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If C<$enable> is false, then the C<encode> method will output key-value |
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pairs in the order Perl stores them (which will likely change between runs |
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of the same script). |
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This option is useful if you want the same data structure to be encoded as |
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1.16 |
the same JSON text (given the same overall settings). If it is disabled, |
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1.2 |
the same hash migh be encoded differently even if contains the same data, |
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as key-value pairs have no inherent ordering in Perl. |
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1.16 |
This setting has no effect when decoding JSON texts. |
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1.2 |
|
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1.7 |
=item $json = $json->allow_nonref ([$enable]) |
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1.3 |
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1.7 |
If C<$enable> is true (or missing), then the C<encode> method can convert a |
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1.3 |
non-reference into its corresponding string, number or null JSON value, |
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which is an extension to RFC4627. Likewise, C<decode> will accept those JSON |
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values instead of croaking. |
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If C<$enable> is false, then the C<encode> method will croak if it isn't |
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1.16 |
passed an arrayref or hashref, as JSON texts must either be an object |
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1.3 |
or array. Likewise, C<decode> will croak if given something that is not a |
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JSON object or array. |
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1.12 |
Example, encode a Perl scalar as JSON value with enabled C<allow_nonref>, |
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resulting in an invalid JSON text: |
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JSON::XS->new->allow_nonref->encode ("Hello, World!") |
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=> "Hello, World!" |
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1.7 |
=item $json = $json->shrink ([$enable]) |
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Perl usually over-allocates memory a bit when allocating space for |
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strings. This flag optionally resizes strings generated by either |
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C<encode> or C<decode> to their minimum size possible. This can save |
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1.16 |
memory when your JSON texts are either very very long or you have many |
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1.8 |
short strings. It will also try to downgrade any strings to octet-form |
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if possible: perl stores strings internally either in an encoding called |
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UTF-X or in octet-form. The latter cannot store everything but uses less |
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space in general. |
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1.7 |
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If C<$enable> is true (or missing), the string returned by C<encode> will be shrunk-to-fit, |
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while all strings generated by C<decode> will also be shrunk-to-fit. |
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If C<$enable> is false, then the normal perl allocation algorithms are used. |
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If you work with your data, then this is likely to be faster. |
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In the future, this setting might control other things, such as converting |
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strings that look like integers or floats into integers or floats |
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internally (there is no difference on the Perl level), saving space. |
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1.23 |
=item $json = $json->max_depth ([$maximum_nesting_depth]) |
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Sets the maximum nesting level (default C<8192>) accepted while encoding |
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or decoding. If the JSON text or Perl data structure has an equal or |
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higher nesting level then this limit, then the encoder and decoder will |
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stop and croak at that point. |
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Nesting level is defined by number of hash- or arrayrefs that the encoder |
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needs to traverse to reach a given point or the number of C<{> or C<[> |
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characters without their matching closing parenthesis crossed to reach a |
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given character in a string. |
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Setting the maximum depth to one disallows any nesting, so that ensures |
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that the object is only a single hash/object or array. |
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The argument to C<max_depth> will be rounded up to the next nearest power |
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of two. |
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See SECURITY CONSIDERATIONS, below, for more info on why this is useful. |
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|
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1.16 |
=item $json_text = $json->encode ($perl_scalar) |
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1.2 |
|
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Converts the given Perl data structure (a simple scalar or a reference |
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to a hash or array) to its JSON representation. Simple scalars will be |
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converted into JSON string or number sequences, while references to arrays |
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become JSON arrays and references to hashes become JSON objects. Undefined |
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Perl values (e.g. C<undef>) become JSON C<null> values. Neither C<true> |
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nor C<false> values will be generated. |
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1.1 |
|
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1.16 |
=item $perl_scalar = $json->decode ($json_text) |
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1.1 |
|
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1.16 |
The opposite of C<encode>: expects a JSON text and tries to parse it, |
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1.2 |
returning the resulting simple scalar or reference. Croaks on error. |
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1.1 |
|
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1.2 |
JSON numbers and strings become simple Perl scalars. JSON arrays become |
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Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes |
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C<1>, C<false> becomes C<0> and C<null> becomes C<undef>. |
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1.1 |
|
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=back |
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|
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1.23 |
|
348 |
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1.10 |
=head1 MAPPING |
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|
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This section describes how JSON::XS maps Perl values to JSON values and |
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vice versa. These mappings are designed to "do the right thing" in most |
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circumstances automatically, preserving round-tripping characteristics |
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(what you put in comes out as something equivalent). |
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For the more enlightened: note that in the following descriptions, |
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lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl> |
357 |
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|
refers to the abstract Perl language itself. |
358 |
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359 |
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=head2 JSON -> PERL |
360 |
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|
361 |
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=over 4 |
362 |
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|
363 |
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=item object |
364 |
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|
365 |
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|
A JSON object becomes a reference to a hash in Perl. No ordering of object |
366 |
root |
1.14 |
keys is preserved (JSON does not preserver object key ordering itself). |
367 |
root |
1.10 |
|
368 |
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=item array |
369 |
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|
370 |
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A JSON array becomes a reference to an array in Perl. |
371 |
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|
372 |
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=item string |
373 |
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|
374 |
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A JSON string becomes a string scalar in Perl - Unicode codepoints in JSON |
375 |
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|
are represented by the same codepoints in the Perl string, so no manual |
376 |
|
|
decoding is necessary. |
377 |
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|
378 |
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|
=item number |
379 |
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|
380 |
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|
A JSON number becomes either an integer or numeric (floating point) |
381 |
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scalar in perl, depending on its range and any fractional parts. On the |
382 |
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|
Perl level, there is no difference between those as Perl handles all the |
383 |
|
|
conversion details, but an integer may take slightly less memory and might |
384 |
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|
represent more values exactly than (floating point) numbers. |
385 |
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|
386 |
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=item true, false |
387 |
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|
388 |
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|
These JSON atoms become C<0>, C<1>, respectively. Information is lost in |
389 |
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this process. Future versions might represent those values differently, |
390 |
|
|
but they will be guarenteed to act like these integers would normally in |
391 |
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|
Perl. |
392 |
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|
393 |
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=item null |
394 |
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|
395 |
|
|
A JSON null atom becomes C<undef> in Perl. |
396 |
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|
397 |
|
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=back |
398 |
|
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|
399 |
|
|
=head2 PERL -> JSON |
400 |
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|
401 |
|
|
The mapping from Perl to JSON is slightly more difficult, as Perl is a |
402 |
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truly typeless language, so we can only guess which JSON type is meant by |
403 |
|
|
a Perl value. |
404 |
|
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|
405 |
|
|
=over 4 |
406 |
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|
407 |
|
|
=item hash references |
408 |
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|
409 |
|
|
Perl hash references become JSON objects. As there is no inherent ordering |
410 |
|
|
in hash keys, they will usually be encoded in a pseudo-random order that |
411 |
|
|
can change between runs of the same program but stays generally the same |
412 |
root |
1.14 |
within a single run of a program. JSON::XS can optionally sort the hash |
413 |
root |
1.10 |
keys (determined by the I<canonical> flag), so the same datastructure |
414 |
|
|
will serialise to the same JSON text (given same settings and version of |
415 |
|
|
JSON::XS), but this incurs a runtime overhead. |
416 |
|
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|
417 |
|
|
=item array references |
418 |
|
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|
419 |
|
|
Perl array references become JSON arrays. |
420 |
|
|
|
421 |
|
|
=item blessed objects |
422 |
|
|
|
423 |
|
|
Blessed objects are not allowed. JSON::XS currently tries to encode their |
424 |
|
|
underlying representation (hash- or arrayref), but this behaviour might |
425 |
|
|
change in future versions. |
426 |
|
|
|
427 |
|
|
=item simple scalars |
428 |
|
|
|
429 |
|
|
Simple Perl scalars (any scalar that is not a reference) are the most |
430 |
|
|
difficult objects to encode: JSON::XS will encode undefined scalars as |
431 |
|
|
JSON null value, scalars that have last been used in a string context |
432 |
|
|
before encoding as JSON strings and anything else as number value: |
433 |
|
|
|
434 |
|
|
# dump as number |
435 |
|
|
to_json [2] # yields [2] |
436 |
|
|
to_json [-3.0e17] # yields [-3e+17] |
437 |
|
|
my $value = 5; to_json [$value] # yields [5] |
438 |
|
|
|
439 |
|
|
# used as string, so dump as string |
440 |
|
|
print $value; |
441 |
|
|
to_json [$value] # yields ["5"] |
442 |
|
|
|
443 |
|
|
# undef becomes null |
444 |
|
|
to_json [undef] # yields [null] |
445 |
|
|
|
446 |
|
|
You can force the type to be a string by stringifying it: |
447 |
|
|
|
448 |
|
|
my $x = 3.1; # some variable containing a number |
449 |
|
|
"$x"; # stringified |
450 |
|
|
$x .= ""; # another, more awkward way to stringify |
451 |
|
|
print $x; # perl does it for you, too, quite often |
452 |
|
|
|
453 |
|
|
You can force the type to be a number by numifying it: |
454 |
|
|
|
455 |
|
|
my $x = "3"; # some variable containing a string |
456 |
|
|
$x += 0; # numify it, ensuring it will be dumped as a number |
457 |
|
|
$x *= 1; # same thing, the choise is yours. |
458 |
|
|
|
459 |
|
|
You can not currently output JSON booleans or force the type in other, |
460 |
|
|
less obscure, ways. Tell me if you need this capability. |
461 |
|
|
|
462 |
root |
1.11 |
=item circular data structures |
463 |
|
|
|
464 |
|
|
Those will be encoded until memory or stackspace runs out. |
465 |
|
|
|
466 |
root |
1.10 |
=back |
467 |
|
|
|
468 |
root |
1.23 |
|
469 |
root |
1.3 |
=head1 COMPARISON |
470 |
|
|
|
471 |
|
|
As already mentioned, this module was created because none of the existing |
472 |
|
|
JSON modules could be made to work correctly. First I will describe the |
473 |
|
|
problems (or pleasures) I encountered with various existing JSON modules, |
474 |
root |
1.4 |
followed by some benchmark values. JSON::XS was designed not to suffer |
475 |
|
|
from any of these problems or limitations. |
476 |
root |
1.3 |
|
477 |
|
|
=over 4 |
478 |
|
|
|
479 |
root |
1.5 |
=item JSON 1.07 |
480 |
root |
1.3 |
|
481 |
|
|
Slow (but very portable, as it is written in pure Perl). |
482 |
|
|
|
483 |
|
|
Undocumented/buggy Unicode handling (how JSON handles unicode values is |
484 |
|
|
undocumented. One can get far by feeding it unicode strings and doing |
485 |
|
|
en-/decoding oneself, but unicode escapes are not working properly). |
486 |
|
|
|
487 |
|
|
No roundtripping (strings get clobbered if they look like numbers, e.g. |
488 |
|
|
the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will |
489 |
|
|
decode into the number 2. |
490 |
|
|
|
491 |
root |
1.5 |
=item JSON::PC 0.01 |
492 |
root |
1.3 |
|
493 |
|
|
Very fast. |
494 |
|
|
|
495 |
|
|
Undocumented/buggy Unicode handling. |
496 |
|
|
|
497 |
|
|
No roundtripping. |
498 |
|
|
|
499 |
root |
1.4 |
Has problems handling many Perl values (e.g. regex results and other magic |
500 |
|
|
values will make it croak). |
501 |
root |
1.3 |
|
502 |
|
|
Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}> |
503 |
root |
1.16 |
which is not a valid JSON text. |
504 |
root |
1.3 |
|
505 |
|
|
Unmaintained (maintainer unresponsive for many months, bugs are not |
506 |
|
|
getting fixed). |
507 |
|
|
|
508 |
root |
1.5 |
=item JSON::Syck 0.21 |
509 |
root |
1.3 |
|
510 |
|
|
Very buggy (often crashes). |
511 |
|
|
|
512 |
root |
1.4 |
Very inflexible (no human-readable format supported, format pretty much |
513 |
|
|
undocumented. I need at least a format for easy reading by humans and a |
514 |
|
|
single-line compact format for use in a protocol, and preferably a way to |
515 |
root |
1.16 |
generate ASCII-only JSON texts). |
516 |
root |
1.3 |
|
517 |
|
|
Completely broken (and confusingly documented) Unicode handling (unicode |
518 |
|
|
escapes are not working properly, you need to set ImplicitUnicode to |
519 |
|
|
I<different> values on en- and decoding to get symmetric behaviour). |
520 |
|
|
|
521 |
|
|
No roundtripping (simple cases work, but this depends on wether the scalar |
522 |
|
|
value was used in a numeric context or not). |
523 |
|
|
|
524 |
|
|
Dumping hashes may skip hash values depending on iterator state. |
525 |
|
|
|
526 |
|
|
Unmaintained (maintainer unresponsive for many months, bugs are not |
527 |
|
|
getting fixed). |
528 |
|
|
|
529 |
|
|
Does not check input for validity (i.e. will accept non-JSON input and |
530 |
|
|
return "something" instead of raising an exception. This is a security |
531 |
|
|
issue: imagine two banks transfering money between each other using |
532 |
|
|
JSON. One bank might parse a given non-JSON request and deduct money, |
533 |
|
|
while the other might reject the transaction with a syntax error. While a |
534 |
|
|
good protocol will at least recover, that is extra unnecessary work and |
535 |
|
|
the transaction will still not succeed). |
536 |
|
|
|
537 |
root |
1.5 |
=item JSON::DWIW 0.04 |
538 |
root |
1.3 |
|
539 |
|
|
Very fast. Very natural. Very nice. |
540 |
|
|
|
541 |
|
|
Undocumented unicode handling (but the best of the pack. Unicode escapes |
542 |
|
|
still don't get parsed properly). |
543 |
|
|
|
544 |
|
|
Very inflexible. |
545 |
|
|
|
546 |
|
|
No roundtripping. |
547 |
|
|
|
548 |
root |
1.16 |
Does not generate valid JSON texts (key strings are often unquoted, empty keys |
549 |
root |
1.4 |
result in nothing being output) |
550 |
|
|
|
551 |
root |
1.3 |
Does not check input for validity. |
552 |
|
|
|
553 |
|
|
=back |
554 |
|
|
|
555 |
|
|
=head2 SPEED |
556 |
|
|
|
557 |
root |
1.4 |
It seems that JSON::XS is surprisingly fast, as shown in the following |
558 |
|
|
tables. They have been generated with the help of the C<eg/bench> program |
559 |
|
|
in the JSON::XS distribution, to make it easy to compare on your own |
560 |
|
|
system. |
561 |
|
|
|
562 |
root |
1.13 |
First comes a comparison between various modules using a very short JSON |
563 |
root |
1.18 |
string: |
564 |
|
|
|
565 |
|
|
{"method": "handleMessage", "params": ["user1", "we were just talking"], "id": null} |
566 |
|
|
|
567 |
|
|
It shows the number of encodes/decodes per second (JSON::XS uses the |
568 |
|
|
functional interface, while JSON::XS/2 uses the OO interface with |
569 |
|
|
pretty-printing and hashkey sorting enabled). Higher is better: |
570 |
root |
1.4 |
|
571 |
|
|
module | encode | decode | |
572 |
|
|
-----------|------------|------------| |
573 |
root |
1.18 |
JSON | 11488.516 | 7823.035 | |
574 |
|
|
JSON::DWIW | 94708.054 | 129094.260 | |
575 |
|
|
JSON::PC | 63884.157 | 128528.212 | |
576 |
|
|
JSON::Syck | 34898.677 | 42096.911 | |
577 |
|
|
JSON::XS | 654027.064 | 396423.669 | |
578 |
|
|
JSON::XS/2 | 371564.190 | 371725.613 | |
579 |
root |
1.4 |
-----------+------------+------------+ |
580 |
|
|
|
581 |
root |
1.18 |
That is, JSON::XS is more than six times faster than JSON::DWIW on |
582 |
|
|
encoding, more than three times faster on decoding, and about thirty times |
583 |
|
|
faster than JSON, even with pretty-printing and key sorting. |
584 |
root |
1.4 |
|
585 |
root |
1.13 |
Using a longer test string (roughly 18KB, generated from Yahoo! Locals |
586 |
root |
1.4 |
search API (http://nanoref.com/yahooapis/mgPdGg): |
587 |
|
|
|
588 |
|
|
module | encode | decode | |
589 |
|
|
-----------|------------|------------| |
590 |
root |
1.18 |
JSON | 273.023 | 44.674 | |
591 |
|
|
JSON::DWIW | 1089.383 | 1145.704 | |
592 |
|
|
JSON::PC | 3097.419 | 2393.921 | |
593 |
|
|
JSON::Syck | 514.060 | 843.053 | |
594 |
|
|
JSON::XS | 6479.668 | 3636.364 | |
595 |
|
|
JSON::XS/2 | 3774.221 | 3599.124 | |
596 |
root |
1.4 |
-----------+------------+------------+ |
597 |
|
|
|
598 |
root |
1.18 |
Again, JSON::XS leads by far. |
599 |
root |
1.4 |
|
600 |
root |
1.18 |
On large strings containing lots of high unicode characters, some modules |
601 |
|
|
(such as JSON::PC) seem to decode faster than JSON::XS, but the result |
602 |
|
|
will be broken due to missing (or wrong) unicode handling. Others refuse |
603 |
|
|
to decode or encode properly, so it was impossible to prepare a fair |
604 |
|
|
comparison table for that case. |
605 |
root |
1.13 |
|
606 |
root |
1.11 |
|
607 |
root |
1.23 |
=head1 SECURITY CONSIDERATIONS |
608 |
|
|
|
609 |
|
|
When you are using JSON in a protocol, talking to untrusted potentially |
610 |
|
|
hostile creatures requires relatively few measures. |
611 |
|
|
|
612 |
|
|
First of all, your JSON decoder should be secure, that is, should not have |
613 |
|
|
any buffer overflows. Obviously, this module should ensure that and I am |
614 |
|
|
trying hard on making that true, but you never know. |
615 |
|
|
|
616 |
|
|
Second, you need to avoid resource-starving attacks. That means you should |
617 |
|
|
limit the size of JSON texts you accept, or make sure then when your |
618 |
|
|
resources run out, thats just fine (e.g. by using a separate process that |
619 |
|
|
can crash safely). The size of a JSON text in octets or characters is |
620 |
|
|
usually a good indication of the size of the resources required to decode |
621 |
|
|
it into a Perl structure. |
622 |
|
|
|
623 |
|
|
Third, JSON::XS recurses using the C stack when decoding objects and |
624 |
|
|
arrays. The C stack is a limited resource: for instance, on my amd64 |
625 |
|
|
machine with 8MB of stack size I can decode around 180k nested arrays |
626 |
|
|
but only 14k nested JSON objects. If that is exceeded, the program |
627 |
|
|
crashes. Thats why the default nesting limit is set to 8192. If your |
628 |
|
|
process has a smaller stack, you should adjust this setting accordingly |
629 |
|
|
with the C<max_depth> method. |
630 |
|
|
|
631 |
|
|
And last but least, something else could bomb you that I forgot to think |
632 |
|
|
of. In that case, you get to keep the pieces. I am alway sopen for hints, |
633 |
|
|
though... |
634 |
|
|
|
635 |
root |
1.11 |
|
636 |
root |
1.4 |
=head1 BUGS |
637 |
|
|
|
638 |
|
|
While the goal of this module is to be correct, that unfortunately does |
639 |
|
|
not mean its bug-free, only that I think its design is bug-free. It is |
640 |
root |
1.23 |
still relatively early in its development. If you keep reporting bugs they |
641 |
|
|
will be fixed swiftly, though. |
642 |
root |
1.4 |
|
643 |
root |
1.2 |
=cut |
644 |
|
|
|
645 |
|
|
1; |
646 |
|
|
|
647 |
root |
1.1 |
=head1 AUTHOR |
648 |
|
|
|
649 |
|
|
Marc Lehmann <schmorp@schmorp.de> |
650 |
|
|
http://home.schmorp.de/ |
651 |
|
|
|
652 |
|
|
=cut |
653 |
|
|
|