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1 | =head1 NAME |
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2 | |
1 | =encoding utf-8 |
3 | =encoding utf-8 |
2 | |
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3 | =head1 NAME |
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4 | |
4 | |
5 | JSON::XS - JSON serialising/deserialising, done correctly and fast |
5 | JSON::XS - JSON serialising/deserialising, done correctly and fast |
6 | |
6 | |
7 | JSON::XS - 正しくて高速な JSON シリアライザ/デシリアライザ |
7 | JSON::XS - 正しくて高速な JSON シリアライザ/デシリアライザ |
8 | (http://fleur.hio.jp/perldoc/mix/lib/JSON/XS.html) |
8 | (http://fleur.hio.jp/perldoc/mix/lib/JSON/XS.html) |
… | |
… | |
103 | |
103 | |
104 | package JSON::XS; |
104 | package JSON::XS; |
105 | |
105 | |
106 | use strict; |
106 | use strict; |
107 | |
107 | |
108 | our $VERSION = '2.01'; |
108 | our $VERSION = '2.1'; |
109 | our @ISA = qw(Exporter); |
109 | our @ISA = qw(Exporter); |
110 | |
110 | |
111 | our @EXPORT = qw(encode_json decode_json to_json from_json); |
111 | our @EXPORT = qw(encode_json decode_json to_json from_json); |
112 | |
112 | |
113 | sub to_json($) { |
113 | sub to_json($) { |
… | |
… | |
245 | |
245 | |
246 | If C<$enable> is false, then the C<encode> method will not escape Unicode |
246 | If C<$enable> is false, then the C<encode> method will not escape Unicode |
247 | characters unless required by the JSON syntax or other flags. This results |
247 | characters unless required by the JSON syntax or other flags. This results |
248 | in a faster and more compact format. |
248 | in a faster and more compact format. |
249 | |
249 | |
|
|
250 | See also the section I<ENCODING/CODESET FLAG NOTES> later in this |
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251 | document. |
|
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252 | |
250 | The main use for this flag is to produce JSON texts that can be |
253 | The main use for this flag is to produce JSON texts that can be |
251 | transmitted over a 7-bit channel, as the encoded JSON texts will not |
254 | transmitted over a 7-bit channel, as the encoded JSON texts will not |
252 | contain any 8 bit characters. |
255 | contain any 8 bit characters. |
253 | |
256 | |
254 | JSON::XS->new->ascii (1)->encode ([chr 0x10401]) |
257 | JSON::XS->new->ascii (1)->encode ([chr 0x10401]) |
… | |
… | |
265 | will not be affected in any way by this flag, as C<decode> by default |
268 | will not be affected in any way by this flag, as C<decode> by default |
266 | expects Unicode, which is a strict superset of latin1. |
269 | expects Unicode, which is a strict superset of latin1. |
267 | |
270 | |
268 | If C<$enable> is false, then the C<encode> method will not escape Unicode |
271 | If C<$enable> is false, then the C<encode> method will not escape Unicode |
269 | characters unless required by the JSON syntax or other flags. |
272 | characters unless required by the JSON syntax or other flags. |
|
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273 | |
|
|
274 | See also the section I<ENCODING/CODESET FLAG NOTES> later in this |
|
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275 | document. |
270 | |
276 | |
271 | The main use for this flag is efficiently encoding binary data as JSON |
277 | The main use for this flag is efficiently encoding binary data as JSON |
272 | text, as most octets will not be escaped, resulting in a smaller encoded |
278 | text, as most octets will not be escaped, resulting in a smaller encoded |
273 | size. The disadvantage is that the resulting JSON text is encoded |
279 | size. The disadvantage is that the resulting JSON text is encoded |
274 | in latin1 (and must correctly be treated as such when storing and |
280 | in latin1 (and must correctly be treated as such when storing and |
… | |
… | |
293 | |
299 | |
294 | If C<$enable> is false, then the C<encode> method will return the JSON |
300 | If C<$enable> is false, then the C<encode> method will return the JSON |
295 | string as a (non-encoded) Unicode string, while C<decode> expects thus a |
301 | string as a (non-encoded) Unicode string, while C<decode> expects thus a |
296 | Unicode string. Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs |
302 | Unicode string. Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs |
297 | to be done yourself, e.g. using the Encode module. |
303 | to be done yourself, e.g. using the Encode module. |
|
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304 | |
|
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305 | See also the section I<ENCODING/CODESET FLAG NOTES> later in this |
|
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306 | document. |
298 | |
307 | |
299 | Example, output UTF-16BE-encoded JSON: |
308 | Example, output UTF-16BE-encoded JSON: |
300 | |
309 | |
301 | use Encode; |
310 | use Encode; |
302 | $jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object); |
311 | $jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object); |
… | |
… | |
672 | => ([], 3) |
681 | => ([], 3) |
673 | |
682 | |
674 | =back |
683 | =back |
675 | |
684 | |
676 | |
685 | |
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686 | =head1 INCREMENTAL PARSING |
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687 | |
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688 | [This section and the API it details is still EXPERIMENTAL] |
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689 | |
|
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690 | In some cases, there is the need for incremental parsing of JSON |
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691 | texts. While this module always has to keep both JSON text and resulting |
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692 | Perl data structure in memory at one time, it does allow you to parse a |
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693 | JSON stream incrementally. It does so by accumulating text until it has |
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694 | a full JSON object, which it then can decode. This process is similar to |
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695 | using C<decode_prefix> to see if a full JSON object is available, but is |
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696 | much more efficient (JSON::XS will only attempt to parse the JSON text |
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697 | once it is sure it has enough text to get a decisive result, using a very |
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698 | simple but truly incremental parser). |
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699 | |
|
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700 | The following two methods deal with this. |
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701 | |
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702 | =over 4 |
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703 | |
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704 | =item [void, scalar or list context] = $json->incr_parse ([$string]) |
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705 | |
|
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706 | This is the central parsing function. It can both append new text and |
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707 | extract objects from the stream accumulated so far (both of these |
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708 | functions are optional). |
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709 | |
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710 | If C<$string> is given, then this string is appended to the already |
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711 | existing JSON fragment stored in the C<$json> object. |
|
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712 | |
|
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713 | After that, if the function is called in void context, it will simply |
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714 | return without doing anything further. This can be used to add more text |
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715 | in as many chunks as you want. |
|
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716 | |
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717 | If the method is called in scalar context, then it will try to extract |
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718 | exactly I<one> JSON object. If that is successful, it will return this |
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719 | object, otherwise it will return C<undef>. If there is a parse error, |
|
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720 | this method will croak just as C<decode> would do (one can then use |
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721 | C<incr_skip> to skip the errornous part). This is the most common way of |
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722 | using the method. |
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723 | |
|
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724 | And finally, in list context, it will try to extract as many objects |
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725 | from the stream as it can find and return them, or the empty list |
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726 | otherwise. For this to work, there must be no separators between the JSON |
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727 | objects or arrays, instead they must be concatenated back-to-back. If |
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728 | an error occurs, an exception will be raised as in the scalar context |
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729 | case. Note that in this case, any previously-parsed JSON texts will be |
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730 | lost. |
|
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731 | |
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732 | =item $lvalue_string = $json->incr_text |
|
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733 | |
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734 | This method returns the currently stored JSON fragment as an lvalue, that |
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735 | is, you can manipulate it. This I<only> works when a preceding call to |
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736 | C<incr_parse> in I<scalar context> successfully returned an object. Under |
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737 | all other circumstances you must not call this function (I mean it. |
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738 | although in simple tests it might actually work, it I<will> fail under |
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739 | real world conditions). As a special exception, you can also call this |
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740 | method before having parsed anything. |
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741 | |
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742 | This function is useful in two cases: a) finding the trailing text after a |
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743 | JSON object or b) parsing multiple JSON objects separated by non-JSON text |
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744 | (such as commas). |
|
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745 | |
|
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746 | =item $json->incr_skip |
|
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747 | |
|
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748 | This will reset the state of the incremental parser and will remove the |
|
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749 | parsed text from the input buffer. This is useful after C<incr_parse> |
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750 | died, in which case the input buffer and incremental parser state is left |
|
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751 | unchanged, to skip the text parsed so far and to reset the parse state. |
|
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752 | |
|
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753 | =back |
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754 | |
|
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755 | =head2 LIMITATIONS |
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756 | |
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757 | All options that affect decoding are supported, except |
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758 | C<allow_nonref>. The reason for this is that it cannot be made to |
|
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759 | work sensibly: JSON objects and arrays are self-delimited, i.e. you can concatenate |
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760 | them back to back and still decode them perfectly. This does not hold true |
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761 | for JSON numbers, however. |
|
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762 | |
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763 | For example, is the string C<1> a single JSON number, or is it simply the |
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764 | start of C<12>? Or is C<12> a single JSON number, or the concatenation |
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765 | of C<1> and C<2>? In neither case you can tell, and this is why JSON::XS |
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766 | takes the conservative route and disallows this case. |
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767 | |
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768 | =head2 EXAMPLES |
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769 | |
|
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770 | Some examples will make all this clearer. First, a simple example that |
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771 | works similarly to C<decode_prefix>: We want to decode the JSON object at |
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772 | the start of a string and identify the portion after the JSON object: |
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773 | |
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774 | my $text = "[1,2,3] hello"; |
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775 | |
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776 | my $json = new JSON::XS; |
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777 | |
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778 | my $obj = $json->incr_parse ($text) |
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779 | or die "expected JSON object or array at beginning of string"; |
|
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780 | |
|
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781 | my $tail = $json->incr_text; |
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782 | # $tail now contains " hello" |
|
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783 | |
|
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784 | Easy, isn't it? |
|
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785 | |
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786 | Now for a more complicated example: Imagine a hypothetical protocol where |
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787 | you read some requests from a TCP stream, and each request is a JSON |
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788 | array, without any separation between them (in fact, it is often useful to |
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789 | use newlines as "separators", as these get interpreted as whitespace at |
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790 | the start of the JSON text, which makes it possible to test said protocol |
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791 | with C<telnet>...). |
|
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792 | |
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793 | Here is how you'd do it (it is trivial to write this in an event-based |
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794 | manner): |
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795 | |
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796 | my $json = new JSON::XS; |
|
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797 | |
|
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798 | # read some data from the socket |
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799 | while (sysread $socket, my $buf, 4096) { |
|
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800 | |
|
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801 | # split and decode as many requests as possible |
|
|
802 | for my $request ($json->incr_parse ($buf)) { |
|
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803 | # act on the $request |
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804 | } |
|
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805 | } |
|
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806 | |
|
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807 | Another complicated example: Assume you have a string with JSON objects |
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808 | or arrays, all separated by (optional) comma characters (e.g. C<[1],[2], |
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809 | [3]>). To parse them, we have to skip the commas between the JSON texts, |
|
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810 | and here is where the lvalue-ness of C<incr_text> comes in useful: |
|
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811 | |
|
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812 | my $text = "[1],[2], [3]"; |
|
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813 | my $json = new JSON::XS; |
|
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814 | |
|
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815 | # void context, so no parsing done |
|
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816 | $json->incr_parse ($text); |
|
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817 | |
|
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818 | # now extract as many objects as possible. note the |
|
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819 | # use of scalar context so incr_text can be called. |
|
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820 | while (my $obj = $json->incr_parse) { |
|
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821 | # do something with $obj |
|
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822 | |
|
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823 | # now skip the optional comma |
|
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824 | $json->incr_text =~ s/^ \s* , //x; |
|
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825 | } |
|
|
826 | |
|
|
827 | Now lets go for a very complex example: Assume that you have a gigantic |
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828 | JSON array-of-objects, many gigabytes in size, and you want to parse it, |
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829 | but you cannot load it into memory fully (this has actually happened in |
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830 | the real world :). |
|
|
831 | |
|
|
832 | Well, you lost, you have to implement your own JSON parser. But JSON::XS |
|
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833 | can still help you: You implement a (very simple) array parser and let |
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834 | JSON decode the array elements, which are all full JSON objects on their |
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835 | own (this wouldn't work if the array elements could be JSON numbers, for |
|
|
836 | example): |
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837 | |
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838 | my $json = new JSON::XS; |
|
|
839 | |
|
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840 | # open the monster |
|
|
841 | open my $fh, "<bigfile.json" |
|
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842 | or die "bigfile: $!"; |
|
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843 | |
|
|
844 | # first parse the initial "[" |
|
|
845 | for (;;) { |
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846 | sysread $fh, my $buf, 65536 |
|
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847 | or die "read error: $!"; |
|
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848 | $json->incr_parse ($buf); # void context, so no parsing |
|
|
849 | |
|
|
850 | # Exit the loop once we found and removed(!) the initial "[". |
|
|
851 | # In essence, we are (ab-)using the $json object as a simple scalar |
|
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852 | # we append data to. |
|
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853 | last if $json->incr_text =~ s/^ \s* \[ //x; |
|
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854 | } |
|
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855 | |
|
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856 | # now we have the skipped the initial "[", so continue |
|
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857 | # parsing all the elements. |
|
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858 | for (;;) { |
|
|
859 | # in this loop we read data until we got a single JSON object |
|
|
860 | for (;;) { |
|
|
861 | if (my $obj = $json->incr_parse) { |
|
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862 | # do something with $obj |
|
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863 | last; |
|
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864 | } |
|
|
865 | |
|
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866 | # add more data |
|
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867 | sysread $fh, my $buf, 65536 |
|
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868 | or die "read error: $!"; |
|
|
869 | $json->incr_parse ($buf); # void context, so no parsing |
|
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870 | } |
|
|
871 | |
|
|
872 | # in this loop we read data until we either found and parsed the |
|
|
873 | # separating "," between elements, or the final "]" |
|
|
874 | for (;;) { |
|
|
875 | # first skip whitespace |
|
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876 | $json->incr_text =~ s/^\s*//; |
|
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877 | |
|
|
878 | # if we find "]", we are done |
|
|
879 | if ($json->incr_text =~ s/^\]//) { |
|
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880 | print "finished.\n"; |
|
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881 | exit; |
|
|
882 | } |
|
|
883 | |
|
|
884 | # if we find ",", we can continue with the next element |
|
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885 | if ($json->incr_text =~ s/^,//) { |
|
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886 | last; |
|
|
887 | } |
|
|
888 | |
|
|
889 | # if we find anything else, we have a parse error! |
|
|
890 | if (length $json->incr_text) { |
|
|
891 | die "parse error near ", $json->incr_text; |
|
|
892 | } |
|
|
893 | |
|
|
894 | # else add more data |
|
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895 | sysread $fh, my $buf, 65536 |
|
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896 | or die "read error: $!"; |
|
|
897 | $json->incr_parse ($buf); # void context, so no parsing |
|
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898 | } |
|
|
899 | |
|
|
900 | This is a complex example, but most of the complexity comes from the fact |
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901 | that we are trying to be correct (bear with me if I am wrong, I never ran |
|
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902 | the above example :). |
|
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903 | |
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|
904 | |
|
|
905 | |
677 | =head1 MAPPING |
906 | =head1 MAPPING |
678 | |
907 | |
679 | This section describes how JSON::XS maps Perl values to JSON values and |
908 | This section describes how JSON::XS maps Perl values to JSON values and |
680 | vice versa. These mappings are designed to "do the right thing" in most |
909 | vice versa. These mappings are designed to "do the right thing" in most |
681 | circumstances automatically, preserving round-tripping characteristics |
910 | circumstances automatically, preserving round-tripping characteristics |
… | |
… | |
816 | my $x = "3"; # some variable containing a string |
1045 | my $x = "3"; # some variable containing a string |
817 | $x += 0; # numify it, ensuring it will be dumped as a number |
1046 | $x += 0; # numify it, ensuring it will be dumped as a number |
818 | $x *= 1; # same thing, the choice is yours. |
1047 | $x *= 1; # same thing, the choice is yours. |
819 | |
1048 | |
820 | You can not currently force the type in other, less obscure, ways. Tell me |
1049 | You can not currently force the type in other, less obscure, ways. Tell me |
821 | if you need this capability (but don't forget to explain why its needed |
1050 | if you need this capability (but don't forget to explain why it's needed |
822 | :). |
1051 | :). |
823 | |
1052 | |
824 | =back |
1053 | =back |
825 | |
1054 | |
826 | |
1055 | |
… | |
… | |
828 | |
1057 | |
829 | The interested reader might have seen a number of flags that signify |
1058 | The interested reader might have seen a number of flags that signify |
830 | encodings or codesets - C<utf8>, C<latin1> and C<ascii>. There seems to be |
1059 | encodings or codesets - C<utf8>, C<latin1> and C<ascii>. There seems to be |
831 | some confusion on what these do, so here is a short comparison: |
1060 | some confusion on what these do, so here is a short comparison: |
832 | |
1061 | |
833 | C<utf8> controls wether the JSON text created by C<encode> (and expected |
1062 | C<utf8> controls whether the JSON text created by C<encode> (and expected |
834 | by C<decode>) is UTF-8 encoded or not, while C<latin1> and C<ascii> only |
1063 | by C<decode>) is UTF-8 encoded or not, while C<latin1> and C<ascii> only |
835 | control wether C<encode> escapes character values outside their respective |
1064 | control whether C<encode> escapes character values outside their respective |
836 | codeset range. Neither of these flags conflict with each other, although |
1065 | codeset range. Neither of these flags conflict with each other, although |
837 | some combinations make less sense than others. |
1066 | some combinations make less sense than others. |
838 | |
1067 | |
839 | Care has been taken to make all flags symmetrical with respect to |
1068 | Care has been taken to make all flags symmetrical with respect to |
840 | C<encode> and C<decode>, that is, texts encoded with any combination of |
1069 | C<encode> and C<decode>, that is, texts encoded with any combination of |
… | |
… | |
920 | proper subset of most 8-bit and multibyte encodings in use in the world. |
1149 | proper subset of most 8-bit and multibyte encodings in use in the world. |
921 | |
1150 | |
922 | =back |
1151 | =back |
923 | |
1152 | |
924 | |
1153 | |
925 | =head1 COMPARISON |
|
|
926 | |
|
|
927 | As already mentioned, this module was created because none of the existing |
|
|
928 | JSON modules could be made to work correctly. First I will describe the |
|
|
929 | problems (or pleasures) I encountered with various existing JSON modules, |
|
|
930 | followed by some benchmark values. JSON::XS was designed not to suffer |
|
|
931 | from any of these problems or limitations. |
|
|
932 | |
|
|
933 | =over 4 |
|
|
934 | |
|
|
935 | =item JSON 2.xx |
|
|
936 | |
|
|
937 | A marvellous piece of engineering, this module either uses JSON::XS |
|
|
938 | directly when available (so will be 100% compatible with it, including |
|
|
939 | speed), or it uses JSON::PP, which is basically JSON::XS translated to |
|
|
940 | Pure Perl, which should be 100% compatible with JSON::XS, just a bit |
|
|
941 | slower. |
|
|
942 | |
|
|
943 | You cannot really lose by using this module, especially as it tries very |
|
|
944 | hard to work even with ancient Perl versions, while JSON::XS does not. |
|
|
945 | |
|
|
946 | =item JSON 1.07 |
|
|
947 | |
|
|
948 | Slow (but very portable, as it is written in pure Perl). |
|
|
949 | |
|
|
950 | Undocumented/buggy Unicode handling (how JSON handles Unicode values is |
|
|
951 | undocumented. One can get far by feeding it Unicode strings and doing |
|
|
952 | en-/decoding oneself, but Unicode escapes are not working properly). |
|
|
953 | |
|
|
954 | No round-tripping (strings get clobbered if they look like numbers, e.g. |
|
|
955 | the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will |
|
|
956 | decode into the number 2. |
|
|
957 | |
|
|
958 | =item JSON::PC 0.01 |
|
|
959 | |
|
|
960 | Very fast. |
|
|
961 | |
|
|
962 | Undocumented/buggy Unicode handling. |
|
|
963 | |
|
|
964 | No round-tripping. |
|
|
965 | |
|
|
966 | Has problems handling many Perl values (e.g. regex results and other magic |
|
|
967 | values will make it croak). |
|
|
968 | |
|
|
969 | Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}> |
|
|
970 | which is not a valid JSON text. |
|
|
971 | |
|
|
972 | Unmaintained (maintainer unresponsive for many months, bugs are not |
|
|
973 | getting fixed). |
|
|
974 | |
|
|
975 | =item JSON::Syck 0.21 |
|
|
976 | |
|
|
977 | Very buggy (often crashes). |
|
|
978 | |
|
|
979 | Very inflexible (no human-readable format supported, format pretty much |
|
|
980 | undocumented. I need at least a format for easy reading by humans and a |
|
|
981 | single-line compact format for use in a protocol, and preferably a way to |
|
|
982 | generate ASCII-only JSON texts). |
|
|
983 | |
|
|
984 | Completely broken (and confusingly documented) Unicode handling (Unicode |
|
|
985 | escapes are not working properly, you need to set ImplicitUnicode to |
|
|
986 | I<different> values on en- and decoding to get symmetric behaviour). |
|
|
987 | |
|
|
988 | No round-tripping (simple cases work, but this depends on whether the scalar |
|
|
989 | value was used in a numeric context or not). |
|
|
990 | |
|
|
991 | Dumping hashes may skip hash values depending on iterator state. |
|
|
992 | |
|
|
993 | Unmaintained (maintainer unresponsive for many months, bugs are not |
|
|
994 | getting fixed). |
|
|
995 | |
|
|
996 | Does not check input for validity (i.e. will accept non-JSON input and |
|
|
997 | return "something" instead of raising an exception. This is a security |
|
|
998 | issue: imagine two banks transferring money between each other using |
|
|
999 | JSON. One bank might parse a given non-JSON request and deduct money, |
|
|
1000 | while the other might reject the transaction with a syntax error. While a |
|
|
1001 | good protocol will at least recover, that is extra unnecessary work and |
|
|
1002 | the transaction will still not succeed). |
|
|
1003 | |
|
|
1004 | =item JSON::DWIW 0.04 |
|
|
1005 | |
|
|
1006 | Very fast. Very natural. Very nice. |
|
|
1007 | |
|
|
1008 | Undocumented Unicode handling (but the best of the pack. Unicode escapes |
|
|
1009 | still don't get parsed properly). |
|
|
1010 | |
|
|
1011 | Very inflexible. |
|
|
1012 | |
|
|
1013 | No round-tripping. |
|
|
1014 | |
|
|
1015 | Does not generate valid JSON texts (key strings are often unquoted, empty keys |
|
|
1016 | result in nothing being output) |
|
|
1017 | |
|
|
1018 | Does not check input for validity. |
|
|
1019 | |
|
|
1020 | =back |
|
|
1021 | |
|
|
1022 | |
|
|
1023 | =head2 JSON and YAML |
1154 | =head2 JSON and YAML |
1024 | |
1155 | |
1025 | You often hear that JSON is a subset of YAML. This is, however, a mass |
1156 | You often hear that JSON is a subset of YAML. This is, however, a mass |
1026 | hysteria(*) and very far from the truth. In general, there is no way to |
1157 | hysteria(*) and very far from the truth (as of the time of this writing), |
|
|
1158 | so let me state it clearly: I<in general, there is no way to configure |
1027 | configure JSON::XS to output a data structure as valid YAML that works for |
1159 | JSON::XS to output a data structure as valid YAML> that works in all |
1028 | all cases. |
1160 | cases. |
1029 | |
1161 | |
1030 | If you really must use JSON::XS to generate YAML, you should use this |
1162 | If you really must use JSON::XS to generate YAML, you should use this |
1031 | algorithm (subject to change in future versions): |
1163 | algorithm (subject to change in future versions): |
1032 | |
1164 | |
1033 | my $to_yaml = JSON::XS->new->utf8->space_after (1); |
1165 | my $to_yaml = JSON::XS->new->utf8->space_after (1); |
… | |
… | |
1036 | This will I<usually> generate JSON texts that also parse as valid |
1168 | This will I<usually> generate JSON texts that also parse as valid |
1037 | YAML. Please note that YAML has hardcoded limits on (simple) object key |
1169 | YAML. Please note that YAML has hardcoded limits on (simple) object key |
1038 | lengths that JSON doesn't have and also has different and incompatible |
1170 | lengths that JSON doesn't have and also has different and incompatible |
1039 | unicode handling, so you should make sure that your hash keys are |
1171 | unicode handling, so you should make sure that your hash keys are |
1040 | noticeably shorter than the 1024 "stream characters" YAML allows and that |
1172 | noticeably shorter than the 1024 "stream characters" YAML allows and that |
1041 | you do not have codepoints with values outside the Unicode BMP (basic |
1173 | you do not have characters with codepoint values outside the Unicode BMP |
1042 | multilingual page). YAML also does not allow C<\/> sequences in strings |
1174 | (basic multilingual page). YAML also does not allow C<\/> sequences in |
1043 | (which JSON::XS does not I<currently> generate). |
1175 | strings (which JSON::XS does not I<currently> generate, but other JSON |
|
|
1176 | generators might). |
1044 | |
1177 | |
1045 | There might be other incompatibilities that I am not aware of (or the YAML |
1178 | There might be other incompatibilities that I am not aware of (or the YAML |
1046 | specification has been changed yet again - it does so quite often). In |
1179 | specification has been changed yet again - it does so quite often). In |
1047 | general you should not try to generate YAML with a JSON generator or vice |
1180 | general you should not try to generate YAML with a JSON generator or vice |
1048 | versa, or try to parse JSON with a YAML parser or vice versa: chances are |
1181 | versa, or try to parse JSON with a YAML parser or vice versa: chances are |
… | |
… | |
1051 | |
1184 | |
1052 | =over 4 |
1185 | =over 4 |
1053 | |
1186 | |
1054 | =item (*) |
1187 | =item (*) |
1055 | |
1188 | |
1056 | This is spread actively by the YAML team, however. For many years now they |
1189 | I have been pressured multiple times by Brian Ingerson (one of the |
1057 | claim YAML were a superset of JSON, even when proven otherwise. |
1190 | authors of the YAML specification) to remove this paragraph, despite him |
|
|
1191 | acknowledging that the actual incompatibilities exist. As I was personally |
|
|
1192 | bitten by this "JSON is YAML" lie, I refused and said I will continue to |
|
|
1193 | educate people about these issues, so others do not run into the same |
|
|
1194 | problem again and again. After this, Brian called me a (quote)I<complete |
|
|
1195 | and worthless idiot>(unquote). |
1058 | |
1196 | |
1059 | Even the author of this manpage was at some point accused of providing |
1197 | In my opinion, instead of pressuring and insulting people who actually |
1060 | "incorrect" information, despite the evidence presented (claims ranged |
1198 | clarify issues with YAML and the wrong statements of some of its |
1061 | from "your documentation contains inaccurate and negative statements about |
1199 | proponents, I would kindly suggest reading the JSON spec (which is not |
1062 | YAML" (the only negative comment is this footnote, and it didn't exist |
1200 | that difficult or long) and finally make YAML compatible to it, and |
1063 | back then; the question on which claims were inaccurate was never answered |
1201 | educating users about the changes, instead of spreading lies about the |
1064 | etc.) to "the YAML spec is not up-to-date" (the *real* and supposedly |
1202 | real compatibility for many I<years> and trying to silence people who |
1065 | JSON-compatible spec is apparently not currently publicly available) |
1203 | point out that it isn't true. |
1066 | to actual requests to replace this section by *incorrect* information, |
|
|
1067 | suppressing information about the real problem). |
|
|
1068 | |
|
|
1069 | So whenever you are told that YAML was a superset of JSON, first check |
|
|
1070 | wether it is really true (it might be when you check it, but it certainly |
|
|
1071 | was not true when this was written). I would much prefer if the YAML team |
|
|
1072 | would spent their time on actually making JSON compatibility a truth |
|
|
1073 | (JSON, after all, has a very small and simple specification) instead of |
|
|
1074 | trying to lobby/force people into reporting untruths. |
|
|
1075 | |
1204 | |
1076 | =back |
1205 | =back |
1077 | |
1206 | |
1078 | |
1207 | |
1079 | =head2 SPEED |
1208 | =head2 SPEED |
… | |
… | |
1081 | It seems that JSON::XS is surprisingly fast, as shown in the following |
1210 | It seems that JSON::XS is surprisingly fast, as shown in the following |
1082 | tables. They have been generated with the help of the C<eg/bench> program |
1211 | tables. They have been generated with the help of the C<eg/bench> program |
1083 | in the JSON::XS distribution, to make it easy to compare on your own |
1212 | in the JSON::XS distribution, to make it easy to compare on your own |
1084 | system. |
1213 | system. |
1085 | |
1214 | |
1086 | First comes a comparison between various modules using a very short |
1215 | First comes a comparison between various modules using |
1087 | single-line JSON string: |
1216 | a very short single-line JSON string (also available at |
|
|
1217 | L<http://dist.schmorp.de/misc/json/short.json>). |
1088 | |
1218 | |
1089 | {"method": "handleMessage", "params": ["user1", "we were just talking"], \ |
1219 | {"method": "handleMessage", "params": ["user1", "we were just talking"], \ |
1090 | "id": null, "array":[1,11,234,-5,1e5,1e7, true, false]} |
1220 | "id": null, "array":[1,11,234,-5,1e5,1e7, true, false]} |
1091 | |
1221 | |
1092 | It shows the number of encodes/decodes per second (JSON::XS uses |
1222 | It shows the number of encodes/decodes per second (JSON::XS uses |
… | |
… | |
1111 | about three times faster on decoding, and over forty times faster |
1241 | about three times faster on decoding, and over forty times faster |
1112 | than JSON, even with pretty-printing and key sorting. It also compares |
1242 | than JSON, even with pretty-printing and key sorting. It also compares |
1113 | favourably to Storable for small amounts of data. |
1243 | favourably to Storable for small amounts of data. |
1114 | |
1244 | |
1115 | Using a longer test string (roughly 18KB, generated from Yahoo! Locals |
1245 | Using a longer test string (roughly 18KB, generated from Yahoo! Locals |
1116 | search API (http://dist.schmorp.de/misc/yahoo.json). |
1246 | search API (L<http://dist.schmorp.de/misc/json/long.json>). |
1117 | |
1247 | |
1118 | module | encode | decode | |
1248 | module | encode | decode | |
1119 | -----------|------------|------------| |
1249 | -----------|------------|------------| |
1120 | JSON 1.x | 55.260 | 34.971 | |
1250 | JSON 1.x | 55.260 | 34.971 | |
1121 | JSON::DWIW | 825.228 | 1082.513 | |
1251 | JSON::DWIW | 825.228 | 1082.513 | |
… | |
… | |
1185 | =head1 THREADS |
1315 | =head1 THREADS |
1186 | |
1316 | |
1187 | This module is I<not> guaranteed to be thread safe and there are no |
1317 | This module is I<not> guaranteed to be thread safe and there are no |
1188 | plans to change this until Perl gets thread support (as opposed to the |
1318 | plans to change this until Perl gets thread support (as opposed to the |
1189 | horribly slow so-called "threads" which are simply slow and bloated |
1319 | horribly slow so-called "threads" which are simply slow and bloated |
1190 | process simulations - use fork, its I<much> faster, cheaper, better). |
1320 | process simulations - use fork, it's I<much> faster, cheaper, better). |
1191 | |
1321 | |
1192 | (It might actually work, but you have been warned). |
1322 | (It might actually work, but you have been warned). |
1193 | |
1323 | |
1194 | |
1324 | |
1195 | =head1 BUGS |
1325 | =head1 BUGS |
1196 | |
1326 | |
1197 | While the goal of this module is to be correct, that unfortunately does |
1327 | While the goal of this module is to be correct, that unfortunately does |
1198 | not mean its bug-free, only that I think its design is bug-free. It is |
1328 | not mean it's bug-free, only that I think its design is bug-free. It is |
1199 | still relatively early in its development. If you keep reporting bugs they |
1329 | still relatively early in its development. If you keep reporting bugs they |
1200 | will be fixed swiftly, though. |
1330 | will be fixed swiftly, though. |
1201 | |
1331 | |
1202 | Please refrain from using rt.cpan.org or any other bug reporting |
1332 | Please refrain from using rt.cpan.org or any other bug reporting |
1203 | service. I put the contact address into my modules for a reason. |
1333 | service. I put the contact address into my modules for a reason. |
… | |
… | |
1225 | "--" => sub { $_[0] = ${$_[0]} - 1 }, |
1355 | "--" => sub { $_[0] = ${$_[0]} - 1 }, |
1226 | fallback => 1; |
1356 | fallback => 1; |
1227 | |
1357 | |
1228 | 1; |
1358 | 1; |
1229 | |
1359 | |
|
|
1360 | =head1 SEE ALSO |
|
|
1361 | |
|
|
1362 | The F<json_xs> command line utility for quick experiments. |
|
|
1363 | |
1230 | =head1 AUTHOR |
1364 | =head1 AUTHOR |
1231 | |
1365 | |
1232 | Marc Lehmann <schmorp@schmorp.de> |
1366 | Marc Lehmann <schmorp@schmorp.de> |
1233 | http://home.schmorp.de/ |
1367 | http://home.schmorp.de/ |
1234 | |
1368 | |