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1 | =encoding utf-8 |
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2 | |
| 1 | =head1 NAME |
3 | =head1 NAME |
| 2 | |
4 | |
| 3 | JSON::XS - JSON serialising/deserialising, done correctly and fast |
5 | JSON::XS - JSON serialising/deserialising, done correctly and fast |
| 4 | |
6 | |
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7 | JSON::XS - 正しくて高速な JSON シリアライザ/デシリアライザ |
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8 | (http://fleur.hio.jp/perldoc/mix/lib/JSON/XS.html) |
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9 | |
| 5 | =head1 SYNOPSIS |
10 | =head1 SYNOPSIS |
| 6 | |
11 | |
| 7 | use JSON::XS; |
12 | use JSON::XS; |
| 8 | |
13 | |
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14 | # exported functions, they croak on error |
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15 | # and expect/generate UTF-8 |
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16 | |
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17 | $utf8_encoded_json_text = to_json $perl_hash_or_arrayref; |
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18 | $perl_hash_or_arrayref = from_json $utf8_encoded_json_text; |
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19 | |
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20 | # OO-interface |
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21 | |
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22 | $coder = JSON::XS->new->ascii->pretty->allow_nonref; |
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23 | $pretty_printed_unencoded = $coder->encode ($perl_scalar); |
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24 | $perl_scalar = $coder->decode ($unicode_json_text); |
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25 | |
| 9 | =head1 DESCRIPTION |
26 | =head1 DESCRIPTION |
| 10 | |
27 | |
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28 | This module converts Perl data structures to JSON and vice versa. Its |
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29 | primary goal is to be I<correct> and its secondary goal is to be |
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30 | I<fast>. To reach the latter goal it was written in C. |
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31 | |
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32 | As this is the n-th-something JSON module on CPAN, what was the reason |
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33 | to write yet another JSON module? While it seems there are many JSON |
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34 | modules, none of them correctly handle all corner cases, and in most cases |
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35 | their maintainers are unresponsive, gone missing, or not listening to bug |
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36 | reports for other reasons. |
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37 | |
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38 | See COMPARISON, below, for a comparison to some other JSON modules. |
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39 | |
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40 | See MAPPING, below, on how JSON::XS maps perl values to JSON values and |
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41 | vice versa. |
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42 | |
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43 | =head2 FEATURES |
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44 | |
| 11 | =over 4 |
45 | =over 4 |
| 12 | |
46 | |
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47 | =item * correct unicode handling |
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48 | |
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49 | This module knows how to handle Unicode, and even documents how and when |
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50 | it does so. |
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51 | |
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52 | =item * round-trip integrity |
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53 | |
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54 | When you serialise a perl data structure using only datatypes supported |
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55 | by JSON, the deserialised data structure is identical on the Perl level. |
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56 | (e.g. the string "2.0" doesn't suddenly become "2" just because it looks |
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57 | like a number). |
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58 | |
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59 | =item * strict checking of JSON correctness |
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60 | |
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61 | There is no guessing, no generating of illegal JSON texts by default, |
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62 | and only JSON is accepted as input by default (the latter is a security |
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63 | feature). |
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64 | |
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65 | =item * fast |
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66 | |
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67 | Compared to other JSON modules, this module compares favourably in terms |
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68 | of speed, too. |
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69 | |
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70 | =item * simple to use |
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71 | |
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72 | This module has both a simple functional interface as well as an OO |
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73 | interface. |
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74 | |
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75 | =item * reasonably versatile output formats |
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76 | |
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77 | You can choose between the most compact guarenteed single-line format |
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78 | possible (nice for simple line-based protocols), a pure-ascii format |
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79 | (for when your transport is not 8-bit clean, still supports the whole |
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80 | unicode range), or a pretty-printed format (for when you want to read that |
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81 | stuff). Or you can combine those features in whatever way you like. |
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82 | |
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83 | =back |
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84 | |
| 13 | =cut |
85 | =cut |
| 14 | |
86 | |
| 15 | package JSON::XS; |
87 | package JSON::XS; |
| 16 | |
88 | |
| 17 | BEGIN { |
89 | use strict; |
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90 | |
| 18 | $VERSION = '0.1'; |
91 | our $VERSION = '1.5'; |
| 19 | @ISA = qw(Exporter); |
92 | our @ISA = qw(Exporter); |
| 20 | |
93 | |
| 21 | require Exporter; |
94 | our @EXPORT = qw(to_json from_json); |
| 22 | |
95 | |
| 23 | require XSLoader; |
96 | use Exporter; |
| 24 | XSLoader::load JSON::XS::, $VERSION; |
97 | use XSLoader; |
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98 | |
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99 | =head1 FUNCTIONAL INTERFACE |
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100 | |
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101 | The following convinience methods are provided by this module. They are |
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102 | exported by default: |
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103 | |
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104 | =over 4 |
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105 | |
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106 | =item $json_text = to_json $perl_scalar |
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107 | |
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108 | Converts the given Perl data structure (a simple scalar or a reference to |
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109 | a hash or array) to a UTF-8 encoded, binary string (that is, the string contains |
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110 | octets only). Croaks on error. |
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111 | |
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112 | This function call is functionally identical to: |
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113 | |
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114 | $json_text = JSON::XS->new->utf8->encode ($perl_scalar) |
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115 | |
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116 | except being faster. |
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117 | |
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118 | =item $perl_scalar = from_json $json_text |
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119 | |
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120 | The opposite of C<to_json>: expects an UTF-8 (binary) string and tries to |
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121 | parse that as an UTF-8 encoded JSON text, returning the resulting simple |
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122 | scalar or reference. Croaks on error. |
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123 | |
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124 | This function call is functionally identical to: |
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125 | |
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126 | $perl_scalar = JSON::XS->new->utf8->decode ($json_text) |
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127 | |
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128 | except being faster. |
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129 | |
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130 | =item $is_boolean = JSON::XS::is_bool $scalar |
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131 | |
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132 | Returns true if the passed scalar represents either JSON::XS::true or |
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133 | JSON::XS::false, two constants that act like C<1> and C<0>, respectively |
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134 | and are used to represent JSON C<true> and C<false> values in Perl. |
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135 | |
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136 | See MAPPING, below, for more information on how JSON values are mapped to |
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137 | Perl. |
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138 | |
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139 | =back |
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140 | |
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141 | |
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142 | =head1 OBJECT-ORIENTED INTERFACE |
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143 | |
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144 | The object oriented interface lets you configure your own encoding or |
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145 | decoding style, within the limits of supported formats. |
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146 | |
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147 | =over 4 |
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148 | |
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149 | =item $json = new JSON::XS |
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150 | |
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151 | Creates a new JSON::XS object that can be used to de/encode JSON |
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152 | strings. All boolean flags described below are by default I<disabled>. |
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153 | |
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154 | The mutators for flags all return the JSON object again and thus calls can |
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155 | be chained: |
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156 | |
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157 | my $json = JSON::XS->new->utf8->space_after->encode ({a => [1,2]}) |
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158 | => {"a": [1, 2]} |
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159 | |
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160 | =item $json = $json->ascii ([$enable]) |
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161 | |
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162 | If C<$enable> is true (or missing), then the C<encode> method will not |
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163 | generate characters outside the code range C<0..127> (which is ASCII). Any |
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164 | unicode characters outside that range will be escaped using either a |
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165 | single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence, |
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166 | as per RFC4627. The resulting encoded JSON text can be treated as a native |
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167 | unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string, |
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168 | or any other superset of ASCII. |
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169 | |
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170 | If C<$enable> is false, then the C<encode> method will not escape Unicode |
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171 | characters unless required by the JSON syntax or other flags. This results |
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172 | in a faster and more compact format. |
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173 | |
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174 | The main use for this flag is to produce JSON texts that can be |
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175 | transmitted over a 7-bit channel, as the encoded JSON texts will not |
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176 | contain any 8 bit characters. |
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177 | |
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178 | JSON::XS->new->ascii (1)->encode ([chr 0x10401]) |
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179 | => ["\ud801\udc01"] |
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180 | |
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181 | =item $json = $json->latin1 ([$enable]) |
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182 | |
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183 | If C<$enable> is true (or missing), then the C<encode> method will encode |
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184 | the resulting JSON text as latin1 (or iso-8859-1), escaping any characters |
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185 | outside the code range C<0..255>. The resulting string can be treated as a |
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186 | latin1-encoded JSON text or a native unicode string. The C<decode> method |
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187 | will not be affected in any way by this flag, as C<decode> by default |
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188 | expects unicode, which is a strict superset of latin1. |
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189 | |
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190 | If C<$enable> is false, then the C<encode> method will not escape Unicode |
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191 | characters unless required by the JSON syntax or other flags. |
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192 | |
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193 | The main use for this flag is efficiently encoding binary data as JSON |
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194 | text, as most octets will not be escaped, resulting in a smaller encoded |
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195 | size. The disadvantage is that the resulting JSON text is encoded |
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196 | in latin1 (and must correctly be treated as such when storing and |
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197 | transfering), a rare encoding for JSON. It is therefore most useful when |
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198 | you want to store data structures known to contain binary data efficiently |
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199 | in files or databases, not when talking to other JSON encoders/decoders. |
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200 | |
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201 | JSON::XS->new->latin1->encode (["\x{89}\x{abc}"] |
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202 | => ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not) |
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203 | |
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204 | =item $json = $json->utf8 ([$enable]) |
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205 | |
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206 | If C<$enable> is true (or missing), then the C<encode> method will encode |
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207 | the JSON result into UTF-8, as required by many protocols, while the |
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208 | C<decode> method expects to be handled an UTF-8-encoded string. Please |
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209 | note that UTF-8-encoded strings do not contain any characters outside the |
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210 | range C<0..255>, they are thus useful for bytewise/binary I/O. In future |
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211 | versions, enabling this option might enable autodetection of the UTF-16 |
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212 | and UTF-32 encoding families, as described in RFC4627. |
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213 | |
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214 | If C<$enable> is false, then the C<encode> method will return the JSON |
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215 | string as a (non-encoded) unicode string, while C<decode> expects thus a |
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216 | unicode string. Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs |
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217 | to be done yourself, e.g. using the Encode module. |
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218 | |
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219 | Example, output UTF-16BE-encoded JSON: |
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220 | |
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221 | use Encode; |
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222 | $jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object); |
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223 | |
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224 | Example, decode UTF-32LE-encoded JSON: |
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225 | |
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226 | use Encode; |
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227 | $object = JSON::XS->new->decode (decode "UTF-32LE", $jsontext); |
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228 | |
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229 | =item $json = $json->pretty ([$enable]) |
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230 | |
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231 | This enables (or disables) all of the C<indent>, C<space_before> and |
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232 | C<space_after> (and in the future possibly more) flags in one call to |
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233 | generate the most readable (or most compact) form possible. |
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234 | |
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235 | Example, pretty-print some simple structure: |
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236 | |
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237 | my $json = JSON::XS->new->pretty(1)->encode ({a => [1,2]}) |
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238 | => |
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239 | { |
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240 | "a" : [ |
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241 | 1, |
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242 | 2 |
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243 | ] |
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244 | } |
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245 | |
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246 | =item $json = $json->indent ([$enable]) |
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247 | |
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248 | If C<$enable> is true (or missing), then the C<encode> method will use a multiline |
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249 | format as output, putting every array member or object/hash key-value pair |
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250 | into its own line, identing them properly. |
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251 | |
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252 | If C<$enable> is false, no newlines or indenting will be produced, and the |
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253 | resulting JSON text is guarenteed not to contain any C<newlines>. |
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254 | |
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255 | This setting has no effect when decoding JSON texts. |
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256 | |
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257 | =item $json = $json->space_before ([$enable]) |
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258 | |
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259 | If C<$enable> is true (or missing), then the C<encode> method will add an extra |
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260 | optional space before the C<:> separating keys from values in JSON objects. |
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261 | |
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262 | If C<$enable> is false, then the C<encode> method will not add any extra |
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263 | space at those places. |
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264 | |
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265 | This setting has no effect when decoding JSON texts. You will also |
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266 | most likely combine this setting with C<space_after>. |
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267 | |
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268 | Example, space_before enabled, space_after and indent disabled: |
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269 | |
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270 | {"key" :"value"} |
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271 | |
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272 | =item $json = $json->space_after ([$enable]) |
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273 | |
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274 | If C<$enable> is true (or missing), then the C<encode> method will add an extra |
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275 | optional space after the C<:> separating keys from values in JSON objects |
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276 | and extra whitespace after the C<,> separating key-value pairs and array |
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277 | members. |
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278 | |
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279 | If C<$enable> is false, then the C<encode> method will not add any extra |
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280 | space at those places. |
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281 | |
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282 | This setting has no effect when decoding JSON texts. |
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283 | |
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284 | Example, space_before and indent disabled, space_after enabled: |
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285 | |
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286 | {"key": "value"} |
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287 | |
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288 | =item $json = $json->relaxed ([$enable]) |
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289 | |
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290 | If C<$enable> is true (or missing), then C<decode> will accept some |
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291 | extensions to normal JSON syntax (see below). C<encode> will not be |
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292 | affected in anyway. I<Be aware that this option makes you accept invalid |
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293 | JSON texts as if they were valid!>. I suggest only to use this option to |
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294 | parse application-specific files written by humans (configuration files, |
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295 | resource files etc.) |
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296 | |
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297 | If C<$enable> is false (the default), then C<decode> will only accept |
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298 | valid JSON texts. |
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299 | |
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300 | Currently accepted extensions are: |
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301 | |
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302 | =over 4 |
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303 | |
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304 | =item * list items can have an end-comma |
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305 | |
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306 | JSON I<separates> array elements and key-value pairs with commas. This |
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307 | can be annoying if you write JSON texts manually and want to be able to |
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308 | quickly append elements, so this extension accepts comma at the end of |
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309 | such items not just between them: |
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310 | |
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311 | [ |
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312 | 1, |
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313 | 2, <- this comma not normally allowed |
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314 | ] |
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315 | { |
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316 | "k1": "v1", |
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317 | "k2": "v2", <- this comma not normally allowed |
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318 | } |
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319 | |
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320 | =item * shell-style '#'-comments |
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321 | |
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322 | Whenever JSON allows whitespace, shell-style comments are additionally |
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323 | allowed. They are terminated by the first carriage-return or line-feed |
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324 | character, after which more white-space and comments are allowed. |
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325 | |
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326 | [ |
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327 | 1, # this comment not allowed in JSON |
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328 | # neither this one... |
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329 | ] |
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330 | |
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331 | =back |
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332 | |
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333 | =item $json = $json->canonical ([$enable]) |
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334 | |
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335 | If C<$enable> is true (or missing), then the C<encode> method will output JSON objects |
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336 | by sorting their keys. This is adding a comparatively high overhead. |
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337 | |
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338 | If C<$enable> is false, then the C<encode> method will output key-value |
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339 | pairs in the order Perl stores them (which will likely change between runs |
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340 | of the same script). |
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341 | |
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342 | This option is useful if you want the same data structure to be encoded as |
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343 | the same JSON text (given the same overall settings). If it is disabled, |
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344 | the same hash migh be encoded differently even if contains the same data, |
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345 | as key-value pairs have no inherent ordering in Perl. |
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346 | |
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347 | This setting has no effect when decoding JSON texts. |
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348 | |
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349 | =item $json = $json->allow_nonref ([$enable]) |
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350 | |
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351 | If C<$enable> is true (or missing), then the C<encode> method can convert a |
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352 | non-reference into its corresponding string, number or null JSON value, |
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353 | which is an extension to RFC4627. Likewise, C<decode> will accept those JSON |
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354 | values instead of croaking. |
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355 | |
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356 | If C<$enable> is false, then the C<encode> method will croak if it isn't |
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357 | passed an arrayref or hashref, as JSON texts must either be an object |
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358 | or array. Likewise, C<decode> will croak if given something that is not a |
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359 | JSON object or array. |
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360 | |
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361 | Example, encode a Perl scalar as JSON value with enabled C<allow_nonref>, |
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362 | resulting in an invalid JSON text: |
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363 | |
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364 | JSON::XS->new->allow_nonref->encode ("Hello, World!") |
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365 | => "Hello, World!" |
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366 | |
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367 | =item $json = $json->allow_blessed ([$enable]) |
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368 | |
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369 | If C<$enable> is true (or missing), then the C<encode> method will not |
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370 | barf when it encounters a blessed reference. Instead, the value of the |
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371 | B<convert_blessed> option will decide wether C<null> (C<convert_blessed> |
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372 | disabled or no C<to_json> method found) or a representation of the |
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373 | object (C<convert_blessed> enabled and C<to_json> method found) is being |
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374 | encoded. Has no effect on C<decode>. |
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375 | |
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376 | If C<$enable> is false (the default), then C<encode> will throw an |
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377 | exception when it encounters a blessed object. |
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378 | |
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379 | =item $json = $json->convert_blessed ([$enable]) |
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380 | |
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381 | If C<$enable> is true (or missing), then C<encode>, upon encountering a |
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382 | blessed object, will check for the availability of the C<TO_JSON> method |
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383 | on the object's class. If found, it will be called in scalar context |
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384 | and the resulting scalar will be encoded instead of the object. If no |
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385 | C<TO_JSON> method is found, the value of C<allow_blessed> will decide what |
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386 | to do. |
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387 | |
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388 | The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON> |
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389 | returns other blessed objects, those will be handled in the same |
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390 | way. C<TO_JSON> must take care of not causing an endless recursion cycle |
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391 | (== crash) in this case. The name of C<TO_JSON> was chosen because other |
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392 | methods called by the Perl core (== not by the user of the object) are |
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393 | usually in upper case letters and to avoid collisions with the C<to_json> |
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394 | function. |
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395 | |
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396 | This setting does not yet influence C<decode> in any way, but in the |
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397 | future, global hooks might get installed that influence C<decode> and are |
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398 | enabled by this setting. |
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399 | |
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400 | If C<$enable> is false, then the C<allow_blessed> setting will decide what |
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401 | to do when a blessed object is found. |
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402 | |
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403 | =item $json = $json->filter_json_object ([$coderef->($hashref)]) |
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404 | |
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405 | When C<$coderef> is specified, it will be called from C<decode> each |
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406 | time it decodes a JSON object. The only argument is a reference to the |
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407 | newly-created hash. If the code references returns a single scalar (which |
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408 | need not be a reference), this value (i.e. a copy of that scalar to avoid |
|
|
409 | aliasing) is inserted into the deserialised data structure. If it returns |
|
|
410 | an empty list (NOTE: I<not> C<undef>, which is a valid scalar), the |
|
|
411 | original deserialised hash will be inserted. This setting can slow down |
|
|
412 | decoding considerably. |
|
|
413 | |
|
|
414 | When C<$coderef> is omitted or undefined, any existing callback will |
|
|
415 | be removed and C<decode> will not change the deserialised hash in any |
|
|
416 | way. |
|
|
417 | |
|
|
418 | Example, convert all JSON objects into the integer 5: |
|
|
419 | |
|
|
420 | my $js = JSON::XS->new->filter_json_object (sub { 5 }); |
|
|
421 | # returns [5] |
|
|
422 | $js->decode ('[{}]') |
|
|
423 | # throw an exception because allow_nonref is not enabled |
|
|
424 | # so a lone 5 is not allowed. |
|
|
425 | $js->decode ('{"a":1, "b":2}'); |
|
|
426 | |
|
|
427 | =item $json = $json->filter_json_single_key_object ($key [=> $coderef->($value)]) |
|
|
428 | |
|
|
429 | Works remotely similar to C<filter_json_object>, but is only called for |
|
|
430 | JSON objects having a single key named C<$key>. |
|
|
431 | |
|
|
432 | This C<$coderef> is called before the one specified via |
|
|
433 | C<filter_json_object>, if any. It gets passed the single value in the JSON |
|
|
434 | object. If it returns a single value, it will be inserted into the data |
|
|
435 | structure. If it returns nothing (not even C<undef> but the empty list), |
|
|
436 | the callback from C<filter_json_object> will be called next, as if no |
|
|
437 | single-key callback were specified. |
|
|
438 | |
|
|
439 | If C<$coderef> is omitted or undefined, the corresponding callback will be |
|
|
440 | disabled. There can only ever be one callback for a given key. |
|
|
441 | |
|
|
442 | As this callback gets called less often then the C<filter_json_object> |
|
|
443 | one, decoding speed will not usually suffer as much. Therefore, single-key |
|
|
444 | objects make excellent targets to serialise Perl objects into, especially |
|
|
445 | as single-key JSON objects are as close to the type-tagged value concept |
|
|
446 | as JSON gets (its basically an ID/VALUE tuple). Of course, JSON does not |
|
|
447 | support this in any way, so you need to make sure your data never looks |
|
|
448 | like a serialised Perl hash. |
|
|
449 | |
|
|
450 | Typical names for the single object key are C<__class_whatever__>, or |
|
|
451 | C<$__dollars_are_rarely_used__$> or C<}ugly_brace_placement>, or even |
|
|
452 | things like C<__class_md5sum(classname)__>, to reduce the risk of clashing |
|
|
453 | with real hashes. |
|
|
454 | |
|
|
455 | Example, decode JSON objects of the form C<< { "__widget__" => <id> } >> |
|
|
456 | into the corresponding C<< $WIDGET{<id>} >> object: |
|
|
457 | |
|
|
458 | # return whatever is in $WIDGET{5}: |
|
|
459 | JSON::XS |
|
|
460 | ->new |
|
|
461 | ->filter_json_single_key_object (__widget__ => sub { |
|
|
462 | $WIDGET{ $_[0] } |
|
|
463 | }) |
|
|
464 | ->decode ('{"__widget__": 5') |
|
|
465 | |
|
|
466 | # this can be used with a TO_JSON method in some "widget" class |
|
|
467 | # for serialisation to json: |
|
|
468 | sub WidgetBase::TO_JSON { |
|
|
469 | my ($self) = @_; |
|
|
470 | |
|
|
471 | unless ($self->{id}) { |
|
|
472 | $self->{id} = ..get..some..id..; |
|
|
473 | $WIDGET{$self->{id}} = $self; |
|
|
474 | } |
|
|
475 | |
|
|
476 | { __widget__ => $self->{id} } |
|
|
477 | } |
|
|
478 | |
|
|
479 | =item $json = $json->shrink ([$enable]) |
|
|
480 | |
|
|
481 | Perl usually over-allocates memory a bit when allocating space for |
|
|
482 | strings. This flag optionally resizes strings generated by either |
|
|
483 | C<encode> or C<decode> to their minimum size possible. This can save |
|
|
484 | memory when your JSON texts are either very very long or you have many |
|
|
485 | short strings. It will also try to downgrade any strings to octet-form |
|
|
486 | if possible: perl stores strings internally either in an encoding called |
|
|
487 | UTF-X or in octet-form. The latter cannot store everything but uses less |
|
|
488 | space in general (and some buggy Perl or C code might even rely on that |
|
|
489 | internal representation being used). |
|
|
490 | |
|
|
491 | The actual definition of what shrink does might change in future versions, |
|
|
492 | but it will always try to save space at the expense of time. |
|
|
493 | |
|
|
494 | If C<$enable> is true (or missing), the string returned by C<encode> will |
|
|
495 | be shrunk-to-fit, while all strings generated by C<decode> will also be |
|
|
496 | shrunk-to-fit. |
|
|
497 | |
|
|
498 | If C<$enable> is false, then the normal perl allocation algorithms are used. |
|
|
499 | If you work with your data, then this is likely to be faster. |
|
|
500 | |
|
|
501 | In the future, this setting might control other things, such as converting |
|
|
502 | strings that look like integers or floats into integers or floats |
|
|
503 | internally (there is no difference on the Perl level), saving space. |
|
|
504 | |
|
|
505 | =item $json = $json->max_depth ([$maximum_nesting_depth]) |
|
|
506 | |
|
|
507 | Sets the maximum nesting level (default C<512>) accepted while encoding |
|
|
508 | or decoding. If the JSON text or Perl data structure has an equal or |
|
|
509 | higher nesting level then this limit, then the encoder and decoder will |
|
|
510 | stop and croak at that point. |
|
|
511 | |
|
|
512 | Nesting level is defined by number of hash- or arrayrefs that the encoder |
|
|
513 | needs to traverse to reach a given point or the number of C<{> or C<[> |
|
|
514 | characters without their matching closing parenthesis crossed to reach a |
|
|
515 | given character in a string. |
|
|
516 | |
|
|
517 | Setting the maximum depth to one disallows any nesting, so that ensures |
|
|
518 | that the object is only a single hash/object or array. |
|
|
519 | |
|
|
520 | The argument to C<max_depth> will be rounded up to the next highest power |
|
|
521 | of two. If no argument is given, the highest possible setting will be |
|
|
522 | used, which is rarely useful. |
|
|
523 | |
|
|
524 | See SECURITY CONSIDERATIONS, below, for more info on why this is useful. |
|
|
525 | |
|
|
526 | =item $json = $json->max_size ([$maximum_string_size]) |
|
|
527 | |
|
|
528 | Set the maximum length a JSON text may have (in bytes) where decoding is |
|
|
529 | being attempted. The default is C<0>, meaning no limit. When C<decode> |
|
|
530 | is called on a string longer then this number of characters it will not |
|
|
531 | attempt to decode the string but throw an exception. This setting has no |
|
|
532 | effect on C<encode> (yet). |
|
|
533 | |
|
|
534 | The argument to C<max_size> will be rounded up to the next B<highest> |
|
|
535 | power of two (so may be more than requested). If no argument is given, the |
|
|
536 | limit check will be deactivated (same as when C<0> is specified). |
|
|
537 | |
|
|
538 | See SECURITY CONSIDERATIONS, below, for more info on why this is useful. |
|
|
539 | |
|
|
540 | =item $json_text = $json->encode ($perl_scalar) |
|
|
541 | |
|
|
542 | Converts the given Perl data structure (a simple scalar or a reference |
|
|
543 | to a hash or array) to its JSON representation. Simple scalars will be |
|
|
544 | converted into JSON string or number sequences, while references to arrays |
|
|
545 | become JSON arrays and references to hashes become JSON objects. Undefined |
|
|
546 | Perl values (e.g. C<undef>) become JSON C<null> values. Neither C<true> |
|
|
547 | nor C<false> values will be generated. |
|
|
548 | |
|
|
549 | =item $perl_scalar = $json->decode ($json_text) |
|
|
550 | |
|
|
551 | The opposite of C<encode>: expects a JSON text and tries to parse it, |
|
|
552 | returning the resulting simple scalar or reference. Croaks on error. |
|
|
553 | |
|
|
554 | JSON numbers and strings become simple Perl scalars. JSON arrays become |
|
|
555 | Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes |
|
|
556 | C<1>, C<false> becomes C<0> and C<null> becomes C<undef>. |
|
|
557 | |
|
|
558 | =item ($perl_scalar, $characters) = $json->decode_prefix ($json_text) |
|
|
559 | |
|
|
560 | This works like the C<decode> method, but instead of raising an exception |
|
|
561 | when there is trailing garbage after the first JSON object, it will |
|
|
562 | silently stop parsing there and return the number of characters consumed |
|
|
563 | so far. |
|
|
564 | |
|
|
565 | This is useful if your JSON texts are not delimited by an outer protocol |
|
|
566 | (which is not the brightest thing to do in the first place) and you need |
|
|
567 | to know where the JSON text ends. |
|
|
568 | |
|
|
569 | JSON::XS->new->decode_prefix ("[1] the tail") |
|
|
570 | => ([], 3) |
|
|
571 | |
|
|
572 | =back |
|
|
573 | |
|
|
574 | |
|
|
575 | =head1 MAPPING |
|
|
576 | |
|
|
577 | This section describes how JSON::XS maps Perl values to JSON values and |
|
|
578 | vice versa. These mappings are designed to "do the right thing" in most |
|
|
579 | circumstances automatically, preserving round-tripping characteristics |
|
|
580 | (what you put in comes out as something equivalent). |
|
|
581 | |
|
|
582 | For the more enlightened: note that in the following descriptions, |
|
|
583 | lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl> |
|
|
584 | refers to the abstract Perl language itself. |
|
|
585 | |
|
|
586 | |
|
|
587 | =head2 JSON -> PERL |
|
|
588 | |
|
|
589 | =over 4 |
|
|
590 | |
|
|
591 | =item object |
|
|
592 | |
|
|
593 | A JSON object becomes a reference to a hash in Perl. No ordering of object |
|
|
594 | keys is preserved (JSON does not preserver object key ordering itself). |
|
|
595 | |
|
|
596 | =item array |
|
|
597 | |
|
|
598 | A JSON array becomes a reference to an array in Perl. |
|
|
599 | |
|
|
600 | =item string |
|
|
601 | |
|
|
602 | A JSON string becomes a string scalar in Perl - Unicode codepoints in JSON |
|
|
603 | are represented by the same codepoints in the Perl string, so no manual |
|
|
604 | decoding is necessary. |
|
|
605 | |
|
|
606 | =item number |
|
|
607 | |
|
|
608 | A JSON number becomes either an integer, numeric (floating point) or |
|
|
609 | string scalar in perl, depending on its range and any fractional parts. On |
|
|
610 | the Perl level, there is no difference between those as Perl handles all |
|
|
611 | the conversion details, but an integer may take slightly less memory and |
|
|
612 | might represent more values exactly than (floating point) numbers. |
|
|
613 | |
|
|
614 | If the number consists of digits only, JSON::XS will try to represent |
|
|
615 | it as an integer value. If that fails, it will try to represent it as |
|
|
616 | a numeric (floating point) value if that is possible without loss of |
|
|
617 | precision. Otherwise it will preserve the number as a string value. |
|
|
618 | |
|
|
619 | Numbers containing a fractional or exponential part will always be |
|
|
620 | represented as numeric (floating point) values, possibly at a loss of |
|
|
621 | precision. |
|
|
622 | |
|
|
623 | This might create round-tripping problems as numbers might become strings, |
|
|
624 | but as Perl is typeless there is no other way to do it. |
|
|
625 | |
|
|
626 | =item true, false |
|
|
627 | |
|
|
628 | These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>, |
|
|
629 | respectively. They are overloaded to act almost exactly like the numbers |
|
|
630 | C<1> and C<0>. You can check wether a scalar is a JSON boolean by using |
|
|
631 | the C<JSON::XS::is_bool> function. |
|
|
632 | |
|
|
633 | =item null |
|
|
634 | |
|
|
635 | A JSON null atom becomes C<undef> in Perl. |
|
|
636 | |
|
|
637 | =back |
|
|
638 | |
|
|
639 | |
|
|
640 | =head2 PERL -> JSON |
|
|
641 | |
|
|
642 | The mapping from Perl to JSON is slightly more difficult, as Perl is a |
|
|
643 | truly typeless language, so we can only guess which JSON type is meant by |
|
|
644 | a Perl value. |
|
|
645 | |
|
|
646 | =over 4 |
|
|
647 | |
|
|
648 | =item hash references |
|
|
649 | |
|
|
650 | Perl hash references become JSON objects. As there is no inherent ordering |
|
|
651 | in hash keys (or JSON objects), they will usually be encoded in a |
|
|
652 | pseudo-random order that can change between runs of the same program but |
|
|
653 | stays generally the same within a single run of a program. JSON::XS can |
|
|
654 | optionally sort the hash keys (determined by the I<canonical> flag), so |
|
|
655 | the same datastructure will serialise to the same JSON text (given same |
|
|
656 | settings and version of JSON::XS), but this incurs a runtime overhead |
|
|
657 | and is only rarely useful, e.g. when you want to compare some JSON text |
|
|
658 | against another for equality. |
|
|
659 | |
|
|
660 | =item array references |
|
|
661 | |
|
|
662 | Perl array references become JSON arrays. |
|
|
663 | |
|
|
664 | =item other references |
|
|
665 | |
|
|
666 | Other unblessed references are generally not allowed and will cause an |
|
|
667 | exception to be thrown, except for references to the integers C<0> and |
|
|
668 | C<1>, which get turned into C<false> and C<true> atoms in JSON. You can |
|
|
669 | also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability. |
|
|
670 | |
|
|
671 | to_json [\0,JSON::XS::true] # yields [false,true] |
|
|
672 | |
|
|
673 | =item JSON::XS::true, JSON::XS::false |
|
|
674 | |
|
|
675 | These special values become JSON true and JSON false values, |
|
|
676 | respectively. You can also use C<\1> and C<\0> directly if you want. |
|
|
677 | |
|
|
678 | =item blessed objects |
|
|
679 | |
|
|
680 | Blessed objects are not allowed. JSON::XS currently tries to encode their |
|
|
681 | underlying representation (hash- or arrayref), but this behaviour might |
|
|
682 | change in future versions. |
|
|
683 | |
|
|
684 | =item simple scalars |
|
|
685 | |
|
|
686 | Simple Perl scalars (any scalar that is not a reference) are the most |
|
|
687 | difficult objects to encode: JSON::XS will encode undefined scalars as |
|
|
688 | JSON null value, scalars that have last been used in a string context |
|
|
689 | before encoding as JSON strings and anything else as number value: |
|
|
690 | |
|
|
691 | # dump as number |
|
|
692 | to_json [2] # yields [2] |
|
|
693 | to_json [-3.0e17] # yields [-3e+17] |
|
|
694 | my $value = 5; to_json [$value] # yields [5] |
|
|
695 | |
|
|
696 | # used as string, so dump as string |
|
|
697 | print $value; |
|
|
698 | to_json [$value] # yields ["5"] |
|
|
699 | |
|
|
700 | # undef becomes null |
|
|
701 | to_json [undef] # yields [null] |
|
|
702 | |
|
|
703 | You can force the type to be a string by stringifying it: |
|
|
704 | |
|
|
705 | my $x = 3.1; # some variable containing a number |
|
|
706 | "$x"; # stringified |
|
|
707 | $x .= ""; # another, more awkward way to stringify |
|
|
708 | print $x; # perl does it for you, too, quite often |
|
|
709 | |
|
|
710 | You can force the type to be a number by numifying it: |
|
|
711 | |
|
|
712 | my $x = "3"; # some variable containing a string |
|
|
713 | $x += 0; # numify it, ensuring it will be dumped as a number |
|
|
714 | $x *= 1; # same thing, the choise is yours. |
|
|
715 | |
|
|
716 | You can not currently output JSON booleans or force the type in other, |
|
|
717 | less obscure, ways. Tell me if you need this capability. |
|
|
718 | |
|
|
719 | =back |
|
|
720 | |
|
|
721 | |
|
|
722 | =head1 COMPARISON |
|
|
723 | |
|
|
724 | As already mentioned, this module was created because none of the existing |
|
|
725 | JSON modules could be made to work correctly. First I will describe the |
|
|
726 | problems (or pleasures) I encountered with various existing JSON modules, |
|
|
727 | followed by some benchmark values. JSON::XS was designed not to suffer |
|
|
728 | from any of these problems or limitations. |
|
|
729 | |
|
|
730 | =over 4 |
|
|
731 | |
|
|
732 | =item JSON 1.07 |
|
|
733 | |
|
|
734 | Slow (but very portable, as it is written in pure Perl). |
|
|
735 | |
|
|
736 | Undocumented/buggy Unicode handling (how JSON handles unicode values is |
|
|
737 | undocumented. One can get far by feeding it unicode strings and doing |
|
|
738 | en-/decoding oneself, but unicode escapes are not working properly). |
|
|
739 | |
|
|
740 | No roundtripping (strings get clobbered if they look like numbers, e.g. |
|
|
741 | the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will |
|
|
742 | decode into the number 2. |
|
|
743 | |
|
|
744 | =item JSON::PC 0.01 |
|
|
745 | |
|
|
746 | Very fast. |
|
|
747 | |
|
|
748 | Undocumented/buggy Unicode handling. |
|
|
749 | |
|
|
750 | No roundtripping. |
|
|
751 | |
|
|
752 | Has problems handling many Perl values (e.g. regex results and other magic |
|
|
753 | values will make it croak). |
|
|
754 | |
|
|
755 | Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}> |
|
|
756 | which is not a valid JSON text. |
|
|
757 | |
|
|
758 | Unmaintained (maintainer unresponsive for many months, bugs are not |
|
|
759 | getting fixed). |
|
|
760 | |
|
|
761 | =item JSON::Syck 0.21 |
|
|
762 | |
|
|
763 | Very buggy (often crashes). |
|
|
764 | |
|
|
765 | Very inflexible (no human-readable format supported, format pretty much |
|
|
766 | undocumented. I need at least a format for easy reading by humans and a |
|
|
767 | single-line compact format for use in a protocol, and preferably a way to |
|
|
768 | generate ASCII-only JSON texts). |
|
|
769 | |
|
|
770 | Completely broken (and confusingly documented) Unicode handling (unicode |
|
|
771 | escapes are not working properly, you need to set ImplicitUnicode to |
|
|
772 | I<different> values on en- and decoding to get symmetric behaviour). |
|
|
773 | |
|
|
774 | No roundtripping (simple cases work, but this depends on wether the scalar |
|
|
775 | value was used in a numeric context or not). |
|
|
776 | |
|
|
777 | Dumping hashes may skip hash values depending on iterator state. |
|
|
778 | |
|
|
779 | Unmaintained (maintainer unresponsive for many months, bugs are not |
|
|
780 | getting fixed). |
|
|
781 | |
|
|
782 | Does not check input for validity (i.e. will accept non-JSON input and |
|
|
783 | return "something" instead of raising an exception. This is a security |
|
|
784 | issue: imagine two banks transfering money between each other using |
|
|
785 | JSON. One bank might parse a given non-JSON request and deduct money, |
|
|
786 | while the other might reject the transaction with a syntax error. While a |
|
|
787 | good protocol will at least recover, that is extra unnecessary work and |
|
|
788 | the transaction will still not succeed). |
|
|
789 | |
|
|
790 | =item JSON::DWIW 0.04 |
|
|
791 | |
|
|
792 | Very fast. Very natural. Very nice. |
|
|
793 | |
|
|
794 | Undocumented unicode handling (but the best of the pack. Unicode escapes |
|
|
795 | still don't get parsed properly). |
|
|
796 | |
|
|
797 | Very inflexible. |
|
|
798 | |
|
|
799 | No roundtripping. |
|
|
800 | |
|
|
801 | Does not generate valid JSON texts (key strings are often unquoted, empty keys |
|
|
802 | result in nothing being output) |
|
|
803 | |
|
|
804 | Does not check input for validity. |
|
|
805 | |
|
|
806 | =back |
|
|
807 | |
|
|
808 | |
|
|
809 | =head2 JSON and YAML |
|
|
810 | |
|
|
811 | You often hear that JSON is a subset (or a close subset) of YAML. This is, |
|
|
812 | however, a mass hysteria and very far from the truth. In general, there is |
|
|
813 | no way to configure JSON::XS to output a data structure as valid YAML. |
|
|
814 | |
|
|
815 | If you really must use JSON::XS to generate YAML, you should use this |
|
|
816 | algorithm (subject to change in future versions): |
|
|
817 | |
|
|
818 | my $to_yaml = JSON::XS->new->utf8->space_after (1); |
|
|
819 | my $yaml = $to_yaml->encode ($ref) . "\n"; |
|
|
820 | |
|
|
821 | This will usually generate JSON texts that also parse as valid |
|
|
822 | YAML. Please note that YAML has hardcoded limits on (simple) object key |
|
|
823 | lengths that JSON doesn't have, so you should make sure that your hash |
|
|
824 | keys are noticably shorter than the 1024 characters YAML allows. |
|
|
825 | |
|
|
826 | There might be other incompatibilities that I am not aware of. In general |
|
|
827 | you should not try to generate YAML with a JSON generator or vice versa, |
|
|
828 | or try to parse JSON with a YAML parser or vice versa: chances are high |
|
|
829 | that you will run into severe interoperability problems. |
|
|
830 | |
|
|
831 | |
|
|
832 | =head2 SPEED |
|
|
833 | |
|
|
834 | It seems that JSON::XS is surprisingly fast, as shown in the following |
|
|
835 | tables. They have been generated with the help of the C<eg/bench> program |
|
|
836 | in the JSON::XS distribution, to make it easy to compare on your own |
|
|
837 | system. |
|
|
838 | |
|
|
839 | First comes a comparison between various modules using a very short |
|
|
840 | single-line JSON string: |
|
|
841 | |
|
|
842 | {"method": "handleMessage", "params": ["user1", "we were just talking"], \ |
|
|
843 | "id": null, "array":[1,11,234,-5,1e5,1e7, true, false]} |
|
|
844 | |
|
|
845 | It shows the number of encodes/decodes per second (JSON::XS uses |
|
|
846 | the functional interface, while JSON::XS/2 uses the OO interface |
|
|
847 | with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables |
|
|
848 | shrink). Higher is better: |
|
|
849 | |
|
|
850 | Storable | 15779.925 | 14169.946 | |
|
|
851 | -----------+------------+------------+ |
|
|
852 | module | encode | decode | |
|
|
853 | -----------|------------|------------| |
|
|
854 | JSON | 4990.842 | 4088.813 | |
|
|
855 | JSON::DWIW | 51653.990 | 71575.154 | |
|
|
856 | JSON::PC | 65948.176 | 74631.744 | |
|
|
857 | JSON::PP | 8931.652 | 3817.168 | |
|
|
858 | JSON::Syck | 24877.248 | 27776.848 | |
|
|
859 | JSON::XS | 388361.481 | 227951.304 | |
|
|
860 | JSON::XS/2 | 227951.304 | 218453.333 | |
|
|
861 | JSON::XS/3 | 338250.323 | 218453.333 | |
|
|
862 | Storable | 16500.016 | 135300.129 | |
|
|
863 | -----------+------------+------------+ |
|
|
864 | |
|
|
865 | That is, JSON::XS is about five times faster than JSON::DWIW on encoding, |
|
|
866 | about three times faster on decoding, and over fourty times faster |
|
|
867 | than JSON, even with pretty-printing and key sorting. It also compares |
|
|
868 | favourably to Storable for small amounts of data. |
|
|
869 | |
|
|
870 | Using a longer test string (roughly 18KB, generated from Yahoo! Locals |
|
|
871 | search API (http://nanoref.com/yahooapis/mgPdGg): |
|
|
872 | |
|
|
873 | module | encode | decode | |
|
|
874 | -----------|------------|------------| |
|
|
875 | JSON | 55.260 | 34.971 | |
|
|
876 | JSON::DWIW | 825.228 | 1082.513 | |
|
|
877 | JSON::PC | 3571.444 | 2394.829 | |
|
|
878 | JSON::PP | 210.987 | 32.574 | |
|
|
879 | JSON::Syck | 552.551 | 787.544 | |
|
|
880 | JSON::XS | 5780.463 | 4854.519 | |
|
|
881 | JSON::XS/2 | 3869.998 | 4798.975 | |
|
|
882 | JSON::XS/3 | 5862.880 | 4798.975 | |
|
|
883 | Storable | 4445.002 | 5235.027 | |
|
|
884 | -----------+------------+------------+ |
|
|
885 | |
|
|
886 | Again, JSON::XS leads by far (except for Storable which non-surprisingly |
|
|
887 | decodes faster). |
|
|
888 | |
|
|
889 | On large strings containing lots of high unicode characters, some modules |
|
|
890 | (such as JSON::PC) seem to decode faster than JSON::XS, but the result |
|
|
891 | will be broken due to missing (or wrong) unicode handling. Others refuse |
|
|
892 | to decode or encode properly, so it was impossible to prepare a fair |
|
|
893 | comparison table for that case. |
|
|
894 | |
|
|
895 | |
|
|
896 | =head1 SECURITY CONSIDERATIONS |
|
|
897 | |
|
|
898 | When you are using JSON in a protocol, talking to untrusted potentially |
|
|
899 | hostile creatures requires relatively few measures. |
|
|
900 | |
|
|
901 | First of all, your JSON decoder should be secure, that is, should not have |
|
|
902 | any buffer overflows. Obviously, this module should ensure that and I am |
|
|
903 | trying hard on making that true, but you never know. |
|
|
904 | |
|
|
905 | Second, you need to avoid resource-starving attacks. That means you should |
|
|
906 | limit the size of JSON texts you accept, or make sure then when your |
|
|
907 | resources run out, thats just fine (e.g. by using a separate process that |
|
|
908 | can crash safely). The size of a JSON text in octets or characters is |
|
|
909 | usually a good indication of the size of the resources required to decode |
|
|
910 | it into a Perl structure. While JSON::XS can check the size of the JSON |
|
|
911 | text, it might be too late when you already have it in memory, so you |
|
|
912 | might want to check the size before you accept the string. |
|
|
913 | |
|
|
914 | Third, JSON::XS recurses using the C stack when decoding objects and |
|
|
915 | arrays. The C stack is a limited resource: for instance, on my amd64 |
|
|
916 | machine with 8MB of stack size I can decode around 180k nested arrays but |
|
|
917 | only 14k nested JSON objects (due to perl itself recursing deeply on croak |
|
|
918 | to free the temporary). If that is exceeded, the program crashes. to be |
|
|
919 | conservative, the default nesting limit is set to 512. If your process |
|
|
920 | has a smaller stack, you should adjust this setting accordingly with the |
|
|
921 | C<max_depth> method. |
|
|
922 | |
|
|
923 | And last but least, something else could bomb you that I forgot to think |
|
|
924 | of. In that case, you get to keep the pieces. I am always open for hints, |
|
|
925 | though... |
|
|
926 | |
|
|
927 | If you are using JSON::XS to return packets to consumption |
|
|
928 | by javascript scripts in a browser you should have a look at |
|
|
929 | L<http://jpsykes.com/47/practical-csrf-and-json-security> to see wether |
|
|
930 | you are vulnerable to some common attack vectors (which really are browser |
|
|
931 | design bugs, but it is still you who will have to deal with it, as major |
|
|
932 | browser developers care only for features, not about doing security |
|
|
933 | right). |
|
|
934 | |
|
|
935 | |
|
|
936 | =head1 BUGS |
|
|
937 | |
|
|
938 | While the goal of this module is to be correct, that unfortunately does |
|
|
939 | not mean its bug-free, only that I think its design is bug-free. It is |
|
|
940 | still relatively early in its development. If you keep reporting bugs they |
|
|
941 | will be fixed swiftly, though. |
|
|
942 | |
|
|
943 | =cut |
|
|
944 | |
|
|
945 | our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" }; |
|
|
946 | our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" }; |
|
|
947 | |
|
|
948 | sub true() { $true } |
|
|
949 | sub false() { $false } |
|
|
950 | |
|
|
951 | sub is_bool($) { |
|
|
952 | UNIVERSAL::isa $_[0], "JSON::XS::Boolean" |
|
|
953 | # or UNIVERSAL::isa $_[0], "JSON::Literal" |
| 25 | } |
954 | } |
| 26 | |
955 | |
| 27 | =item |
956 | XSLoader::load "JSON::XS", $VERSION; |
| 28 | |
957 | |
| 29 | =cut |
958 | package JSON::XS::Boolean; |
| 30 | |
959 | |
| 31 | use JSON::DWIW; |
960 | use overload |
| 32 | use Benchmark; |
961 | "0+" => sub { ${$_[0]} }, |
| 33 | |
962 | "++" => sub { $_[0] = ${$_[0]} + 1 }, |
| 34 | use utf8; |
963 | "--" => sub { $_[0] = ${$_[0]} - 1 }, |
| 35 | #my $json = '{"ü":1,"a":[1,{"3":4},2],"b":5,"üü":2}'; |
964 | fallback => 1; |
| 36 | my $json = '{"test":9555555555555555555,"hu" : -1e+5, "arr" : [ 1,2,3,4,5]}'; |
|
|
| 37 | |
|
|
| 38 | my $js = JSON::XS->new; |
|
|
| 39 | warn $js->indent (0); |
|
|
| 40 | warn $js->canonical (0); |
|
|
| 41 | warn $js->ascii (0); |
|
|
| 42 | warn $js->space_after (0); |
|
|
| 43 | use Data::Dumper; |
|
|
| 44 | warn Dumper $js->decode ($json); |
|
|
| 45 | warn Dumper $js->encode ($js->decode ($json)); |
|
|
| 46 | #my $x = {"üü" => 2, "ü" => 1, "a" => [1,{3,4},2], b => 5}; |
|
|
| 47 | |
|
|
| 48 | #my $js2 = JSON::DWIW->new; |
|
|
| 49 | # |
|
|
| 50 | #timethese 200000, { |
|
|
| 51 | # a => sub { $js->encode ($x) }, |
|
|
| 52 | # b => sub { $js2->to_json ($x) }, |
|
|
| 53 | #}; |
|
|
| 54 | |
965 | |
| 55 | 1; |
966 | 1; |
| 56 | |
|
|
| 57 | =back |
|
|
| 58 | |
967 | |
| 59 | =head1 AUTHOR |
968 | =head1 AUTHOR |
| 60 | |
969 | |
| 61 | Marc Lehmann <schmorp@schmorp.de> |
970 | Marc Lehmann <schmorp@schmorp.de> |
| 62 | http://home.schmorp.de/ |
971 | http://home.schmorp.de/ |
