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alisdair sullivan 2012-05-25 11:55:26 -07:00
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@ -304,242 +304,245 @@ however, it is important to recognize that jsx is greedy by default. jsx will co
## exports ## ## exports ##
### encoder/3, decoder/3 and parser/3 ### * ### encoder/3, decoder/3 and parser/3 ###
```erlang ```erlang
decoder(Module, Args, Opts) -> Fun((JSONText) -> any()) decoder(Module, Args, Opts) -> Fun((JSONText) -> any())
encoder(Module, Args, Opts) -> Fun((JSONTerm) -> any()) encoder(Module, Args, Opts) -> Fun((JSONTerm) -> any())
parser(Module, Args, Opts) -> Fun((Tokens) -> any()) parser(Module, Args, Opts) -> Fun((Tokens) -> any())
Module = atom() Module = atom()
Args = any() Args = any()
Opts = options() Opts = options()
JSONText = json_text() JSONText = json_text()
JSONTerm = json_term() JSONTerm = json_term()
Tokens = tokens() Tokens = tokens()
``` ```
jsx is a json compiler with distinct tokenizing, syntactic analysis and semantic analysis stages (actually, semantic analysis takes place during syntactic analysis, for efficiency). included are two tokenizers; one that handles json texts (`decoder/3`) and one that handles erlang terms (`encoder/3`). there is also an entry point to the syntactic analysis stage for use with user-defined tokenizers (`parser/3`) jsx is a json compiler with distinct tokenizing, syntactic analysis and semantic analysis stages (actually, semantic analysis takes place during syntactic analysis, for efficiency). included are two tokenizers; one that handles json texts (`decoder/3`) and one that handles erlang terms (`encoder/3`). there is also an entry point to the syntactic analysis stage for use with user-defined tokenizers (`parser/3`)
all three functions return an anonymous function that takes the appropriate type of input and returns the result of performing semantic analysis, the tuple `{incomplete, F}` where `F` is a new anonymous function (see [incomplete input](#incomplete_input)) or a `badarg` error exception if syntactic analysis fails all three functions return an anonymous function that takes the appropriate type of input and returns the result of performing semantic analysis, the tuple `{incomplete, F}` where `F` is a new anonymous function (see [incomplete input](#incomplete_input)) or a `badarg` error exception if syntactic analysis fails
`Module` is the name of the callback module `Module` is the name of the callback module
`Args` is any term that will be passed to `Module:init/1` prior to syntactic analysis to produce an initial state `Args` is any term that will be passed to `Module:init/1` prior to syntactic analysis to produce an initial state
`Opts` are detailed [above](#data_types) `Opts` are detailed [above](#data_types)
see [below](#callback_exports) for details on the callback module see [below](#callback_exports) for details on the callback module
* ### decode/1,2 ###
```erlang
decode(JSON) -> Term
decode(JSON, Opts) -> Term
JSON = json_text()
Term = json_term()
Opts = [option() | labels | {labels, Label} | {post_decode, F}]
Label = binary | atom | existing_atom
F = fun((any()) -> any())
```
`decode` parses a json text (a `utf8` encoded binary) and produces an erlang term (see [json <-> erlang mapping](#json---erlang-mapping))
the option `labels` controls how keys are converted from json to erlang terms. `binary` does no conversion beyond normal escaping. `atom` converts keys to erlang atoms and results in a badarg error if the keys fall outside the range of erlang atoms. `existing_atom` is identical to `atom` except it will not add new atoms to the atom table
`{post_decode, F}` is a user defined function of arity 1 that is called on each output value (objects, arrays, strings, numbers and literals). it may return any value to be substituted in the returned term. for example:
```erlang
1> F = fun(V) when is_list(V) -> V; (V) -> false end.
2> jsx:decode(<<"{\"a list\": [true, \"a string\", 1]}">>, [{post_decode, F}]).
[{<<"a list">>, [false, false, false]}]
```
declaring more than one post-decoder will result in a `badarg` error exception
raises a `badarg` error exception if input is not valid json
### decode/1,2 ### * ### encode/1,2 ###
```erlang ```erlang
decode(JSON) -> Term encode(Term) -> JSON
decode(JSON, Opts) -> Term encode(Term, Opts) -> JSON
JSON = json_text() Term = json_term()
Term = json_term() JSON = json_text()
Opts = [option() | labels | {labels, Label} | {post_decode, F}] Opts = [option() | {pre_encode, F} | space | {space, N} | indent | {indent, N}]
Label = binary | atom | existing_atom F = fun((any()) -> any())
F = fun((any()) -> any()) N = pos_integer()
``` ```
`decode` parses a json text (a `utf8` encoded binary) and produces an erlang term (see [json <-> erlang mapping](#json---erlang-mapping)) `encode` parses a json text (a `utf8` encoded binary) and produces an erlang term (see [json <-> erlang mapping](#json---erlang-mapping))
the option `labels` controls how keys are converted from json to erlang terms. `binary` does no conversion beyond normal escaping. `atom` converts keys to erlang atoms and results in a badarg error if the keys fall outside the range of erlang atoms. `existing_atom` is identical to `atom` except it will not add new atoms to the atom table the option `{space, N}` inserts `N` spaces after every comma and colon in your json output. `space` is an alias for `{space, 1}`. the default is `{space, 0}`
`{post_decode, F}` is a user defined function of arity 1 that is called on each output value (objects, arrays, strings, numbers and literals). it may return any value to be substituted in the returned term. for example: the option `{indent, N}` inserts a newline and `N` spaces for each level of indentation in your json output. note that this overrides spaces inserted after a comma. `indent` is an alias for `{indent, 1}`. the default is `{indent, 0}`
```erlang `{pre_encode, F}` is a user defined function of arity 1 that is called on each input value. it may return any valid json value to be substituted in the returned json. for example:
1> F = fun(V) when is_list(V) -> V; (V) -> false end.
2> jsx:decode(<<"{\"a list\": [true, \"a string\", 1]}">>, [{post_decode, F}]).
[{<<"a list">>, [false, false, false]}]
```
declaring more than one post-decoder will result in a `badarg` error exception ```erlang
1> F = fun(V) when is_list(V) -> V; (V) -> false end.
2> jsx:encode([{<<"a list">>, [true, <<"a string">>, 1]}], [{pre_encode, F}]).
<<"{\"a list\": [false, false, false]}">>
```
raises a `badarg` error exception if input is not valid json declaring more than one pre-encoder will result in a `badarg` error exception
raises a `badarg` error exception if input is not a valid erlang representation of json
### encode/1,2 ### * ### format/1,2 ###
```erlang ```erlang
encode(Term) -> JSON format(JSON) -> JSON
encode(Term, Opts) -> JSON format(JSON, Opts) -> JSON
Term = json_term() JSON = json_text()
JSON = json_text() Opts = [option() | space | {space, N} | indent | {indent, N}]
Opts = [option() | {pre_encode, F} | space | {space, N} | indent | {indent, N}] N = pos_integer()
F = fun((any()) -> any()) ```
N = pos_integer()
```
`encode` parses a json text (a `utf8` encoded binary) and produces an erlang term (see [json <-> erlang mapping](#json---erlang-mapping)) `format` parses a json text (a `utf8` encoded binary) and produces a new json text according to the format rules specified by `Opts`
`{pre_encode, F}` is a user defined function of arity 1 that is called on each input value. it may return any valid json value to be substituted in the returned json. for example: the option `{space, N}` inserts `N` spaces after every comma and colon in your json output. `space` is an alias for `{space, 1}`. the default is `{space, 0}`
the option `{indent, N}` inserts a newline and `N` spaces for each level of indentation in your json output. note that this overrides spaces inserted after a comma. `indent` is an alias for `{indent, 1}`. the default is `{indent, 0}`
```erlang raises a `badarg` error exception if input is not valid json
1> F = fun(V) when is_list(V) -> V; (V) -> false end.
2> jsx:encode([{<<"a list">>, [true, <<"a string">>, 1]}], [{pre_encode, F}]).
<<"{\"a list\": [false, false, false]}">>
```
declaring more than one pre-encoder will result in a `badarg` error exception
the option `{space, N}` inserts `N` spaces after every comma and colon in your json output. `space` is an alias for `{space, 1}`. the default is `{space, 0}`
the option `{indent, N}` inserts a newline and `N` spaces for each level of indentation in your json output. note that this overrides spaces inserted after a comma. `indent` is an alias for `{indent, 1}`. the default is `{indent, 0}`
raises a `badarg` error exception if input is not a valid erlang representation of json
### format/1,2 ### * ### minify/1 ###
```erlang ```erlang
format(JSON) -> JSON minify(JSON) -> JSON
format(JSON, Opts) -> JSON
JSON = json_text() JSON = json_text()
Opts = [option() | space | {space, N} | indent | {indent, N}] ```
N = pos_integer()
```
`format` parses a json text (a `utf8` encoded binary) and produces a new json text according to the format rules specified by `Opts` `minify` parses a json text (a `utf8` encoded binary) and produces a new json text stripped of whitespace
the option `{space, N}` inserts `N` spaces after every comma and colon in your json output. `space` is an alias for `{space, 1}`. the default is `{space, 0}` raises a `badarg` error exception if input is not valid json
the option `{indent, N}` inserts a newline and `N` spaces for each level of indentation in your json output. note that this overrides spaces inserted after a comma. `indent` is an alias for `{indent, 1}`. the default is `{indent, 0}`
raises a `badarg` error exception if input is not valid json
### minify/1 ### * ### prettify/1 ###
```erlang ```erlang
minify(JSON) -> JSON prettify(JSON) -> JSON
JSON = json_text() JSON = json_text()
``` ```
`minify` parses a json text (a `utf8` encoded binary) and produces a new json text stripped of whitespace `prettify` parses a json text (a `utf8` encoded binary) and produces a new json text equivalent to `format(JSON, [{space, 1}, {indent, 2}])`
raises a `badarg` error exception if input is not valid json raises a `badarg` error exception if input is not valid json
### prettify/1 ### * ### is_json/1,2 ###
```erlang ```erlang
prettify(JSON) -> JSON is_json(MaybeJSON) -> true | false
is_json(MaybeJSON, Opts) -> true | false
JSON = json_text() MaybeJSON = any()
``` Opts = options()
```
`prettify` parses a json text (a `utf8` encoded binary) and produces a new json text equivalent to `format(JSON, [{space, 1}, {indent, 2}])` returns true if input is a valid json text, false if not
raises a `badarg` error exception if input is not valid json what exactly constitutes valid json may be altered per [options](#data_types)
### is_json/1,2 ### * ### is_term/1,2 ###
```erlang ```erlang
is_json(MaybeJSON) -> true | false is_term(MaybeJSON) -> true | false
is_json(MaybeJSON, Opts) -> true | false is_term(MaybeJSON, Opts) -> true | false
MaybeJSON = any() MaybeJSON = any()
Opts = options() Opts = options()
``` ```
returns true if input is a valid json text, false if not returns true if input is a valid erlang representation of json, false if not
what exactly constitutes valid json may be altered per [options](#data_types) what exactly constitutes valid json may be altered per [options](#data_types)
### is_term/1,2 ###
```erlang
is_term(MaybeJSON) -> true | false
is_term(MaybeJSON, Opts) -> true | false
MaybeJSON = any()
Opts = options()
```
returns true if input is a valid erlang representation of json, false if not
what exactly constitutes valid json may be altered per [options](#data_types)
## callback exports ## ## callback exports ##
the following functions should be exported from a jsx callback module the following functions should be exported from a jsx callback module
### Module:init/1 ### * ### Module:init/1 ###
```erlang ```erlang
Module:init(Args) -> InitialState Module:init(Args) -> InitialState
Args = any() Args = any()
InitialState = any() InitialState = any()
``` ```
whenever any of `encoder/3`, `decoder/3` or `parser/3` are called, this function is called with the `Args` argument provided in the calling function to obtain `InitialState` whenever any of `encoder/3`, `decoder/3` or `parser/3` are called, this function is called with the `Args` argument provided in the calling function to obtain `InitialState`
### Module:handle_event/2 ### * ### Module:handle_event/2 ###
```erlang ```erlang
Module:handle_event(Event, State) -> NewState Module:handle_event(Event, State) -> NewState
Event = events() Event = events()
State = any() State = any()
NewState = any() NewState = any()
``` ```
semantic analysis is performed by repeatedly calling `handle_event/2` with a stream of events emitted by the tokenizer and the current state. the new state returned is used as the input to the next call to `handle_event/2`. the following events must be handled: semantic analysis is performed by repeatedly calling `handle_event/2` with a stream of events emitted by the tokenizer and the current state. the new state returned is used as the input to the next call to `handle_event/2`. the following events must be handled:
* `start_object`<p>the start of a json object</p> - `start_object`
the start of a json object
* `end_object`<p>the end of a json object</p> - `end_object`
the end of a json object
* `start_array` - `start_array`
the start of a json array the start of a json array
* `end_array` - `end_array`
the end of a json array the end of a json array
* `{key, binary()}` - `{key, binary()}`
a key in a json object. this is guaranteed to follow either `start_object` or a json value. it will usually be a `utf8` encoded binary. see [options](#data_types) for possible exceptions a key in a json object. this is guaranteed to follow either `start_object` or a json value. it will usually be a `utf8` encoded binary. see [options](#data_types) for possible exceptions
* `{string, binary()}` - `{string, binary()}`
a json string. it will usually be a `utf8` encoded binary. see [options](#data_types) for possible exceptions a json string. it will usually be a `utf8` encoded binary. see [options](#data_types) for possible exceptions
* `{integer, integer()}` - `{integer, integer()}`
an erlang integer (bignum) an erlang integer (bignum)
* `{float, float()}` - `{float, float()}`
an erlang float an erlang float
* `{literal, true}` - `{literal, true}`
the atom `true` the atom `true`
* `{literal, false}` - `{literal, false}`
the atom `false` the atom `false`
* `{literal, null}` - `{literal, null}`
the atom `null` the atom `null`
* `end_json` - `end_json`
this event is emitted when syntactic analysis is completed. you should do any cleanup and return the result of your semantic analysis this event is emitted when syntactic analysis is completed. you should do any cleanup and return the result of your semantic analysis
## acknowledgements ## ## acknowledgements ##