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|
=encoding utf-8
=head1 Name
lua-cjson - Fast JSON encoding/parsing
=head1 Description
This fork of L<mpxE<sol>lua-cjson|https://github.com/mpx/lua-cjson> is included in
the L<OpenResty|https://openresty.org/> bundle and includes a few bugfixes and
improvements, especially to facilitate the encoding of empty tables as JSON Arrays.
Please refer to the L<lua-cjson documentation|https://kyne.au/~mark/software/lua-cjson.php>
for standard usage, this README only provides informations regarding this fork's additions.
See L<`mpxE<sol>master..openrestyE<sol>master`|https://github.com/mpx/lua-cjson/compare/master...openresty:master>
for the complete history of changes.
=head1 Additions
=head2 encode_empty_table_as_object
B<syntax:> C<cjson.encode_empty_table_as_object(true|false|"on"|"off")>
Change the default behavior when encoding an empty Lua table.
By default, empty Lua tables are encoded as empty JSON Objects (C<{}>). If this is set to false,
empty Lua tables will be encoded as empty JSON Arrays instead (C<[]>).
This method either accepts a boolean or a string (C<"on">, C<"off">).
=head2 empty_array
B<syntax:> C<cjson.empty_array>
A lightuserdata, similar to C<cjson.null>, which will be encoded as an empty JSON Array by
C<cjson.encode()>.
For example, since C<encode_empty_table_as_object> is C<true> by default:
local cjson = require "cjson"
local json = cjson.encode({
foo = "bar",
some_object = {},
some_array = cjson.empty_array
})
This will generate:
{
"foo": "bar",
"some_object": {},
"some_array": []
}
=head2 array_mt
B<syntax:> C<setmetatable({}, cjson.array_mt)>
When lua-cjson encodes a table with this metatable, it will systematically
encode it as a JSON Array. The resulting, encoded Array will contain the array
part of the table, and will be of the same length as the C<#> operator on that
table. Holes in the table will be encoded with the C<null> JSON value.
Example:
local t = { "hello", "world" }
setmetatable(t, cjson.array_mt)
cjson.encode(t) -- ["hello","world"]
Or:
local t = {}
t[1] = "one"
t[2] = "two"
t[4] = "three"
t.foo = "bar"
setmetatable(t, cjson.array_mt)
cjson.encode(t) -- ["one","two",null,"three"]
This value was introduced in the C<2.1.0.5> release of this module.
=head2 empty_array_mt
B<syntax:> C<setmetatable({}, cjson.empty_array_mt)>
A metatable which can "tag" a table as a JSON Array in case it is empty (that is, if the
table has no elements, C<cjson.encode()> will encode it as an empty JSON Array).
Instead of:
local function serialize(arr)
if #arr < 1 then
arr = cjson.empty_array
end
return cjson.encode({some_array = arr})
end
This is more concise:
local function serialize(arr)
setmetatable(arr, cjson.empty_array_mt)
return cjson.encode({some_array = arr})
end
Both will generate:
{
"some_array": []
}
=head2 encode_number_precision
B<syntax:> C<cjson.encode_number_precision(precision)>
This fork allows encoding of numbers with a C<precision> up to 16 decimals (vs. 14 in mpx/lua-cjson).
=head2 encode_escape_forward_slash
B<syntax:> C<cjson.encode_escape_forward_slash(enabled)>
B<default:> true
If enabled, forward slash '/' will be encoded as '\\/'.
If disabled, forward slash '/' will be encoded as '/' (no escape is applied).
=head2 encode_skip_unsupported_value_types
B<syntax:> C<cjson.encode_skip_unsupported_value_types(enabled)>
B<default:> false
If enabled, cjson will not throw exception when there are unsupported types
in the Lua table.
For example:
local ffi = require "ffi"
local cjson = require "cjson"
cjson.encode_skip_unsupported_value_types(true)
local t = {key = "val"}
t.cdata = ffi.new("char[?]", 100)
print(cjson.encode(t))
This will generate:
{"key":"val"}
=head2 decode_array_with_array_mt
B<syntax:> C<cjson.decode_array_with_array_mt(enabled)>
B<default:> false
If enabled, JSON Arrays decoded by C<cjson.decode> will result in Lua
tables with the L<`array_mt`> metatable. This can ensure a 1-to-1
relationship between arrays upon multiple encoding/decoding of your
JSON data with this module.
If disabled, JSON Arrays will be decoded to plain Lua tables, without
the C<array_mt> metatable.
The C<enabled> argument is a boolean.
Example:
local cjson = require "cjson"
-- default behavior
local my_json = [[{"my_array":[]}]]
local t = cjson.decode(my_json)
cjson.encode(t) -- {"my_array":{}} back to an object
-- now, if this behavior is enabled
cjson.decode_array_with_array_mt(true)
local my_json = [[{"my_array":[]}]]
local t = cjson.decode(my_json)
cjson.encode(t) -- {"my_array":[]} properly re-encoded as an array
|
