lua_parson

A lua json encode/decode c module base on parson. See more about parson at https://github.com/kgabis/parson

Installation

• Make sure lua develop environment already installed
• git clone https://github.com/changnet/lua_parson.git
• cd lua_parson
• git submodule update --init --recursive
• make
• make test
• Copy lua_parson.so to your lua project's c module directory or link against liblua_parsion.a

Api

-- encode a lua table to json string. a lua error will throw if any error occur
-- @param tbl a lua table to be encode
-- @param pretty boolean, format json string to pretty human readable or not
-- @param opt number, option to set the table as array or object
-- @return json string
encode(tbl, pretty, opt)

-- encode a lua table to json string. a lua error will throw if any error occur
-- @param tbl a lua table to be encode
-- @param file a file path that json string will be written in
-- @param pretty boolean, format json string to pretty human readable or not
-- @param opt number, option to set the table as array or object
-- @return boolean
encode_to_file(tbl, file, pretty, opt)

-- decode a json string to a lua table.a lua error will throw if any error occur
-- @param a json string
-- @param comment boolean, is the str containt comments
-- @param opt number, enable integer key convertion if set
-- @return a lua table
decode(str, comment, opt)

-- decode a file content to a lua table.a lua error will throw if any error occur
-- @param a json file path
-- @param comment boolean, is the file content containt comments
-- @param opt number, enable integer key convertion if set
-- @return a lua table
decode_from_file(file, comment, opt)

Array or Object

• No opt(no opt pass to encode、decode and no __opt in metatable)

  • Empty table is an object
  • If a table has only integer keys, consider it an array

• Detect by opt

  • If a table's metatable has field __opt = 1 consider it an array
  • If a table's metatable has field __opt = 0 consider it an object
  • modf(opt) the integral part means the table is array if table max key <= this value. The fractional part means table is array when (table size)/(max key) >= this value.

  -- opt = 8.6
  
  -- max key 7 <= 8, it encode as array
  local tbl = {[7] = 1}
  
  -- table size = 6, max key = 10, 6/10 >= 0.6, it encode as array
  local tbl = {1,2,3,4,5, [10] = 10}
  
  -- max key 1024 > 8 and table size = 1, 1/1024 < 0.6, it encode as object
  local tbl = {[1024] = 1}

Note:

If a table is converted to an object, a field __opt will be append to the object. When decode, if __opt is found in the object, it's number key will be converted to number. e.g.

local tbl = {
    [1024] = "abc",
}

to json

{"1024": "abc", "__opt": 0}

to lua again

local tbl = {
    [1024] = "abc",
}

-- not
-- local tbl = {
--     ["1024"] = "abc",
-- }

This feature allows convertion between json and lua table.

Example

See test.lua

• normal

[1,"a",true,2.5,false,987654321123]

{
    [1] = 1,
    [2] = "a",
    [3] = true,
    [4] = 2.5,
    [5] = false,
    [6] = 987654321123,
}

• table to json(array) to table

{
    phone1 = "123456789",
    phone2 = "987654321"
}

["123456789","987654321"]

{
    [1] = "123456789",
    [2] = "987654321",
}

• table to json(object) to table

{"AA","BB","CC"}

{"1":"AA","2":"BB","3":"CC","__opt":0}

{
    [1] = "AA",
    [2] = "BB",
    [3] = "CC",
}