lua-json

骑猪看日落 2022-08-21 02:26 5阅读 0赞

**myjson.lua文件：**

-----------------------------------------------------------------------------
    -- JSON4Lua: JSON encoding / decoding support for the Lua language.
    -- json Module.
    -- Author: Craig Mason-Jones
    -- Homepage: http://github.com/craigmj/json4lua/
    -- Version: 1.0.0
    -- This module is released under the MIT License (MIT).
    -- Please see LICENCE.txt for details.
    --
    -- USAGE:
    -- This module exposes two functions:
    --   json.encode(o)
    --     Returns the table / string / boolean / number / nil / json.null value as a JSON-encoded string.
    --   json.decode(json_string)
    --     Returns a Lua object populated with the data encoded in the JSON string json_string.
    --
    -- REQUIREMENTS:
    --   compat-5.1 if using Lua 5.0
    --
    -- CHANGELOG
    --   0.9.20 Introduction of local Lua functions for private functions (removed _ function prefix). 
    --          Fixed Lua 5.1 compatibility issues.
    --   		Introduced json.null to have null values in associative arrays.
    --          json.encode() performance improvement (more than 50%) through table.concat rather than ..
    --          Introduced decode ability to ignore /**/ comments in the JSON string.
    --   0.9.10 Fix to array encoding / decoding to correctly manage nil/null values in arrays.
    -----------------------------------------------------------------------------
    
    -----------------------------------------------------------------------------
    -- Imports and dependencies
    -----------------------------------------------------------------------------
    local math = require('math')
    local string = require("string")
    local table = require("table")
    
    -----------------------------------------------------------------------------
    -- Module declaration
    -----------------------------------------------------------------------------
    local json = {}             -- Public namespace
    local json_private = {}     -- Private namespace
    
    -- Public functions
    
    -- Private functions
    local decode_scanArray
    local decode_scanComment
    local decode_scanConstant
    local decode_scanNumber
    local decode_scanObject
    local decode_scanString
    local decode_scanWhitespace
    local encodeString
    local isArray
    local isEncodable
    
    -----------------------------------------------------------------------------
    -- PUBLIC FUNCTIONS
    -----------------------------------------------------------------------------
    --- Encodes an arbitrary Lua object / variable.
    -- @param v The Lua object / variable to be JSON encoded.
    -- @return String containing the JSON encoding in internal Lua string format (i.e. not unicode)
    function json.encode (v)
      -- Handle nil values
      if v==nil then
        return "null"
      end
      
      local vtype = type(v)
    
      -- Handle strings
      if vtype=='string' then    
        return '"' .. json_private.encodeString(v) .. '"'	    -- Need to handle encoding in string
      end
      
      -- Handle booleans
      if vtype=='number' or vtype=='boolean' then
        return tostring(v)
      end
      
      -- Handle tables
      if vtype=='table' then
        local rval = {}
        -- Consider arrays separately
        local bArray, maxCount = isArray(v)
        if bArray then
          for i = 1,maxCount do
            table.insert(rval, json.encode(v[i]))
          end
        else	-- An object, not an array
          for i,j in pairs(v) do
            if isEncodable(i) and isEncodable(j) then
              table.insert(rval, '"' .. json_private.encodeString(i) .. '":' .. json.encode(j))
            end
          end
        end
        if bArray then
          return '[' .. table.concat(rval,',') ..']'
        else
          return '{' .. table.concat(rval,',') .. '}'
        end
      end
      
      -- Handle null values
      if vtype=='function' and v==null then
        return 'null'
      end
      
      assert(false,'encode attempt to encode unsupported type ' .. vtype .. ':' .. tostring(v))
    end
    
    
    --- Decodes a JSON string and returns the decoded value as a Lua data structure / value.
    -- @param s The string to scan.
    -- @param [startPos] Optional starting position where the JSON string is located. Defaults to 1.
    -- @param Lua object, number The object that was scanned, as a Lua table / string / number / boolean or nil,
    -- and the position of the first character after
    -- the scanned JSON object.
    function json.decode(s, startPos)
      startPos = startPos and startPos or 1
      startPos = decode_scanWhitespace(s,startPos)
      assert(startPos<=string.len(s), 'Unterminated JSON encoded object found at position in [' .. s .. ']')
      local curChar = string.sub(s,startPos,startPos)
      -- Object
      if curChar=='{' then
        return decode_scanObject(s,startPos)
      end
      -- Array
      if curChar=='[' then
        return decode_scanArray(s,startPos)
      end
      -- Number
      if string.find("+-0123456789.e", curChar, 1, true) then
        return decode_scanNumber(s,startPos)
      end
      -- String
      if curChar==[["]] or curChar==[[']] then
        return decode_scanString(s,startPos)
      end
      if string.sub(s,startPos,startPos+1)=='/*' then
        return decode(s, decode_scanComment(s,startPos))
      end
      -- Otherwise, it must be a constant
      return decode_scanConstant(s,startPos)
    end
    
    --- The null function allows one to specify a null value in an associative array (which is otherwise
    -- discarded if you set the value with 'nil' in Lua. Simply set t = { first=json.null }
    function null()
      return null -- so json.null() will also return null ;-)
    end
    -----------------------------------------------------------------------------
    -- Internal, PRIVATE functions.
    -- Following a Python-like convention, I have prefixed all these 'PRIVATE'
    -- functions with an underscore.
    -----------------------------------------------------------------------------
    
    --- Scans an array from JSON into a Lua object
    -- startPos begins at the start of the array.
    -- Returns the array and the next starting position
    -- @param s The string being scanned.
    -- @param startPos The starting position for the scan.
    -- @return table, int The scanned array as a table, and the position of the next character to scan.
    function decode_scanArray(s,startPos)
      local array = {}	-- The return value
      local stringLen = string.len(s)
      assert(string.sub(s,startPos,startPos)=='[','decode_scanArray called but array does not start at position ' .. startPos .. ' in string:\n'..s )
      startPos = startPos + 1
      -- Infinite loop for array elements
      repeat
        startPos = decode_scanWhitespace(s,startPos)
        assert(startPos<=stringLen,'JSON String ended unexpectedly scanning array.')
        local curChar = string.sub(s,startPos,startPos)
        if (curChar==']') then
          return array, startPos+1
        end
        if (curChar==',') then
          startPos = decode_scanWhitespace(s,startPos+1)
        end
        assert(startPos<=stringLen, 'JSON String ended unexpectedly scanning array.')
        object, startPos = json.decode(s,startPos)
        table.insert(array,object)
      until false
    end
    
    --- Scans a comment and discards the comment.
    -- Returns the position of the next character following the comment.
    -- @param string s The JSON string to scan.
    -- @param int startPos The starting position of the comment
    function decode_scanComment(s, startPos)
      assert( string.sub(s,startPos,startPos+1)=='/*', "decode_scanComment called but comment does not start at position " .. startPos)
      local endPos = string.find(s,'*/',startPos+2)
      assert(endPos~=nil, "Unterminated comment in string at " .. startPos)
      return endPos+2  
    end
    
    --- Scans for given constants: true, false or null
    -- Returns the appropriate Lua type, and the position of the next character to read.
    -- @param s The string being scanned.
    -- @param startPos The position in the string at which to start scanning.
    -- @return object, int The object (true, false or nil) and the position at which the next character should be 
    -- scanned.
    function decode_scanConstant(s, startPos)
      local consts = { ["true"] = true, ["false"] = false, ["null"] = nil }
      local constNames = {"true","false","null"}
    
      for i,k in pairs(constNames) do
        if string.sub(s,startPos, startPos + string.len(k) -1 )==k then
          return consts[k], startPos + string.len(k)
        end
      end
      assert(nil, 'Failed to scan constant from string ' .. s .. ' at starting position ' .. startPos)
    end
    
    --- Scans a number from the JSON encoded string.
    -- (in fact, also is able to scan numeric +- eqns, which is not
    -- in the JSON spec.)
    -- Returns the number, and the position of the next character
    -- after the number.
    -- @param s The string being scanned.
    -- @param startPos The position at which to start scanning.
    -- @return number, int The extracted number and the position of the next character to scan.
    function decode_scanNumber(s,startPos)
      local endPos = startPos+1
      local stringLen = string.len(s)
      local acceptableChars = "+-0123456789.e"
      while (string.find(acceptableChars, string.sub(s,endPos,endPos), 1, true)
    	and endPos<=stringLen
    	) do
        endPos = endPos + 1
      end
      local stringValue = 'return ' .. string.sub(s,startPos, endPos-1)
      local stringEval = loadstring(stringValue)
      assert(stringEval, 'Failed to scan number [ ' .. stringValue .. '] in JSON string at position ' .. startPos .. ' : ' .. endPos)
      return stringEval(), endPos
    end
    
    --- Scans a JSON object into a Lua object.
    -- startPos begins at the start of the object.
    -- Returns the object and the next starting position.
    -- @param s The string being scanned.
    -- @param startPos The starting position of the scan.
    -- @return table, int The scanned object as a table and the position of the next character to scan.
    function decode_scanObject(s,startPos)
      local object = {}
      local stringLen = string.len(s)
      local key, value
      assert(string.sub(s,startPos,startPos)=='{','decode_scanObject called but object does not start at position ' .. startPos .. ' in string:\n' .. s)
      startPos = startPos + 1
      repeat
        startPos = decode_scanWhitespace(s,startPos)
        assert(startPos<=stringLen, 'JSON string ended unexpectedly while scanning object.')
        local curChar = string.sub(s,startPos,startPos)
        if (curChar=='}') then
          return object,startPos+1
        end
        if (curChar==',') then
          startPos = decode_scanWhitespace(s,startPos+1)
        end
        assert(startPos<=stringLen, 'JSON string ended unexpectedly scanning object.')
        -- Scan the key
        key, startPos = json.decode(s,startPos)
        assert(startPos<=stringLen, 'JSON string ended unexpectedly searching for value of key ' .. key)
        startPos = decode_scanWhitespace(s,startPos)
        assert(startPos<=stringLen, 'JSON string ended unexpectedly searching for value of key ' .. key)
        assert(string.sub(s,startPos,startPos)==':','JSON object key-value assignment mal-formed at ' .. startPos)
        startPos = decode_scanWhitespace(s,startPos+1)
        assert(startPos<=stringLen, 'JSON string ended unexpectedly searching for value of key ' .. key)
        value, startPos = json.decode(s,startPos)
        object[key]=value
      until false	-- infinite loop while key-value pairs are found
    end
    
    -- START SoniEx2
    -- Initialize some things used by decode_scanString
    -- You know, for efficiency
    local escapeSequences = {
      ["\\t"] = "\t",
      ["\\f"] = "\f",
      ["\\r"] = "\r",
      ["\\n"] = "\n",
      ["\\b"] = "\b"
    }
    setmetatable(escapeSequences, {__index = function(t,k)
      -- skip "\" aka strip escape
      return string.sub(k,2)
    end})
    -- END SoniEx2
    
    --- Scans a JSON string from the opening inverted comma or single quote to the
    -- end of the string.
    -- Returns the string extracted as a Lua string,
    -- and the position of the next non-string character
    -- (after the closing inverted comma or single quote).
    -- @param s The string being scanned.
    -- @param startPos The starting position of the scan.
    -- @return string, int The extracted string as a Lua string, and the next character to parse.
    function decode_scanString(s,startPos)
      assert(startPos, 'decode_scanString(..) called without start position')
      local startChar = string.sub(s,startPos,startPos)
      -- START SoniEx2
      -- PS: I don't think single quotes are valid JSON
      assert(startChar == [["]] or startChar == [[']],'decode_scanString called for a non-string')
      --assert(startPos, "String decoding failed: missing closing " .. startChar .. " for string at position " .. oldStart)
      local t = {}
      local i,j = startPos,startPos
      while string.find(s, startChar, j+1) ~= j+1 do
        local oldj = j
        i,j = string.find(s, "\\.", j+1)
        local x,y = string.find(s, startChar, oldj+1)
        if not i or x < i then
          i,j = x,y-1
        end
        table.insert(t, string.sub(s, oldj+1, i-1))
        if string.sub(s, i, j) == "\\u" then
          local a = string.sub(s,j+1,j+4)
          j = j + 4
          local n = tonumber(a, 16)
          assert(n, "String decoding failed: bad Unicode escape " .. a .. " at position " .. i .. " : " .. j)
          -- math.floor(x/2^y) == lazy right shift
          -- a % 2^b == bitwise_and(a, (2^b)-1)
          -- 64 = 2^6
          -- 4096 = 2^12 (or 2^6 * 2^6)
          local x
          if n < 0x80 then
            x = string.char(n % 0x80)
          elseif n < 0x800 then
            -- [110x xxxx] [10xx xxxx]
            x = string.char(0xC0 + (math.floor(n/64) % 0x20), 0x80 + (n % 0x40))
          else
            -- [1110 xxxx] [10xx xxxx] [10xx xxxx]
            x = string.char(0xE0 + (math.floor(n/4096) % 0x10), 0x80 + (math.floor(n/64) % 0x40), 0x80 + (n % 0x40))
          end
          table.insert(t, x)
        else
          table.insert(t, escapeSequences[string.sub(s, i, j)])
        end
      end
      table.insert(t,string.sub(j, j+1))
      assert(string.find(s, startChar, j+1), "String decoding failed: missing closing " .. startChar .. " at position " .. j .. "(for string at position " .. startPos .. ")")
      return table.concat(t,""), j+2
      -- END SoniEx2
    end
    
    --- Scans a JSON string skipping all whitespace from the current start position.
    -- Returns the position of the first non-whitespace character, or nil if the whole end of string is reached.
    -- @param s The string being scanned
    -- @param startPos The starting position where we should begin removing whitespace.
    -- @return int The first position where non-whitespace was encountered, or string.len(s)+1 if the end of string
    -- was reached.
    function decode_scanWhitespace(s,startPos)
      local whitespace=" \n\r\t"
      local stringLen = string.len(s)
      while ( string.find(whitespace, string.sub(s,startPos,startPos), 1, true)  and startPos <= stringLen) do
        startPos = startPos + 1
      end
      return startPos
    end
    
    --- Encodes a string to be JSON-compatible.
    -- This just involves back-quoting inverted commas, back-quotes and newlines, I think ;-)
    -- @param s The string to return as a JSON encoded (i.e. backquoted string)
    -- @return The string appropriately escaped.
    
    local escapeList = {
        ['"']  = '\\"',
        ['\\'] = '\\\\',
        ['/']  = '\\/', 
        ['\b'] = '\\b',
        ['\f'] = '\\f',
        ['\n'] = '\\n',
        ['\r'] = '\\r',
        ['\t'] = '\\t'
    }
    
    function json_private.encodeString(s)
     local s = tostring(s)
     return s:gsub(".", function(c) return escapeList[c] end) -- SoniEx2: 5.0 compat
    end
    
    -- Determines whether the given Lua type is an array or a table / dictionary.
    -- We consider any table an array if it has indexes 1..n for its n items, and no
    -- other data in the table.
    -- I think this method is currently a little 'flaky', but can't think of a good way around it yet...
    -- @param t The table to evaluate as an array
    -- @return boolean, number True if the table can be represented as an array, false otherwise. If true,
    -- the second returned value is the maximum
    -- number of indexed elements in the array. 
    function isArray(t)
      -- Next we count all the elements, ensuring that any non-indexed elements are not-encodable 
      -- (with the possible exception of 'n')
      local maxIndex = 0
      for k,v in pairs(t) do
        if (type(k)=='number' and math.floor(k)==k and 1<=k) then	-- k,v is an indexed pair
          if (not isEncodable(v)) then return false end	-- All array elements must be encodable
          maxIndex = math.max(maxIndex,k)
        else
          if (k=='n') then
            if v ~= table.getn(t) then return false end  -- False if n does not hold the number of elements
          else -- Else of (k=='n')
            if isEncodable(v) then return false end
          end  -- End of (k~='n')
        end -- End of k,v not an indexed pair
      end  -- End of loop across all pairs
      return true, maxIndex
    end
    
    --- Determines whether the given Lua object / table / variable can be JSON encoded. The only
    -- types that are JSON encodable are: string, boolean, number, nil, table and json.null.
    -- In this implementation, all other types are ignored.
    -- @param o The object to examine.
    -- @return boolean True if the object should be JSON encoded, false if it should be ignored.
    function isEncodable(o)
      local t = type(o)
      return (t=='string' or t=='boolean' or t=='number' or t=='nil' or t=='table') or (t=='function' and o==null) 
    end
    
    return json

测试：

\--\[\[  
JSON4Lua example script.  
Demonstrates the simple functionality of the json module.  
\]\]--  
json = require('myjson')  
  
  
\-- Object to JSON encode  
test = \{  
  one='first',two='second',three=\{2,3,5\}  
\}  
  
\--table转json  
jsonTest = json.encode(test)  
print('JSON\_str=: ' .. jsonTest)  
  
\-- Now JSON decode the json string  
result = json.decode(jsonTest)   --json转table  
  
print ("decoded\_json:")  
table.foreach(result, print)  
  
  
print ("The decoded table result.three")  
table.foreach(result.three, print)

lua-json

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