319 lines
7.9 KiB
Lua
319 lines
7.9 KiB
Lua
--
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-- variant of https://github.com/rxi/json.lua decoding from channels of
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-- characters rather than strings
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--
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-- Copyright (c) 2020 rxi
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--
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-- Permission is hereby granted, free of charge, to any person obtaining a copy of
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-- this software and associated documentation files (the "Software"), to deal in
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-- the Software without restriction, including without limitation the rights to
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-- use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
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-- of the Software, and to permit persons to whom the Software is furnished to do
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-- so, subject to the following conditions:
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--
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-- The above copyright notice and this permission notice shall be included in all
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-- copies or substantial portions of the Software.
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--
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-- THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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-- IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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-- FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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-- AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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-- LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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-- OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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-- SOFTWARE.
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--
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local jsonf = { _version = "0.1.2" }
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local escape_char_map = {
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[ "\\" ] = "\\",
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[ "\"" ] = "\"",
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[ "\b" ] = "b",
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[ "\f" ] = "f",
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[ "\n" ] = "n",
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[ "\r" ] = "r",
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[ "\t" ] = "t",
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}
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local escape_char_map_inv = { [ "/" ] = "/" }
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for k, v in pairs(escape_char_map) do
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escape_char_map_inv[v] = k
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end
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-------------------------------------------------------------------------------
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-- Decode
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-------------------------------------------------------------------------------
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local function create_set(...)
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local res = {}
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for i = 1, select("#", ...) do
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res[ select(i, ...) ] = true
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end
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return res
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end
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local space_chars = create_set(" ", "\t", "\r", "\n")
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local delim_chars = create_set(" ", "\t", "\r", "\n", "]", "}", ",")
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local escape_chars = create_set("\\", "/", '"', "b", "f", "n", "r", "t", "u")
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local literals = create_set("true", "false", "null")
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local literal_map = {
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[ "true" ] = true,
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[ "false" ] = false,
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[ "null" ] = nil,
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}
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local function skip_spaces(infile)
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while true do
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local c = infile.read(1)
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if c == nil then break end
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if space_chars[c] == nil then return c end
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end
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return nil
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end
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local function next_chars(infile, set, firstc)
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local res = {firstc}
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local nextc
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while true do
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nextc = infile.read(1)
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if nextc == nil then break end
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if set[nextc] then break end
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table.insert(res, nextc)
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end
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return table.concat(res), nextc
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end
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local function codepoint_to_utf8(n)
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-- http://scripts.sil.org/cms/scripts/page.php?site_id=nrsi&id=iws-appendixa
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local f = math.floor
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if n <= 0x7f then
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return string.char(n)
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elseif n <= 0x7ff then
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return string.char(f(n / 64) + 192, n % 64 + 128)
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elseif n <= 0xffff then
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return string.char(f(n / 4096) + 224, f(n % 4096 / 64) + 128, n % 64 + 128)
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elseif n <= 0x10ffff then
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return string.char(f(n / 262144) + 240, f(n % 262144 / 4096) + 128,
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f(n % 4096 / 64) + 128, n % 64 + 128)
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end
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error( string.format("invalid unicode codepoint '%x'", n) )
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end
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local function parse_unicode_escape(s)
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local n1 = tonumber( s:sub(1, 4), 16 )
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local n2 = tonumber( s:sub(7, 10), 16 )
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-- Surrogate pair?
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if n2 then
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return codepoint_to_utf8((n1 - 0xd800) * 0x400 + (n2 - 0xdc00) + 0x10000)
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else
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return codepoint_to_utf8(n1)
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end
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end
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local function parse_string(infile, firstc)
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local res = {}
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while true do
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local chr = infile.read(1)
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if chr == nil then break end
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local x = chr:byte()
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if x < 32 then
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error("control character in string")
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elseif chr == '\\' then
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local c = infile.read(1)
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if c == nil then break end
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if c == "u" then
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local hex = ''
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c = infile.read(1)
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if c == nil then break end
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hex = hex..c
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c = infile.read(1)
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if c == nil then break end
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hex = hex..c
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c = infile.read(1)
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if c == nil then break end
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hex = hex..c
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c = infile.read(1)
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if c == nil then break end
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hex = hex..c
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if not hex:match('^%x%x%x%x') then
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error('invalid unicode escape in string')
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end
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table.insert(res, parse_unicode_escape(hex))
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else
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if not escape_chars[c] then
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error("invalid escape char '" .. c .. "' in string")
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end
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table.insert(res, escape_char_map_inv[c])
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end
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elseif chr == '"' then
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return table.concat(res), infile.read(1)
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else
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table.insert(res, chr)
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end
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end
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error("expected closing quote for string")
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end
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local function parse_number(infile, firstc)
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--? print('parse_number')
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local res = {firstc}
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local nextc
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while true do
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nextc = infile.read(1)
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if nextc == nil then break end
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if delim_chars[nextc] then break end
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table.insert(res, nextc)
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end
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local s = table.concat(res)
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--? print('parse_number: '..s)
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local n = tonumber(s)
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if not n then
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error("invalid number '" .. s .. "'")
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end
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return n, nextc
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end
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local function parse_literal(infile, firstc)
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--? print('parse_literal')
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local word, nextc = next_chars(infile, delim_chars, firstc)
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if not literals[word] then
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error("invalid literal '" .. word .. "'")
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end
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--? print('parse_literal: '..word)
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return literal_map[word], nextc
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end
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local function parse_array(infile, firstc)
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local res = {}
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local x, nextc
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while true do
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nextc = skip_spaces(infile)
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if nextc == nil then
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error("expected ']' or ','")
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end
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if nextc == ']' then break end -- empty array
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-- Read token
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x, nextc = parse(infile, nextc)
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--? print('array elem: '..str(x))
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table.insert(res, x)
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-- Next token
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if space_chars[nextc] then
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nextc = skip_spaces(infile)
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end
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if nextc == ']' then break end
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if nextc ~= ',' then
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error("expected ']' or ','")
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end
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end
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return res, skip_spaces(infile)
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end
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local function parse_object(infile, firstc)
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local res = {}
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local nextc
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while true do
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local key, val
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nextc = skip_spaces(infile)
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if nextc == nil then
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error("expected '}' or ','")
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end
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if nextc == '}' then break end -- empty object
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-- Read key
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if nextc ~= '"' then
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error("expected string for key")
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end
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key, nextc = parse(infile, nextc)
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--? print('object key: '..key)
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-- Read ':' delimiter
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if space_chars[nextc] then
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nextc = skip_spaces(infile)
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end
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if nextc ~= ':' then
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error("expected ':' after key")
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end
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-- Read value
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nextc = skip_spaces(infile)
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val, nextc = parse(infile, nextc)
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--? print('object val: '..str(val))
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-- Set
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res[key] = val
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-- Next token
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if space_chars[nextc] then
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nextc = skip_spaces(infile)
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end
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if nextc == '}' then break end
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if nextc ~= ',' then
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error("expected '}' or ','")
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end
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end
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return res, skip_spaces(infile)
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end
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local char_func_map = {
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[ '"' ] = parse_string,
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[ "0" ] = parse_number,
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[ "1" ] = parse_number,
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[ "2" ] = parse_number,
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[ "3" ] = parse_number,
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[ "4" ] = parse_number,
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[ "5" ] = parse_number,
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[ "6" ] = parse_number,
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[ "7" ] = parse_number,
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[ "8" ] = parse_number,
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[ "9" ] = parse_number,
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[ "-" ] = parse_number,
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[ "t" ] = parse_literal,
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[ "f" ] = parse_literal,
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[ "n" ] = parse_literal,
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[ "[" ] = parse_array,
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[ "{" ] = parse_object,
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}
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parse = function(infile, chr)
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local f = char_func_map[chr]
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if f then
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return f(infile, chr)
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end
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error("unexpected character '" .. chr .. "'")
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end
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function jsonf.decode(infile)
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local firstc = skip_spaces(infile)
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local res, nextc = parse(infile, firstc)
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if nextc then
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error("trailing garbage")
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end
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return res
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end
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-- test cases:
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-- "abc"
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-- 234
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-- true
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-- false
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-- nil
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-- ["abc", 234, true, false, nil]
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-- ["abc", 234, true, false, nil
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-- ["abc",
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-- {"abc": 234, "def": true}
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return jsonf
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