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--- Stateful parser for the data send by a language server.
-- Note the chunks received may not end with the end of a message.
-- In the worst case a data chunk contains two partial messages one
-- at the beginning and one at the end.
-- @module parser
-- @author Florian Fischer
-- @license GPL-3
-- @copyright Florian Fischer 2021-2024
local parser = {}
local Parser = {}
function parser.new()
local self = {exp_len = nil, data = '', msgs = {}}
setmetatable(self, {__index = Parser})
return self
end
function Parser:add(data)
self.data = self.data .. data
-- we have not seen a complete header in data yet
if not self.exp_len then
-- search for the end of a header
-- LSP message format: header\r\n(header\r\n)?\r\nbody'
local header_end, content_start = self.data:find('\r\n\r\n')
-- header is not complete yet -> save data and wait for more
if not header_end then
return
end
-- got a complete header
local header = self.data:sub(1, header_end)
-- extract content length from the header
local length = header:match('Content%-Length: %d+')
self.exp_len = tonumber(length:match('%d+'))
if not self.exp_len then
return 'invalid header in data: ' .. self.data
end
-- consume header from data
self.data = self.data:sub(content_start + 1)
end
local data_avail = string.len(self.data)
-- we have no complete message yet -> await more data
if self.exp_len > data_avail then
return
end
local complete_msg = self.data:sub(1, self.exp_len)
table.insert(self.msgs, complete_msg)
-- consume complete_msg from data
self.data = self.data:sub(self.exp_len + 1)
local leftover = data_avail - self.exp_len
-- reset exp_len to search for a new header
self.exp_len = nil
if leftover > 0 then
return self:add('')
end
end
function Parser:get_msgs()
local msgs = self.msgs
self.msgs = {}
return msgs
end
return parser
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