parser.lua


1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75

-- Copyright (c) 2021 Florian Fischer. All rights reserved.
-- Use of this source code is governed by a MIT license found in the LICENSE file.

-- Parse 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 on at the beginning
-- and one at the end

local function add(p, data)
  p.data = p.data .. data

  -- we have not seen a complete header in data yet
  if not p.exp_len then
    -- search for the end of a header
    -- LSP message format: 'header\r\n\r\nbody'
    local header_end, content_start = p.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 = p.data:sub(1, header_end)

    -- extract content length from the header
    p.exp_len = tonumber(header:match('%d+'))
    if not p.exp_len then
      return 'invalid header in data: ' .. p.data
    end

    -- consume header from data
    p.data = p.data:sub(content_start + 1)
  end

  local data_avail = string.len(p.data)
  -- we have no complete message yet -> await more data
  if p.exp_len > data_avail then
    return
  end

  local complete_msg = p.data:sub(1, p.exp_len)
  table.insert(p.msgs, complete_msg)

  -- consume complete_msg from data
  p.data = p.data:sub(p.exp_len + 1)

  local leftover = data_avail - p.exp_len

  -- reset exp_len to search for a new header
  p.exp_len = nil

  if leftover > 0 then
    return p:add('')
  end
end

local function get_msgs(p)
  local msgs = p.msgs
  p.msgs = {}
  return msgs
end

local function Parser()
  local parser = {
    add = add,
    get_msgs = get_msgs,
    exp_len = nil,
    data = '',
    msgs = {},
  }
  return parser
end

return {Parser = Parser}