Merge pull request #17 from fischerling/parser

Improve message parsing

1 files changed, 75 insertions, 0 deletions

diff --git a/parser.lua b/parser.lua
new file mode 100644
index 0000000..f1b09f5
--- /dev/null
+++ b/parser.lua
@@ -0,0 +1,75 @@
+-- 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}