Merge pull request #32686 from lewis6991/lsp-rpc-perf

perf(lsp): improve rpc loop performance (with shim)

2 files changed, 147 insertions, 98 deletions

diff --git a/runtime/lua/vim/_stringbuffer.lua b/runtime/lua/vim/_stringbuffer.lua
new file mode 100644
index 0000000000..92965ee54d
--- /dev/null
+++ b/runtime/lua/vim/_stringbuffer.lua
@@ -0,0 +1,110 @@
+-- Basic shim for LuaJIT's stringbuffer.
+-- Note this does not implement the full API.
+-- This is intentionally internal-only. If we want to expose it, we should
+-- reimplement this a userdata and ship it as `string.buffer`
+-- (minus the FFI stuff) for Lua 5.1.
+local M = {}
+
+local has_strbuffer, strbuffer = pcall(require, 'string.buffer')
+
+if has_strbuffer then
+  M.new = strbuffer.new
+
+  -- Lua 5.1 does not have __len metamethod so we need to provide a len()
+  -- function to use instead.
+
+  --- @param buf vim._stringbuffer
+  --- @return integer
+  function M.len(buf)
+    return #buf
+  end
+
+  return M
+end
+
+--- @class vim._stringbuffer
+--- @field private buf string[]
+--- @field package len integer absolute length of the `buf`
+--- @field package skip_ptr integer
+local StrBuffer = {}
+StrBuffer.__index = StrBuffer
+
+--- @return string
+function StrBuffer:tostring()
+  if #self.buf > 1 then
+    self.buf = { table.concat(self.buf) }
+  end
+
+  -- assert(self.len == #(self.buf[1] or ''), 'len mismatch')
+
+  if self.skip_ptr > 0 then
+    if self.buf[1] then
+      self.buf[1] = self.buf[1]:sub(self.skip_ptr + 1)
+      self.len = self.len - self.skip_ptr
+    end
+    self.skip_ptr = 0
+  end
+
+  -- assert(self.len == #(self.buf[1] or ''), 'len mismatch')
+
+  return self.buf[1] or ''
+end
+
+StrBuffer.__tostring = StrBuffer.tostring
+
+--- @private
+--- Efficiently peak at the first `n` characters of the buffer.
+--- @param n integer
+--- @return string
+function StrBuffer:_peak(n)
+  local skip, buf1 = self.skip_ptr, self.buf[1]
+  if buf1 and (n + skip) < #buf1 then
+    return buf1:sub(skip + 1, skip + n)
+  end
+  return self:tostring():sub(1, n)
+end
+
+--- @param chunk string
+function StrBuffer:put(chunk)
+  local s = tostring(chunk)
+  self.buf[#self.buf + 1] = s
+  self.len = self.len + #s
+  return self
+end
+
+--- @param str string
+function StrBuffer:set(str)
+  return self:reset():put(str)
+end
+
+--- @param n integer
+--- @return string
+function StrBuffer:get(n)
+  local r = self:_peak(n)
+  self:skip(n)
+  return r
+end
+
+--- @param n integer
+function StrBuffer:skip(n)
+  self.skip_ptr = math.min(self.len, self.skip_ptr + n)
+  return self
+end
+
+function StrBuffer:reset()
+  self.buf = {}
+  self.skip_ptr = 0
+  self.len = 0
+  return self
+end
+
+function M.new()
+  return setmetatable({}, StrBuffer):reset()
+end
+
+--- @param buf vim._stringbuffer
+function M.len(buf)
+  return buf.len - buf.skip_ptr
+end
+
+return M
diff --git a/runtime/lua/vim/lsp/rpc.lua b/runtime/lua/vim/lsp/rpc.lua
index d31d94cab7..637cda84d3 100644
--- a/runtime/lua/vim/lsp/rpc.lua
+++ b/runtime/lua/vim/lsp/rpc.lua
@@ -5,8 +5,8 @@ local validate, schedule_wrap = vim.validate, vim.schedule_wrap
 
 --- Embeds the given string into a table and correctly computes `Content-Length`.
 ---
----@param message string
----@return string message with `Content-Length` attribute
+--- @param message string
+--- @return string message with `Content-Length` attribute
 local function format_message_with_content_length(message)
   return table.concat({
     'Content-Length: ',
@@ -16,104 +16,21 @@ local function format_message_with_content_length(message)
   })
 end
 
----@class (private) vim.lsp.rpc.Headers: {string: any}
----@field content_length integer
-
---- Parses an LSP Message's header
+--- Extract content-length from the header
 ---
----@param header string The header to parse.
----@return vim.lsp.rpc.Headers#parsed headers
-local function parse_headers(header)
-  assert(type(header) == 'string', 'header must be a string')
-  --- @type vim.lsp.rpc.Headers
-  local headers = {}
-  for line in vim.gsplit(header, '\r\n', { plain = true }) do
+--- @param header string The header to parse
+--- @return integer
+local function get_content_length(header)
+  for line in header:gmatch('(.-)\r\n') do
     if line == '' then
       break
     end
-    --- @type string?, string?
-    local key, value = line:match('^%s*(%S+)%s*:%s*(.+)%s*$')
-    if key then
-      key = key:lower():gsub('%-', '_') --- @type string
-      headers[key] = value
-    else
-      log.error('invalid header line %q', line)
-      error(string.format('invalid header line %q', line))
-    end
-  end
-  headers.content_length = tonumber(headers.content_length)
-    or error(string.format('Content-Length not found in headers. %q', header))
-  return headers
-end
-
--- This is the start of any possible header patterns. The gsub converts it to a
--- case insensitive pattern.
-local header_start_pattern = ('content'):gsub('%w', function(c)
-  return '[' .. c .. c:upper() .. ']'
-end)
-
---- The actual workhorse.
-local function request_parser_loop()
-  local buffer = '' -- only for header part
-  while true do
-    -- A message can only be complete if it has a double CRLF and also the full
-    -- payload, so first let's check for the CRLFs
-    local start, finish = buffer:find('\r\n\r\n', 1, true)
-    -- Start parsing the headers
-    if start then
-      -- This is a workaround for servers sending initial garbage before
-      -- sending headers, such as if a bash script sends stdout. It assumes
-      -- that we know all of the headers ahead of time. At this moment, the
-      -- only valid headers start with "Content-*", so that's the thing we will
-      -- be searching for.
-      -- TODO(ashkan) I'd like to remove this, but it seems permanent :(
-      local buffer_start = buffer:find(header_start_pattern)
-      if not buffer_start then
-        error(
-          string.format(
-            "Headers were expected, a different response was received. The server response was '%s'.",
-            buffer
-          )
-        )
-      end
-      local headers = parse_headers(buffer:sub(buffer_start, start - 1))
-      local content_length = headers.content_length
-      -- Use table instead of just string to buffer the message. It prevents
-      -- a ton of strings allocating.
-      -- ref. http://www.lua.org/pil/11.6.html
-      ---@type string[]
-      local body_chunks = { buffer:sub(finish + 1) }
-      local body_length = #body_chunks[1]
-      -- Keep waiting for data until we have enough.
-      while body_length < content_length do
-        ---@type string
-        local chunk = coroutine.yield()
-          or error('Expected more data for the body. The server may have died.') -- TODO hmm.
-        table.insert(body_chunks, chunk)
-        body_length = body_length + #chunk
-      end
-      local last_chunk = body_chunks[#body_chunks]
-
-      body_chunks[#body_chunks] = last_chunk:sub(1, content_length - body_length - 1)
-      local rest = ''
-      if body_length > content_length then
-        rest = last_chunk:sub(content_length - body_length)
-      end
-      local body = table.concat(body_chunks)
-      -- Yield our data.
-
-      --- @type string
-      local data = coroutine.yield(headers, body)
-        or error('Expected more data for the body. The server may have died.')
-      buffer = rest .. data
-    else
-      -- Get more data since we don't have enough.
-      --- @type string
-      local data = coroutine.yield()
-        or error('Expected more data for the header. The server may have died.')
-      buffer = buffer .. data
+    local key, value = line:match('^%s*(%S+)%s*:%s*(%d+)%s*$')
+    if key and key:lower() == 'content-length' then
+      return assert(tonumber(value))
     end
   end
+  error('Content-Length not found in header: ' .. header)
 end
 
 local M = {}
@@ -232,12 +149,34 @@ local default_dispatchers = {
   end,
 }
 
+local strbuffer = require('vim._stringbuffer')
+
+local function request_parser_loop()
+  local buf = strbuffer.new()
+  while true do
+    local msg = buf:tostring()
+    local header_end = msg:find('\r\n\r\n', 1, true)
+    if header_end then
+      local header = buf:get(header_end + 1)
+      buf:skip(2) -- skip past header boundary
+      local content_length = get_content_length(header)
+      while strbuffer.len(buf) < content_length do
+        buf:put(coroutine.yield())
+      end
+      local body = buf:get(content_length)
+      buf:put(coroutine.yield(body))
+    else
+      buf:put(coroutine.yield())
+    end
+  end
+end
+
 --- @private
 --- @param handle_body fun(body: string)
 --- @param on_exit? fun()
 --- @param on_error fun(err: any)
 function M.create_read_loop(handle_body, on_exit, on_error)
-  local parse_chunk = coroutine.wrap(request_parser_loop) --[[@as fun(chunk: string?): vim.lsp.rpc.Headers?, string?]]
+  local parse_chunk = coroutine.wrap(request_parser_loop) --[[@as fun(chunk: string?): string]]
   parse_chunk()
   return function(err, chunk)
     if err then
@@ -253,9 +192,9 @@ function M.create_read_loop(handle_body, on_exit, on_error)
     end
 
     while true do
-      local headers, body = parse_chunk(chunk)
-      if headers then
-        handle_body(assert(body))
+      local body = parse_chunk(chunk)
+      if body then
+        handle_body(body)
         chunk = ''
       else
         break