feat: first draft

lua/oil/adapters/files/permissions.lua

@@ -0,0 +1,103 @@
+local M = {}
+
+---@param exe_modifier nil|string
+---@param num integer
+---@return string
+local function perm_to_str(exe_modifier, num)
+  local str = (bit.band(num, 4) ~= 0 and "r" or "-") .. (bit.band(num, 2) ~= 0 and "w" or "-")
+  if exe_modifier then
+    if bit.band(num, 1) ~= 0 then
+      return str .. exe_modifier
+    else
+      return str .. exe_modifier:upper()
+    end
+  else
+    return str .. (bit.band(num, 1) ~= 0 and "x" or "-")
+  end
+end
+
+---@param mode integer
+---@return string
+M.mode_to_str = function(mode)
+  local extra = bit.rshift(mode, 9)
+  return perm_to_str(bit.band(extra, 4) ~= 0 and "s", bit.rshift(mode, 6))
+    .. perm_to_str(bit.band(extra, 2) ~= 0 and "s", bit.rshift(mode, 3))
+    .. perm_to_str(bit.band(extra, 1) ~= 0 and "t", mode)
+end
+
+---@param mode integer
+---@return string
+M.mode_to_octal_str = function(mode)
+  local mask = 7
+  return tostring(bit.band(mask, bit.rshift(mode, 9)))
+    .. tostring(bit.band(mask, bit.rshift(mode, 6)))
+    .. tostring(bit.band(mask, bit.rshift(mode, 3)))
+    .. tostring(bit.band(mask, mode))
+end
+
+---@param str string String of 3 characters
+---@return integer
+local function str_to_mode(str)
+  local r, w, x = unpack(vim.split(str, ""))
+  local mode = 0
+  if r == "r" then
+    mode = bit.bor(mode, 4)
+  elseif r ~= "-" then
+    return nil
+  end
+  if w == "w" then
+    mode = bit.bor(mode, 2)
+  elseif w ~= "-" then
+    return nil
+  end
+  -- t means sticky and executable
+  -- T means sticky, not executable
+  -- s means setuid/setgid and executable
+  -- S means setuid/setgid and not executable
+  if x == "x" or x == "t" or x == "s" then
+    mode = bit.bor(mode, 1)
+  elseif x ~= "-" and x ~= "T" and x ~= "S" then
+    return nil
+  end
+  return mode
+end
+
+---@param perm string
+---@return integer
+local function parse_extra_bits(perm)
+  perm = perm:lower()
+  local mode = 0
+  if perm:sub(3, 3) == "s" then
+    mode = bit.bor(mode, 4)
+  end
+  if perm:sub(6, 6) == "s" then
+    mode = bit.bor(mode, 2)
+  end
+  if perm:sub(9, 9) == "t" then
+    mode = bit.bor(mode, 1)
+  end
+  return mode
+end
+
+---@param line string
+---@return nil|integer
+---@return nil|string
+M.parse = function(line)
+  local strval, rem = line:match("^([r%-][w%-][xsS%-][r%-][w%-][xsS%-][r%-][w%-][xtT%-])%s*(.*)$")
+  if not strval then
+    return
+  end
+  local user_mode = str_to_mode(strval:sub(1, 3))
+  local group_mode = str_to_mode(strval:sub(4, 6))
+  local any_mode = str_to_mode(strval:sub(7, 9))
+  local extra = parse_extra_bits(strval)
+  if not user_mode or not group_mode or not any_mode then
+    return
+  end
+  local mode = bit.bor(bit.lshift(user_mode, 6), bit.lshift(group_mode, 3))
+  mode = bit.bor(mode, any_mode)
+  mode = bit.bor(mode, bit.lshift(extra, 9))
+  return mode, rem
+end
+
+return M