perf: range string instead of regex

bench/space_or_tab.lua

@@ -0,0 +1,34 @@
+local function only_spaces_or_tabs(text)
+  for i = 1, #text do
+    local c = text:sub(i, i)
+    if c ~= ' ' and c ~= '\t' then
+      return false
+    end
+  end
+  return true
+end
+
+local function only_spaces_or_tabs_regex(text)
+  return not text:find('[^ \t]')
+end
+
+local function benchmark(func, text, iterations)
+  local start_time = os.clock()
+  for _ = 1, iterations do
+    func(text)
+  end
+  local end_time = os.clock()
+  return end_time - start_time
+end
+
+local text = '    \t\t    ' -- Example text to test
+local iterations = 1000000 -- Number of iterations for the benchmark
+
+local time1 = benchmark(only_spaces_or_tabs, text, iterations)
+local time2 = benchmark(only_spaces_or_tabs_regex, text, iterations)
+
+print('Time for only_spaces_or_tabs:', time1)
+print('Time for only_spaces_or_tabs_regex:', time2)
+
+-- Time for only_spaces_or_tabs: 0.07258
+-- Time for only_spaces_or_tabs_regex: 0.093389

lua/indentmini/init.lua

@@ -38,11 +38,17 @@ local get_sw_value, get_indent_lnum = C.get_sw_value, C.get_indent_lnum
 --- @field snapshot table<integer, Snapshot>
 local context = { snapshot = {} }
 
---- check text only has space or tab
+--- check text only has space or tab see bench/space_or_tab.lua
 --- @param text string
 --- @return boolean true only have space or tab
 local function only_spaces_or_tabs(text)
-  return text:match('^[ \t]*$') ~= nil
+  for i = 1, #text do
+    local c = text:sub(i, i)
+    if c ~= ' ' and c ~= '\t' then
+      return false
+    end
+  end
+  return true
 end
 
 --- @param bufnr integer
@@ -62,10 +68,7 @@ local function make_snapshot(lnum)
   if is_empty then
     local prev_lnum = lnum - 1
     while prev_lnum >= 1 do
-      if not context.snapshot[prev_lnum] then
-        context.snapshot[prev_lnum] = make_snapshot(prev_lnum)
-      end
-      local sp = context.snapshot[prev_lnum]
+      local sp = context.snapshot[prev_lnum] or make_snapshot(prev_lnum)
       if (not sp.is_empty and sp.indent == 0) or (sp.indent > 0) then
         if sp.indent > 0 then
           indent = sp.indent