further large table optimizations

1. s:get_aligned_rows(): getting 2 last rows is enough for having been
   formatted tables
2. vimwiki#tbl#get_cells(): using faster strpart() instead concatenating
   every new character into variables cell and quote
3. checking by getline() whether the line was changed before setline()
   does matter on slower computers

autoload/vimwiki/tbl.vim

@@ -124,11 +124,10 @@ function! s:create_row_sep(cols) "{{{
   return row
 endfunction "}}}
 
-function! vimwiki#tbl#get_cells(line) "{{{
+function! vimwiki#tbl#get_cells(line, ...) "{{{
   let result = []
-  let cell = ''
-  let quote = ''
   let state = 'NONE'
+  let cell_start = -1
 
   " 'Simple' FSM
   for idx in range(strlen(a:line))
@@ -136,44 +135,39 @@ function! vimwiki#tbl#get_cells(line) "{{{
     let ch = a:line[idx]
     if state == 'NONE'
       if ch == '|'
+        let cell_start = idx + 1
         let state = 'CELL'
       endif
     elseif state == 'CELL'
       if ch == '[' || ch == '{'
         let state = 'BEFORE_QUOTE_START'
-        let quote = ch
       elseif ch == '|'
-        call add(result, vimwiki#u#trim(cell))
-        let cell = ""
-      else
-        let cell .= ch
+        let cell = strpart(a:line, cell_start, idx - cell_start)
+        if a:0 && a:1
+          let cell = substitute(cell, '^ \(.*\) $', '\1', '')
+        else
+          let cell = vimwiki#u#trim(cell)
+        endif
+        call add(result, cell)
+        let cell_start = idx + 1
       endif
     elseif state == 'BEFORE_QUOTE_START'
       if ch == '[' || ch == '{'
         let state = 'QUOTE'
-        let quote .= ch
       else
         let state = 'CELL'
-        let cell .= quote.ch
-        let quote = ''
       endif
     elseif state == 'QUOTE'
       if ch == ']' || ch == '}'
         let state = 'BEFORE_QUOTE_END'
       endif
-      let quote .= ch
     elseif state == 'BEFORE_QUOTE_END'
       if ch == ']' || ch == '}'
         let state = 'CELL'
       endif
-      let cell .= quote.ch
-      let quote = ''
     endif
   endfor
 
-  if cell.quote != ''
-    call add(result, vimwiki#u#trim(cell.quote, '|'))
-  endif
   return result
 endfunction "}}}
 
@@ -201,7 +195,7 @@ function! s:get_indent(lnum) "{{{
   return indent
 endfunction " }}}
 
-function! s:get_rows(lnum) "{{{
+function! s:get_rows(lnum, ...) "{{{
   if !s:is_table(getline(a:lnum))
     return
   endif
@@ -210,7 +204,9 @@ function! s:get_rows(lnum) "{{{
   let lower_rows = []
 
   let lnum = a:lnum - 1
-  while lnum >= 1
+  let depth = a:0 > 0 ? a:1 : 0
+  let ldepth = 0
+  while lnum >= 1 && (depth == 0 || ldepth < depth)
     let line = getline(lnum)
     if s:is_table(line)
       call add(upper_rows, [lnum, line])
@@ -218,6 +214,7 @@ function! s:get_rows(lnum) "{{{
       break
     endif
     let lnum -= 1
+    let ldepth += 1
   endwhile
   call reverse(upper_rows)
 
@@ -229,6 +226,9 @@ function! s:get_rows(lnum) "{{{
     else
       break
     endif
+    if depth > 0
+      break
+    endif
     let lnum += 1
   endwhile
 
@@ -237,7 +237,8 @@ endfunction "}}}
 
 function! s:get_cell_max_lens(lnum, ...) "{{{
   let max_lens = {}
-  for [lnum, row] in s:get_rows(a:lnum)
+  let rows = a:0 > 2 ? a:3 : s:get_rows(a:lnum)
+  for [lnum, row] in rows
     if s:is_separator(row)
       continue
     endif
@@ -255,13 +256,32 @@ function! s:get_cell_max_lens(lnum, ...) "{{{
 endfunction "}}}
 
 function! s:get_aligned_rows(lnum, col1, col2) "{{{
-  let rows = s:get_rows(a:lnum)
+  " getting 2 last rows is enough for having been formatted tables
+  let depth = 2
+  let rows = s:get_rows(a:lnum, depth)
   let startlnum = rows[0][0]
   let cells = []
-  for [lnum, row] in rows
-    call add(cells, vimwiki#tbl#get_cells(row))
-  endfor
-  let max_lens = s:get_cell_max_lens(a:lnum, cells, startlnum)
+  let max_lens = {}
+  let lrows = len(rows)
+  if lrows == depth + 1
+    let i = 1
+    for [lnum, row] in rows
+      call add(cells, vimwiki#tbl#get_cells(row, i == lrows - 1 ? 0 : 1))
+      let i += 1
+    endfor
+    let max_lens = s:get_cell_max_lens(a:lnum, cells, startlnum, rows)
+    let fst_lens = s:get_cell_max_lens(a:lnum, cells, startlnum, rows[0:0])
+    if max_lens != fst_lens
+      " all the table must be re-formatted
+      let rows = s:get_rows(a:lnum)
+      let startlnum = rows[0][0]
+      let cells = []
+      for [lnum, row] in rows
+        call add(cells, vimwiki#tbl#get_cells(row))
+      endfor
+      let max_lens = s:get_cell_max_lens(a:lnum, cells, startlnum, rows)
+    endif
+  endif
   let result = []
   for [lnum, row] in rows
     if s:is_separator(row)
@@ -520,7 +540,9 @@ function! vimwiki#tbl#format(lnum, ...) "{{{
 
   for [lnum, row] in s:get_aligned_rows(a:lnum, col1, col2)
     let row = indentstring.row
-    call setline(lnum, row)
+    if getline(lnum) != row
+      call setline(lnum, row)
+    endif
   endfor
   
   let &tw = s:textwidth