how to close all buffers in vim code example

Example: how to close current buffer in vim

" Delete buffer while keeping window layout (don't close buffer's windows).
" Version 2008-11-18 from http://vim.wikia.com/wiki/VimTip165
if v:version < 700 || exists('loaded_bclose') || &cp
  finish
endif
let loaded_bclose = 1
if !exists('bclose_multiple')
  let bclose_multiple = 1
endif

" Display an error message.
function! s:Warn(msg)
  echohl ErrorMsg
  echomsg a:msg
  echohl NONE
endfunction

" Command ':Bclose' executes ':bd' to delete buffer in current window.
" The window will show the alternate buffer (Ctrl-^) if it exists,
" or the previous buffer (:bp), or a blank buffer if no previous.
" Command ':Bclose!' is the same, but executes ':bd!' (discard changes).
" An optional argument can specify which buffer to close (name or number).
function! s:Bclose(bang, buffer)
  if empty(a:buffer)
    let btarget = bufnr('%')
  elseif a:buffer =~ '^\d\+$'
    let btarget = bufnr(str2nr(a:buffer))
  else
    let btarget = bufnr(a:buffer)
  endif
  if btarget < 0
    call s:Warn('No matching buffer for '.a:buffer)
    return
  endif
  if empty(a:bang) && getbufvar(btarget, '&modified')
    call s:Warn('No write since last change for buffer '.btarget.' (use :Bclose!)')
    return
  endif
  " Numbers of windows that view target buffer which we will delete.
  let wnums = filter(range(1, winnr('$')), 'winbufnr(v:val) == btarget')
  if !g:bclose_multiple && len(wnums) > 1
    call s:Warn('Buffer is in multiple windows (use ":let bclose_multiple=1")')
    return
  endif
  let wcurrent = winnr()
  for w in wnums
    execute w.'wincmd w'
    let prevbuf = bufnr('#')
    if prevbuf > 0 && buflisted(prevbuf) && prevbuf != btarget
      buffer #
    else
      bprevious
    endif
    if btarget == bufnr('%')
      " Numbers of listed buffers which are not the target to be deleted.
      let blisted = filter(range(1, bufnr('$')), 'buflisted(v:val) && v:val != btarget')
      " Listed, not target, and not displayed.
      let bhidden = filter(copy(blisted), 'bufwinnr(v:val) < 0')
      " Take the first buffer, if any (could be more intelligent).
      let bjump = (bhidden + blisted + [-1])[0]
      if bjump > 0
        execute 'buffer '.bjump
      else
        execute 'enew'.a:bang
      endif
    endif
  endfor
  execute 'bdelete'.a:bang.' '.btarget
  execute wcurrent.'wincmd w'
endfunction
command! -bang -complete=buffer -nargs=? Bclose call <SID>Bclose(<q-bang>, <q-args>)
nnoremap <silent> <Leader>bd :Bclose<CR>