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Read base64 raw string/email in Vim

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Tip 1134 Printable Monobook Previous Next

created 2006 · complexity intermediate · author TonyLiu · version 6.0

Although this tip is very useful for me, but I think it is somehow complex for needing a outter command tool. The most important things today I do with the internet is receiving and sending emails.

But sometimes I just got some base64 raw string like aGFwcHkgdmltbWluZyA=.

Here is how to use a system command to read it in Vim directly.

You need a program like decode64.exe to encode/decode strings. You can can download it from (unfortunately I tested it under WIN2K/2003 only).

Put the decode64.exe/base64dll.dll somewhere in your %path% enviroment variable.

You need write some script in your vimrc:

vnoremap ;mme "ey:call CalcEncode64(1)<CR>
vnoremap ;mmd "ey:call CalcEncode64(0)<CR>
function! CalcEncode64(pattern) " #region
  let has_equal = 0
  let l:rege=@e
  let l:regk=@k
  let l:regl=@l
  " 1=encode 0=decode
  let l:elen = strlen(@e) " TOTAL length
  let l:rightmark=strpart(@e, l:elen-4, 3)
  if l:rightmark == "==="
    let @e = strpart(@e,0,l:elen-4)
    let has_equal = 1
  if a:pattern == 1
    let @k = @e
  elseif a:pattern == 0
    let @k = substitute (@e, "\n", "", "g")
    return ""
  let l:nsize = 1200 " nsize must be multiples of 4 (byte, for base64 code 4 byte is an unit)
  let l:len = strlen(@k) " TOTAL length
  let l:vleft=l:len/l:nsize " the .n block
  let l:vright=l:len/l:nsize " the .n block total
  let l:answerstr = ""
  while 0< l:vleft
    let l:answerstr = l:answerstr . s:normalExecode(l:vleft,l:nsize,l:len,l:vright,a:pattern)
    let l:vleft = l:vleft-1
  " last block < nsize byte
  let l:answerstr = l:answerstr . s:lastExecode(l:vleft,l:nsize,l:len,l:vright,a:pattern)
  let @k=l:answerstr
  if has_equal == 1
    :normal `>"kp
    echo "answer = ".l:answerstr
  let @l=l:regl
  let @k=l:regk
  let @e=l:rege
endfunction " #endregion

function! s:lastExecode(vleft,nsize,len,vright,pattern) " #region
  let l:answer=""
  let l:nstart=a:nsize*a:vright
  let @l=strpart(@k, l:nstart, a:len-a:nsize*a:vright)
  let l:answer = s:ExeDecode(a:vleft,a:nsize,a:len,a:vright,a:pattern)
  return l:answer
endfunction " #endregion

function! s:normalExecode(vleft,nsize,len,vright,pattern) " #region
  let l:nstart=(a:vright-a:vleft)*a:nsize
  let @l=strpart(@k, l:nstart, a:nsize)
  let l:answer = s:ExeDecode(a:vleft,a:nsize,a:len,a:vright,a:pattern)
  return l:answer
endfunction " #endregion

function! s:ExeDecode(vleft,nsize,len,vright,pattern) " #region
  " 1=encode 0=decode
  " TODO: when encode,the string must NOT contains any char of pipe '|'
  " which conflicts whith the windows shell command, I really dont know
  " how to deal with it.
  if a:pattern == 1
    let @l = substitute (@l, "\n", "", "g")
    let @l = substitute (@l, "\r", "", "g")
    let l:answer = system("echo " . @l . " \| ENCODE64.exe ")
    let @*="echo " . @l . " \| ENCODE64.exe "
  elseif a:pattern == 0
    "let l:answer = system("echo " . @l . " \| DECODE64.exe -D")
    let l:answer = system("echo " . @l . " \| ENCODE64.exe -D")
    return ""
  return l:answer
endfunction " #endregion

Now open a new gvim instance and copy and paste aGFwcHkgdmltbWluZyA= into it. Use virtual mode to select it, then press ;mmd

You can see the output text at the bottom of the window: answer = happy vimming

Sometimes the raw base64 string is encoded from Unicode original string. If you want to read it please type:

:set enc=utf8

first. See :help 'enc'.


It's not really acceptable for the Vim Tips wiki to link to unsupported executables with no source. Who knows what the code does? Besides, this tip is far too long and complex when all it does is to run an unknown executable with a number of shortcomings (see the comments above and the readme with the zip file).

Maybe you would like to install Ruby some time.

:ruby require "base64"
:.rubydo $_=Base64.decode64 $_

or with Perl

:perl require MIME::Base64
:.perldo $_=MIME::Base64::decode($_)

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