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btoa


btoa

 

  2  definitions  found 
 
  From  The  Free  On-line  Dictionary  of  Computing  (13  Mar  01)  [foldoc]: 
 
  btoa 
 
  algorithm,  file  format>  /B  too  A/  A  {binary} 
  to  {ASCII}  conversion  utility. 
 
  btoa  is  a  {uuencode}  or  {base  64}  equivalent  which  addresses 
  some  of  the  problems  with  the  uuencode  standard  but  not  as 
  many  as  the  base  64  standard.  It  avoids  problems  that  some 
  {hosts}  have  with  spaces  (e.g.  conversion  of  groups  of  spaces 
  to  tabs)  by  not  including  them  in  its  character  set  but  may 
  still  have  problems  on  non-ASCII  systems  (e.g.  {EBCDIC}). 
 
  btoa  is  primarily  used  to  transfer  {binary  files}  between 
  systems  across  connections  which  are  not  {eight-bit  clean}, 
  e.g.  {electronic  mail}. 
 
  btoa  takes  adjacent  sets  of  four  binary  {octets}  and  encodes 
  them  as  five  ASCII  {octets}  using  ASCII  characters  '!'  through 
  to  'u'.  Special  characters  are  also  used:  'x'  marks  the 
  beginning  or  end  of  the  archive;  'z'  marks  four  consecutive 
  zeros  and  'y'  (version  5.2)  four  consecutive  spaces. 
 
  Each  group  of  four  octets  is  processed  as  a  32-bit  integer. 
  Call  this  'I'.  Let  'D'  =  85^4.  Divide  I  by  D.  Call  this 
  result  'R'.  Make  I  =  I  -  (R  *  D)  to  avoid  {overflow}  on  the 
  next  step.  Repeat,  for  values  of  D  =  85^3,  85^2,  85  and  1. 
  At  each  step,  to  convert  R  to  the  output  character  add  decimal 
  33  (output  octet  =  R  +  ASCII  value  for  '!').  Five  output 
  octets  are  produced. 
 
  btoa  provides  some  integrity  checking  in  the  form  of  a  line 
  {checksum},  and  facilities  for  patching  corrupted  downloads. 
 
  The  {algorithm}  used  by  btoa  is  more  efficient  than  uuencode 
  or  base  64.  ASCII  files  are  encoded  to  about  120%  the  size  of 
  their  binary  sources.  This  compares  with  135%  for  uuencode  or 
  base  64. 
 
  {C  source  (ftp://hpux.csc.liv.ac.uk/hpux/Misc/btoa-5.2/)} 
  (version  5.2  -  ~1994). 
 
  Pre-compiled  {MS-DOS}  versions  are  also  available. 
 
  (1997-08-08) 
 
 
 
  From  V.E.R.A.  --  Virtual  Entity  of  Relevant  Acronyms  13  March  2001  [vera]: 
 
  BTOA 
  Binary  TO  ASCII  (ASCII)