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   36: .\" Author: Archie Cobbs <archie@freebsd.org>
   37: .\"
   38: .\" $Id: base64.3,v 1.1.1.1 2012/02/21 23:25:53 misho Exp $
   39: .\"
   40: .Dd April 22, 2002
   41: .Dt BASE64 3
   42: .Os
   43: .Sh NAME
   44: .Nm b64_encoder_create ,
   45: .Nm b64_decoder_create
   46: .Nd base-64 encoder and decoder
   47: .Sh LIBRARY
   48: PDEL Library (libpdel, \-lpdel)
   49: .Sh SYNOPSIS
   50: .In pdel/io/filter.h
   51: .In pdel/io/base64.h
   52: .Ft "struct filter *"
   53: .Fn b64_encoder_create "const char *charset"
   54: .Ft "struct filter *"
   55: .Fn b64_decoder_create "const char *charset" "int strict"
   56: .Vt extern const char "b64_rfc2045_charset[]" ;
   57: .Sh DESCRIPTION
   58: These routines create filter objects (see
   59: .Xr filter 3)
   60: that encode and decode binary data using base-64 encoding.
   61: .Pp
   62: Both functions take a
   63: .Fa charset
   64: argument.
   65: If equal to
   66: .Dv NULL ,
   67: then the default (RFC 2045) character set is used.
   68: Otherwise,
   69: .Fa charset
   70: must point to a string with 65 unique characters.
   71: The first 64 are used to encode the data, while the last character is used
   72: as a pad character when the data length is not a multiple of three.
   73: .Pp
   74: .Fn b64_encoder_create
   75: returns a new encoding filter.
   76: For every three bytes input to the filter, four bytes from the chosen
   77: character set will be output.
   78: If the input length is not a multiple of three, then one or two pad
   79: characters will be added at the end of the output, so that the output
   80: length of the filter is always a multiple of four.
   81: .Pp
   82: .Fn b64_decoder_create
   83: returns a new decoding filter.
   84: Every four bytes input to the filter are decoded into up to three bytes
   85: of output.
   86: If
   87: .Fa strict
   88: is non-zero, then any malformed input causes an internal error to be
   89: generated in the filter, with
   90: .Va errno
   91: set to
   92: .Er EINVAL.
   93: Malformed input is any input character not from the chosen character set.
   94: In any case, the pad character is always ignored.
   95: If
   96: .Fa strict
   97: is zero, then any unrecognized characters are simply ignored, rather than
   98: causing an error.
   99: .Pp
  100: .Fn b64_encoder_create
  101: always generates strings that are accepted by
  102: .Fn b64_decoder_create
  103: in strict mode, when created with the same character set.
  104: .Pp
  105: The RFC 2045 character set is avilable in
  106: .Va b64_rfc2045_charset .
  107: .Sh RETURN VALUES
  108: If there was a system error,
  109: .Fn b64_encoder_create
  110: and
  111: .Fn b64_encoder_create
  112: return
  113: .Dv NULL
  114: with
  115: .Va errno
  116: set to the appropriate value.
  117: If an invalid
  118: .Fa charset
  119: is passed,
  120: .Va errno
  121: will be set to
  122: .Er EINVAL.
  123: .Sh SEE ALSO
  124: .Xr filter 3 ,
  125: .Xr libpdel 3
  126: .Rs
  127: .%A N. Freed
  128: .%A N. Borenstein
  129: .%T "Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies"
  130: .%O RFC 2045
  131: .Re
  132: .Sh HISTORY
  133: The PDEL library was developed at Packet Design, LLC.
  134: .Dv "http://www.packetdesign.com/"
  135: .Sh AUTHORS
  136: .An Archie Cobbs Aq archie@freebsd.org