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Annotation of embedaddon/libpdel/io/base64.3, revision 1.1.1.1

1.1       misho       1: .\" Copyright (c) 2001-2002 Packet Design, LLC.
                      2: .\" All rights reserved.
                      3: .\" 
                      4: .\" Subject to the following obligations and disclaimer of warranty,
                      5: .\" use and redistribution of this software, in source or object code
                      6: .\" forms, with or without modifications are expressly permitted by
                      7: .\" Packet Design; provided, however, that:
                      8: .\" 
                      9: .\"    (i)  Any and all reproductions of the source or object code
                     10: .\"         must include the copyright notice above and the following
                     11: .\"         disclaimer of warranties; and
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                     17: .\" THIS SOFTWARE IS BEING PROVIDED BY PACKET DESIGN "AS IS", AND
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                     24: .\" OF THE USE OF THIS SOFTWARE IN TERMS OF ITS CORRECTNESS, ACCURACY,
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                     35: .\"
                     36: .\" Author: Archie Cobbs <archie@freebsd.org>
                     37: .\"
                     38: .\" $Id: base64.3,v 1.6 2004/06/02 17:24:37 archie 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