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| 129 | .\" ======================================================================== |
| 130 | .\" |
| 131 | .IX Title "MIME::Base64 3" |
| 132 | .TH MIME::Base64 3 "2001-09-21" "perl v5.8.8" "Perl Programmers Reference Guide" |
| 133 | .SH "NAME" |
| 134 | MIME::Base64 \- Encoding and decoding of base64 strings |
| 135 | .SH "SYNOPSIS" |
| 136 | .IX Header "SYNOPSIS" |
| 137 | .Vb 1 |
| 138 | \& use MIME::Base64; |
| 139 | .Ve |
| 140 | .PP |
| 141 | .Vb 2 |
| 142 | \& $encoded = encode_base64('Aladdin:open sesame'); |
| 143 | \& $decoded = decode_base64($encoded); |
| 144 | .Ve |
| 145 | .SH "DESCRIPTION" |
| 146 | .IX Header "DESCRIPTION" |
| 147 | This module provides functions to encode and decode strings into and from the |
| 148 | base64 encoding specified in \s-1RFC\s0 2045 \- \fI\s-1MIME\s0 (Multipurpose Internet |
| 149 | Mail Extensions)\fR. The base64 encoding is designed to represent |
| 150 | arbitrary sequences of octets in a form that need not be humanly |
| 151 | readable. A 65\-character subset ([A\-Za\-z0\-9+/=]) of US-ASCII is used, |
| 152 | enabling 6 bits to be represented per printable character. |
| 153 | .PP |
| 154 | The following functions are provided: |
| 155 | .IP "encode_base64($str)" 4 |
| 156 | .IX Item "encode_base64($str)" |
| 157 | .PD 0 |
| 158 | .ie n .IP "encode_base64($str, $eol);" 4 |
| 159 | .el .IP "encode_base64($str, \f(CW$eol\fR);" 4 |
| 160 | .IX Item "encode_base64($str, $eol);" |
| 161 | .PD |
| 162 | Encode data by calling the \fIencode_base64()\fR function. The first |
| 163 | argument is the string to encode. The second argument is the |
| 164 | line-ending sequence to use. It is optional and defaults to \*(L"\en\*(R". The |
| 165 | returned encoded string is broken into lines of no more than 76 |
| 166 | characters each and it will end with \f(CW$eol\fR unless it is empty. Pass an |
| 167 | empty string as second argument if you do not want the encoded string |
| 168 | to be broken into lines. |
| 169 | .IP "decode_base64($str)" 4 |
| 170 | .IX Item "decode_base64($str)" |
| 171 | Decode a base64 string by calling the \fIdecode_base64()\fR function. This |
| 172 | function takes a single argument which is the string to decode and |
| 173 | returns the decoded data. |
| 174 | .Sp |
| 175 | Any character not part of the 65\-character base64 subset is |
| 176 | silently ignored. Characters occurring after a '=' padding character |
| 177 | are never decoded. |
| 178 | .Sp |
| 179 | If the length of the string to decode, after ignoring |
| 180 | non\-base64 chars, is not a multiple of 4 or if padding occurs too early, |
| 181 | then a warning is generated if perl is running under \f(CW\*(C`\-w\*(C'\fR. |
| 182 | .PP |
| 183 | If you prefer not to import these routines into your namespace, you can |
| 184 | call them as: |
| 185 | .PP |
| 186 | .Vb 3 |
| 187 | \& use MIME::Base64 (); |
| 188 | \& $encoded = MIME::Base64::encode($decoded); |
| 189 | \& $decoded = MIME::Base64::decode($encoded); |
| 190 | .Ve |
| 191 | .SH "DIAGNOSTICS" |
| 192 | .IX Header "DIAGNOSTICS" |
| 193 | The following warnings can be generated if perl is invoked with the |
| 194 | \&\f(CW\*(C`\-w\*(C'\fR switch: |
| 195 | .IP "Premature end of base64 data" 4 |
| 196 | .IX Item "Premature end of base64 data" |
| 197 | The number of characters to decode is not a multiple of 4. Legal |
| 198 | base64 data should be padded with one or two \*(L"=\*(R" characters to make |
| 199 | its length a multiple of 4. The decoded result will be the same |
| 200 | whether the padding is present or not. |
| 201 | .IP "Premature padding of base64 data" 4 |
| 202 | .IX Item "Premature padding of base64 data" |
| 203 | The '=' padding character occurs as the first or second character |
| 204 | in a base64 quartet. |
| 205 | .PP |
| 206 | The following exception can be raised: |
| 207 | .IP "Wide character in subroutine entry" 4 |
| 208 | .IX Item "Wide character in subroutine entry" |
| 209 | The string passed to \fIencode_base64()\fR contains characters with code |
| 210 | above 255. The base64 encoding is only defined for single-byte |
| 211 | characters. Use the Encode module to select the byte encoding you |
| 212 | want. |
| 213 | .SH "EXAMPLES" |
| 214 | .IX Header "EXAMPLES" |
| 215 | If you want to encode a large file, you should encode it in chunks |
| 216 | that are a multiple of 57 bytes. This ensures that the base64 lines |
| 217 | line up and that you do not end up with padding in the middle. 57 |
| 218 | bytes of data fills one complete base64 line (76 == 57*4/3): |
| 219 | .PP |
| 220 | .Vb 1 |
| 221 | \& use MIME::Base64 qw(encode_base64); |
| 222 | .Ve |
| 223 | .PP |
| 224 | .Vb 4 |
| 225 | \& open(FILE, "/var/log/wtmp") or die "$!"; |
| 226 | \& while (read(FILE, $buf, 60*57)) { |
| 227 | \& print encode_base64($buf); |
| 228 | \& } |
| 229 | .Ve |
| 230 | .PP |
| 231 | or if you know you have enough memory |
| 232 | .PP |
| 233 | .Vb 3 |
| 234 | \& use MIME::Base64 qw(encode_base64); |
| 235 | \& local($/) = undef; # slurp |
| 236 | \& print encode_base64(<STDIN>); |
| 237 | .Ve |
| 238 | .PP |
| 239 | The same approach as a command line: |
| 240 | .PP |
| 241 | .Vb 1 |
| 242 | \& perl -MMIME::Base64 -0777 -ne 'print encode_base64($_)' <file |
| 243 | .Ve |
| 244 | .PP |
| 245 | Decoding does not need slurp mode if every line contains a multiple |
| 246 | of four base64 chars: |
| 247 | .PP |
| 248 | .Vb 1 |
| 249 | \& perl -MMIME::Base64 -ne 'print decode_base64($_)' <file |
| 250 | .Ve |
| 251 | .PP |
| 252 | Perl v5.8 and better allow extended Unicode characters in strings. |
| 253 | Such strings cannot be encoded directly, as the base64 |
| 254 | encoding is only defined for single-byte characters. The solution is |
| 255 | to use the Encode module to select the byte encoding you want. For |
| 256 | example: |
| 257 | .PP |
| 258 | .Vb 2 |
| 259 | \& use MIME::Base64 qw(encode_base64); |
| 260 | \& use Encode qw(encode); |
| 261 | .Ve |
| 262 | .PP |
| 263 | .Vb 2 |
| 264 | \& $encoded = encode_base64(encode("UTF-8", "\ex{FFFF}\en")); |
| 265 | \& print $encoded; |
| 266 | .Ve |
| 267 | .SH "COPYRIGHT" |
| 268 | .IX Header "COPYRIGHT" |
| 269 | Copyright 1995\-1999, 2001\-2004 Gisle Aas. |
| 270 | .PP |
| 271 | This library is free software; you can redistribute it and/or |
| 272 | modify it under the same terms as Perl itself. |
| 273 | .PP |
| 274 | Distantly based on LWP::Base64 written by Martijn Koster |
| 275 | <m.koster@nexor.co.uk> and Joerg Reichelt <j.reichelt@nexor.co.uk> and |
| 276 | code posted to comp.lang.perl <3pd2lp$6gf@wsinti07.win.tue.nl> by Hans |
| 277 | Mulder <hansm@wsinti07.win.tue.nl> |
| 278 | .PP |
| 279 | The \s-1XS\s0 implementation uses code from metamail. Copyright 1991 Bell |
| 280 | Communications Research, Inc. (Bellcore) |
| 281 | .SH "SEE ALSO" |
| 282 | .IX Header "SEE ALSO" |
| 283 | MIME::QuotedPrint |