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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 |