basE91 - 将二进制数据转换为ASCII文本

Copyright (c) 2000-2006 Joachim Henke


basE91 is an advanced method for encoding binary data as ASCII characters. It
is similar to UUencode or base64, but is more efficient. The overhead produced
by basE91 depends on the input data. It amounts at most to 23% (versus 33% for
base64) and can range down to 14%, which typically occurs on 0-byte blocks.
This makes basE91 very useful for transferring larger files over binary
insecure connections like e-mail or terminal lines.

The current algorithm has been written with portability and simplicity in mind
an is therefore not necessarily optimised for speed.


* Alphabet

As the name suggests, basE91 needs 91 characters to represent the encoded
binary data in ASCII. From the 94 printable ASCII characters (0x21-0x7E), the
following three ones have been omitted to build the basE91 alphabet:

- (dash, 0x2D)
' (apostrophe, 0x27)
\ (backslash, 0x5C)

The translation table is composed of the remaining characters as shown below.

 0 A    13 N    26 a    39 n    52 0    65 %    78 >
 1 B    14 O    27 b    40 o    53 1    66 &    79 ?
 2 C    15 P    28 c    41 p    54 2    67 (    80 @
 3 D    16 Q    29 d    42 q    55 3    68 )    81 [
 4 E    17 R    30 e    43 r    56 4    69 *    82 ]
 5 F    18 S    31 f    44 s    57 5    70 +    83 ^
 6 G    19 T    32 g    45 t    58 6    71 ,    84 _
 7 H    20 U    33 h    46 u    59 7    72 .    85 `
 8 I    21 V    34 i    47 v    60 8    73 /    86 {
 9 J    22 W    35 j    48 w    61 9    74 :    87 |
10 K    23 X    36 k    49 x    62 !    75 ;    88 }
11 L    24 Y    37 l    50 y    63 #    76 <    89 ~
12 M    25 Z    38 m    51 z    64 $    77 =    90 "


* Building

1. `cd' to the directory containing the package's source code and type `make'
   to compile the package

2. optionally, type `make check' to run any self-tests that come with the
   package

3. type `make install' to install the program and documentation in `/usr/local'
   (to specify another installation prefix than `/usr/local', type
   `make prefix=PATH install' instead)

4. you can remove the program binaries and object files from the source code
   directory by typing `make clean'


* Developer

Joachim Henke <[email protected]>


* Copying

All source code in this package is released under the terms of the BSD license.
See the file LICENSE for copying permission.


* See also

Please visit the basE91 home page [http://base91.sourceforge.net/] for the
latest version and pre-compiled binaries.