2. xxencode
It is not possible that UUENCODE does not mention XXencode, XxEncode's encoding algorithm and uuencode basically, but uses different character sets. The characters used by Xxencode encoding are:
" 0123456789abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyz" Compared with UUENCODE, its special characters are less. Many tools that support UUENCODE codec are simultaneously supporting XXencode.
This feature of this coding is that each line starts with the "H" flag. Here is an example of xxencode:
Begin 644 mogao.txt
H0EY760 U684QKH90UWJXHUWOWWFCPQB0UBLXXLTCAPJNQ3JCUMKPXH4IWou
HPXKYCUVONKLINLINLINLINLU9MWMA16IAH2M9X6K9X2NAXCMAUCDGWBIGO4X1EC760 U
H60 UL8ESRWXHJDUTDBTRMH8XIAVOR5 U9MXHPQRVPMTWNKTOOLJI9ATZR O8
H0EY7FKPVOKLOPNDHPQRVPO NBN2IPAJO1EC760 U8WCE8WCE8WCE8WCE8WCE
H8WCE8WCE8WCE8WCE8WCE8WCE8WCE8WCE8WCE8WCE60 U60 U60 U60 U60 U
H1EC760 U8W0NZQ59Jatgtaemkvgqj98vhdxlrucgggzr-mxtxj8d8ggcohfmm
Hiw5onw6e1ec760 u8Wce8Wce8Wce8Wce8Wce8Wce8Wce8Wce8Wce8Wce8Wce
A8WCE8WCE8WCE8WCE
end
You can separate it into a file: Mogao.xxe, then open with Winzip, decompress Mogao.txt.
The encoding algorithm of xxencode and UUENCODE are basically the same, and it is more simple to implement, it will not be detailed here.
The C language description for xxencode encoding and decoding is given below:
/ * Xxencode encoding * /
Void xxe (unsigned char chasc [3], unsigned char chxxe [4])
/ *
CHASC: Uncoded binary code
CHXXE: Coded XXE code
* /
{INT I;
Static char set [] =
" 0123456789abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyz";
CHXXE [0] = CHASC [0] >> 2;
CHXXE [1] = (chasc [0] << 4) & 48 | (Chasc [1] >> 4) & 15;
CHXXE [2] = (ChaSC [1] << 2) & 60 | (Chasc [2] >> 6) & 3;
CHXXE [3] = Chasc [2] & 63;
For (i = 0; i <4; i ) chxxe [i] = set [chxxe [i]]; / * Chart * /
}
/ * Try to note, the first letter of each line in the text section of the xxencode file is: After the ASCII value of the number of characters actually read in the source file, it is obtained after the SET [] checksum. * /
/ * Xxencode decoding * /
Unsigned char set / * Chart Function * / {IF (CH == 43) CH = 0;
ELSE IF (CH == 45) CH = 1;
ELSE IF (CH> = 48 && Ch <= 57) CH- = 46;
ELSE IF (CH> = 65 && Ch <= 90) CH- = 53;
ELSE IF (CH> = 97 && Ch <= 122) CH- = 59;
Return ch;
}
Void unxxe (unsigned char chxxe [4], unsigned char chasc [3])
/ *
CHXXE: Unresolved XXE code
CHASC: Decoded binary code
* /
{INT K = 2, I;
UNSIGNED CHAR T;
T = NULL;
* chxxe = set (* chxxe);
For (i = 0; i <3; i )
{* (CHXXE 1) = set (* (chXXE i 1));
(ChHEX I) = * (CHXXE I) << k;
K = 2;
T = * (CHXXE I 1) >> 8-K;
* (ChHEX I) | = T;
}
}
