The standard output is a text file (encoded in the character set of the current locale) that begins with the line:
"begin%s%s\n", <mode>, decode_pathname
and ends with the line:
end\n
In both cases, the lines have no preceding or trailing blank characters.
The algorithm that is used for lines in between begin and end takes three octets as input and writes four characters of output by splitting the input at six-bit
intervals into four octets, containing data in the lower six bits only. These octets are converted to characters by adding a value of 0x20 to each octet, so that each octet is in the range 0x20-0x5f,
and then it is assumed to represent a printable character. It then will be translated into the corresponding character codes for the codeset in use in the current locale. (For example, the octet 0x41, representing A , would be translated to A in the current codeset, such as 0xc1 if it were EBCDIC.)
Where the bits of two octets are combined, the least significant bits of the first octet are shifted left and combined with the most significant bits of the second octet shifted right. Thus the three
octets A, B, C are converted into the four octets:
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0x20 + (( A >> 2 ) & 0x3F)
0x20 + (((A << 4) ((B >> 4) & 0xF)) & 0x3F)
0x20 + (((B << 2) ((C >> 6) & 0x3)) & 0x3F)
0x20 + (( C ) & 0x3F)
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These octets are then translated into the local character set.
Each encoded line contains a length character, equal to the number of characters to be decoded plus 0x20 translated to the local character set as described above, followed by the encoded characters.
The maximum number of octets to be encoded on each line is 45.
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