a64l, l64a - convert between long and base-64

#include <stdlib.h>
long a64l(const char *str64);
char *l64a(long value);

Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

    _XOPEN_SOURCE >= 500
        || /* glibc >= 2.19: */ _DEFAULT_SOURCE
        || /* glibc <= 2.19: */ _SVID_SOURCE

These functions provide a conversion between 32-bit long integers and little-endian base-64 ASCII strings (of length zero to six). If the string used as argument for a64l() has length greater than six, only the first six bytes are used. If the type long has more than 32 bits, then l64a() uses only the low order 32 bits of value, and a64l() sign-extends its 32-bit result.

The 64 digits in the base-64 system are:

'.'	represents a 0
'/'	represents a 1
0-9	represent  2-11
A-Z	represent 12-37
a-z	represent 38-63

So 123 = 59*64^0 + 1*64^1 = "v/".

uuencode(1), strtoul(3)