a64l, l64a - convert between long and base-64

       For an explanation of the terms used in this section, see attributes(7).
       ┌─────────────────────────────────────────────────────────────────┬───────────────┬─────────────────────┐
       │ Interface                                                       │ Attribute     │ Value               │
       ├─────────────────────────────────────────────────────────────────┼───────────────┼─────────────────────┤
       │ l64a()                                                          │ Thread safety │ MT-Unsafe race:l64a │
       ├─────────────────────────────────────────────────────────────────┼───────────────┼─────────────────────┤
       │ a64l()                                                          │ Thread safety │ MT-Safe             │
       └─────────────────────────────────────────────────────────────────┴───────────────┴─────────────────────┘

       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/".

       POSIX.1-2001.

       Standard C library (libc, -lc)

       a64l, l64a - convert between long and base-64

       The value returned by l64a() may be a pointer to a static buffer, possibly overwritten by later calls.

       The  behavior  of  l64a()  is  undefined  when  value is negative.  If value is zero, it returns an empty
       string.

       These functions are broken before glibc 2.2.5 (puts most significant digit first).

       This is not the encoding used by uuencode(1).

uuencode(1), strtoul(3)

Linux man-pages 6.9.1                              2024-05-02                                            a64l(3)

       POSIX.1-2008.

#include<stdlib.h>longa64l(constchar*str64);char*l64a(longvalue);

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

       a64l(), l64a():
           _XOPEN_SOURCE >= 500
               || /* glibc >= 2.19: */ _DEFAULT_SOURCE
               || /* glibc <= 2.19: */ _SVID_SOURCE