a64l, l64a - convert between long and base-64
long a64l(const char *str64);
char *l64a(long value);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
_XOPEN_SOURCE >= 500
|| /* Glibc since 2.19: */ _DEFAULT_SOURCE
|| /* Glibc versions <= 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/".
For an explanation of the terms used in this section, see attributes(7).
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 in glibc before 2.2.5 (puts most
significant digit first).
This is not the encoding used by uuencode(1).
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