xref: /openbsd-src/lib/libc/stdlib/a64l.3 (revision bf198cc6eba0ca1f6d79f71e8e2243d386241fa8)

.\" $OpenBSD: a64l.3,v 1.13 2019/01/25 00:19:25 millert Exp $
.\"
.\" Copyright (c) 1997 Todd C. Miller <millert@openbsd.org>
.\"
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.Dd $Mdocdate: January 25 2019 $
.Dt A64L 3
.Os
.Sh NAME
.Nm a64l ,
.Nm l64a
.Nd convert between 32-bit integer and radix-64 ASCII string
.Sh SYNOPSIS
.In stdlib.h
.Ft long
.Fn a64l "const char *s"
.Ft char *
.Fn l64a "long l"
.Sh DESCRIPTION
The
.Fn a64l
and
.Fn l64a
functions are used to maintain numbers stored in radix-64
.Tn ASCII
characters.
This is a notation by which 32-bit integers
can be represented by up to six characters; each character represents a
.Dq digit
in a radix-64 notation.
.Pp
The characters used to represent digits are
.Ql \&.
for 0,
.Ql /
for 1,
.Ql 0
through
.Ql 9
for 2-11,
.Ql A
through
.Ql Z
for 12-37, and
.Ql a
through
.Ql z
for 38-63.
.Pp
The
.Fn a64l
function takes a pointer to a NUL-terminated radix-64 representation
and returns a corresponding 32-bit value.
If the string pointed to by
.Fa s
contains more than six characters,
.Fn a64l
will use the first six.
.Fn a64l
scans the character string from left to right, decoding
each character as a 6-bit radix-64 number.
If a long integer is
larger than 32 bits, the return value will be sign-extended.
.Pp
.Fn l64a
takes a long integer argument
.Fa l
and returns a pointer to the corresponding radix-64 representation.
.Sh RETURN VALUES
On success,
.Fn a64l
returns a 32-bit representation of
.Fa s .
If
.Fa s
is a null pointer or if it contains digits other than those described above,
.Fn a64l
returns \-1 and sets the global variable
.Va errno
to
.Er EINVAL .
.Pp
On success,
.Fn l64a
returns a pointer to a string containing the radix-64 representation of
.Fa l .
If
.Fa l
is 0,
.Fn l64a
returns a pointer to the empty string.
If
.Fa l
is negative,
.Fn l64a
returns a null pointer and sets the global variable
.Va errno
to
.Er EINVAL .
.Sh STANDARDS
The
.Fn a64l
and
.Fn l64a
functions conform to
.St -xpg4.2 .
.Sh CAVEATS
The value returned by
.Fn l64a
is a pointer into a static buffer, the contents of which
will be overwritten by subsequent calls.
.Pp
The value returned by
.Fn a64l
may be incorrect if the value is too large; for that reason, only strings
that resulted from a call to
.Fn l64a
should be used to call
.Fn a64l .
.Pp
If a long integer is larger than 32 bits, only the low-order
32 bits are used.