---
name: "a64l"
section: "3"
platform: "freebsd"
package: "base"
version: "16.0-CURRENT-20261027-61c70dc16a79"
release: "FreeBSD 16.0-CURRENT (2026-10-27)"
platforms: ["linux", "freebsd", "macos"]
url: "https://new.carta.tech/a64l"
---

# a64l(3)

convert between a long integer and a base-64 ASCII string

## NAME

**a64l**, **l64a**, **l64a\_r** – convert between a long integer and a base-64 ASCII string

## LIBRARY

Standard C Library (libc, -lc)

## SYNOPSIS

**#include \<stdlib.h\>**

*long*\

**a64l**(*const char \*s*);

*char* *\**\

**l64a**(*long int l*);

*int*\

**l64a\_r**(*long int l*, *char \*buffer*, *int buflen*);

## DESCRIPTION

These functions are used to maintain numbers stored in radix-64 ASCII characters. This is a notation by which 32-bit integers can be represented by up to six characters; each character represents a digit in radix-64 notation. If the type long contains more than 32 bits, only the low-order 32 bits are used for these operations.

The characters used to represent “digits” are ‘.’ for 0, ‘/’ for 1, ‘0’ - ‘9’ for 2 - 11, ‘A’ - ‘Z’ for 12 - 37, and ‘a’ - ‘z’ for 38 - 63.

The **a64l**() function takes a pointer to a radix-64 representation, in which the first digit is the least significant, and returns a corresponding *long* value. If the string pointed to by *s* contains more than six characters, **a64l**() uses the first six. If the first six characters of the string contain a null terminator, **a64l**() uses only characters preceding the null terminator. The **a64l**() function scans the character string from left to right with the least significant digit on the left, decoding each character as a 6-bit radix-64 number. If the type long contains more than 32 bits, the resulting value is sign-extended. The behavior of **a64l**() is unspecified if *s* is a null pointer or the string pointed to by *s* was not generated by a previous call to **l64a**().

The **l64a**() function takes a *long* argument and returns a pointer to the corresponding radix-64 representation. The behavior of **l64a**() is unspecified if value is negative.

The value returned by **l64a**() is a pointer into a static buffer. Subsequent calls to **l64a**() may overwrite the buffer.

The **l64a\_r**() function performs a conversion identical to that of **l64a**() and stores the resulting representation in the memory area pointed to by *buffer*, consuming at most *buflen* characters including the terminating NUL character.

## RETURN VALUES

On successful completion, **a64l**() returns the *long* value resulting from conversion of the input string. If a string pointed to by *s* is an empty string, **a64l**() returns 0.

The **l64a**() function returns a pointer to the radix-64 representation. If value is 0, **l64a**() returns a pointer to an empty string.

## SEE ALSO

[strtoul(3)](/strtoul/3.md)

## HISTORY

The **a64l**(), **l64a**(), and **l64a\_r**() functions are derived from NetBSD with modifications. They appeared in FreeBSD 6.1.

## AUTHORS

The **a64l**(), **l64a**(), and **l64a\_r**() functions were added to FreeBSD by Tom Rhodes ⟨*trhodes@FreeBSD.org*⟩. Almost all of this manual page came from the POSIX standard.