---
name: "a64l"
section: "3"
platform: "macos"
package: "Libc"
version: "1752.120.2"
release: "macOS 26.5"
platforms: ["linux", "freebsd", "macos"]
url: "https://new.carta.tech/a64l"
---

# a64l(3)

convert between 32-bit integer and radix-64 ASCII string

## NAME

**a64l**, **l64a** – convert between 32-bit integer and radix-64 ASCII string

## SYNOPSIS

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

*long*\

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

*char* *\**\

**l64a**(*long value*);

## DESCRIPTION

The **a64l**() and **l64a**() 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 a radix-64 notation.

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

The **a64l**() function takes a pointer to a null-terminated radix-64 representation and returns a corresponding 32-bit value. If the string pointed to by *s* contains more than six characters, **a64l**() will use the first six. **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.

**l64a**() takes a long integer argument *value* and returns a pointer to the corresponding radix-64 representation.

## RETURN VALUES

On success, **a64l**() returns a 32-bit representation of *s*. If *s* is a null pointer or if it contains digits other than those described above. **a64l**() returns -1 and sets the global variable *errno* to EINVAL.

On success, **l64a**() returns a pointer to a string containing the radix-64 representation of *value*. If *value* is 0, **l64a**() returns a pointer to the empty string. If *value* is negative, **l64a**() returns a null pointer and sets the global variable *errno* to EINVAL.

## WARNINGS

The value returned by **l64a**() is a pointer into a static buffer, the contents of which will be overwritten by subsequent calls.

The value returned by **a64l**() may be incorrect if the value is too large; for that reason, only strings that resulted from a call to **l64a**() should be used to call **a64l**().

If a long integer is larger than 32 bits, only the low-order 32 bits are used.

## STANDARDS

The **a64l**() and **l64a**() functions conform to X/Open Portability Guide Issue 4, Version 2 (“XPG4.2”).