The Open Group Base Specifications Issue 7, 2018 edition
IEEE Std 1003.1-2017 (Revision of IEEE Std 1003.1-2008)
Copyright © 2001-2018 IEEE and The Open Group


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


[XSI] [Option Start] #include <stdlib.h>

long a64l(const char *
char *l64a(long
value); [Option End]


These functions 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 shall be used for these operations.

The characters used to represent digits are '.' (dot) 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 shall take a pointer to a radix-64 representation, in which the first digit is the least significant, and return the corresponding long value. If the string pointed to by s contains more than six characters, a64l() shall use the first six. If the first six characters of the string contain a null terminator, a64l() shall use only characters preceding the null terminator. The a64l() function shall scan 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 shall take a long argument and return a pointer to the corresponding radix-64 representation. The behavior of l64a() is unspecified if value is negative.

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

The l64a() function need not be thread-safe.


Upon successful completion, a64l() shall return the long value resulting from conversion of the input string. If a string pointed to by s is an empty string, a64l() shall return 0L.

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


No errors are defined.

The following sections are informative.




If the type long contains more than 32 bits, the result of a64l(l64a(x)) is x in the low-order 32 bits.


This is not the same encoding as used by either encoding variant of the uuencode utility.





XBD <stdlib.h>

XCU uuencode


First released in Issue 4, Version 2.

Issue 5

Moved from X/OPEN UNIX extension to BASE.

Normative text previously in the APPLICATION USAGE section is moved to the DESCRIPTION.

A note indicating that the l64a() function need not be reentrant is added to the DESCRIPTION.

Issue 7

Austin Group Interpretation 1003.1-2001 #156 is applied.

End of informative text.


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