function converts an Internet network number from network format (usually a
.Vt struct in_addr
or some other binary form, in network byte order) to CIDR presentation format
(suitable for external display purposes).
is the number of bits in
that are the network number.
if a system error occurs (in which case,
will have been set), or it returns a pointer to the destination string.
function converts a presentation format Internet network number (that is,
printable form as held in a character string) to network format (usually a
.Vt struct in_addr
or some other internal binary representation, in network byte order).
It returns the number of bits (either computed based on the class, or
specified with /CIDR), or -1 if a failure occurred
(in which case
will have been set.
It will be set to
if the Internet network number was not valid).
The currently supported values for
is the size of the result buffer
Internet network numbers may be specified in one of the following forms:
When four parts are specified, each is interpreted
as a byte of data and assigned, from left to right,
to the four bytes of an Internet network number.
that when an Internet network number is viewed as a 32-bit
integer quantity on a system that uses little-endian
byte order (such as the
Intel 386, 486,
processors) the bytes referred to above appear as
That is, little-endian bytes are ordered from right to left.
When a three part number is specified, the last
part is interpreted as a 16-bit quantity and placed
in the rightmost two bytes of the Internet network number.
This makes the three part number format convenient
for specifying Class B network numbers as
When a two part number is supplied, the last part
is interpreted as a 24-bit quantity and placed in
the rightmost three bytes of the Internet network number.
This makes the two part number format convenient
for specifying Class A network numbers as
When only one part is given, the value is stored
directly in the Internet network number without any byte
All numbers supplied as
may be decimal, octal, or hexadecimal, as specified
in the C language (i.e., a leading 0x or 0X implies
hexadecimal; otherwise, a leading 0 implies octal;
otherwise, the number is interpreted as decimal).