.Dd January 15, 2017
.Dt ADLER32 3
.Os
.
.Sh NAME
.Nm adler32 ,
.Nm adler32_z
.Nd update Adler-32 checksum
.
.Sh LIBRARY
.Lb libz
.
.Sh SYNOPSIS
.In zlib.h
.Ft uLong
.Fn adler32 "uLong adler" "const Bytef *buf" "uInt len"
.Ft uLong
.Fn adler32_z "uLong adler" "const Bytef *buf" "z_size_t len"
.
.Sh DESCRIPTION
Update a running Adler-32 checksum with the bytes
.Fa "buf[0..len-1]"
and return the updated checksum.
If
.Fa buf
is
.Dv Z_NULL ,
this function returns
the required initial value for the checksum.
.
.Pp
An Adler-32 checksum is almost as reliable as a CRC-32
but can be computed much faster.
.
.Pp
.Fn adler32_z
is the same as
.Fn adler32 ,
but with a
.Vt size_t
length.
.
.Sh EXAMPLES
.Bd -literal -offset indent
uLong adler = adler32(0L, Z_NULL, 0);

while (read_buffer(buffer, length) != EOF) {
	adler = adler32(adler, buffer, length);
}
if (adler != original_adler) error();
.Ed
.
.Sh SEE ALSO
.Xr adler32_combine 3 ,
.Xr crc32 3
.
.Sh HISTORY
This manual page was converted from
.In zlib.h
to mdoc format by
.An C. McEnroe Aq Mt june@causal.agency .
.
.Sh AUTHORS
.An Jean-loup Gailly Aq Mt jloup@gzip.org
.An Mark Adler Aq Mt madler@alumni.caltech.edu