.Dd January 15, 2017
.Dt CRC32 3
.Os
.
.Sh NAME
.Nm crc32 ,
.Nm crc32_z
.Nd update CRC-32 checksum
.
.Sh LIBRARY
.Lb libz
.
.Sh SYNOPSIS
.In zlib.h
.Ft uLong
.Fn crc32 "uLong crc" "const Bytef *buf" "uInt len"
.Ft uLong
.Fn crc32_z "uLong crc" "const Bytef *buf" "z_size_t len"
.
.Sh DESCRIPTION
Update a running CRC-32 with the bytes
.Fa "buf[0..len-1]"
and return the updated CRC-32.
If
.Fa buf
is
.Dv Z_NULL ,
this function returns
the required initial value for the CRC.
Pre- and post-conditioning
(one's complement)
is performed within this function
so it shouldn't be done
by the application.
.
.Pp
.Fn crc32_z
is the same as
.Fn crc32 ,
but with a
.Vt size_t
length.
.
.Sh EXAMPLES
.Bd -literal -offset indent
uLong crc = crc32(0L, Z_NULL, 0);

while (read_buffer(buffer, length) != EOF) {
	crc = crc32(crc, buffer, length);
}
if (crc != original_crc) error();
.Ed
.
.Sh SEE ALSO
.Xr adler32 3 ,
.Xr crc32_combine 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