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/*++
/* NAME
/* mask_addr 3
/* SUMMARY
/* address bit banging
/* SYNOPSIS
/* #include <mask_addr.h>
/*
/* void mask_addr(addr_bytes, addr_byte_count, network_bits)
/* unsigned char *addr_bytes;
/* unsigned addr_byte_count;
/* unsigned network_bits;
/* DESCRIPTION
/* mask_addr() clears all the host bits in the specified
/* address. The code can handle addresses of any length,
/* and bytes of any width.
/*
/* Arguments:
/* .IP addr_bytes
/* The network address in network byte order.
/* .IP addr_byte_count
/* The network address length in bytes.
/* .IP network_bits
/* The number of initial bits that will not be cleared.
/* DIAGNOSTICS
/* Fatal errors: the number of network bits exceeds the address size.
/* LICENSE
/* .ad
/* .fi
/* The Secure Mailer license must be distributed with this software.
/* AUTHOR(S)
/* Wietse Venema
/* IBM T.J. Watson Research
/* P.O. Box 704
/* Yorktown Heights, NY 10598, USA
/*--*/
/* System library. */
#include <sys_defs.h>
#include <limits.h> /* CHAR_BIT */
/* Utility library. */
#include <msg.h>
#include <mask_addr.h>
/* mask_addr - mask off a variable-length address */
void mask_addr(unsigned char *addr_bytes,
unsigned addr_byte_count,
unsigned network_bits)
{
unsigned char *p;
if (network_bits > addr_byte_count * CHAR_BIT)
msg_panic("mask_addr: address byte count %d too small for bit count %d",
addr_byte_count, network_bits);
p = addr_bytes + network_bits / CHAR_BIT;
network_bits %= CHAR_BIT;
if (network_bits != 0)
*p++ &= ~0U << (CHAR_BIT - network_bits);
while (p < addr_bytes + addr_byte_count)
*p++ = 0;
}
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