diff options
Diffstat (limited to 'src/util/mask_addr.c')
| -rw-r--r-- | src/util/mask_addr.c | 68 |
1 files changed, 68 insertions, 0 deletions
diff --git a/src/util/mask_addr.c b/src/util/mask_addr.c new file mode 100644 index 0000000..5ddd0ca --- /dev/null +++ b/src/util/mask_addr.c @@ -0,0 +1,68 @@ +/*++ +/* 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; +} |