summaryrefslogtreecommitdiffstats
path: root/src/util/mask_addr.c
diff options
context:
space:
mode:
Diffstat (limited to '')
-rw-r--r--src/util/mask_addr.c68
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;
+}