old stuff: algorithms

1 files changed, 131 insertions, 0 deletions

diff --git a/algorithms/ip.c b/algorithms/ip.c
new file mode 100644
index 0000000..6db600f
--- /dev/null
+++ b/algorithms/ip.c
@@ -0,0 +1,131 @@
+#include <stdio.h>
+
+#define IPSTRLEN 20
+
+
+int
+ip_str_to_ip_tuple(char ip_str[], int ip_tuple[])
+{
+	int retval;
+	
+	if (4!=(retval=sscanf(ip_str, "%d.%d.%d.%d", 
+			&ip_tuple[0], &ip_tuple[1], &ip_tuple[2], &ip_tuple[3]))) {
+		fprintf(stderr, "Error: sscanf failed, retval was: %d\n", retval);
+		return retval;
+	}
+	
+	return 0;
+}
+
+int
+ip_tuple_to_ip_str(int ip_tuple[], char ip_str[], int ip_str_size)
+{	
+	int retval;
+	
+	if (IPSTRLEN<(retval=snprintf(ip_str, ip_str_size, "%d.%d.%d.%d", 
+			ip_tuple[3], ip_tuple[2], ip_tuple[1], ip_tuple[0]))) {
+		return retval;
+	}
+	
+	return 0;
+}
+
+unsigned long
+ip_tuple_to_addr(int ip_tuple[])
+{
+	unsigned long result=0;
+	
+	for (int i = 0; i < 4; i += 1) {
+		result = result<<8;
+		result = ip_tuple[i]|result;
+	}
+	
+	return result;
+}
+
+int
+addr_to_ip_tuple(unsigned long addr, int ip_tuple[])
+{
+	for (int i = 0; i < 4; i += 1) {
+		ip_tuple[i] = (addr>>i*8)&255;
+	}
+	
+	return 0;
+}
+
+unsigned long
+compute_netmask_for_size(int net_size)
+{
+	unsigned long netmask = 0xffffffff;
+	
+	netmask = netmask<<net_size;
+	
+	return netmask;
+}
+
+unsigned long
+compute_network_address(unsigned long host_addr, unsigned long netmask)
+{
+	unsigned long net_addr;
+	
+	net_addr = host_addr&netmask;
+	
+	return net_addr;
+}
+
+unsigned long
+computer_router_address(unsigned long host_addr, unsigned long netmask)
+{
+	unsigned long router_addr;
+	
+	router_addr = compute_network_address(host_addr, netmask)+1;
+	
+	return router_addr;
+}
+
+int
+addr_to_ip_str(unsigned long addr, char ip_str[], int ip_str_size)
+{
+	int ip_tuple[4];
+	
+	addr_to_ip_tuple(addr, ip_tuple);
+	
+	if (ip_tuple_to_ip_str(ip_tuple, ip_str, ip_str_size)) {
+		fprintf(stderr, "Error: IP Address malformed.\n");
+	}
+	
+	return 0;
+}
+
+
+int
+main(void)
+{
+	char the_ip[]="147.142.207.19", new_ip[IPSTRLEN];
+	int net_size=8;
+	int ip_tuple[4];
+	unsigned long ip_addr;
+	
+	if (ip_str_to_ip_tuple(the_ip, ip_tuple)) {
+		fprintf(stderr, "Invalid IP address: %s\n", the_ip);
+		return 1;
+	}
+	ip_addr = ip_tuple_to_addr(ip_tuple);
+	printf("IP Address: %lx\n", ip_addr);
+	if (addr_to_ip_str(compute_network_address(ip_addr,
+			compute_netmask_for_size(net_size)), new_ip, IPSTRLEN)) {
+		fprintf(stderr, "Couldn't format network address.\n");
+		return 1;
+	}
+	printf("Network for this host (netmask %lx): %s\n",
+		compute_netmask_for_size(net_size), new_ip);
+	if (addr_to_ip_str(computer_router_address(ip_addr,
+			compute_netmask_for_size(net_size)), new_ip, IPSTRLEN)) {
+		fprintf(stderr, "Couldn't format router address.\n");
+		return 1;
+	}
+	printf("Probable router for this host (netmask %lx): %s\n",
+		compute_netmask_for_size(net_size), new_ip);
+
+	return 0;
+}