c/decip4.c: Finally, the ability to turn an IPv4 address into an integer

c/decip4.c

@@ -0,0 +1,26 @@
+#include <stdint.h>
+#include <stdio.h>
+
+uint32_t numeric_ip4(const char *ip) {
+  uint32_t octets = 0;
+  uint8_t octet = 0;
+  
+  for(; *ip; ip += 1) {
+    if(*ip == '.') {
+      octets = (octets << 8) | octet; 
+      octet = 0;
+    } else {
+      octet = (octet * 10) + (*ip - '0');
+    }
+  }
+  
+  return (octets << 8) | octet;
+}
+
+int main(int argc, char **argv) {
+  for(argv += 1, argc -= 1; *argv; argv += 1, argc -= 1) {
+    printf("%s: %u\n", *argv, numeric_ip4(*argv));
+  }
+
+  return 0;
+}