Merge pull request #114 from bschaatsbergen/f/separate-host-from-all-address-count

feat: separate host address count from address count

Author: bschaatsbergen

Makefile

@@ -1,4 +1,4 @@
-default: fmt lint build install
+default: fmt lint build install test
 
 build:
 	go build -v ./...

README.md

@@ -25,20 +25,20 @@ To get more information on a CIDR range:
 ```
 $ cidr explain 10.0.0.0/16
 Base Address:            10.0.0.0
-Usable Address Range:    10.0.0.1 to 10.0.255.254
+Usable Address Range:    10.0.0.1 to 10.0.255.254 (65,534)
 Broadcast Address:       10.0.255.255
-Address Count:           65,534
+Addresses:               65,536
 Netmask:                 255.255.0.0 (/16 bits)
 ```
 
 This also works with IPv6 CIDR ranges, for example:
 
 ```
-$ cidr explain 2001:db8:1234:1a00::/64
+$ cidr explain 2001:db8:1234:1a00::/110
 Base Address:            2001:db8:1234:1a00::
-Usable Address Range:    2001:db8:1234:1a00:: to 2001:db8:1234:1a00:ffff:ffff:ffff:ffff
-Address Count:           18,446,744,073,709,551,614
-Netmask:                 ffff:ffff:ffff:ffff:: (/64 bits)
+Usable Address Range:    2001:db8:1234:1a00:: to 2001:db8:1234:1a00::3:ffff (262,142)
+Addresses:               262,144
+Netmask:                 ffff:ffff:ffff:ffff:ffff:ffff:fffc:0 (/110 bits)
 ```
 
 ### Check whether an address belongs to a CIDR range
@@ -57,20 +57,20 @@ $ cidr contains 2001:db8:1234:1a00::/106 2001:db8:1234:1a00::
 true
 ```
 
-### Count distinct host addresses
+### Count
 
-To get all distinct host addresses part of a given CIDR range:
+To get a count of all addresses in a CIDR range:
 
 ```
 $ cidr count 10.0.0.0/16
-65534
+65536
 ```
 
 This also works with a IPv6 CIDR range, for example:
 
 ```
 $ cidr count 2001:db8:1234:1a00::/106
-4194302
+4194304
 ```
 
 Or with a large prefix like a point-to-point link CIDR range:

cmd/count.go

@@ -11,17 +11,17 @@ import (
 )
 
 const (
-	countExample = "# Return the count of all distinct host addresses within a given IPv4 CIDR range\n" +
+	countExample = "# Return the count of all addresses within a given IPv4 CIDR range\n" +
 		"cidr count 10.0.0.0/16\n" +
 		"\n" +
-		"# Return the count of all distinct host addresses within a given IPv6 CIDR range\n" +
+		"# Return the count of all addresses within a given IPv6 CIDR range\n" +
 		"cidr count 2001:db8:1234:1a00::/106"
 )
 
 var (
 	countCmd = &cobra.Command{
 		Use:     "count",
-		Short:   "Return the count of all distinct host addresses in a given CIDR range",
+		Short:   "Return the count of all addresses in a given CIDR range",
 		Example: countExample,
 		Run: func(cmd *cobra.Command, args []string) {
 			if len(args) != 1 {

cmd/explain.go

@@ -55,6 +55,7 @@ type networkDetailsToDisplay struct {
 	PrefixLength               int
 	BaseAddress                net.IP
 	Count                      string
+	HostCount                  string
 	UsableAddressRangeHasError bool
 	FirstUsableIPAddress       string
 	LastUsableIPAddress        string
@@ -94,6 +95,11 @@ func getNetworkDetails(network *net.IPNet) *networkDetailsToDisplay {
 	// Format the count as a human-readable string and store it in the details struct.
 	details.Count = helper.FormatNumber(count.String())
 
+	// Obtain the total count of distinct host addresses in the network.
+	hostCount := core.GetHostAddressCount(network)
+	// Format the count as a human-readable string and store it in the details struct.
+	details.HostCount = helper.FormatNumber(hostCount.String())
+
 	// Obtain the first and last usable IP addresses, handling errors if they occur.
 	firstUsableIP, err := core.GetFirstUsableIPAddress(network)
 	if err != nil {
@@ -120,17 +126,20 @@ func explain(details *networkDetailsToDisplay) {
 	var lengthIndicator string
 
 	fmt.Printf(color.BlueString("Base Address:\t\t ")+"%s\n", details.BaseAddress)
+
 	if !details.UsableAddressRangeHasError {
-		fmt.Printf(color.BlueString("Usable Address Range:\t ")+"%s to %s\n", details.FirstUsableIPAddress, details.LastUsableIPAddress)
+		fmt.Printf(color.BlueString("Usable Address Range:\t ")+"%s to %s (%s)\n", details.FirstUsableIPAddress, details.LastUsableIPAddress, details.HostCount)
 	} else {
 		fmt.Printf(color.RedString("Usable Address Range:\t ")+"%s\n", "unable to calculate usable address range")
 	}
+
 	if !details.BroadcastAddressHasError && details.IsIPV4Network {
 		fmt.Printf(color.BlueString("Broadcast Address:\t ")+"%s\n", details.BroadcastAddress)
 	} else if details.BroadcastAddressHasError && details.IsIPV4Network {
 		fmt.Printf(color.RedString("Broadcast Address:\t ")+"%s\n", details.BroadcastAddress)
 	}
-	fmt.Printf(color.BlueString("Host Addresses:\t\t ")+"%s\n", details.Count)
+
+	fmt.Printf(color.BlueString("Addresses:\t\t ")+"%s\n", details.Count)
 
 	if details.PrefixLength > 1 {
 		lengthIndicator = "bits"

pkg/core/core.go

@@ -18,23 +18,48 @@ func ParseCIDR(network string) (*net.IPNet, error) {
 	return ip, err
 }
 
-// GetAddressCount returns the number of addresses in the given IP network.
-// It considers the network type (IPv4 or IPv6) and handles edge cases for specific prefix lengths.
-// The result excludes the network address and broadcast address.
+// GetAddressCount returns the total number of addresses in the given IP network.
+// It accounts for both IPv4 and IPv6 networks, and handles specific cases for certain prefix lengths.
 func GetAddressCount(network *net.IPNet) *big.Int {
 	prefixLen, bits := network.Mask.Size()
 
+	// Handle specific cases for IPv4 prefix lengths.
+	if network.IP.To4() != nil {
+		switch prefixLen {
+		case 32:
+			// A /32 prefix contains a single address.
+			return big.NewInt(1)
+		case 31:
+			// A /31 prefix is used for point-to-point links and contains two addresses.
+			return big.NewInt(2)
+		}
+	}
+
+	// Calculate the total number of addresses based on the prefix length.
+	return new(big.Int).Lsh(big.NewInt(1), uint(bits-prefixLen))
+}
+
+// GetHostAddressCount returns the number of distinct host addresses in the given IP network.
+// It considers the network type (IPv4 or IPv6) and handles edge cases for specific prefix lengths.
+// The result excludes the network address and the broadcast address, if applicable.
+func GetHostAddressCount(network *net.IPNet) *big.Int {
+	prefixLen, bits := network.Mask.Size()
+
 	// Handle edge cases for specific IPv4 prefix lengths.
-	if network.Mask != nil && network.IP.To4() != nil {
+	if network.IP.To4() != nil {
 		switch prefixLen {
 		case 32:
+			// Single IP address for /32 (e.g., point-to-point link).
 			return big.NewInt(1)
 		case 31:
+			// Two IP addresses for /31 (point-to-point link).
 			return big.NewInt(2)
 		}
 	}
 
-	return big.NewInt(0).Lsh(big.NewInt(1), uint(bits-prefixLen))
+	// Calculate the total number of addresses and subtract 2 (network and broadcast addresses).
+	totalAddresses := new(big.Int).Exp(big.NewInt(2), big.NewInt(int64(bits-prefixLen)), nil)
+	return totalAddresses.Sub(totalAddresses, big.NewInt(2))
 }
 
 // ContainsAddress checks if the given IP network contains the specified IP address.

pkg/core/core_test.go

@@ -40,22 +40,22 @@ func TestGetAddressCount(t *testing.T) {
 		expectedCount *big.Int
 	}{
 		{
-			name:          "Return the count of all distinct host addresses in a common IPv4 CIDR",
+			name:          "Return the count of all addresses in a common IPv4 CIDR",
 			cidr:          IPv4CIDR,
 			expectedCount: big.NewInt(65536),
 		},
 		{
-			name:          "Return the count of all distinct host addresses in a common IPv6 CIDR",
+			name:          "Return the count of all addresses in a common IPv6 CIDR",
 			cidr:          IPv6CIDR,
 			expectedCount: big.NewInt(4194304),
 		},
 		{
-			name:          "Return the count of all distinct host addresses in an uncommon (large prefix) IPv4 CIDR",
+			name:          "Return the count of all addresses in an uncommon (large prefix) IPv4 CIDR",
 			cidr:          largeIPv4PrefixCIDR,
 			expectedCount: big.NewInt(2),
 		},
 		{
-			name:          "Return the count of all distinct host addresses in an uncommon (largest prefix) IPv4 CIDR",
+			name:          "Return the count of all addresses in an uncommon (largest prefix) IPv4 CIDR",
 			cidr:          largestIPv4PrefixCIDR,
 			expectedCount: big.NewInt(1),
 		},