Added basic pubkey generation from private key

README.md

@@ -43,6 +43,7 @@ View the generated [documentation](https://pkg.go.dev/github.com/bitcoinschema/g
 - [Private key (string) to Address (string)](address.go)
 - [Address from Private key (bsvec.PrivateKey)](address.go)
 - [Create Private Key](private_key.go)
+- [Create PubKey From Private Key](pubkey.go)
 
 
 <details>

examples/create_pubkey/create_pubkey.go

@@ -0,0 +1,25 @@
+package main
+
+import (
+	"log"
+
+	"github.com/bitcoinschema/go-bitcoin"
+)
+
+func main() {
+
+	// Start with a private key
+	privateKey, err := bitcoin.CreatePrivateKeyString()
+	if err != nil {
+		log.Fatalf("error occurred: %s", err.Error())
+	}
+
+	// Create a pubkey
+	var pubKey string
+	if pubKey, err = bitcoin.PubKeyFromPrivateKey(privateKey); err != nil {
+		log.Fatalf("error occurred: %s", err.Error())
+	}
+
+	// Success!
+	log.Printf("created pubkey: %s from private key: %s", pubKey, privateKey)
+}

pubkey.go

@@ -0,0 +1,15 @@
+package bitcoin
+
+import (
+	"encoding/hex"
+)
+
+// PubKeyFromPrivateKey will derive a pubKey (hex encoded) from a given private key
+func PubKeyFromPrivateKey(privateKey string) (string, error) {
+	rawKey, err := PrivateKeyFromString(privateKey)
+	if err != nil {
+		return "", err
+	}
+
+	return hex.EncodeToString(rawKey.PubKey().SerializeCompressed()), nil
+}

pubkey_test.go

@@ -0,0 +1,52 @@
+package bitcoin
+
+import (
+	"fmt"
+	"testing"
+)
+
+// TestPubKeyFromPrivateKey will test the method PubKeyFromPrivateKey()
+func TestPubKeyFromPrivateKey(t *testing.T) {
+	t.Parallel()
+
+	// Create the list of tests
+	var tests = []struct {
+		inputKey       string
+		expectedPubKey string
+		expectedError  bool
+	}{
+		{"54035dd4c7dda99ac473905a3d82f7864322b49bab1ff441cc457183b9bd8abd", "031b8c93100d35bd448f4646cc4678f278351b439b52b303ea31ec9edb5475e73f", false},
+		{"0", "", true},
+		{"", "", true},
+	}
+
+	// Run tests
+	for _, test := range tests {
+		if pubKey, err := PubKeyFromPrivateKey(test.inputKey); err != nil && !test.expectedError {
+			t.Errorf("%s Failed: [%s] inputted and error not expected but got: %s", t.Name(), test.inputKey, err.Error())
+		} else if err == nil && test.expectedError {
+			t.Errorf("%s Failed: [%s] inputted and error was expected", t.Name(), test.inputKey)
+		} else if pubKey != test.expectedPubKey {
+			t.Errorf("%s Failed: [%s] inputted and [%s] expected, but got: %s", t.Name(), test.inputKey, test.expectedPubKey, pubKey)
+		}
+	}
+}
+
+// ExamplePubKeyFromPrivateKey example using PubKeyFromPrivateKey()
+func ExamplePubKeyFromPrivateKey() {
+	pubKey, err := PubKeyFromPrivateKey("54035dd4c7dda99ac473905a3d82f7864322b49bab1ff441cc457183b9bd8abd")
+	if err != nil {
+		fmt.Printf("error occurred: %s", err.Error())
+		return
+	}
+	fmt.Printf("pubkey generated: %s", pubKey)
+	// Output:pubkey generated: 031b8c93100d35bd448f4646cc4678f278351b439b52b303ea31ec9edb5475e73f
+}
+
+// BenchmarkPubKeyFromPrivateKey benchmarks the method PubKeyFromPrivateKey()
+func BenchmarkPubKeyFromPrivateKey(b *testing.B) {
+	key, _ := CreatePrivateKeyString()
+	for i := 0; i < b.N; i++ {
+		_, _ = PubKeyFromPrivateKey(key)
+	}
+}