Add String() methods for BlockHash and Txid (#15)

Implements Go `Stringer` interface for `BlockHash` and `Txid` types to return hex-encoded hash strings in standard display order (reversed from internal byte order), enabling automatic formatting in fmt functions. Also adds test coverage.

Author: stringintech

kernel/block_hash.go

@@ -5,6 +5,7 @@ package kernel
 */
 import "C"
 import (
+	"encoding/hex"
 	"unsafe"
 )
 
@@ -85,3 +86,9 @@ func (bh *blockHashApi) Copy() *BlockHash {
 func (bh *blockHashApi) Equals(other BlockHashLike) bool {
 	return C.btck_block_hash_equals(bh.ptr, other.blockHashPtr()) != 0
 }
+
+// String returns the block hash as a hex string in display order (reversed).
+func (bh *blockHashApi) String() string {
+	hashBytes := bh.Bytes()
+	return hex.EncodeToString(ReverseBytes(hashBytes[:]))
+}

kernel/block_hash_test.go

@@ -1,6 +1,7 @@
 package kernel
 
 import (
+	"encoding/hex"
 	"testing"
 )
 
@@ -37,4 +38,10 @@ func TestBlockHash(t *testing.T) {
 	if hash.Equals(differentHash) {
 		t.Errorf("hash.Equals(differentHash) = true, want false")
 	}
+
+	// Test String()
+	expected := hex.EncodeToString(ReverseBytes(hashBytes[:]))
+	if hash.String() != expected {
+		t.Errorf("hash.String() = %s, want %s", hash.String(), expected)
+	}
 }

kernel/block_test.go

@@ -48,7 +48,7 @@ func TestBlock(t *testing.T) {
 		// Expected genesis block hash (reversed byte order for display)
 		expectedHash := "000000000019d6689c085ae165831e934ff763ae46a2a6c172b3f1b60a8ce26f"
 		hashBytes := hash.Bytes()
-		actualHashHex := hex.EncodeToString(reverseBytes(hashBytes[:]))
+		actualHashHex := hex.EncodeToString(ReverseBytes(hashBytes[:]))
 		if actualHashHex != expectedHash {
 			t.Errorf("Expected hash %s, got %s", expectedHash, actualHashHex)
 		}
@@ -134,11 +134,3 @@ func TestBlock(t *testing.T) {
 		}
 	})
 }
-
-func reverseBytes(data []byte) []byte {
-	result := make([]byte, len(data))
-	for i, b := range data {
-		result[len(data)-1-i] = b
-	}
-	return result
-}

kernel/common.go

@@ -92,3 +92,11 @@ func (h *handle) Destroy() {
 func go_delete_handle(handle unsafe.Pointer) {
 	cgo.Handle(handle).Delete()
 }
+
+func ReverseBytes(data []byte) []byte {
+	result := make([]byte, len(data))
+	for i, b := range data {
+		result[len(data)-1-i] = b
+	}
+	return result
+}

kernel/txid.go

@@ -5,6 +5,7 @@ package kernel
 */
 import "C"
 import (
+	"encoding/hex"
 	"unsafe"
 )
 
@@ -60,3 +61,9 @@ func (t *txidApi) Bytes() [32]byte {
 	C.btck_txid_to_bytes(t.ptr, &output[0])
 	return *(*[32]byte)(unsafe.Pointer(&output[0]))
 }
+
+// String returns the txid as a hex string in display order (reversed).
+func (t *txidApi) String() string {
+	hashBytes := t.Bytes()
+	return hex.EncodeToString(ReverseBytes(hashBytes[:]))
+}

kernel/txid_test.go

@@ -39,4 +39,11 @@ func TestTxid(t *testing.T) {
 	if !txid.Equals(copiedTxid) {
 		t.Error("txid.Equals(copiedTxid) = false, want true")
 	}
+
+	// Test String()
+	expected := hex.EncodeToString(ReverseBytes(txidBytes[:]))
+	txidStr := txid.String()
+	if txidStr != expected {
+		t.Errorf("hash.String() = %s, want %s", txidStr, expected)
+	}
 }