feat: new method--HStrLen(#136)

structure/hash.go

@@ -616,3 +616,40 @@ func (hs *HashStructure) HDecrBy(key, field []byte, decrement int64) (int64, err
 
 	return val, nil
 }
+
+// HStrLen returns the string length of the value associated with field in the hash stored at key.
+func (hs *HashStructure) HStrLen(key, field []byte) (int, error) {
+	// Check the parameters
+	if len(key) == 0 || len(field) == 0 {
+		return 0, _const.ErrKeyIsEmpty
+	}
+
+	// Find the hash metadata by the given key
+	hashMeta, err := hs.findHashMeta(key, Hash)
+	if err != nil {
+		return 0, err
+	}
+
+	// If the counter is 0, return 0
+	if hashMeta.counter == 0 {
+		return 0, nil
+	}
+
+	// Create a new HashField
+	hf := &HashField{
+		field:   field,
+		key:     key,
+		version: hashMeta.version,
+	}
+
+	// Encode the HashField
+	hfBuf := hf.encodeHashField()
+
+	// Get the field from the database
+	value, err := hs.db.Get(hfBuf)
+	if err != nil && err == _const.ErrKeyNotFound {
+		return 0, nil
+	}
+
+	return len(value), nil
+}

structure/hash_test.go

@@ -241,3 +241,36 @@ func TestHashStructure_HDecrBy(t *testing.T) {
 	assert.Equal(t, v4, int64(0))
 
 }
+
+func TestHashStructure_HStrLen(t *testing.T) {
+	hash := initHashDB()
+
+	ok1, err := hash.HSet(randkv.GetTestKey(1), []byte("field1"), []byte("1000"))
+	assert.Nil(t, err)
+	assert.True(t, ok1)
+
+	ok2, err := hash.HSet(randkv.GetTestKey(1), []byte("field2"), []byte("100"))
+	assert.Nil(t, err)
+	assert.True(t, ok2)
+
+	ok3, err := hash.HSet(randkv.GetTestKey(1), []byte("field3"), []byte("10"))
+	assert.Nil(t, err)
+	assert.True(t, ok3)
+
+	l1, err := hash.HStrLen(randkv.GetTestKey(1), []byte("field1"))
+	assert.Nil(t, err)
+	assert.Equal(t, l1, 4)
+
+	l2, err := hash.HStrLen(randkv.GetTestKey(1), []byte("field2"))
+	assert.Nil(t, err)
+	assert.Equal(t, l2, 3)
+
+	l3, err := hash.HStrLen(randkv.GetTestKey(1), []byte("field3"))
+	assert.Nil(t, err)
+	assert.Equal(t, l3, 2)
+
+	l4, err := hash.HStrLen(randkv.GetTestKey(1), []byte("field4"))
+	assert.Nil(t, err)
+	assert.Equal(t, l4, 0)
+
+}