// incrementOffset is a common incrementor method used between Increment and
// Decrement. If the key isn't set before, we will set the initial value. If
// there is a value present, we will add the given offset to that value and
// update the value with the new TTL.
func (c *Cache) incrementOffset(key string, initial, offset, ttl int64) error {
c.client.Do("WATCH", key)
if err := c.exists(key); err != nil {
c.client.Do("MULTI")
defer c.client.Do("EXEC")
return c.Set(key, encoding.Int64Bytes(initial), ttl)
}
getValue, _, err := c.Get(key)
if err != nil {
return err
}
val, ok := encoding.BytesInt64(getValue)
if !ok {
return errors.NewEncoding(key)
}
// We are watching our key. With using a transaction, we can check that this
// increment doesn't inflect with another concurrent request that might
// happen.
c.client.Do("MULTI")
defer c.client.Do("EXEC")
val += offset
if val < 0 {
return errors.NewValueBelowZero(key)
}
return c.Set(key, encoding.Int64Bytes(val), ttl)
}
// incrementOffset is a common incrementor method used between Increment and
// Decrement. If the key isn't set before, we will set the initial value. If
// there is a value present, we will add the given offset to that value and
// update the value with the new TTL.
func (c *Cache) incrementOffset(key string, initial, offset, ttl int64) error {
if err := c.exists(key); err != nil {
return c.Set(key, encoding.Int64Bytes(initial), ttl)
}
val, ok := encoding.BytesInt64(c.items[key].value)
if !ok {
return errors.NewEncoding(key)
}
val += offset
if val < 0 {
return errors.NewValueBelowZero(key)
}
return c.Set(key, encoding.Int64Bytes(val), ttl)
}