func (c RedisCache) Decrement(key string, delta uint64) (newValue uint64, err error) {
conn := c.pool.Get()
defer conn.Close()
// Check for existance *before* increment as per the cache contract.
// redis will auto create the key, and we don't want that, hence the exists call
existed, err := exists(conn, key)
if err != nil {
return 0, err
} else if !existed {
return 0, ErrCacheMiss
}
// Decrement contract says you can only go to 0
// so we go fetch the value and if the delta is greater than the amount,
// 0 out the value
currentVal, err := redis.Int64(conn.Do("GET", key))
if err != nil {
return 0, err
}
if delta > uint64(currentVal) {
tempint, err := redis.Int64(conn.Do("DECRBY", key, currentVal))
return uint64(tempint), err
}
tempint, err := redis.Int64(conn.Do("DECRBY", key, delta))
return uint64(tempint), err
}
func (c RedisCache) Increment(key string, delta uint64) (uint64, error) {
conn := c.pool.Get()
defer conn.Close()
// Check for existance *before* increment as per the cache contract.
// redis will auto create the key, and we don't want that. Since we need to do increment
// ourselves instead of natively via INCRBY (redis doesn't support wrapping), we get the value
// and do the exists check this way to minimize calls to Redis
val, err := conn.Do("GET", key)
if err != nil {
return 0, err
} else if val == nil {
return 0, ErrCacheMiss
}
currentVal, err := redis.Int64(val, nil)
if err != nil {
return 0, err
}
var sum int64 = currentVal + int64(delta)
_, err = conn.Do("SET", key, sum)
if err != nil {
return 0, err
}
return uint64(sum), nil
}