LoadOrNew loads the value associated with key from the pool if it already exists. If the key doesn't exist, it will call construct to create a new value and then stores that in the pool. An error is only returned if the constructor returns an error. The loaded or constructed value is returned. The l
(key any, construct Constructor)
| 75 | // if the value already existed and was loaded, or false if it was |
| 76 | // newly constructed. |
| 77 | func (up *UsagePool) LoadOrNew(key any, construct Constructor) (value any, loaded bool, err error) { |
| 78 | var upv *usagePoolVal |
| 79 | up.Lock() |
| 80 | upv, loaded = up.pool[key] |
| 81 | if loaded { |
| 82 | upv.refs.Add(1) |
| 83 | up.Unlock() |
| 84 | upv.RLock() |
| 85 | value = upv.value |
| 86 | err = upv.err |
| 87 | upv.RUnlock() |
| 88 | } else { |
| 89 | upv = &usagePoolVal{} |
| 90 | upv.refs.Store(1) |
| 91 | upv.Lock() |
| 92 | up.pool[key] = upv |
| 93 | up.Unlock() |
| 94 | value, err = construct() |
| 95 | if err == nil { |
| 96 | upv.value = value |
| 97 | } else { |
| 98 | upv.err = err |
| 99 | up.Lock() |
| 100 | // this *should* be safe, I think, because we have a |
| 101 | // write lock on upv, but we might also need to ensure |
| 102 | // that upv.err is nil before doing this, since we |
| 103 | // released the write lock on up during construct... |
| 104 | // but then again it's also after midnight... |
| 105 | delete(up.pool, key) |
| 106 | up.Unlock() |
| 107 | } |
| 108 | upv.Unlock() |
| 109 | } |
| 110 | return value, loaded, err |
| 111 | } |
| 112 | |
| 113 | // LoadOrStore loads the value associated with key from the pool if it |
| 114 | // already exists, or stores it if it does not exist. It returns the |
no test coverage detected