Laziter

Lazy iterator experimentation. The aim of this lib is to enable lazy loading an iterator's content. The lazy loading is achieved using a goroutine and two channels per iterator.

Example

Base use

func main() {
    iter := laziter.New[int](false) // No persistence needed here
    defer iter.Close() // Close() should always be called to prevent leaking goroutines

    // Start values provider goroutine
    go sampleValuesGenerator(iter.GetValuesProvider(), 5)

    // Iterate over values
    for iter.Next() {
        value, _ := iter.GetCurrentValue()
    }
}

func sampleValuesGenerator(vp *laziter.ValuesProvider[int], valuesCount int) {
    defer vp.Close()
    for i := 0; i < valuesCount; i++ {
        if !vp.Wait() {
            // Iterator stopped iteration, quit
            break
        }
        vp.Yield(i) // Produce value
    }
}

Partial iteration

The following example shows a partial iteration with the lazy iterator. Once sampleFunction() returns, sampleValuesGenerator() goroutine will end, skipping the last 2 values that won't be evaluated (3 & 4). You may stop the iteration early by calling iter.Done(), here it is called in a defer statement.

func sampleFunction() {
    iter := laziter.New[int](false) // No persistence needed here
    defer iter.Close()

    // Start values provider goroutine
    go sampleValuesGenerator(iter.GetValuesProvider(), 5)

    // Get 3 values
    for i := 0; i < 4; i++ {
        value, _ := iter.GetCurrentValue()
    }
}

func sampleValuesGenerator(vp *laziter.ValuesProvider[int], valuesCount int) {
    // [...] (same as above)
}

Values persistence

The current Iterator implementation allows values persistence which enables, for example, multiple for iter.Next() { [...] } statements. It is also possible to call ResetIteratorPosition() while iterating. This will pause values retrieval until the iterator needs more.

func main() {
    iter := laziter.New[int](true) // Persistence enabled
    defer iter.Close()

    go sampleValuesGenerator(iter.GetValuesProvider(), 5)

    // Iterate over values once
    for iter.Next() {
        value, _ := iter.GetCurrentValue()
    }

    // Reset the iterator position
    iter.ResetIteratorPosition()
    // From now on, values are fetched from the iterator's persisted storage.
    // sampleValuesGenerator() goroutine already exited.
    
    // Iterate over values again
    for iter.Next() {
        value, _ := iter.GetCurrentValue()
    }
}

func sampleValuesGenerator(vp *laziter.ValuesProvider[int], valuesCount int) {
    // [...] (same as above)
}