func()

in tsdb/chunkenc/histogram.go [749:935]

• 159 lines of code
• 30 McCabe index (conditional complexity)

func (it *histogramIterator) Next() ValueType {
	if it.err != nil || it.numRead == it.numTotal {
		return ValNone
	}

	if it.numRead == 0 {
		// The first read is responsible for reading the chunk layout
		// and for initializing fields that depend on it. We give
		// counter reset info at chunk level, hence we discard it here.
		schema, zeroThreshold, posSpans, negSpans, err := readHistogramChunkLayout(&it.br)
		if err != nil {
			it.err = err
			return ValNone
		}
		it.schema = schema
		it.zThreshold = zeroThreshold
		it.pSpans, it.nSpans = posSpans, negSpans
		numPBuckets, numNBuckets := countSpans(posSpans), countSpans(negSpans)
		// The code below recycles existing slices in case this iterator
		// was reset and already has slices of a sufficient capacity.
		if numPBuckets > 0 {
			it.pBuckets = append(it.pBuckets, make([]int64, numPBuckets)...)
			it.pBucketsDelta = append(it.pBucketsDelta, make([]int64, numPBuckets)...)
			it.pFloatBuckets = append(it.pFloatBuckets, make([]float64, numPBuckets)...)
		}
		if numNBuckets > 0 {
			it.nBuckets = append(it.nBuckets, make([]int64, numNBuckets)...)
			it.nBucketsDelta = append(it.nBucketsDelta, make([]int64, numNBuckets)...)
			it.nFloatBuckets = append(it.nFloatBuckets, make([]float64, numNBuckets)...)
		}

		// Now read the actual data.
		t, err := readVarbitInt(&it.br)
		if err != nil {
			it.err = err
			return ValNone
		}
		it.t = t

		cnt, err := readVarbitUint(&it.br)
		if err != nil {
			it.err = err
			return ValNone
		}
		it.cnt = cnt

		zcnt, err := readVarbitUint(&it.br)
		if err != nil {
			it.err = err
			return ValNone
		}
		it.zCnt = zcnt

		sum, err := it.br.readBits(64)
		if err != nil {
			it.err = err
			return ValNone
		}
		it.sum = math.Float64frombits(sum)

		var current int64
		for i := range it.pBuckets {
			v, err := readVarbitInt(&it.br)
			if err != nil {
				it.err = err
				return ValNone
			}
			it.pBuckets[i] = v
			current += it.pBuckets[i]
			it.pFloatBuckets[i] = float64(current)
		}
		current = 0
		for i := range it.nBuckets {
			v, err := readVarbitInt(&it.br)
			if err != nil {
				it.err = err
				return ValNone
			}
			it.nBuckets[i] = v
			current += it.nBuckets[i]
			it.nFloatBuckets[i] = float64(current)
		}

		it.numRead++
		return ValHistogram
	}

	// The case for the 2nd sample with single deltas is implicitly handled correctly with the double delta code,
	// so we don't need a separate single delta logic for the 2nd sample.

	// Recycle bucket slices that have not been returned yet. Otherwise,
	// copy them.
	if it.atHistogramCalled {
		it.atHistogramCalled = false
		if len(it.pBuckets) > 0 {
			newBuckets := make([]int64, len(it.pBuckets))
			copy(newBuckets, it.pBuckets)
			it.pBuckets = newBuckets
		} else {
			it.pBuckets = nil
		}
		if len(it.nBuckets) > 0 {
			newBuckets := make([]int64, len(it.nBuckets))
			copy(newBuckets, it.nBuckets)
			it.nBuckets = newBuckets
		} else {
			it.nBuckets = nil
		}
	}
	// FloatBuckets are set from scratch, so simply create empty ones.
	if it.atFloatHistogramCalled {
		it.atFloatHistogramCalled = false
		if len(it.pFloatBuckets) > 0 {
			it.pFloatBuckets = make([]float64, len(it.pFloatBuckets))
		} else {
			it.pFloatBuckets = nil
		}
		if len(it.nFloatBuckets) > 0 {
			it.nFloatBuckets = make([]float64, len(it.nFloatBuckets))
		} else {
			it.nFloatBuckets = nil
		}
	}

	tDod, err := readVarbitInt(&it.br)
	if err != nil {
		it.err = err
		return ValNone
	}
	it.tDelta += tDod
	it.t += it.tDelta

	cntDod, err := readVarbitInt(&it.br)
	if err != nil {
		it.err = err
		return ValNone
	}
	it.cntDelta += cntDod
	it.cnt = uint64(int64(it.cnt) + it.cntDelta)

	zcntDod, err := readVarbitInt(&it.br)
	if err != nil {
		it.err = err
		return ValNone
	}
	it.zCntDelta += zcntDod
	it.zCnt = uint64(int64(it.zCnt) + it.zCntDelta)

	ok := it.readSum()
	if !ok {
		return ValNone
	}

	if value.IsStaleNaN(it.sum) {
		it.numRead++
		return ValHistogram
	}

	var current int64
	for i := range it.pBuckets {
		dod, err := readVarbitInt(&it.br)
		if err != nil {
			it.err = err
			return ValNone
		}
		it.pBucketsDelta[i] += dod
		it.pBuckets[i] += it.pBucketsDelta[i]
		current += it.pBuckets[i]
		it.pFloatBuckets[i] = float64(current)
	}

	current = 0
	for i := range it.nBuckets {
		dod, err := readVarbitInt(&it.br)
		if err != nil {
			it.err = err
			return ValNone
		}
		it.nBucketsDelta[i] += dod
		it.nBuckets[i] += it.nBucketsDelta[i]
		current += it.nBuckets[i]
		it.nFloatBuckets[i] = float64(current)
	}

	it.numRead++
	return ValHistogram
}