mirror of
https://github.com/VictoriaMetrics/VictoriaMetrics.git
synced 2024-11-21 14:44:00 +00:00
83 lines
2.2 KiB
Go
83 lines
2.2 KiB
Go
package encoding
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import (
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"fmt"
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"github.com/VictoriaMetrics/VictoriaMetrics/lib/logger"
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)
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// marshalInt64NearestDelta2 encodes src using `nearest delta2` encoding
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// with the given precisionBits and appends the encoded value to dst.
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//
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// precisionBits must be in the range [1...64], where 1 means 50% precision,
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// while 64 means 100% precision, i.e. lossless encoding.
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func marshalInt64NearestDelta2(dst []byte, src []int64, precisionBits uint8) (result []byte, firstValue int64) {
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if len(src) < 2 {
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logger.Panicf("BUG: src must contain at least 2 items; got %d items", len(src))
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}
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if err := CheckPrecisionBits(precisionBits); err != nil {
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logger.Panicf("BUG: %s", err)
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}
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firstValue = src[0]
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d1 := src[1] - src[0]
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dst = MarshalVarInt64(dst, d1)
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v := src[1]
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src = src[2:]
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is := GetInt64s(len(src))
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if precisionBits == 64 {
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// Fast path.
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for i, next := range src {
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d2 := next - v - d1
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d1 += d2
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v += d1
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is.A[i] = d2
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}
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} else {
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// Slower path.
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trailingZeros := getTrailingZeros(v, precisionBits)
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for i, next := range src {
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d2, tzs := nearestDelta(next-v, d1, precisionBits, trailingZeros)
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trailingZeros = tzs
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d1 += d2
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v += d1
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is.A[i] = d2
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}
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}
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dst = MarshalVarInt64s(dst, is.A)
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PutInt64s(is)
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return dst, firstValue
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}
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// unmarshalInt64NearestDelta2 decodes src using `nearest delta2` encoding,
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// appends the result to dst and returns the appended result.
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//
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// firstValue must be the value returned from marshalInt64NearestDelta2.
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func unmarshalInt64NearestDelta2(dst []int64, src []byte, firstValue int64, itemsCount int) ([]int64, error) {
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if itemsCount < 2 {
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logger.Panicf("BUG: itemsCount must be greater than 1; got %d", itemsCount)
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}
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is := GetInt64s(itemsCount - 1)
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defer PutInt64s(is)
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tail, err := UnmarshalVarInt64s(is.A, src)
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if err != nil {
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return nil, fmt.Errorf("cannot unmarshal nearest delta: %s", err)
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}
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if len(tail) > 0 {
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return nil, fmt.Errorf("unexpected tail left after unmarshaling %d items; tail size=%d, value=%X", itemsCount, len(tail), tail)
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}
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v := firstValue
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d1 := is.A[0]
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dst = append(dst, v)
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v += d1
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dst = append(dst, v)
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for _, d2 := range is.A[1:] {
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d1 += d2
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v += d1
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dst = append(dst, v)
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}
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return dst, nil
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}
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