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batch_timestamp.go
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/
batch_timestamp.go
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package tsm1
import (
"encoding/binary"
"fmt"
"math"
"unsafe"
"github.com/influxdata/influxdb/pkg/encoding/simple8b"
)
var (
timeBatchDecoderFunc = [...]func(b []byte, dst []int64) ([]int64, error){
timeBatchDecodeAllUncompressed,
timeBatchDecodeAllSimple,
timeBatchDecodeAllRLE,
timeBatchDecodeAllInvalid,
}
)
func TimeBatchDecodeAll(b []byte, dst []int64) ([]int64, error) {
if len(b) == 0 {
return []int64{}, nil
}
encoding := b[0] >> 4
if encoding > timeCompressedRLE {
encoding = 3 // timeBatchDecodeAllInvalid
}
return timeBatchDecoderFunc[encoding&3](b, dst)
}
func timeBatchDecodeAllUncompressed(b []byte, dst []int64) ([]int64, error) {
b = b[1:]
if len(b)&0x7 != 0 {
return []int64{}, fmt.Errorf("TimeBatchDecodeAll: expected multiple of 8 bytes")
}
count := len(b) / 8
if cap(dst) < count {
dst = make([]int64, count)
} else {
dst = dst[:count]
}
prev := uint64(0)
for i := range dst {
prev += binary.BigEndian.Uint64(b[i*8:])
dst[i] = int64(prev)
}
return dst, nil
}
func timeBatchDecodeAllSimple(b []byte, dst []int64) ([]int64, error) {
if len(b) < 9 {
return []int64{}, fmt.Errorf("TimeBatchDecodeAll: not enough data to decode packed timestamps")
}
div := uint64(math.Pow10(int(b[0] & 0xF))) // multiplier
count, err := simple8b.CountBytes(b[9:])
if err != nil {
return []int64{}, err
}
count += 1
if cap(dst) < count {
dst = make([]int64, count)
} else {
dst = dst[:count]
}
buf := *(*[]uint64)(unsafe.Pointer(&dst))
// first value
buf[0] = binary.BigEndian.Uint64(b[1:9])
n, err := simple8b.DecodeBytesBigEndian(buf[1:], b[9:])
if err != nil {
return []int64{}, err
}
if n != count-1 {
return []int64{}, fmt.Errorf("TimeBatchDecodeAll: unexpected number of values decoded; got=%d, exp=%d", n, count-1)
}
// Compute the prefix sum and scale the deltas back up
last := buf[0]
if div > 1 {
for i := 1; i < len(buf); i++ {
dgap := buf[i] * div
buf[i] = last + dgap
last = buf[i]
}
} else {
for i := 1; i < len(buf); i++ {
buf[i] += last
last = buf[i]
}
}
return dst, nil
}
func timeBatchDecodeAllRLE(b []byte, dst []int64) ([]int64, error) {
if len(b) < 9 {
return []int64{}, fmt.Errorf("TimeBatchDecodeAll: not enough data to decode RLE starting value")
}
var k, n int
// Lower 4 bits hold the 10 based exponent so we can scale the values back up
mod := int64(math.Pow10(int(b[k] & 0xF)))
k++
// Next 8 bytes is the starting timestamp
first := binary.BigEndian.Uint64(b[k:])
k += 8
// Next 1-10 bytes is our (scaled down by factor of 10) run length delta
delta, n := binary.Uvarint(b[k:])
if n <= 0 {
return []int64{}, fmt.Errorf("TimeBatchDecodeAll: invalid run length in decodeRLE")
}
k += n
// Scale the delta back up
delta *= uint64(mod)
// Last 1-10 bytes is how many times the value repeats
count, n := binary.Uvarint(b[k:])
if n <= 0 {
return []int64{}, fmt.Errorf("TimeDecoder: invalid repeat value in decodeRLE")
}
if cap(dst) < int(count) {
dst = make([]int64, count)
} else {
dst = dst[:count]
}
acc := first
for i := range dst {
dst[i] = int64(acc)
acc += delta
}
return dst, nil
}
func timeBatchDecodeAllInvalid(b []byte, _ []int64) ([]int64, error) {
return []int64{}, fmt.Errorf("unknown encoding %v", b[0]>>4)
}