/usr/share/gocode/src/github.com/influxdata/influxdb/tsdb/engine/tsm1/bool.go is in golang-github-influxdb-influxdb-dev 1.1.1+dfsg1-4.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 | package tsm1
// boolean encoding uses 1 bit per value. Each compressed byte slice contains a 1 byte header
// indicating the compression type, followed by a variable byte encoded length indicating
// how many booleans are packed in the slice. The remaining bytes contains 1 byte for every
// 8 boolean values encoded.
import (
"encoding/binary"
"fmt"
)
const (
// booleanUncompressed is an uncompressed boolean format.
// Not yet implemented.
booleanUncompressed = 0
// booleanCompressedBitPacked is an bit packed format using 1 bit per boolean
booleanCompressedBitPacked = 1
)
// BooleanEncoder encodes a series of booleans to an in-memory buffer.
type BooleanEncoder struct {
// The encoded bytes
bytes []byte
// The current byte being encoded
b byte
// The number of bools packed into b
i int
// The total number of bools written
n int
}
// NewBooleanEncoder returns a new instance of BooleanEncoder.
func NewBooleanEncoder(sz int) BooleanEncoder {
return BooleanEncoder{
bytes: make([]byte, 0, (sz+7)/8),
}
}
func (e *BooleanEncoder) Reset() {
e.bytes = e.bytes[:0]
e.b = 0
e.i = 0
e.n = 0
}
func (e *BooleanEncoder) Write(b bool) {
// If we have filled the current byte, flush it
if e.i >= 8 {
e.flush()
}
// Use 1 bit for each boolean value, shift the current byte
// by 1 and set the least signficant bit acordingly
e.b = e.b << 1
if b {
e.b |= 1
}
// Increment the current boolean count
e.i++
// Increment the total boolean count
e.n++
}
func (e *BooleanEncoder) flush() {
// Pad remaining byte w/ 0s
for e.i < 8 {
e.b = e.b << 1
e.i++
}
// If we have bits set, append them to the byte slice
if e.i > 0 {
e.bytes = append(e.bytes, e.b)
e.b = 0
e.i = 0
}
}
func (e *BooleanEncoder) Bytes() ([]byte, error) {
// Ensure the current byte is flushed
e.flush()
b := make([]byte, 10+1)
// Store the encoding type in the 4 high bits of the first byte
b[0] = byte(booleanCompressedBitPacked) << 4
i := 1
// Encode the number of booleans written
i += binary.PutUvarint(b[i:], uint64(e.n))
// Append the packed booleans
return append(b[:i], e.bytes...), nil
}
// BooleanDecoder decodes a series of booleans from an in-memory buffer.
type BooleanDecoder struct {
b []byte
i int
n int
err error
}
// SetBytes initializes the decoder with a new set of bytes to read from.
// This must be called before calling any other methods.
func (e *BooleanDecoder) SetBytes(b []byte) {
if len(b) == 0 {
return
}
// First byte stores the encoding type, only have 1 bit-packet format
// currently ignore for now.
b = b[1:]
count, n := binary.Uvarint(b)
if n <= 0 {
e.err = fmt.Errorf("BooleanDecoder: invalid count")
return
}
e.b = b[n:]
e.i = -1
e.n = int(count)
if min := len(e.b) * 8; min < e.n {
// Shouldn't happen - TSM file was truncated/corrupted
e.n = min
}
}
func (e *BooleanDecoder) Next() bool {
if e.err != nil {
return false
}
e.i++
return e.i < e.n
}
func (e *BooleanDecoder) Read() bool {
// Index into the byte slice
idx := e.i >> 3 // integer division by 8
// Bit position
pos := 7 - (e.i & 0x7)
// The mask to select the bit
mask := byte(1 << uint(pos))
// The packed byte
v := e.b[idx]
// Returns true if the bit is set
return v&mask == mask
}
func (e *BooleanDecoder) Error() error {
return e.err
}
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