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common.go
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common.go
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package kope
import (
"bytes"
"encoding/binary"
)
// type marks
const (
typeInvalid = byte(iota)
typeMin
typeNormal
typeMax = ^typeMin
)
// extended alphabet
const (
extListBegin = byte(0x01)
extListEnd = byte(0x02)
extSeparator = byte(0x80)
extZero = byte(0xff)
)
var (
MinimalKey = &minKeyPlaceholder
MaximumKey = &maxKeyPlaceholder
minKeyPlaceholder = "I'm less than all real keys"
maxKeyPlaceholder = "I'm greater than all real keys"
separator = []byte{0, extSeparator}
listBegin = []byte{0, extListBegin}
listEnd = []byte{0, extListEnd}
)
func packString(s []byte) []byte {
buf := new(bytes.Buffer)
buf.WriteByte(typeNormal)
for _, b := range s {
buf.WriteByte(b)
if b == 0 {
buf.WriteByte(extZero)
}
}
return buf.Bytes()
}
func packList(e [][]byte) []byte {
buf := new(bytes.Buffer)
buf.WriteByte(typeNormal)
buf.Write(listBegin)
buf.Write(bytes.Join(e, separator))
buf.Write(listEnd)
return buf.Bytes()
}
func PackList(e [][]byte) []byte {
return packList(e)
}
func unpackList(d []byte) [][]byte {
s := len(d)
r := [][]byte{}
if s >= 5 && d[0] == typeNormal && bytes.HasPrefix(d[1:], listBegin) && bytes.HasSuffix(d, listEnd) {
p, last, depth, begin := 0, -1, 0, -1
for p < s {
c := d[p]
if last == 0 {
if c == extListBegin {
depth++
if depth == 1 {
begin = p + 1
}
} else if c == extListEnd {
depth--
if depth == 0 {
r = append(r, d[begin:p-1])
begin = -1
}
} else if c == extSeparator {
if depth == 1 {
r = append(r, d[begin:p-1])
begin = p + 1
}
}
}
last = int(c)
p++
}
}
return r
}
func catLists(lists [][]byte) []byte {
e := [][]byte{}
for _, lst := range lists {
e = append(e, unpackList(lst)...)
}
return packList(e)
}
func bigEndianBytes(value interface{}) ([]byte, error) {
buf := new(bytes.Buffer)
err := binary.Write(buf, binary.BigEndian, value)
if err != nil {
return nil, err
}
return buf.Bytes(), nil
}
func encodeSignedInteger(value interface{}) ([]byte, error) {
data, err := bigEndianBytes(value)
if err == nil {
data[0] ^= 0x80
return packString(data), nil
}
return nil, err
}
func encodeUnsignedInteger(value interface{}) ([]byte, error) {
data, err := bigEndianBytes(value)
if err == nil {
return packString(data), nil
}
return nil, err
}
func encodeFloat(value interface{}) ([]byte, error) {
data, err := bigEndianBytes(value)
if err == nil {
isZero := true
for _, b := range data[1:] {
if b != 0 {
isZero = false
break
}
}
if isZero = isZero && (data[0]&0x7f) == 0; isZero {
data[0] = 0
}
if isNegative := (data[0] & 0x80) != 0; isNegative {
for i, b := range data {
data[i] = ^b
}
} else {
data[0] ^= 0x80
}
return packString(data), nil
}
return nil, err
}
func encodeMinMaxKey(min bool) ([]byte, error) {
p := uint8(typeMin)
if !min {
p = typeMax
}
return []byte{p}, nil
}
func encodeSlice(encodedElements [][]byte) ([]byte, error) {
return packList(encodedElements), nil
}
func encodeNil() ([]byte, error) {
return []byte{typeNormal}, nil
}