tidb number 源码
tidb number 代码
文件路径：/util/codec/number.go
// Copyright 2015 PingCAP, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package codec
import (
"encoding/binary"
"math"
"github.com/pingcap/errors"
)
const signMask uint64 = 0x8000000000000000
// EncodeIntToCmpUint make int v to comparable uint type
func EncodeIntToCmpUint(v int64) uint64 {
return uint64(v) ^ signMask
}
// DecodeCmpUintToInt decodes the u that encoded by EncodeIntToCmpUint
func DecodeCmpUintToInt(u uint64) int64 {
return int64(u ^ signMask)
}
// EncodeInt appends the encoded value to slice b and returns the appended slice.
// EncodeInt guarantees that the encoded value is in ascending order for comparison.
func EncodeInt(b []byte, v int64) []byte {
var data [8]byte
u := EncodeIntToCmpUint(v)
binary.BigEndian.PutUint64(data[:], u)
return append(b, data[:]...)
}
// EncodeIntDesc appends the encoded value to slice b and returns the appended slice.
// EncodeIntDesc guarantees that the encoded value is in descending order for comparison.
func EncodeIntDesc(b []byte, v int64) []byte {
var data [8]byte
u := EncodeIntToCmpUint(v)
binary.BigEndian.PutUint64(data[:], ^u)
return append(b, data[:]...)
}
// DecodeInt decodes value encoded by EncodeInt before.
// It returns the leftover un-decoded slice, decoded value if no error.
func DecodeInt(b []byte) ([]byte, int64, error) {
if len(b) < 8 {
return nil, 0, errors.New("insufficient bytes to decode value")
}
u := binary.BigEndian.Uint64(b[:8])
v := DecodeCmpUintToInt(u)
b = b[8:]
return b, v, nil
}
// DecodeIntDesc decodes value encoded by EncodeInt before.
// It returns the leftover un-decoded slice, decoded value if no error.
func DecodeIntDesc(b []byte) ([]byte, int64, error) {
if len(b) < 8 {
return nil, 0, errors.New("insufficient bytes to decode value")
}
u := binary.BigEndian.Uint64(b[:8])
v := DecodeCmpUintToInt(^u)
b = b[8:]
return b, v, nil
}
// EncodeUint appends the encoded value to slice b and returns the appended slice.
// EncodeUint guarantees that the encoded value is in ascending order for comparison.
func EncodeUint(b []byte, v uint64) []byte {
var data [8]byte
binary.BigEndian.PutUint64(data[:], v)
return append(b, data[:]...)
}
// EncodeUintDesc appends the encoded value to slice b and returns the appended slice.
// EncodeUintDesc guarantees that the encoded value is in descending order for comparison.
func EncodeUintDesc(b []byte, v uint64) []byte {
var data [8]byte
binary.BigEndian.PutUint64(data[:], ^v)
return append(b, data[:]...)
}
// DecodeUint decodes value encoded by EncodeUint before.
// It returns the leftover un-decoded slice, decoded value if no error.
func DecodeUint(b []byte) ([]byte, uint64, error) {
if len(b) < 8 {
return nil, 0, errors.New("insufficient bytes to decode value")
}
v := binary.BigEndian.Uint64(b[:8])
b = b[8:]
return b, v, nil
}
// DecodeUintDesc decodes value encoded by EncodeInt before.
// It returns the leftover un-decoded slice, decoded value if no error.
func DecodeUintDesc(b []byte) ([]byte, uint64, error) {
if len(b) < 8 {
return nil, 0, errors.New("insufficient bytes to decode value")
}
data := b[:8]
v := binary.BigEndian.Uint64(data)
b = b[8:]
return b, ^v, nil
}
// EncodeVarint appends the encoded value to slice b and returns the appended slice.
// Note that the encoded result is not memcomparable.
func EncodeVarint(b []byte, v int64) []byte {
var data [binary.MaxVarintLen64]byte
n := binary.PutVarint(data[:], v)
return append(b, data[:n]...)
}
// DecodeVarint decodes value encoded by EncodeVarint before.
// It returns the leftover un-decoded slice, decoded value if no error.
func DecodeVarint(b []byte) ([]byte, int64, error) {
v, n := binary.Varint(b)
if n > 0 {
return b[n:], v, nil
}
if n < 0 {
return nil, 0, errors.New("value larger than 64 bits")
}
return nil, 0, errors.New("insufficient bytes to decode value")
}
// EncodeUvarint appends the encoded value to slice b and returns the appended slice.
// Note that the encoded result is not memcomparable.
func EncodeUvarint(b []byte, v uint64) []byte {
var data [binary.MaxVarintLen64]byte
n := binary.PutUvarint(data[:], v)
return append(b, data[:n]...)
}
// DecodeUvarint decodes value encoded by EncodeUvarint before.
// It returns the leftover un-decoded slice, decoded value if no error.
func DecodeUvarint(b []byte) ([]byte, uint64, error) {
v, n := binary.Uvarint(b)
if n > 0 {
return b[n:], v, nil
}
if n < 0 {
return nil, 0, errors.New("value larger than 64 bits")
}
return nil, 0, errors.New("insufficient bytes to decode value")
}
const (
negativeTagEnd = 8 // negative tag is (negativeTagEnd - length).
positiveTagStart = 0xff - 8 // Positive tag is (positiveTagStart + length).
)
// EncodeComparableVarint encodes an int64 to a mem-comparable bytes.
func EncodeComparableVarint(b []byte, v int64) []byte {
if v < 0 {
// All negative value has a tag byte prefix (negativeTagEnd - length).
// Smaller negative value encodes to more bytes, has smaller tag.
if v >= -0xff {
return append(b, negativeTagEnd-1, byte(v))
} else if v >= -0xffff {
return append(b, negativeTagEnd-2, byte(v>>8), byte(v))
} else if v >= -0xffffff {
return append(b, negativeTagEnd-3, byte(v>>16), byte(v>>8), byte(v))
} else if v >= -0xffffffff {
return append(b, negativeTagEnd-4, byte(v>>24), byte(v>>16), byte(v>>8), byte(v))
} else if v >= -0xffffffffff {
return append(b, negativeTagEnd-5, byte(v>>32), byte(v>>24), byte(v>>16), byte(v>>8), byte(v))
} else if v >= -0xffffffffffff {
return append(b, negativeTagEnd-6, byte(v>>40), byte(v>>32), byte(v>>24), byte(v>>16), byte(v>>8),
byte(v))
} else if v >= -0xffffffffffffff {
return append(b, negativeTagEnd-7, byte(v>>48), byte(v>>40), byte(v>>32), byte(v>>24), byte(v>>16),
byte(v>>8), byte(v))
}
return append(b, negativeTagEnd-8, byte(v>>56), byte(v>>48), byte(v>>40), byte(v>>32), byte(v>>24),
byte(v>>16), byte(v>>8), byte(v))
}
return EncodeComparableUvarint(b, uint64(v))
}
// EncodeComparableUvarint encodes uint64 into mem-comparable bytes.
func EncodeComparableUvarint(b []byte, v uint64) []byte {
// The first byte has 256 values, [0, 7] is reserved for negative tags,
// [248, 255] is reserved for larger positive tags,
// So we can store value [0, 239] in a single byte.
// Values cannot be stored in single byte has a tag byte prefix (positiveTagStart+length).
// Larger value encodes to more bytes, has larger tag.
if v <= positiveTagStart-negativeTagEnd {
return append(b, byte(v)+negativeTagEnd)
} else if v <= 0xff {
return append(b, positiveTagStart+1, byte(v))
} else if v <= 0xffff {
return append(b, positiveTagStart+2, byte(v>>8), byte(v))
} else if v <= 0xffffff {
return append(b, positiveTagStart+3, byte(v>>16), byte(v>>8), byte(v))
} else if v <= 0xffffffff {
return append(b, positiveTagStart+4, byte(v>>24), byte(v>>16), byte(v>>8), byte(v))
} else if v <= 0xffffffffff {
return append(b, positiveTagStart+5, byte(v>>32), byte(v>>24), byte(v>>16), byte(v>>8), byte(v))
} else if v <= 0xffffffffffff {
return append(b, positiveTagStart+6, byte(v>>40), byte(v>>32), byte(v>>24), byte(v>>16), byte(v>>8),
byte(v))
} else if v <= 0xffffffffffffff {
return append(b, positiveTagStart+7, byte(v>>48), byte(v>>40), byte(v>>32), byte(v>>24), byte(v>>16),
byte(v>>8), byte(v))
}
return append(b, positiveTagStart+8, byte(v>>56), byte(v>>48), byte(v>>40), byte(v>>32), byte(v>>24),
byte(v>>16), byte(v>>8), byte(v))
}
var (
errDecodeInsufficient = errors.New("insufficient bytes to decode value")
errDecodeInvalid = errors.New("invalid bytes to decode value")
)
// DecodeComparableUvarint decodes mem-comparable uvarint.
func DecodeComparableUvarint(b []byte) ([]byte, uint64, error) {
if len(b) == 0 {
return nil, 0, errDecodeInsufficient
}
first := b[0]
b = b[1:]
if first < negativeTagEnd {
return nil, 0, errors.Trace(errDecodeInvalid)
}
if first <= positiveTagStart {
return b, uint64(first) - negativeTagEnd, nil
}
length := int(first) - positiveTagStart
if len(b) < length {
return nil, 0, errors.Trace(errDecodeInsufficient)
}
var v uint64
for _, c := range b[:length] {
v = (v << 8) | uint64(c)
}
return b[length:], v, nil
}
// DecodeComparableVarint decodes mem-comparable varint.
func DecodeComparableVarint(b []byte) ([]byte, int64, error) {
if len(b) == 0 {
return nil, 0, errors.Trace(errDecodeInsufficient)
}
first := b[0]
if first >= negativeTagEnd && first <= positiveTagStart {
return b, int64(first) - negativeTagEnd, nil
}
b = b[1:]
var length int
var v uint64
if first < negativeTagEnd {
length = negativeTagEnd - int(first)
v = math.MaxUint64 // negative value has all bits on by default.
} else {
length = int(first) - positiveTagStart
}
if len(b) < length {
return nil, 0, errors.Trace(errDecodeInsufficient)
}
for _, c := range b[:length] {
v = (v << 8) | uint64(c)
}
if first > positiveTagStart && v > math.MaxInt64 {
return nil, 0, errors.Trace(errDecodeInvalid)
} else if first < negativeTagEnd && v <= math.MaxInt64 {
return nil, 0, errors.Trace(errDecodeInvalid)
}
return b[length:], int64(v), nil
}
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