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