68 lines
2.0 KiB
Go
68 lines
2.0 KiB
Go
// 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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"math"
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"github.com/juju/errors"
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)
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// Float64ToUint64 converts float to a uint for lexicographical comparation.
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func Float64ToUint64(f float64) uint64 {
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u := math.Float64bits(f)
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if f >= 0 {
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u |= 0x8000000000000000
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} else {
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u = ^u
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}
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return u
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}
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// Uint64ToFloat64 converts the uint generated with Float64ToUint64 before to a float.
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func Uint64ToFloat64(u uint64) float64 {
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if u&0x8000000000000000 > 0 {
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u &= ^uint64(0x8000000000000000)
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} else {
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u = ^u
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}
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return math.Float64frombits(u)
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}
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// EncodeFloat encodes a float v into a byte slice which can be sorted lexicographically later.
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// EncodeFloat guarantees that the encoded value is in ascending order for comparison.
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func EncodeFloat(b []byte, v float64) []byte {
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u := Float64ToUint64(v)
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return EncodeUint(b, u)
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}
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// DecodeFloat decodes a float from a byte slice generated with EncodeFloat before.
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func DecodeFloat(b []byte) ([]byte, float64, error) {
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b, u, err := DecodeUint(b)
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return b, Uint64ToFloat64(u), errors.Trace(err)
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}
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// EncodeFloatDesc encodes a float v into a byte slice which can be sorted lexicographically later.
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// EncodeFloatDesc guarantees that the encoded value is in descending order for comparison.
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func EncodeFloatDesc(b []byte, v float64) []byte {
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u := Float64ToUint64(v)
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return EncodeUintDesc(b, u)
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}
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// DecodeFloatDesc decodes a float from a byte slice generated with EncodeFloatDesc before.
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func DecodeFloatDesc(b []byte) ([]byte, float64, error) {
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b, u, err := DecodeUintDesc(b)
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return b, Uint64ToFloat64(u), errors.Trace(err)
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}
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