tidb float 源码
tidb float 代码
文件路径：/util/codec/float.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 (
"math"
"github.com/pingcap/errors"
)
func encodeFloatToCmpUint64(f float64) uint64 {
u := math.Float64bits(f)
if f >= 0 {
u |= signMask
} else {
u = ^u
}
return u
}
func decodeCmpUintToFloat(u uint64) float64 {
if u&signMask > 0 {
u &= ^signMask
} else {
u = ^u
}
return math.Float64frombits(u)
}
// EncodeFloat encodes a float v into a byte slice which can be sorted lexicographically later.
// EncodeFloat guarantees that the encoded value is in ascending order for comparison.
func EncodeFloat(b []byte, v float64) []byte {
u := encodeFloatToCmpUint64(v)
return EncodeUint(b, u)
}
// DecodeFloat decodes a float from a byte slice generated with EncodeFloat before.
func DecodeFloat(b []byte) ([]byte, float64, error) {
b, u, err := DecodeUint(b)
return b, decodeCmpUintToFloat(u), errors.Trace(err)
}
// EncodeFloatDesc encodes a float v into a byte slice which can be sorted lexicographically later.
// EncodeFloatDesc guarantees that the encoded value is in descending order for comparison.
func EncodeFloatDesc(b []byte, v float64) []byte {
u := encodeFloatToCmpUint64(v)
return EncodeUintDesc(b, u)
}
// DecodeFloatDesc decodes a float from a byte slice generated with EncodeFloatDesc before.
func DecodeFloatDesc(b []byte) ([]byte, float64, error) {
b, u, err := DecodeUintDesc(b)
return b, decodeCmpUintToFloat(u), errors.Trace(err)
}
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