107 lines
2.8 KiB
Go
107 lines
2.8 KiB
Go
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// 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 mysql
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import (
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"fmt"
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"strconv"
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"strings"
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"github.com/juju/errors"
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)
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// Bit is for mysql bit type.
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type Bit struct {
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// Value holds the value for bit type.
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Value uint64
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// Width is the display with for bit value.
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// e.g, with is 8, 0 is for 0b00000000.
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Width int
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}
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// String implements fmt.Stringer interface.
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func (b Bit) String() string {
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format := fmt.Sprintf("0b%%0%db", b.Width)
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return fmt.Sprintf(format, b.Value)
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}
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// ToNumber changes bit type to float64 for numeric operation.
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// MySQL treats bit as double type.
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func (b Bit) ToNumber() float64 {
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return float64(b.Value)
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}
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// ToString returns the binary string for bit type.
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func (b Bit) ToString() string {
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byteSize := (b.Width + 7) / 8
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buf := make([]byte, byteSize)
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for i := byteSize - 1; i >= 0; i-- {
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buf[byteSize-i-1] = byte(b.Value >> uint(i*8))
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}
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return string(buf)
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}
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// Min and Max bit width.
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const (
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MinBitWidth = 1
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MaxBitWidth = 64
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// UnspecifiedBitWidth is the unspecified with if you want to calculate bit width dynamically.
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UnspecifiedBitWidth = -1
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)
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// ParseBit parses bit string.
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// The string format can be b'val', B'val' or 0bval, val must be 0 or 1.
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// Width is the display width for bit representation. -1 means calculating
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// width dynamically, using following algorithm: (len("011101") + 7) & ^7,
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// e.g, if bit string is 0b01, the above will return 8 for its bit width.
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func ParseBit(s string, width int) (Bit, error) {
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if len(s) == 0 {
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return Bit{}, errors.Errorf("invalid empty string for parsing bit type")
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}
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if s[0] == 'b' || s[0] == 'B' {
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// format is b'val' or B'val'
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s = strings.Trim(s[1:], "'")
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} else if strings.HasPrefix(s, "0b") {
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s = s[2:]
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} else {
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// here means format is not b'val', B'val' or 0bval.
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return Bit{}, errors.Errorf("invalid bit type format %s", s)
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}
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if width == UnspecifiedBitWidth {
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width = (len(s) + 7) & ^7
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}
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if width == 0 {
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width = MinBitWidth
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}
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if width < MinBitWidth || width > MaxBitWidth {
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return Bit{}, errors.Errorf("invalid display width for bit type, must in [1, 64], but %d", width)
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}
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n, err := strconv.ParseUint(s, 2, 64)
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if err != nil {
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return Bit{}, errors.Trace(err)
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}
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if n > (uint64(1)<<uint64(width))-1 {
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return Bit{}, errors.Errorf("bit %s is too long for width %d", s, width)
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}
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return Bit{Value: n, Width: width}, nil
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}
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