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// Copyright (C) 2022-2023 Luke Shumaker <lukeshu@lukeshu.com>
//
// SPDX-License-Identifier: GPL-2.0-or-later
package btrfssum
import (
"fmt"
"io"
"math"
"strings"
"git.lukeshu.com/go/lowmemjson"
)
type ShortSum string
var (
_ lowmemjson.Encodable = ShortSum("")
_ lowmemjson.Decodable = (*ShortSum)(nil)
)
func (sum ShortSum) ToFullSum() CSum {
var ret CSum
copy(ret[:], sum)
return ret
}
func (sum ShortSum) EncodeJSON(w io.Writer) error {
const hextable = "0123456789abcdef"
var buf [2]byte
buf[0] = '"'
if _, err := w.Write(buf[:1]); err != nil {
return err
}
for i := 0; i < len(sum); i++ {
buf[0] = hextable[sum[i]>>4]
buf[1] = hextable[sum[i]&0x0f]
if _, err := w.Write(buf[:]); err != nil {
return err
}
}
buf[0] = '"'
if _, err := w.Write(buf[:1]); err != nil {
return err
}
return nil
}
func deHex(r rune) (byte, bool) {
if r > math.MaxUint8 {
return 0, false
}
c := byte(r)
//nolint:gomnd // Hex conversion.
switch {
case '0' <= c && c <= '9':
return c - '0', true
case 'a' <= c && c <= 'f':
return c - 'a' + 10, true
case 'A' <= c && c <= 'F':
return c - 'A' + 10, true
default:
return 0, false
}
}
func (sum *ShortSum) DecodeJSON(r io.RuneScanner) error {
var out strings.Builder
if c, _, err := r.ReadRune(); err != nil {
return err
} else if c != '"' {
return fmt.Errorf("expected %q, got %q", '"', c)
}
for {
a, _, err := r.ReadRune()
if err != nil {
return err
}
if a == '"' {
break
}
aN, ok := deHex(a)
if !ok {
return fmt.Errorf("expected a hex digit, got %q", a)
}
b, _, err := r.ReadRune()
if err != nil {
return err
}
bN, ok := deHex(b)
if !ok {
return fmt.Errorf("expected a hex digit, got %q", b)
}
out.WriteByte(aN<<4 | bN)
}
*sum = ShortSum(out.String())
return nil
}
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