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// Copyright (C) 2022 Luke Shumaker <lukeshu@lukeshu.com>
//
// SPDX-License-Identifier: GPL-2.0-or-later
package btrfssum
import (
"context"
"fmt"
"io"
"strings"
"git.lukeshu.com/go/lowmemjson"
"git.lukeshu.com/btrfs-progs-ng/lib/btrfs/btrfsvol"
"git.lukeshu.com/btrfs-progs-ng/lib/diskio"
)
const BlockSize = 4 * 1024
// ShortSum //////////////////////////////////////////////////////////
type ShortSum string
var (
_ lowmemjson.Encodable = ShortSum("")
_ lowmemjson.Decodable = (*ShortSum)(nil)
)
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 > 0xff {
return 0, false
}
c := byte(r)
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
}
// SumRun ////////////////////////////////////////////////////////////
type SumRun[Addr btrfsvol.IntAddr[Addr]] struct {
// How big a ShortSum is in this Run.
ChecksumSize int
// Base address where this run starts.
Addr Addr `json:",omitempty"`
// All of the ShortSums in this run, concatenated together.
Sums ShortSum
}
func (run SumRun[Addr]) NumSums() int {
return len(run.Sums) / run.ChecksumSize
}
func (run SumRun[Addr]) Size() btrfsvol.AddrDelta {
return btrfsvol.AddrDelta(run.NumSums()) * BlockSize
}
// Get implements diskio.Sequence[int, ShortSum]
func (run SumRun[Addr]) Get(sumIdx int64) (ShortSum, error) {
if sumIdx < 0 || int(sumIdx) >= run.NumSums() {
return "", io.EOF
}
off := int(sumIdx) * run.ChecksumSize
return ShortSum(run.Sums[off : off+run.ChecksumSize]), nil
}
func (run SumRun[Addr]) SumForAddr(addr Addr) (ShortSum, bool) {
if addr < run.Addr || addr >= run.Addr.Add(run.Size()) {
return "", false
}
off := int((addr-run.Addr)/BlockSize) * run.ChecksumSize
return ShortSum(run.Sums[off : off+run.ChecksumSize]), true
}
func (run SumRun[Addr]) Walk(ctx context.Context, fn func(Addr, ShortSum) error) error {
for addr, off := run.Addr, 0; off < len(run.Sums); addr, off = addr+BlockSize, off+run.ChecksumSize {
if err := ctx.Err(); err != nil {
return err
}
if err := fn(addr, ShortSum(run.Sums[off:off+run.ChecksumSize])); err != nil {
return err
}
}
return nil
}
// SumRunWithGaps ////////////////////////////////////////////////////
type SumRunWithGaps[Addr btrfsvol.IntAddr[Addr]] struct {
// Store the start address and size, in order to facilitate
// leading and trailing gaps.
Addr Addr
Size btrfsvol.AddrDelta
Runs []SumRun[Addr]
}
func (sg SumRunWithGaps[Addr]) NumSums() int {
return int(sg.Size / BlockSize)
}
func (sg SumRunWithGaps[Addr]) PctFull() float64 {
total := sg.NumSums()
var full int
for _, run := range sg.Runs {
full += run.NumSums()
}
return float64(full) / float64(total)
}
func (sg SumRunWithGaps[Addr]) SumForAddr(addr Addr) (ShortSum, error) {
if addr < sg.Addr || addr >= sg.Addr.Add(sg.Size) {
return "", io.EOF
}
for _, run := range sg.Runs {
if run.Addr > addr {
return "", diskio.ErrWildcard
}
if run.Addr.Add(run.Size()) <= addr {
continue
}
off := int((addr-run.Addr)/BlockSize) * run.ChecksumSize
return ShortSum(run.Sums[off : off+run.ChecksumSize]), nil
}
return "", diskio.ErrWildcard
}
// Get implements diskio.Sequence[int, ShortSum]
func (sg SumRunWithGaps[Addr]) Get(sumIdx int64) (ShortSum, error) {
addr := sg.Addr.Add(btrfsvol.AddrDelta(sumIdx) * BlockSize)
return sg.SumForAddr(addr)
}
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