reader.go

   1 /*
   2 glocate -- ZFS-diff-friendly locate-like utility
   3 Copyright (C) 2022-2023 Sergey Matveev <stargrave@stargrave.org>
   4
   5 This program is free software: you can redistribute it and/or modify
   6 it under the terms of the GNU General Public License as published by
   7 the Free Software Foundation, version 3 of the License.
   8
   9 This program is distributed in the hope that it will be useful,
  10 but WITHOUT ANY WARRANTY; without even the implied warranty of
  11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12 GNU General Public License for more details.
  13
  14 You should have received a copy of the GNU General Public License
  15 along with this program.  If not, see <http://www.gnu.org/licenses/>.
  16 */
  17
  18 package main
  19
  20 import (
  21         "bufio"
  22         "encoding/binary"
  23         "io"
  24         "log"
  25
  26         "github.com/klauspost/compress/zstd"
  27 )
  28
  29 func mustReadFull(r io.Reader, buf []byte) {
  30         if _, err := io.ReadFull(r, buf); err != nil {
  31                 log.Fatalln(err)
  32         }
  33 }
  34
  35 func reader(src io.Reader, sink chan Ent) {
  36         comp, err := zstd.NewReader(src)
  37         if err != nil {
  38                 log.Fatalln(err)
  39         }
  40         br := bufio.NewReaderSize(comp, 1<<17)
  41
  42         num := make([]byte, 8)
  43         var cols []string
  44         var namePrev string
  45         var nameLen uint16
  46         var depth, depthPrev uint8
  47         for {
  48                 _, err = io.ReadFull(br, num[:2])
  49                 if err != nil {
  50                         if err == io.EOF {
  51                                 break
  52                         }
  53                         log.Fatalln(err)
  54                 }
  55                 nameLen = binary.BigEndian.Uint16(num[:2])
  56                 nameRaw := make([]byte, nameLen)
  57                 mustReadFull(br, nameRaw)
  58                 name := string(nameRaw)
  59                 mustReadFull(br, num[:1])
  60                 depth = uint8(num[0])
  61                 mustReadFull(br, num)
  62                 ent := Ent{mtime: int64(binary.BigEndian.Uint64(num))}
  63                 mustReadFull(br, num)
  64                 ent.size = int64(binary.BigEndian.Uint64(num))
  65                 if depth > depthPrev {
  66                         cols = append(cols, namePrev[:len(namePrev)-1])
  67                 } else if depth < depthPrev {
  68                         cols = cols[:len(cols)-int(depthPrev-depth)]
  69                 }
  70                 ent.name = append([]string{}, append(cols, name)...)
  71                 sink <- ent
  72                 namePrev = name
  73                 depthPrev = depth
  74         }
  75         close(sink)
  76         comp.Close()
  77 }