extra/7z2lzma/7z2lzma.bash

   1 #!/bin/bash
   2 # SPDX-License-Identifier: 0BSD
   3
   4 #############################################################################
   5 #
   6 # 7z2lzma.bash is very primitive .7z to .lzma converter. The input file must
   7 # have exactly one LZMA compressed stream, which has been created with the
   8 # default lc, lp, and pb values. The CRC32 in the .7z archive is not checked,
   9 # and the script may seem to succeed while it actually created a corrupt .lzma
  10 # file. You should always try uncompressing both the original .7z and the
  11 # created .lzma and compare that the output is identical.
  12 #
  13 # This script requires basic GNU tools and 7z or 7za tool from p7zip.
  14 #
  15 # Last modified: 2009-01-15 14:25+0200
  16 #
  17 #############################################################################
  18 #
  19 # Author: Lasse Collin <lasse.collin@tukaani.org>
  20 #
  21 #############################################################################
  22
  23 # You can use 7z or 7za, both will work.
  24 SEVENZIP=7za
  25
  26 if [ $# != 2 -o -z "$1" -o -z "$2" ]; then
  27         echo "Usage: $0 input.7z output.lzma"
  28         exit 1
  29 fi
  30
  31 # Converts an integer variable to little endian binary integer.
  32 int2bin()
  33 {
  34         local LEN=$1
  35         local NUM=$2
  36         local HEX=(0 1 2 3 4 5 6 7 8 9 A B C D E F)
  37         local I
  38         for ((I=0; I < "$LEN"; ++I)); do
  39                 printf "\\x${HEX[(NUM >> 4) & 0x0F]}${HEX[NUM & 0x0F]}"
  40                 NUM=$((NUM >> 8))
  41         done
  42 }
  43
  44 # Make sure we get possible errors from pipes.
  45 set -o pipefail
  46
  47 # Get information about the input file. At least older 7z and 7za versions
  48 # may return with zero exit status even when an error occurred, so check
  49 # if the output has any lines beginning with "Error".
  50 INFO=$("$SEVENZIP" l -slt "$1")
  51 if [ $? != 0 ] || printf '%s\n' "$INFO" | grep -q ^Error; then
  52         printf '%s\n' "$INFO"
  53         exit 1
  54 fi
  55
  56 # Check if the input file has more than one compressed block.
  57 if printf '%s\n' "$INFO" | grep -q '^Block = 1'; then
  58         echo "Cannot convert, because the input file has more than"
  59         echo "one compressed block."
  60         exit 1
  61 fi
  62
  63 # Get compressed, uncompressed, and dictionary size.
  64 CSIZE=$(printf '%s\n' "$INFO" | sed -rn 's|^Packed Size = ([0-9]+$)|\1|p')
  65 USIZE=$(printf '%s\n' "$INFO" | sed -rn 's|^Size = ([0-9]+$)|\1|p')
  66 DICT=$(printf '%s\n' "$INFO" | sed -rn 's|^Method = LZMA:([0-9]+[bkm]?)$|\1|p')
  67
  68 if [ -z "$CSIZE" -o -z "$USIZE" -o -z "$DICT" ]; then
  69         echo "Parsing output of $SEVENZIP failed. Maybe the file uses some"
  70         echo "other compression method than plain LZMA."
  71         exit 1
  72 fi
  73
  74 # The following assumes that the default lc, lp, and pb settings were used.
  75 # Otherwise the output will be corrupt.
  76 printf '\x5D' > "$2"
  77
  78 # Dictionary size can be either was power of two, bytes, kibibytes, or
  79 # mebibytes. We need to convert it to bytes.
  80 case $DICT in
  81         *b)
  82                 DICT=${DICT%b}
  83                 ;;
  84         *k)
  85                 DICT=${DICT%k}
  86                 DICT=$((DICT << 10))
  87                 ;;
  88         *m)
  89                 DICT=${DICT%m}
  90                 DICT=$((DICT << 20))
  91                 ;;
  92         *)
  93                 DICT=$((1 << DICT))
  94                 ;;
  95 esac
  96 int2bin 4 "$DICT" >> "$2"
  97
  98 # Uncompressed size
  99 int2bin 8 "$USIZE" >> "$2"
 100
 101 # Copy the actual compressed data. Using multiple dd commands to avoid
 102 # copying large amount of data with one-byte block size, which would be
 103 # annoyingly slow.
 104 BS=8192
 105 BIGSIZE=$((CSIZE / BS))
 106 CSIZE=$((CSIZE % BS))
 107 {
 108         dd of=/dev/null bs=32 count=1 \
 109                 && dd bs="$BS" count="$BIGSIZE" \
 110                 && dd bs=1 count="$CSIZE"
 111 } < "$1" >> "$2"
 112
 113 exit $?