gzexe.in

GNU 系统开发的基于Iz77语法的压缩 学习lz77压缩算法

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#!/bin/sh
# gzexe: compressor for Unix executables.
# Use this only for binaries that you do not use frequently.
#
# The compressed version is a shell script which decompresses itself after
# skipping $skip lines of shell commands.  We try invoking the compressed
# executable with the original name (for programs looking at their name).
# We also try to retain the original file permissions on the compressed file.
# For safety reasons, gzexe will not create setuid or setgid shell scripts.

# Warning: the first line of this file must be either : or #!/bin/sh
# The : is required for some old versions of csh.

x=`basename $0`
if test $# = 0; then
  echo compress executables. original file foo is renamed to foo~
  echo usage: ${x} [-d] files...
  echo   "   -d  decompress the executables"
  exit 1
fi

tmp=gz$$
trap "rm -f $tmp; exit 1" 1 2 3 5 10 13 15

decomp=0
res=0
test "$x" = "ungzexe" && decomp=1
if test "$1" = "-d"; then
  decomp=1
  shift
fi

echo hi > zfoo1$$
echo hi > zfoo2$$
if test -z "`(${CPMOD-cpmod} zfoo1$$ zfoo2$$) 2>&1`"; then
  cpmod=${CPMOD-cpmod}
fi
rm -f zfoo[12]$$

for i do
  if test ! -f "$i" ; then
    echo ${x}: $i not a file
    res=1
    continue
  fi
  if test $decomp -eq 0; then
    if sed -e 1d -e 2q "$i" | grep "^skip=[0-9]*$" >/dev/null; then
      echo "${x}: $i is already gzexe'd"
      continue
    fi
  fi
  if ls -l "$i" | grep '^...[sS]' > /dev/null; then
    echo "${x}: $i has setuid permission, unchanged"
    continue
  fi
  if ls -l "$i" | grep '^......[sS]' > /dev/null; then
    echo "${x}: $i has setgid permission, unchanged"
    continue
  fi
  if test "`basename $i`" = gzip; then
    echo "${x}: cannot compress gzip itself"
    continue
  fi
  if test -z "$cpmod"; then
    cp -p "$i" $tmp 2>/dev/null || cp "$i" $tmp
    if test -w $tmp 2>/dev/null; then
      writable=1
    else
      writable=0
      chmod u+w $tmp 2>/dev/null
    fi
  fi
  if test $decomp -eq 0; then
    sed 1q $0 > $tmp
    cat >> $tmp <<'EOF'
skip=18
if tail +$skip $0 | gzip -cd > /tmp/gztmp$$; then
  chmod 755 /tmp/gztmp$$
  prog="`basename $0`"
  if ln /tmp/gztmp$$ "/tmp/$prog" 2>/dev/null; then
    trap '/bin/rm -f /tmp/gztmp$$ "/tmp/$prog"; exit $res' 0
    (sleep 5; /bin/rm -f /tmp/gztmp$$ "/tmp/$prog") 2>/dev/null &
    /tmp/"$prog" ${1+"$@"}; res=$?
  else
    trap '/bin/rm -f /tmp/gztmp$$; exit $res' 0
    (sleep 5; /bin/rm -f /tmp/gztmp$$) 2>/dev/null &
    /tmp/gztmp$$ ${1+"$@"}; res=$?
  fi
else
  echo Cannot decompress $0; exit 1
fi; exit $res
EOF
    gzip -cv9 "$i" >> $tmp || {
      /bin/rm -f $tmp
      echo ${x}: compression not possible for $i, file unchanged.
      res=1
      continue
    }

  else
    # decompression
    skip=18
    if sed -e 1d -e 2q "$i" | grep "^skip=[0-9]*$" >/dev/null; then
      eval `sed -e 1d -e 2q "$i"`
    fi
    if tail +$skip "$i" | gzip -cd > $tmp; then
      :
    else
      echo ${x}: $i probably not in gzexe format, file unchanged.
      res=1
      continue
    fi
  fi
  rm -f "$i~"
  mv "$i" "$i~" || {
    echo ${x}: cannot backup $i as $i~
    rm -f $tmp
    res=1
    continue
  }
  mv $tmp "$i" || cp -p $tmp "$i" 2>/dev/null || cp $tmp "$i" || {
    echo ${x}: cannot create $i
    rm -f $tmp
    res=1
    continue
  }
  rm -f $tmp
  if test -n "$cpmod"; then
    $cpmod "$i~" "$i" 2>/dev/null
  elif test $writable -eq 0; then
    chmod u-w $i 2>/dev/null
  fi
done
exit $res