path: root/extract.cc

/*  Tarlz - Archiver with multimember lzip compression
    Copyright (C) 2013-2019 Antonio Diaz Diaz.

    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 2 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

#define _FILE_OFFSET_BITS 64

#include <algorithm>
#include <cctype>
#include <cerrno>
#include <climits>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <string>
#include <vector>
#include <pthread.h>
#include <stdint.h>
#include <unistd.h>
#include <utime.h>
#include <sys/stat.h>
#include <sys/types.h>
#if defined(__GNU_LIBRARY__)
#include <sys/sysmacros.h>		// for major, minor, makedev
#endif
#include <lzlib.h>

#include "arg_parser.h"
#include "lzip_index.h"
#include "tarlz.h"


namespace {

Resizable_buffer grbuf;
bool archive_is_uncompressed_seekable = false;
bool archive_has_lz_ext;			// local var for archive_read

bool skip_warn( const bool reset = false )	// avoid duplicate warnings
  {
  static bool skipping = false;

  if( reset ) skipping = false;
  else if( !skipping )
    { skipping = true; show_error( "Skipping to next header." ); return true; }
  return false;
  }


bool make_path( const std::string & name )
  {
  const mode_t mode = S_IRWXU | S_IRGRP | S_IXGRP | S_IROTH | S_IXOTH;
  unsigned end = name.size();	// first slash before last component

  while( end > 0 && name[end-1] == '/' ) --end;	// remove trailing slashes
  while( end > 0 && name[end-1] != '/' ) --end;	// remove last component
  while( end > 0 && name[end-1] == '/' ) --end;	// remove more slashes

  unsigned index = 0;
  while( index < end )
    {
    while( index < end && name[index] == '/' ) ++index;
    unsigned first = index;
    while( index < end && name[index] != '/' ) ++index;
    if( first < index )
      {
      const std::string partial( name, 0, index );
      struct stat st;
      if( stat( partial.c_str(), &st ) == 0 )
        { if( !S_ISDIR( st.st_mode ) ) return false; }
      else if( mkdir( partial.c_str(), mode ) != 0 )
        return false;
      }
    }
  return true;
  }


// Return value: 0 = OK, 1 = damaged member, 2 = fatal error.
// If sizep and error, return in *sizep the number of bytes read.
// The first 6 bytes of the archive must be intact for islz to be meaningful.
int archive_read( const char * const archive_namep, const int infd,
                  uint8_t * const buf, const int size, int * const sizep = 0 )
  {
  static LZ_Decoder * decoder = 0;
  static bool at_eof = false;
  static bool fatal = false;
  static bool first_call = true;

  if( sizep ) *sizep = 0;
  if( fatal ) return 2;
  if( first_call )					// check format
    {
    first_call = false;
    if( size != header_size )
      internal_error( "size != header_size on first call." );
    const int rd = readblock( infd, buf, size );
    if( sizep ) *sizep = rd;
    if( rd != size && errno )
      { show_file_error( archive_namep, "Error reading archive", errno );
        fatal = true; return 2; }
    const Lzip_header & header = (*(const Lzip_header *)buf);
    bool islz = ( rd >= min_member_size && header.verify_magic() &&
                  header.verify_version() &&
                  isvalid_ds( header.dictionary_size() ) );
    const bool istar = ( rd == size && verify_ustar_chksum( buf ) );
    const bool iseof =
      ( !islz && !istar && rd == size && block_is_zero( buf, size ) );
    if( !islz && !istar && !iseof )		// corrupt or invalid format
      {
      show_file_error( archive_namep, posix_msg );
      if( archive_has_lz_ext && rd >= min_member_size ) islz = true;
      if( !islz ) return 1;
      }
    if( !islz )						// uncompressed
      { if( rd == size ) return 0; fatal = true; return 2; }
    archive_is_uncompressed_seekable = false;		// compressed
    decoder = LZ_decompress_open();
    if( !decoder || LZ_decompress_errno( decoder ) != LZ_ok )
      { show_error( mem_msg );
        LZ_decompress_close( decoder ); fatal = true; return 2; }
    if( LZ_decompress_write( decoder, buf, rd ) != rd )
      internal_error( "library error (LZ_decompress_write)." );
    const int res = archive_read( archive_namep, infd, buf, size, sizep );
    if( res != 0 ) { if( res == 2 ) fatal = true; return res; }
    if( verify_ustar_chksum( buf ) || block_is_zero( buf, size ) ) return 0;
    show_file_error( archive_namep, posix_lz_msg );
    fatal = true; return 2;
    }

  if( !decoder )					// uncompressed
    {
    const int rd = readblock( infd, buf, size ); if( rd == size ) return 0;
    if( sizep ) *sizep = rd;
    show_file_error( archive_namep, end_msg ); fatal = true; return 2;
    }
  const int ibuf_size = 16384;
  uint8_t ibuf[ibuf_size];
  int sz = 0;
  while( sz < size )
    {
    const int rd = LZ_decompress_read( decoder, buf + sz, size - sz );
    if( rd < 0 )
      {
      if( LZ_decompress_sync_to_member( decoder ) < 0 )
        internal_error( "library error (LZ_decompress_sync_to_member)." );
      skip_warn(); set_error_status( 2 ); return 1;
      }
    if( rd == 0 && LZ_decompress_finished( decoder ) == 1 )
      { LZ_decompress_close( decoder );
        show_file_error( archive_namep, end_msg ); fatal = true; return 2; }
    sz += rd; if( sizep ) *sizep = sz;
    if( sz < size && !at_eof && LZ_decompress_write_size( decoder ) > 0 )
      {
      const int rsize = std::min( ibuf_size, LZ_decompress_write_size( decoder ) );
      const int rd = readblock( infd, ibuf, rsize );
      if( LZ_decompress_write( decoder, ibuf, rd ) != rd )
        internal_error( "library error (LZ_decompress_write)." );
      if( rd < rsize )
        {
        at_eof = true; LZ_decompress_finish( decoder );
        if( errno )
          { show_file_error( archive_namep, "Error reading archive", errno );
            fatal = true; return 2; }
        }
      }
    }
  return 0;
  }


enum { mode_string_size = 10,
       group_string_size = 1 + uname_l + 1 + gname_l + 1 };	// 67

void format_mode_string( const Tar_header header, char buf[mode_string_size] )
  {
  const Typeflag typeflag = (Typeflag)header[typeflag_o];

  std::memcpy( buf, "----------", mode_string_size );
  switch( typeflag )
    {
    case tf_regular: break;
    case tf_link: buf[0] = 'h'; break;
    case tf_symlink: buf[0] = 'l'; break;
    case tf_chardev: buf[0] = 'c'; break;
    case tf_blockdev: buf[0] = 'b'; break;
    case tf_directory: buf[0] = 'd'; break;
    case tf_fifo: buf[0] = 'p'; break;
    case tf_hiperf: buf[0] = 'C'; break;
    default: buf[0] = '?';
    }
  const mode_t mode = parse_octal( header + mode_o, mode_l );	// 12 bits
  const bool setuid = mode & S_ISUID;
  const bool setgid = mode & S_ISGID;
  const bool sticky = mode & S_ISVTX;
  if( mode & S_IRUSR ) buf[1] = 'r';
  if( mode & S_IWUSR ) buf[2] = 'w';
  if( mode & S_IXUSR ) buf[3] = setuid ? 's' : 'x';
  else if( setuid ) buf[3] = 'S';
  if( mode & S_IRGRP ) buf[4] = 'r';
  if( mode & S_IWGRP ) buf[5] = 'w';
  if( mode & S_IXGRP ) buf[6] = setgid ? 's' : 'x';
  else if( setgid ) buf[6] = 'S';
  if( mode & S_IROTH ) buf[7] = 'r';
  if( mode & S_IWOTH ) buf[8] = 'w';
  if( mode & S_IXOTH ) buf[9] = sticky ? 't' : 'x';
  else if( sticky ) buf[9] = 'T';
  }


int format_user_group_string( const Tar_header header,
                              char buf[group_string_size] )
  {
  int len;
  if( header[uname_o] && header[gname_o] )
    len = snprintf( buf, group_string_size,
                    " %.32s/%.32s", header + uname_o, header + gname_o );
  else
    {
    const unsigned uid = parse_octal( header + uid_o, uid_l );
    const unsigned gid = parse_octal( header + gid_o, gid_l );
    len = snprintf( buf, group_string_size, " %u/%u", uid, gid );
    }
  return len;
  }

} // end namespace

bool block_is_zero( const uint8_t * const buf, const int size )
  {
  for( int i = 0; i < size; ++i ) if( buf[i] != 0 ) return false;
  return true;
  }


bool format_member_name( const Extended & extended, const Tar_header header,
                         Resizable_buffer & rbuf, const bool long_format )
  {
  if( long_format )
    {
    format_mode_string( header, rbuf() );
    const int group_string_len =
      format_user_group_string( header, rbuf() + mode_string_size );
    int offset = mode_string_size + group_string_len;
    const time_t mtime = parse_octal( header + mtime_o, mtime_l ); // 33 bits
    struct tm tms;
    const struct tm * tm = localtime_r( &mtime, &tms );
    if( !tm )
      { time_t z = 0; tm = localtime_r( &z, &tms ); if( !tm ) tm = &tms; }
    const Typeflag typeflag = (Typeflag)header[typeflag_o];
    const bool islink = ( typeflag == tf_link || typeflag == tf_symlink );
    const char * const link_string = !islink ? "" :
                         ( ( typeflag == tf_link ) ? " link to " : " -> " );
    if( typeflag == tf_chardev || typeflag == tf_blockdev )
      offset += snprintf( rbuf() + offset, rbuf.size() - offset, " %5u,%u",
                  (unsigned)parse_octal( header + devmajor_o, devmajor_l ),
                  (unsigned)parse_octal( header + devminor_o, devminor_l ) );
    else
      offset += snprintf( rbuf() + offset, rbuf.size() - offset, " %9llu",
                          extended.file_size() );
    for( int i = 0; i < 2; ++i )
      {
      const int len = snprintf( rbuf() + offset, rbuf.size() - offset,
                " %4d-%02u-%02u %02u:%02u %s%s%s\n",
                1900 + tm->tm_year, 1 + tm->tm_mon, tm->tm_mday,
                tm->tm_hour, tm->tm_min, extended.path().c_str(),
                link_string, islink ? extended.linkpath().c_str() : "" );
      if( (int)rbuf.size() > len + offset ) break;
      if( !rbuf.resize( len + offset + 1 ) ) return false;
      }
    }
  else
    {
    if( rbuf.size() < extended.path().size() + 2 &&
        !rbuf.resize( extended.path().size() + 2 ) ) return false;
    snprintf( rbuf(), rbuf.size(), "%s\n", extended.path().c_str() );
    }
  return true;
  }


bool show_member_name( const Extended & extended, const Tar_header header,
                       const int vlevel, Resizable_buffer & rbuf )
  {
  if( verbosity >= vlevel )
    {
    if( !format_member_name( extended, header, rbuf, verbosity > vlevel ) )
      { show_error( mem_msg ); return false; }
    std::fputs( rbuf(), stdout );
    std::fflush( stdout );
    }
  return true;
  }

namespace {

int skip_member( const char * const archive_namep, const int infd,
                 const Extended & extended )
  {
  long long rest = extended.file_size();
  const int rem = rest % header_size;
  if( rem ) rest += header_size - rem;		// padding
  if( archive_is_uncompressed_seekable && lseek( infd, rest, SEEK_CUR ) > 0 )
    return 0;
  const int bufsize = 32 * header_size;
  uint8_t buf[bufsize];
  while( rest > 0 )
    {
    const int rsize = ( rest >= bufsize ) ? bufsize : rest;
    const int ret = archive_read( archive_namep, infd, buf, rsize );
    if( ret != 0 ) { if( ret == 2 ) return 2; else break; }
    rest -= rsize;
    }
  return 0;
  }


void show_file_diff( const char * const filename, const char * const msg )
  {
  if( verbosity >= 0 )
    { std::printf( "%s: %s\n", filename, msg ); std::fflush( stdout ); }
  }


int compare_member( const char * const archive_namep, const int infd1,
                    const Extended & extended, const Tar_header header,
                    const bool ignore_ids )
  {
  if( !show_member_name( extended, header, 1, grbuf ) ) return 1;
  long long rest = extended.file_size();
  const char * const filename = extended.path().c_str();
  const Typeflag typeflag = (Typeflag)header[typeflag_o];
  bool diff = false, size_differs = false, type_differs = true;
  struct stat st;
  if( hstat( filename, &st ) != 0 )
    show_file_error( filename, "Warning: Can't stat", errno );
  else if( ( typeflag == tf_regular || typeflag == tf_hiperf ) &&
           !S_ISREG( st.st_mode ) )
    show_file_diff( filename, "Is not a regular file" );
  else if( typeflag == tf_symlink && !S_ISLNK( st.st_mode ) )
    show_file_diff( filename, "Is not a symlink" );
  else if( typeflag == tf_chardev && !S_ISCHR( st.st_mode ) )
    show_file_diff( filename, "Is not a character device" );
  else if( typeflag == tf_blockdev && !S_ISBLK( st.st_mode ) )
    show_file_diff( filename, "Is not a block device" );
  else if( typeflag == tf_directory && !S_ISDIR( st.st_mode ) )
    show_file_diff( filename, "Is not a directory" );
  else if( typeflag == tf_fifo && !S_ISFIFO( st.st_mode ) )
    show_file_diff( filename, "Is not a FIFO" );
  else
    {
    type_differs = false;
    if( typeflag != tf_symlink )
      {
      const mode_t mode = parse_octal( header + mode_o, mode_l );  // 12 bits
      if( mode != ( st.st_mode & ( S_ISUID | S_ISGID | S_ISVTX |
                                   S_IRWXU | S_IRWXG | S_IRWXO ) ) )
        { show_file_diff( filename, "Mode differs" ); diff = true; }
      }
    if( !ignore_ids )
      {
      if( (uid_t)parse_octal( header + uid_o, uid_l ) != st.st_uid )
        { show_file_diff( filename, "Uid differs" ); diff = true; }
      if( (gid_t)parse_octal( header + gid_o, gid_l ) != st.st_gid )
        { show_file_diff( filename, "Gid differs" ); diff = true; }
      }
    if( typeflag != tf_symlink )
      {
      if( typeflag != tf_directory )
        {
        const time_t mtime = parse_octal( header + mtime_o, mtime_l ); // 33 bits
        if( mtime != st.st_mtime )
          { show_file_diff( filename, "Mod time differs" ); diff = true; }
        }
      if( ( typeflag == tf_regular || typeflag == tf_hiperf ) &&
          rest != st.st_size )			// don't compare contents
        { show_file_diff( filename, "Size differs" ); size_differs = true; }
      if( ( typeflag == tf_chardev || typeflag == tf_blockdev ) &&
          ( parse_octal( header + devmajor_o, devmajor_l ) !=
            (unsigned)major( st.st_rdev ) ||
            parse_octal( header + devminor_o, devminor_l ) !=
            (unsigned)minor( st.st_rdev ) ) )
        { show_file_diff( filename, "Device number differs" ); diff = true; }
      }
    else
      {
      char * const buf = new char[st.st_size+1];
      long len = readlink( filename, buf, st.st_size );
      bool e = ( len != st.st_size );
      if( !e )
        {
        while( len > 1 && buf[len-1] == '/' ) --len;	// trailing '/'
        buf[len] = 0;
        if( extended.linkpath() != buf ) e = true;
        }
      delete[] buf;
      if( e ) { show_file_diff( filename, "Symlink differs" ); diff = true; }
      }
    }
  if( diff || size_differs || type_differs )
    { diff = false; set_error_status( 1 ); }
  if( rest <= 0 ) return 0;
  if( ( typeflag != tf_regular && typeflag != tf_hiperf ) ||
      size_differs || type_differs )
    return skip_member( archive_namep, infd1, extended );
  // else compare file contents
  const int rem = rest % header_size;
  const int padding = rem ? header_size - rem : 0;
  const int bufsize = 32 * header_size;
  uint8_t buf1[bufsize];
  uint8_t buf2[bufsize];
  const int infd2 = open_instream( filename );
  if( infd2 < 0 )
    { set_error_status( 1 );
      return skip_member( archive_namep, infd1, extended ); }
  int retval = 0;
  while( rest > 0 )
    {
    const int rsize1 = ( rest >= bufsize ) ? bufsize : rest + padding;
    const int rsize2 = ( rest >= bufsize ) ? bufsize : rest;
    const int ret = archive_read( archive_namep, infd1, buf1, rsize1 );
    if( ret != 0 ) { if( ret == 2 ) retval = 2; diff = true; break; }
    if( !diff )
      {
      const int rd = readblock( infd2, buf2, rsize2 );
      if( rd != rsize2 )
        {
        if( errno ) show_file_error( filename, "Read error", errno );
        else show_file_diff( filename, "EOF found in file" );
        diff = true;
        }
      else
        {
        int i = 0; while( i < rsize2 && buf1[i] == buf2[i] ) ++i;
        if( i < rsize2 )
          { show_file_diff( filename, "Contents differ" ); diff = true; }
        }
      }
    if( rest < bufsize ) break;
    rest -= rsize1;
    }
  if( diff ) set_error_status( 1 );
  close( infd2 );
  return retval;
  }


int list_member( const char * const archive_namep, const int infd,
                 const Extended & extended, const Tar_header header )
  {
  if( !show_member_name( extended, header, 0, grbuf ) ) return 1;
  return skip_member( archive_namep, infd, extended );
  }


bool contains_dotdot( const char * const filename )
  {
  for( int i = 0; filename[i]; ++i )
    if( dotdot_at_i( filename, i ) ) return true;
  return false;
  }


int extract_member( const char * const archive_namep, const int infd,
                    const Extended & extended, const Tar_header header,
                    const bool keep_damaged )
  {
  const char * const filename = extended.path().c_str();
  if( contains_dotdot( filename ) )
    {
    show_file_error( filename, "Contains a '..' component, skipping." );
    return skip_member( archive_namep, infd, extended );
    }
  const mode_t mode = parse_octal( header + mode_o, mode_l );	 // 12 bits
  const time_t mtime = parse_octal( header + mtime_o, mtime_l ); // 33 bits
  const Typeflag typeflag = (Typeflag)header[typeflag_o];
  const bool islink = ( typeflag == tf_link || typeflag == tf_symlink );
  int outfd = -1;

  if( !show_member_name( extended, header, 1, grbuf ) ) return 1;
  std::remove( filename );
  make_path( filename );
  switch( typeflag )
    {
    case tf_regular:
    case tf_hiperf:
      outfd = open_outstream( filename );
      if( outfd < 0 ) return 2;
      chmod( filename, mode );			// ignore errors
      break;
    case tf_link:
    case tf_symlink:
      {
      const char * const linkname = extended.linkpath().c_str();
      const bool hard = typeflag == tf_link;
      if( ( hard && link( linkname, filename ) != 0 ) ||
          ( !hard && symlink( linkname, filename ) != 0 ) )
        {
        if( verbosity >= 0 )
          std::fprintf( stderr, "Can't %slink file '%s' to '%s': %s.\n",
                        hard ? "" : "sym", linkname, filename,
                        std::strerror( errno ) );
        return 2;
        }
      } break;
    case tf_directory:
      if( mkdir( filename, mode ) != 0 && errno != EEXIST )
        {
        show_file_error( filename, "Can't create directory", errno );
        return 2;
        }
      break;
    case tf_chardev:
    case tf_blockdev:
      {
      const unsigned dev =
        makedev( parse_octal( header + devmajor_o, devmajor_l ),
                 parse_octal( header + devminor_o, devminor_l ) );
      const int dmode = ( typeflag == tf_chardev ? S_IFCHR : S_IFBLK ) | mode;
      if( mknod( filename, dmode, dev ) != 0 )
        {
        show_file_error( filename, "Can't create device node", errno );
        return 2;
        }
      break;
      }
    case tf_fifo:
      if( mkfifo( filename, mode ) != 0 && errno != EEXIST )
        {
        show_file_error( filename, "Can't create FIFO file", errno );
        return 2;
        }
      break;
    default:
      if( verbosity >= 0 )
        std::fprintf( stderr, "File type '%c' not supported for file '%s'.\n",
                      typeflag, filename );
      return 2;
    }

  const uid_t uid = (uid_t)parse_octal( header + uid_o, uid_l );
  const gid_t gid = (gid_t)parse_octal( header + gid_o, gid_l );
  if( !islink && chown( filename, uid, gid ) != 0 &&
      errno != EPERM && errno != EINVAL )
    {
    show_file_error( filename, "Can't change file owner", errno );
    return 2;
    }

  const int bufsize = 32 * header_size;
  uint8_t buf[bufsize];
  long long rest = extended.file_size();
  const int rem = rest % header_size;
  const int padding = rem ? header_size - rem : 0;
  while( rest > 0 )
    {
    const int rsize = ( rest >= bufsize ) ? bufsize : rest + padding;
    int rd;
    const int ret = archive_read( archive_namep, infd, buf, rsize, &rd );
    if( ret != 0 )
      {
      if( outfd >= 0 )
        {
        if( keep_damaged )
          { writeblock( outfd, buf, std::min( rest, (long long)rd ) );
            close( outfd ); }
        else { close( outfd ); std::remove( filename ); }
        }
      if( ret == 2 ) return 2; else return 0;
      }
    const int wsize = ( rest >= bufsize ) ? bufsize : rest;
    if( outfd >= 0 && writeblock( outfd, buf, wsize ) != wsize )
      { show_file_error( filename, "Error writing file", errno ); return 2; }
    rest -= wsize;
    }
  if( outfd >= 0 && close( outfd ) != 0 )
    { show_file_error( filename, "Error closing file", errno ); return 2; }
  if( !islink )
    {
    struct utimbuf t;
    t.actime = mtime;
    t.modtime = mtime;
    utime( filename, &t );			// ignore errors
    }
  return 0;
  }

} // end namespace


// return true if dir is a parent directory of name
bool compare_prefix_dir( const char * const dir, const char * const name )
  {
  int len = 0;
  while( dir[len] && dir[len] == name[len] ) ++len;
  return ( !dir[len] && len > 0 && ( dir[len-1] == '/' || name[len] == '/' ) );
  }


// compare two file names ignoring trailing slashes
bool compare_tslash( const char * const name1, const char * const name2 )
  {
  const char * p = name1;
  const char * q = name2;
  while( *p && *p == *q ) { ++p; ++q; }
  while( *p == '/' ) ++p;
  while( *q == '/' ) ++q;
  return ( !*p && !*q );
  }

namespace {

bool parse_records( const char * const archive_namep, const int infd,
                    Extended & extended, const Tar_header header,
                    Resizable_buffer & rbuf, const bool permissive )
  {
  const long long edsize = parse_octal( header + size_o, size_l );
  const long long bufsize = round_up( edsize );
  if( edsize <= 0 || edsize >= 1LL << 33 || bufsize >= INT_MAX )
    return false;				// overflow or no extended data
  if( !rbuf.resize( bufsize ) ) return false;	// extended records buffer
  return ( archive_read( archive_namep, infd, (uint8_t *)rbuf(), bufsize ) == 0 &&
           extended.parse( rbuf(), edsize, permissive ) );
  }

} // end namespace


/* Returns the number of bytes really read.
   If (returned value < size) and (errno == 0), means EOF was reached.
*/
int readblock( const int fd, uint8_t * const buf, const int size )
  {
  int sz = 0;
  errno = 0;
  while( sz < size )
    {
    const int n = read( fd, buf + sz, size - sz );
    if( n > 0 ) sz += n;
    else if( n == 0 ) break;				// EOF
    else if( errno != EINTR ) break;
    errno = 0;
    }
  return sz;
  }


/* Returns the number of bytes really written.
   If (returned value < size), it is always an error.
*/
int writeblock( const int fd, const uint8_t * const buf, const int size )
  {
  int sz = 0;
  errno = 0;
  while( sz < size )
    {
    const int n = write( fd, buf + sz, size - sz );
    if( n > 0 ) sz += n;
    else if( n < 0 && errno != EINTR ) break;
    errno = 0;
    }
  return sz;
  }


unsigned long long parse_octal( const uint8_t * const ptr, const int size )
  {
  unsigned long long result = 0;
  int i = 0;
  while( i < size && std::isspace( ptr[i] ) ) ++i;
  for( ; i < size && ptr[i] >= '0' && ptr[i] <= '7'; ++i )
    { result <<= 3; result += ptr[i] - '0'; }
  return result;
  }


int decode( const std::string & archive_name, const Arg_parser & parser,
            const int filenames, const int num_workers, const int debug_level,
            const Program_mode program_mode, const bool ignore_ids,
            const bool keep_damaged, const bool missing_crc,
            const bool permissive )
  {
  const bool from_stdin = archive_name.empty();
  const char * const archive_namep =
    from_stdin ? "(stdin)" : archive_name.c_str();
  const int infd = from_stdin ? STDIN_FILENO : open_instream( archive_name );
  if( infd < 0 ) return 1;

  // Execute -C options and mark filenames to be compared, extracted or listed.
  // name_pending is of type char instead of bool to allow concurrent update.
  std::vector< char > name_pending( parser.arguments(), false );
  for( int i = 0; i < parser.arguments(); ++i )
    {
    const int code = parser.code( i );
    if( code == 'C' && program_mode != m_list )
      {
      const char * const dir = parser.argument( i ).c_str();
      if( chdir( dir ) != 0 )
        { show_file_error( dir, "Error changing working directory", errno );
          return 1; }
      }
    if( !code && parser.argument( i ).size() &&
        !Exclude::excluded( parser.argument( i ).c_str() ) )
      name_pending[i] = true;
    }

  // multi-threaded --list is faster even with 1 thread and 1 file in archive
  if( program_mode == m_list && num_workers > 0 )
    {
    const Lzip_index lzip_index( infd, true, false );	// only regular files
    const long members = lzip_index.members();
    if( lzip_index.retval() == 0 && members >= 2 )	// one file + eof
      {
      // show_file_error( archive_namep, "Is compressed seekable" );
      return list_lz( archive_namep, parser, name_pending, lzip_index,
                      filenames, debug_level, infd,
                      std::min( (long)num_workers, members ),
                      missing_crc, permissive );
      }
    if( lseek( infd, 0, SEEK_SET ) == 0 && lzip_index.retval() != 0 &&
        lzip_index.file_size() > 3 * header_size )
      archive_is_uncompressed_seekable = true;	// unless compressed corrupt
    }

  archive_has_lz_ext = has_lz_ext( archive_name );	// var for archive_read
  Extended extended;			// metadata from extended records
  int retval = 0;
  bool prev_extended = false;		// prev header was extended
  while( true )				// process one tar header per iteration
    {
    Tar_header header;
    const int ret = archive_read( archive_namep, infd, header, header_size );
    if( ret == 2 ) { retval = 2; break; }
    if( ret != 0 || !verify_ustar_chksum( header ) )
      {
      if( ret == 0 && block_is_zero( header, header_size ) )
        {
        if( !prev_extended || permissive ) break;		// EOF
        show_file_error( archive_namep, fv_msg1 );
        retval = 2; break;
        }
      if( skip_warn() && verbosity >= 2 )
        std::fprintf( stderr, "ustar chksum = %07o\n", ustar_chksum( header ) );
      set_error_status( 2 ); continue;
      }
    skip_warn( true );				// reset warning

    const Typeflag typeflag = (Typeflag)header[typeflag_o];
    if( typeflag == tf_global )
      {
      if( prev_extended && !permissive )
        { show_file_error( archive_namep, fv_msg2 ); retval = 2; break; }
      Extended dummy;		// global headers are parsed and ignored
      if( !parse_records( archive_namep, infd, dummy, header, grbuf, true ) )
        { show_file_error( archive_namep,
            "Error in global extended records. Skipping to next header." );
          set_error_status( 2 ); }
      continue;
      }
    if( typeflag == tf_extended )
      {
      if( prev_extended && !permissive )
        { show_file_error( archive_namep, fv_msg3 ); retval = 2; break; }
      if( !parse_records( archive_namep, infd, extended, header, grbuf,
                          permissive ) )
        { show_file_error( archive_namep,
            "Error in extended records. Skipping to next header." );
          extended.reset(); set_error_status( 2 ); }
      else if( !extended.crc_present() && missing_crc )
        { show_file_error( archive_namep, mcrc_msg ); retval = 2; break; }
      prev_extended = true;
      continue;
      }
    prev_extended = false;

    extended.fill_from_ustar( header );		// copy metadata from header

    if( check_skip_filename( parser, name_pending, extended.path().c_str(),
                             filenames ) )
      retval = skip_member( archive_namep, infd, extended );
    else if( program_mode == m_list )
      retval = list_member( archive_namep, infd, extended, header );
    else if( program_mode == m_diff )
      retval = compare_member( archive_namep, infd, extended, header, ignore_ids );
    else retval = extract_member( archive_namep, infd, extended, header,
                                  keep_damaged );
    extended.reset();
    if( retval )
      { show_error( "Error is not recoverable: exiting now." ); break; }
    }

  if( close( infd ) != 0 && !retval )
    { show_file_error( archive_namep, "Error closing archive", errno );
      retval = 1; }

  if( retval == 0 ) for( int i = 0; i < parser.arguments(); ++i )
    if( !parser.code( i ) && parser.argument( i ).size() && name_pending[i] )
      {
      show_file_error( parser.argument( i ).c_str(), "Not found in archive." );
      retval = 1;
      }
  return final_exit_status( retval, program_mode != m_diff );
  }