pkzip.h

Go to the documentation of this file.

/*
 Copyright (C) 2001-2006, William Joseph.
 All Rights Reserved.

 This file is part of GtkRadiant.

 GtkRadiant 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.

 GtkRadiant 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 GtkRadiant; if not, write to the Free Software
 Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */

#if !defined(INCLUDED_PKZIP_H)
#define INCLUDED_PKZIP_H

#include "bytestreamutils.h"
#include "idatastream.h"
#include <algorithm>

class zip_magic
{
    public:
        bool operator== (const zip_magic& other) const
        {
            return m_value[0] == other.m_value[0] && m_value[1] == other.m_value[1] && m_value[2] == other.m_value[2]
                    && m_value[3] == other.m_value[3];
        }
        bool operator!= (const zip_magic& other) const
        {
            return !(*this == other);
        }
        char m_value[4];
};

inline void istream_read_zip_magic (InputStream& istream, zip_magic& magic)
{
    istream.read(reinterpret_cast<InputStream::byte_type*> (magic.m_value), 4);
}

struct zip_version
{
        char version;
        char ostype;
};

inline void istream_read_zip_version (InputStream& istream, zip_version& version)
{
    version.version = istream_read_byte(istream);
    version.ostype = istream_read_byte(istream);
}

struct zip_dostime
{
        unsigned short time;
        unsigned short date;
};

inline void istream_read_zip_dostime (InputStream& istream, zip_dostime& dostime)
{
    dostime.time = istream_read_int16_le(istream);
    dostime.date = istream_read_int16_le(istream);
}

const zip_magic zip_file_header_magic = { { 'P', 'K', 0x03, 0x04 } };

/* A. Local file header */
struct zip_file_header
{
        zip_magic z_magic; /* local file header signature (0x04034b50) */
        zip_version z_extract; /* version needed to extract */
        unsigned short z_flags; /* general purpose bit flag */
        unsigned short z_compr; /* compression method */
        zip_dostime z_dostime; /* last mod file time (dos format) */
        unsigned int z_crc32; /* crc-32 */
        unsigned int z_csize; /* compressed size */
        unsigned int z_usize; /* uncompressed size */
        unsigned short z_namlen; /* filename length (null if stdin) */
        unsigned short z_extras; /* extra field length */
        /* followed by filename (of variable size) */
        /* followed by extra field (of variable size) */
};

inline void istream_read_zip_file_header (SeekableInputStream& istream, zip_file_header& file_header)
{
    istream_read_zip_magic(istream, file_header.z_magic);
    istream_read_zip_version(istream, file_header.z_extract);
    file_header.z_flags = istream_read_uint16_le(istream);
    file_header.z_compr = istream_read_uint16_le(istream);
    istream_read_zip_dostime(istream, file_header.z_dostime);
    file_header.z_crc32 = istream_read_uint32_le(istream);
    file_header.z_csize = istream_read_uint32_le(istream);
    file_header.z_usize = istream_read_uint32_le(istream);
    file_header.z_namlen = istream_read_uint16_le(istream);
    file_header.z_extras = istream_read_uint16_le(istream);
    istream.seek(file_header.z_namlen + file_header.z_extras, SeekableInputStream::cur);
}
;

/* B. data descriptor
 * the data descriptor exists only if bit 3 of z_flags is set. It is byte aligned
 * and immediately follows the last byte of compressed data. It is only used if
 * the output media of the compressor was not seekable, eg. standard output.
 */
const zip_magic zip_file_trailer_magic = { { 'P', 'K', 0x07, 0x08 } };

struct zip_file_trailer
{
        zip_magic z_magic;
        unsigned int z_crc32; /* crc-32 */
        unsigned int z_csize; /* compressed size */
        unsigned int z_usize; /* uncompressed size */
};

inline void istream_read_zip_file_trailer (InputStream& istream, zip_file_trailer& file_trailer)
{
    istream_read_zip_magic(istream, file_trailer.z_magic);
    file_trailer.z_crc32 = istream_read_uint32_le(istream);
    file_trailer.z_csize = istream_read_uint32_le(istream);
    file_trailer.z_usize = istream_read_uint32_le(istream);
}
;

/* C. central directory structure:
 [file header] . . . end of central dir record
 */

/* directory file header
 * - a single entry including filename, extras and comment may not exceed 64k.
 */

const zip_magic zip_root_dirent_magic = { { 'P', 'K', 0x01, 0x02 } };

struct zip_root_dirent
{
        zip_magic z_magic;
        zip_version z_encoder; /* version made by */
        zip_version z_extract; /* version need to extract */
        unsigned short z_flags; /* general purpose bit flag */
        unsigned short z_compr; /* compression method */
        zip_dostime z_dostime; /* last mod file time&date (dos format) */
        unsigned int z_crc32; /* crc-32 */
        unsigned int z_csize; /* compressed size */
        unsigned int z_usize; /* uncompressed size */
        unsigned short z_namlen; /* filename length (null if stdin) */
        unsigned short z_extras; /* extra field length */
        unsigned short z_comment; /* file comment length */
        unsigned short z_diskstart; /* disk number of start (if spanning zip over multiple disks) */
        unsigned short z_filetype; /* internal file attributes, bit0 = ascii */
        unsigned int z_filemode; /* extrnal file attributes, eg. msdos attrib byte */
        unsigned int z_off; /* relative offset of local file header, seekval if singledisk */
        /* followed by filename (of variable size) */
        /* followed by extra field (of variable size) */
        /* followed by file comment (of variable size) */
};

inline void istream_read_zip_root_dirent (SeekableInputStream& istream, zip_root_dirent& root_dirent)
{
    istream_read_zip_magic(istream, root_dirent.z_magic);
    istream_read_zip_version(istream, root_dirent.z_encoder);
    istream_read_zip_version(istream, root_dirent.z_extract);
    root_dirent.z_flags = istream_read_uint16_le(istream);
    root_dirent.z_compr = istream_read_uint16_le(istream);
    istream_read_zip_dostime(istream, root_dirent.z_dostime);
    root_dirent.z_crc32 = istream_read_uint32_le(istream);
    root_dirent.z_csize = istream_read_uint32_le(istream);
    root_dirent.z_usize = istream_read_uint32_le(istream);
    root_dirent.z_namlen = istream_read_uint16_le(istream);
    root_dirent.z_extras = istream_read_uint16_le(istream);
    root_dirent.z_comment = istream_read_uint16_le(istream);
    root_dirent.z_diskstart = istream_read_uint16_le(istream);
    root_dirent.z_filetype = istream_read_uint16_le(istream);
    root_dirent.z_filemode = istream_read_uint32_le(istream);
    root_dirent.z_off = istream_read_uint32_le(istream);
    istream.seek(root_dirent.z_namlen + root_dirent.z_extras + root_dirent.z_comment, SeekableInputStream::cur);
}

/* end of central dir record */
const zip_magic zip_disk_trailer_magic = { { 'P', 'K', 0x05, 0x06 } };
const unsigned int disk_trailer_length = 22;
struct zip_disk_trailer
{
        zip_magic z_magic;
        unsigned short z_disk; /* number of this disk */
        unsigned short z_finaldisk; /* number of the disk with the start of the central dir */
        unsigned short z_entries; /* total number of entries in the central dir on this disk */
        unsigned short z_finalentries; /* total number of entries in the central dir */
        unsigned int z_rootsize; /* size of the central directory */
        unsigned int z_rootseek; /* offset of start of central directory with respect to *
         * the starting disk number */
        unsigned short z_comment; /* zipfile comment length */
        /* followed by zipfile comment (of variable size) */
};

inline void istream_read_zip_disk_trailer (SeekableInputStream& istream, zip_disk_trailer& disk_trailer)
{
    istream_read_zip_magic(istream, disk_trailer.z_magic);
    disk_trailer.z_disk = istream_read_uint16_le(istream);
    disk_trailer.z_finaldisk = istream_read_uint16_le(istream);
    disk_trailer.z_entries = istream_read_uint16_le(istream);
    disk_trailer.z_finalentries = istream_read_uint16_le(istream);
    disk_trailer.z_rootsize = istream_read_uint32_le(istream);
    disk_trailer.z_rootseek = istream_read_uint32_le(istream);
    disk_trailer.z_comment = istream_read_uint16_le(istream);
    istream.seek(disk_trailer.z_comment, SeekableInputStream::cur);
}

inline SeekableStream::position_type pkzip_find_disk_trailer (SeekableInputStream& istream)
{
    istream.seek(0, SeekableInputStream::end);
    SeekableStream::position_type start_position = istream.tell();
    if (start_position < disk_trailer_length)
        return 0;
    start_position -= disk_trailer_length;

    zip_magic magic;
    istream.seek(start_position);
    istream_read_zip_magic(istream, magic);

    if (magic == zip_disk_trailer_magic)
        return start_position;
    else {
        const SeekableStream::position_type max_comment = 0x10000;
        const SeekableStream::position_type bufshift = 6;
        const SeekableStream::position_type bufsize = max_comment >> bufshift;
        unsigned char buffer[bufsize];

        SeekableStream::position_type search_end = (max_comment < start_position) ? start_position - max_comment : 0;
        SeekableStream::position_type position = start_position;
        while (position != search_end) {
            StreamBase::size_type to_read = std::min(bufsize, position - search_end);
            position -= to_read;

            istream.seek(position);
            StreamBase::size_type size = istream.read(buffer, to_read);

            unsigned char* p = buffer + size;
            while (p != buffer) {
                --p;
                magic.m_value[3] = magic.m_value[2];
                magic.m_value[2] = magic.m_value[1];
                magic.m_value[1] = magic.m_value[0];
                magic.m_value[0] = *p;
                if (magic == zip_disk_trailer_magic) {
                    return position + (p - buffer);
                }
            }
        }
        return 0;
    }
}

#endif