pole.cpp

/*  POLE - Portable C++ library to access OLE Storage
 Copyright (C) 2002-2007 Ariya Hidayat (ariya@kde.org).
 
 Redistribution and use in source and binary forms, with or without
 modification, are permitted provided that the following conditions
 are met:
 
 1. Redistributions of source code must retain the above copyright
 notice, this list of conditions and the following disclaimer.
 2. Redistributions in binary form must reproduce the above copyright
 notice, this list of conditions and the following disclaimer in the
 documentation and/or other materials provided with the distribution.
 
 THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include <fstream>
#include <iostream>
#include <list>
#include <string>
#include <vector>
#include <cassert>

#include "pole.h"

// enable to activate debugging output
// #define POLE_DEBUG

namespace POLE
{
    
    
} // namespace POLE

using namespace POLE;

static inline unsigned long readU16( const unsigned char* ptr )
{
    return ptr[0]+(ptr[1]<<8);
}

static inline unsigned long readU32( const unsigned char* ptr )
{
    return ptr[0]+(ptr[1]<<8)+(ptr[2]<<16)+(ptr[3]<<24);
}

static inline void writeU16( unsigned char* ptr, unsigned long data )
{
    ptr[0] = (unsigned char)(data & 0xff);
    ptr[1] = (unsigned char)((data >> 8) & 0xff);
}

static inline void writeU32( unsigned char* ptr, unsigned long data )
{
    ptr[0] = (unsigned char)(data & 0xff);
    ptr[1] = (unsigned char)((data >> 8) & 0xff);
    ptr[2] = (unsigned char)((data >> 16) & 0xff);
    ptr[3] = (unsigned char)((data >> 24) & 0xff);
}

static const unsigned char pole_magic[] =
{ 0xd0, 0xcf, 0x11, 0xe0, 0xa1, 0xb1, 0x1a, 0xe1 };

// =========== Header ==========

Header::Header():
b_shift( 9 ),
s_shift( 6 ),
num_bat( 0 ),
dirent_start( 0 ),
threshold( 4096 ),
sbat_start( 0 ),
num_sbat( 0 ),
mbat_start( 0 ),
num_mbat( 0 )
{
    for( unsigned i = 0; i < 8; i++ )
        id[i] = pole_magic[i];
    for( unsigned i=0; i<109; i++ )
        bb_blocks[i] = AllocTable::Avail;
}

bool Header::valid()
{
    if( threshold != 4096 ) return false;
    if( num_bat == 0 ) return false;
    if( (num_bat > 109) && (num_bat > (num_mbat * 127) + 109)) return false;
    if( (num_bat < 109) && (num_mbat != 0) ) return false;
    if( s_shift > b_shift ) return false;
    if( b_shift <= 6 ) return false;
    if( b_shift >=31 ) return false;
    
    return true;
}

void Header::load( const unsigned char* buffer )
{
    b_shift      = readU16( buffer + 0x1e );
    s_shift      = readU16( buffer + 0x20 );
    num_bat      = readU32( buffer + 0x2c );
    dirent_start = readU32( buffer + 0x30 );
    threshold    = readU32( buffer + 0x38 );
    sbat_start   = readU32( buffer + 0x3c );
    num_sbat     = readU32( buffer + 0x40 );
    mbat_start   = readU32( buffer + 0x44 );
    num_mbat     = readU32( buffer + 0x48 );
    
    for( unsigned i = 0; i < 8; i++ )
        id[i] = buffer[i];
    for( unsigned i=0; i<109; i++ )
        bb_blocks[i] = readU32( buffer + 0x4C+i*4 );
}

void Header::save( unsigned char* buffer )
{
    memset( buffer, 0, 0x4c );
    memcpy( buffer, pole_magic, 8 );        // ole signature
    writeU32( buffer + 8, 0 );              // unknown
    writeU32( buffer + 12, 0 );             // unknown
    writeU32( buffer + 16, 0 );             // unknown
    writeU16( buffer + 24, 0x003e );        // revision ?
    writeU16( buffer + 26, 3 );             // version ?
    writeU16( buffer + 28, 0xfffe );        // unknown
    writeU16( buffer + 0x1e, b_shift );
    writeU16( buffer + 0x20, s_shift );
    writeU32( buffer + 0x2c, num_bat );
    writeU32( buffer + 0x30, dirent_start );
    writeU32( buffer + 0x38, threshold );
    writeU32( buffer + 0x3c, sbat_start );
    writeU32( buffer + 0x40, num_sbat );
    writeU32( buffer + 0x44, mbat_start );
    writeU32( buffer + 0x48, num_mbat );
    
    for( unsigned i=0; i<109; i++ )
        writeU32( buffer + 0x4C+i*4, bb_blocks[i] );
}

void Header::debug()
{
    std::cout << std::endl;
    std::cout << "b_shift " << b_shift << std::endl;
    std::cout << "s_shift " << s_shift << std::endl;
    std::cout << "num_bat " << num_bat << std::endl;
    std::cout << "dirent_start " << dirent_start << std::endl;
    std::cout << "threshold " << threshold << std::endl;
    std::cout << "sbat_start " << sbat_start << std::endl;
    std::cout << "num_sbat " << num_sbat << std::endl;
    std::cout << "mbat_start " << mbat_start << std::endl;
    std::cout << "num_mbat " << num_mbat << std::endl;
    
    unsigned s = (num_bat<=109) ? num_bat : 109;
    std::cout << "bat blocks: ";
    for( unsigned i = 0; i < s; i++ )
        std::cout << bb_blocks[i] << " ";
    std::cout << std::endl;
}

// =========== AllocTable ==========

const unsigned AllocTable::Avail = 0xffffffff;
const unsigned AllocTable::Eof = 0xfffffffe;
const unsigned AllocTable::Bat = 0xfffffffd;
const unsigned AllocTable::MetaBat = 0xfffffffc;

AllocTable::AllocTable(): blockSize( 4096 ), data()
{
    // initial size
    resize( 128 );
}

unsigned long AllocTable::count()
{
    return data.size();
}

void AllocTable::resize( unsigned long newsize )
{
    unsigned oldsize = data.size();
    data.resize( newsize );
    if( newsize > oldsize )
        for( unsigned i = oldsize; i<newsize; i++ )
            data[i] = Avail;
}

// make sure there're still free blocks
void AllocTable::preserve( unsigned long n )
{
    std::vector<unsigned long> pre;
    for( unsigned i=0; i < n; i++ )
        pre.push_back( unused() );
}

unsigned long AllocTable::operator[]( unsigned long index )
{
    unsigned long result;
    result = data[index];
    return result;
}

void AllocTable::set( unsigned long index, unsigned long value )
{
    if( index >= count() ) resize( index + 1);
    data[ index ] = value;
}

void AllocTable::setChain( std::vector<unsigned long> chain )
{
    if( chain.size() )
    {
        for( unsigned i=0; i<chain.size()-1; i++ )
            set( chain[i], chain[i+1] );
        set( chain[ chain.size()-1 ], AllocTable::Eof );
    }
}

// TODO: optimize this with better search
static bool already_exist(const std::vector<unsigned long>& chain,
                          unsigned long item)
{
    for(unsigned i = 0; i < chain.size(); i++)
        if(chain[i] == item) return true;
    
    return false;
}

// follow
std::vector<unsigned long> AllocTable::follow( unsigned long start )
{
    std::vector<unsigned long> chain;
    
    if( start >= count() ) return chain;
    
    unsigned long p = start;
    while( p < count() )
    {
        if( p == (unsigned long)Eof ) break;
        if( p == (unsigned long)Bat ) break;
        if( p == (unsigned long)MetaBat ) break;
        if( already_exist(chain, p) ) break;
        chain.push_back(p);
        if( data[p] >= count() ) break;
        p = data[ p ];
    }
    
    return chain;
}

unsigned AllocTable::unused()
{
    // find first available block
    for( unsigned i = 0; i < data.size(); i++ )
        if( data[i] == Avail )
            return i;
    
    // completely full, so enlarge the table
    unsigned block = data.size();
    resize( data.size()+10 );
    return block;
}

void AllocTable::load( const unsigned char* buffer, unsigned len )
{
    resize( len / 4 );
    for( unsigned i = 0; i < count(); i++ )
        set( i, readU32( buffer + i*4 ) );
}

// return space required to save this dirtree
unsigned AllocTable::size()
{
    return count() * 4;
}

void AllocTable::save( unsigned char* buffer )
{
    for( unsigned i = 0; i < count(); i++ )
        writeU32( buffer + i*4, data[i] );
}

void AllocTable::debug()
{
    std::cout << "block size " << data.size() << std::endl;
    for( unsigned i=0; i< data.size(); i++ )
    {
        if( data[i] == Avail ) continue;
        std::cout << i << ": ";
        if( data[i] == Eof ) std::cout << "[eof]";
        else if( data[i] == Bat ) std::cout << "[bat]";
        else if( data[i] == MetaBat ) std::cout << "[metabat]";
        else std::cout << data[i];
        std::cout << std::endl;
    }
}

// =========== DirTree ==========

const unsigned DirTree::End = 0xffffffff;

DirTree::DirTree(): entries()
{
    clear();
}

void DirTree::clear()
{
    // leave only root entry
    entries.resize( 1 );
    entries[0].valid = true;
    entries[0].name = "Root Entry";
    entries[0].dir = true;
    entries[0].size = 0;
    entries[0].start = End;
    entries[0].prev = End;
    entries[0].next = End;
    entries[0].child = End;
}

unsigned DirTree::entryCount()
{
    return entries.size();
}

DirEntry* DirTree::entry( unsigned index )
{
    if( index >= entryCount() ) return (DirEntry*) 0;
    return &entries[ index ];
}

int DirTree::indexOf( DirEntry* e )
{
    for( unsigned i = 0; i < entryCount(); i++ )
        if( entry( i ) == e ) return i;
    
    return -1;
}

int DirTree::parent( unsigned index )
{
    // brute-force, basically we iterate for each entries, find its children
    // and check if one of the children is 'index'
    for( unsigned j=0; j<entryCount(); j++ )
    {
        std::vector<unsigned> chi = children( j );
        for( unsigned i=0; i<chi.size();i++ )
            if( chi[i] == index )
                return j;
    }
    
    return -1;
}

std::string DirTree::fullName( unsigned index )
{
    // don't use root name ("Root Entry"), just give "/"
    if( index == 0 ) return "/";
    
    std::string result = entry( index )->name;
    result.insert( 0,  "/" );
    int p = parent( index );
    DirEntry * _entry = 0;
    while( p > 0 )
    {
        _entry = entry( p );
        if (_entry->dir && _entry->valid)
        {
            result.insert( 0,  _entry->name);
            result.insert( 0,  "/" );
        }
        --p;
        index = p;
        if( index <= 0 ) break;
    }
    return result;
}

// given a fullname (e.g "/ObjectPool/_1020961869"), find the entry
// if not found and create is false, return 0
// if create is true, a new entry is returned
DirEntry* DirTree::entry( const std::string& name, bool create )
{
    if( !name.length() ) return (DirEntry*)0;
    
    // quick check for "/" (that's root)
    if( name == "/" ) return entry( 0 );
    
    // split the names, e.g  "/ObjectPool/_1020961869" will become:
    // "ObjectPool" and "_1020961869"
    std::list<std::string> names;
    std::string::size_type start = 0, end = 0;
    if( name[0] == '/' ) start++;
    while( start < name.length() )
    {
        end = name.find_first_of( '/', start );
        if( end == std::string::npos ) end = name.length();
        names.push_back( name.substr( start, end-start ) );
        start = end+1;
    }
    
    // start from root
    int index = 0 ;
    
    // trace one by one
    std::list<std::string>::iterator it;
    
    for( it = names.begin(); it != names.end(); ++it )
    {
        // find among the children of index
        std::vector<unsigned> chi = children( index );
        unsigned child = 0;
        for( unsigned i = 0; i < chi.size(); i++ )
        {
            DirEntry* ce = entry( chi[i] );
            if( ce )
                if( ce->valid && ( ce->name.length()>1 ) )
                    if( ce->name == *it )
                        child = chi[i];
        }
        
        // traverse to the child
        if( child > 0 ) index = child;
        else
        {
            // not found among children
            if( !create ) return (DirEntry*)0;
            
            // create a new entry
            unsigned parent = index;
            entries.push_back( DirEntry() );
            index = entryCount()-1;
            DirEntry* e = entry( index );
            e->valid = true;
            e->name = *it;
            e->dir = false;
            e->size = 0;
            e->start = 0;
            e->child = End;
            e->prev = End;
            e->next = entry(parent)->child;
            entry(parent)->child = index;
        }
    }
    
    return entry( index );
}

// helper function: recursively find siblings of index
void dirtree_find_siblings( DirTree* dirtree, std::vector<unsigned>& result,
                           unsigned index )
{
    DirEntry* e = dirtree->entry( index );
    if( !e ) return;
    if( !e->valid ) return;
    
    // prevent infinite loop
    for( unsigned i = 0; i < result.size(); i++ )
        if( result[i] == index ) return;
    
    // add myself
    result.push_back( index );
    
    // visit previous sibling, don't go infinitely
    unsigned prev = e->prev;
    if( ( prev > 0 ) && ( prev < dirtree->entryCount() ) )
    {
        for( unsigned i = 0; i < result.size(); i++ )
            if( result[i] == prev ) prev = 0;
        if( prev ) dirtree_find_siblings( dirtree, result, prev );
    }
    
    // visit next sibling, don't go infinitely
    unsigned next = e->next;
    if( ( next > 0 ) && ( next < dirtree->entryCount() ) )
    {
        for( unsigned i = 0; i < result.size(); i++ )
            if( result[i] == next ) next = 0;
        if( next ) dirtree_find_siblings( dirtree, result, next );
    }
}

std::vector<unsigned> DirTree::children( unsigned index )
{
    std::vector<unsigned> result;
    
    DirEntry* e = entry( index );
    if( e ) if( e->valid && e->child < entryCount() )
        dirtree_find_siblings( this, result, e->child );
    
    return result;
}

void DirTree::load( unsigned char* buffer, unsigned size )
{
    entries.clear();
    
    for( unsigned i = 0; i < size/128; i++ )
    {
        unsigned p = i * 128;
        
        // would be < 32 if first char in the name isn't printable
        unsigned prefix = 32;
        
        // parse name of this entry, which stored as Unicode 16-bit
        std::string name;
        int name_len = readU16( buffer + 0x40+p );
        if( name_len > 64 ) name_len = 64;
        for( int j=0; ( buffer[j+p]) && (j<name_len); j+= 2 )
            name.append( 1, buffer[j+p] );
        
        // first char isn't printable ? remove it...
        if( buffer[p] < 32 )
        {
            prefix = buffer[0];
            name.erase( 0,1 );
        }
        
        // 2 = file (aka stream), 1 = directory (aka storage), 5 = root
        unsigned type = buffer[ 0x42 + p];
        
        DirEntry e;
        e.valid = true;
        e.name = name;
        e.start = readU32( buffer + 0x74+p );
        e.size = readU32( buffer + 0x78+p );
        e.prev = readU32( buffer + 0x44+p );
        e.next = readU32( buffer + 0x48+p );
        e.child = readU32( buffer + 0x4C+p );
        e.dir = ( type!=2 );
        
        // sanity checks
        if( (type != 2) && (type != 1 ) && (type != 5 ) ) e.valid = false;
        if( name_len < 1 ) e.valid = false;
        
        entries.push_back( e );
    }
}

// return space required to save this dirtree
unsigned DirTree::size()
{
    return entryCount() * 128;
}

void DirTree::save( unsigned char* buffer )
{
    memset( buffer, 0, size() );
    
    // root is fixed as "Root Entry"
    DirEntry* root = entry( 0 );
    std::string name = "Root Entry";
    for( unsigned j = 0; j < name.length(); j++ )
        buffer[ j*2 ] = name[j];
    writeU16( buffer + 0x40, name.length()*2 + 2 );
    writeU32( buffer + 0x74, 0xffffffff );
    writeU32( buffer + 0x78, 0 );
    writeU32( buffer + 0x44, 0xffffffff );
    writeU32( buffer + 0x48, 0xffffffff );
    writeU32( buffer + 0x4c, root->child );
    buffer[ 0x42 ] = 5;
    buffer[ 0x43 ] = 1;
    
    for( unsigned i = 1; i < entryCount(); i++ )
    {
        DirEntry* e = entry( i );
        if( !e ) continue;
        if( e->dir )
        {
            e->start = 0xffffffff;
            e->size = 0;
        }
        
        // max length for name is 32 chars
        std::string name = e->name;
        if( name.length() > 32 )
            name.erase( 32, name.length() );
        
        // write name as Unicode 16-bit
        for( unsigned j = 0; j < name.length(); j++ )
            buffer[ i*128 + j*2 ] = name[j];
        
        writeU16( buffer + i*128 + 0x40, name.length()*2 + 2 );
        writeU32( buffer + i*128 + 0x74, e->start );
        writeU32( buffer + i*128 + 0x78, e->size );
        writeU32( buffer + i*128 + 0x44, e->prev );
        writeU32( buffer + i*128 + 0x48, e->next );
        writeU32( buffer + i*128 + 0x4c, e->child );
        buffer[ i*128 + 0x42 ] = e->dir ? 1 : 2;
        buffer[ i*128 + 0x43 ] = 1; // always black
    }
}

void DirTree::debug()
{
    for( unsigned i = 0; i < entryCount(); i++ )
    {
        DirEntry* e = entry( i );
        if( !e ) continue;
        std::cout << i << ": ";
        if( !e->valid ) std::cout << "INVALID ";
        std::cout << e->name << " ";
        if( e->dir ) std::cout << "(Dir) ";
        else std::cout << "(File) ";
        std::cout << e->size << " ";
        std::cout << "s:" << e->start << " ";
        std::cout << "(";
        if( e->child == End ) std::cout << "-"; else std::cout << e->child;
        std::cout << " ";
        if( e->prev == End ) std::cout << "-"; else std::cout << e->prev;
        std::cout << ":";
        if( e->next == End ) std::cout << "-"; else std::cout << e->next;
        std::cout << ")";
        std::cout << std::endl;
    }
}

// =========== StorageIO ==========

StorageIO::StorageIO( Storage* st, char* bytes, unsigned long length ):
storage( st ),
filedata((unsigned char *)bytes),
dataLength(length),
result( Storage::Ok ),
opened( false ),
filesize( 0 ),
header( new Header() ),
dirtree( new DirTree() ),
bbat ( new AllocTable() ),
sbat ( new AllocTable() ),
sb_blocks(),
streams()
{
    bbat->blockSize = 1 << header->b_shift;
    sbat->blockSize = 1 << header->s_shift;
}

StorageIO::~StorageIO()
{
    if( opened ) close();
    delete sbat;
    delete bbat;
    delete dirtree;
    delete header;
}

bool StorageIO::open()
{
    // already opened ? close first
    if( opened ) close();
    
    load();
    
    return result == Storage::Ok;
}

void StorageIO::load()
{
    unsigned char* buffer = 0;
    unsigned long buflen = 0;
    std::vector<unsigned long> blocks;
    
    // open the file, check for error
    result = Storage::OpenFailed;
    //FSTREAM file.open( filename.c_str(), std::ios::binary | std::ios::in );
    //FSTREAM if( !file.good() ) return;
    
    // find size of input file
    //FSTREAM file.seekg( 0, std::ios::end );
    //FSTREAM filesize = file.tellg();
    filesize = dataLength;
    
    // load header
    buffer = new unsigned char[512];
    //FSTREAM file.seekg( 0 );
    //FSTREAM file.read( (char*)buffer, 512 );
    memcpy(buffer, filedata, 512);
    header->load( buffer );
    delete[] buffer;
    
    // check OLE magic id
    result = Storage::NotOLE;
    for( unsigned i=0; i<8; i++ )
        if( header->id[i] != pole_magic[i] )
            return;
    
    // sanity checks
    result = Storage::BadOLE;
    if( !header->valid() ) return;
    if( header->threshold != 4096 ) return;
    
    // important block size
    bbat->blockSize = 1 << header->b_shift;
    sbat->blockSize = 1 << header->s_shift;
    
    // find blocks allocated to store big bat
    // the first 109 blocks are in header, the rest in meta bat
    blocks.clear();
    blocks.resize( header->num_bat );
    for( unsigned i = 0; i < 109; i++ )
        if( i >= header->num_bat ) break;
        else blocks[i] = header->bb_blocks[i];
    if( (header->num_bat > 109) && (header->num_mbat > 0) )
    {
        unsigned char* buffer2 = new unsigned char[ bbat->blockSize ];
        memset(buffer2, 0, bbat->blockSize);
        unsigned k = 109;
        unsigned mblock = header->mbat_start;
        for( unsigned r = 0; r < header->num_mbat; r++ )
        {
            loadBigBlock( mblock, buffer2, bbat->blockSize );
            for( unsigned s=0; s < bbat->blockSize-4; s+=4 )
            {
                if( k >= header->num_bat ) break;
                else  blocks[k++] = readU32( buffer2 + s );
            }
            mblock = readU32( buffer2 + bbat->blockSize-4 );
        }
        delete[] buffer2;
    }
    
    // load big bat
    buflen = blocks.size()*bbat->blockSize;
    if( buflen > 0 )
    {
        buffer = new unsigned char[ buflen ];
        memset(buffer, 0, buflen);
        loadBigBlocks( blocks, buffer, buflen );
        bbat->load( buffer, buflen );
        delete[] buffer;
    }
    
    // load small bat
    blocks.clear();
    blocks = bbat->follow( header->sbat_start );
    buflen = blocks.size()*bbat->blockSize;
    if( buflen > 0 )
    {
        buffer = new unsigned char[ buflen ];
        memset(buffer, 0, buflen);
        loadBigBlocks( blocks, buffer, buflen );
        sbat->load( buffer, buflen );
        delete[] buffer;
    }
    
    // load directory tree
    blocks.clear();
    blocks = bbat->follow( header->dirent_start );
    buflen = blocks.size()*bbat->blockSize;
    buffer = new unsigned char[ buflen ];
    memset(buffer, 0, buflen);
    loadBigBlocks( blocks, buffer, buflen );
    dirtree->load( buffer, buflen );
    unsigned sb_start = readU32( buffer + 0x74 );
    delete[] buffer;
    
    // fetch block chain as data for small-files
    sb_blocks = bbat->follow( sb_start ); // small files
    
    // for troubleshooting, just enable this block
#if 0
    header->debug();
    sbat->debug();
    bbat->debug();
    dirtree->debug();
#endif
    
    // so far so good
    result = Storage::Ok;
    opened = true;
}

void StorageIO::create()
{
    // std::cout << "Creating " << filename << std::endl;
    
    /*FSTREAM file.open( filename.c_str(), std::ios::out|std::ios::binary );
    if( !file.good() )
    {
        std::cerr << "Can't create " << filename << std::endl;
        result = Storage::OpenFailed;
        return;
    }*/
    
    // so far so good
    opened = true;
    result = Storage::Ok;
}

void StorageIO::flush()
{
    /* Note on Microsoft implementation:
     - directory entries are stored in the last block(s)
     - BATs are as second to the last
     - Meta BATs are third to the last
     */
}

void StorageIO::close()
{
    if( !opened ) return;
    
    //FSTREAM file.close();
    opened = false;
    
    std::list<Stream*>::iterator it;
    for( it = streams.begin(); it != streams.end(); ++it )
        delete *it;
}

StreamIO* StorageIO::streamIO( const std::string& name )
{
    // sanity check
    if( !name.length() ) return (StreamIO*)0;
    
    // search in the entries
    DirEntry* entry = dirtree->entry( name );
    //if( entry) std::cout << "FOUND\n";
    if( !entry ) return (StreamIO*)0;
    //if( !entry->dir ) std::cout << "  NOT DIR\n";
    if( entry->dir ) return (StreamIO*)0;
    
    StreamIO* result = new StreamIO( this, entry );
    result->fullName = name;
    
    return result;
}

unsigned long StorageIO::loadBigBlocks( std::vector<unsigned long> blocks,
                                       unsigned char* data, unsigned long maxlen )
{
    // sentinel
    if( !data ) return 0;
    if( blocks.size() < 1 ) return 0;
    if( maxlen == 0 ) return 0;
    
    // read block one by one, seems fast enough
    unsigned long bytes = 0;
    for( unsigned long i=0; (i < blocks.size() ) && ( bytes<maxlen ); i++ )
    {
        unsigned long block = blocks[i];
        unsigned long pos =  bbat->blockSize * ( block+1 );
        unsigned long p = (bbat->blockSize < maxlen-bytes) ? bbat->blockSize : maxlen-bytes;
        if( pos + p > filesize ) p = filesize - pos;
        //FSTREAM file.seekg( pos );
        //FSTREAM file.read( (char*)data + bytes, p );
        memcpy((char*)data + bytes, filedata + pos, p);
        bytes += p;
    }
    
    return bytes;
}

unsigned long StorageIO::loadBigBlock( unsigned long block,
                                      unsigned char* data, unsigned long maxlen )
{
    // sentinel
    if( !data ) return 0;
    
    // wraps call for loadBigBlocks
    std::vector<unsigned long> blocks;
    blocks.resize( 1 );
    blocks[ 0 ] = block;
    
    return loadBigBlocks( blocks, data, maxlen );
}

// return number of bytes which has been read
unsigned long StorageIO::loadSmallBlocks( std::vector<unsigned long> blocks,
                                         unsigned char* data, unsigned long maxlen )
{
    // sentinel
    if( !data ) return 0;
    if( blocks.size() < 1 ) return 0;
    if( maxlen == 0 ) return 0;
    
    // our own local buffer
    unsigned char* buf = new unsigned char[ bbat->blockSize ];
    
    // read small block one by one
    unsigned long bytes = 0;
    for( unsigned long i=0; ( i<blocks.size() ) && ( bytes<maxlen ); i++ )
    {
        unsigned long block = blocks[i];
        
        // find where the small-block exactly is
        unsigned long pos = block * sbat->blockSize;
        unsigned long bbindex = pos / bbat->blockSize;
        if( bbindex >= sb_blocks.size() ) break;
        
        loadBigBlock( sb_blocks[ bbindex ], buf, bbat->blockSize );
        
        // copy the data
        unsigned offset = pos % bbat->blockSize;
        unsigned long p = (maxlen-bytes < bbat->blockSize-offset ) ? maxlen-bytes :  bbat->blockSize-offset;
        p = (sbat->blockSize<p ) ? sbat->blockSize : p;
        memcpy( data + bytes, buf + offset, p );
        bytes += p;
    }
    
    delete[] buf;
    
    return bytes;
}

unsigned long StorageIO::loadSmallBlock( unsigned long block,
                                        unsigned char* data, unsigned long maxlen )
{
    // sentinel
    if( !data ) return 0;
    
    // wraps call for loadSmallBlocks
    std::vector<unsigned long> blocks;
    blocks.resize( 1 );
    blocks.assign( 1, block );
    
    return loadSmallBlocks( blocks, data, maxlen );
}

// =========== StreamIO ==========

StreamIO::StreamIO( StorageIO* s, DirEntry* e ):
io( s ),
entry( e ),
fullName(),
eof( false ),
fail( false ),
blocks(),
m_pos( 0 ),
cache_data( 0 ),
cache_size( 4096 ), // optimal ?
cache_pos( 0 )
{
    if( entry->size >= io->header->threshold )
        blocks = io->bbat->follow( entry->start );
    else
        blocks = io->sbat->follow( entry->start );
    
    // prepare cache
    cache_data = new unsigned char[cache_size];
    updateCache();
}

// FIXME tell parent we're gone
StreamIO::~StreamIO()
{
    delete[] cache_data;
}

void StreamIO::seek( unsigned long pos )
{
    m_pos = pos;
}

unsigned long StreamIO::tell()
{
    return m_pos;
}

int StreamIO::getch()
{
    // past end-of-file ?
    if( m_pos > entry->size ) return -1;
    
    // need to update cache ?
    if( !cache_size || ( m_pos < cache_pos ) ||
       ( m_pos >= cache_pos + cache_size ) )
        updateCache();
    
    // something bad if we don't get good cache
    if( !cache_size ) return -1;
    
    int data = cache_data[m_pos - cache_pos];
    m_pos++;
    
    return data;
}

unsigned long StreamIO::read( unsigned long pos, unsigned char* data, unsigned long maxlen )
{
    // sanity checks
    if( !data ) return 0;
    if( maxlen == 0 ) return 0;
    
    unsigned long totalbytes = 0;
    
    if ( entry->size < io->header->threshold )
    {
        // small file
        unsigned long index = pos / io->sbat->blockSize;
        
        if( index >= blocks.size() ) return 0;
        
        unsigned char* buf = new unsigned char[ io->sbat->blockSize ];
        unsigned long offset = pos % io->sbat->blockSize;
        while( totalbytes < maxlen )
        {
            if( index >= blocks.size() ) break;
            io->loadSmallBlock( blocks[index], buf, io->bbat->blockSize );
            unsigned long count = io->sbat->blockSize - offset;
            if( count > maxlen-totalbytes ) count = maxlen-totalbytes;
            memcpy( data+totalbytes, buf + offset, count );
            totalbytes += count;
            offset = 0;
            index++;
        }
        delete[] buf;
        
    }
    else
    {
        // big file
        unsigned long index = pos / io->bbat->blockSize;
        
        if( index >= blocks.size() ) return 0;
        
        unsigned char* buf = new unsigned char[ io->bbat->blockSize ];
        unsigned long offset = pos % io->bbat->blockSize;
        while( totalbytes < maxlen )
        {
            if( index >= blocks.size() ) break;
            io->loadBigBlock( blocks[index], buf, io->bbat->blockSize );
            unsigned long count = io->bbat->blockSize - offset;
            if( count > maxlen-totalbytes ) count = maxlen-totalbytes;
            memcpy( data+totalbytes, buf + offset, count );
            totalbytes += count;
            index++;
            offset = 0;
        }
        delete [] buf;
        
    }
    
    return totalbytes;
}

unsigned long StreamIO::read( unsigned char* data, unsigned long maxlen )
{
    unsigned long bytes = read( tell(), data, maxlen );
    m_pos += bytes;
    return bytes;
}

void StreamIO::updateCache()
{
    // sanity check
    if( !cache_data ) return;
    
    cache_pos = m_pos - ( m_pos % cache_size );
    unsigned long bytes = cache_size;
    if( cache_pos + bytes > entry->size ) bytes = entry->size - cache_pos;
    cache_size = read( cache_pos, cache_data, bytes );
}


// =========== Storage ==========

Storage::Storage( char* bytes, unsigned long length ):
io( new StorageIO( this, bytes, length ) )
{
}

Storage::~Storage()
{
    delete io;
}

int Storage::result()
{
    return io->result;
}

bool Storage::open()
{
    return io->open();
}

void Storage::close()
{
    io->close();
}

std::list<std::string> Storage::entries( const std::string& path )
{
    std::list<std::string> result;
    DirTree* dt = io->dirtree;
    DirEntry* e = dt->entry( path, false );
    if( e  && e->dir )
    {
        unsigned parent = dt->indexOf( e );
        std::vector<unsigned> children = dt->children( parent );
        for( unsigned i = 0; i < children.size(); i++ )
            result.push_back( dt->entry( children[i] )->name );
    }
    
    return result;
}

bool Storage::isDirectory( const std::string& name )
{
    DirEntry* e = io->dirtree->entry( name, false );
    return e ? e->dir : false;
}

DirTree* Storage::dirTree()
{
    return io->dirtree;
}


StorageIO* Storage::storageIO()
{
    return io;
}

std::list<DirEntry*> Storage::dirEntries( const std::string& path )
{
    std::list<DirEntry*> result;
    DirTree* dt = io->dirtree;
    DirEntry* e = dt->entry( path, false );
    if( e  && e->dir )
    {
        unsigned parent = dt->indexOf( e );
        std::vector<unsigned> children = dt->children( parent );
        for( unsigned i = 0; i < children.size(); i++ )
            result.push_back( dt->entry( children[i] ) );
    }
    
    return result;
}

// =========== Stream ==========

Stream::Stream( Storage* storage, const std::string& name ):
io( storage->io->streamIO( name ) )
{
}

// FIXME tell parent we're gone
Stream::~Stream()
{
    delete io;
}

std::string Stream::fullName()
{
    return io ? io->fullName : std::string();
}

unsigned long Stream::tell()
{
    return io ? io->tell() : 0;
}

void Stream::seek( unsigned long newpos )
{
    if( io ) io->seek( newpos );
}

unsigned long Stream::size()
{
    return io ? io->entry->size : 0;
}

int Stream::getch()
{
    return io ? io->getch() : 0;
}

unsigned long Stream::read( unsigned char* data, unsigned long maxlen )
{
    return io ? io->read( data, maxlen ) : 0;
}

bool Stream::eof()
{
    return io ? io->eof : false;
}

bool Stream::fail()
{
    return io ? io->fail : true;
}