/
btreeidx.cc
1581 lines (1241 loc) · 42.5 KB
/
btreeidx.cc
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/* This file is (c) 2008-2012 Konstantin Isakov <[email protected]>
* Part of GoldenDict. Licensed under GPLv3 or later, see the LICENSE file */
#include "btreeidx.hh"
#include "folding.hh"
#include "utf8.hh"
#include <QRunnable>
#include <QThreadPool>
#include <QSemaphore>
#include <math.h>
#include <string.h>
#include <stdlib.h>
#include "gddebug.hh"
#include "wstring_qt.hh"
#include "qt4x5.hh"
#if QT_VERSION >= QT_VERSION_CHECK( 5, 0, 0 )
#include <QRegularExpression>
#include "wildcard.hh"
#endif
//#define __BTREE_USE_LZO
// LZO mode is experimental and unsupported. Tests didn't show any substantial
// speed improvements.
#ifdef __BTREE_USE_LZO
#include <lzo/lzo1x.h>
namespace {
struct __LzoInit
{
__LzoInit()
{
lzo_init();
}
} __lzoInit;
}
#else
#include <zlib.h>
#endif
namespace BtreeIndexing {
using gd::wstring;
using gd::wchar;
using std::pair;
enum
{
BtreeMinElements = 64,
BtreeMaxElements = 8192
};
BtreeIndex::BtreeIndex():
idxFile( 0 ), rootNodeLoaded( false )
{
}
BtreeDictionary::BtreeDictionary( string const & id,
vector< string > const & dictionaryFiles ):
Dictionary::Class( id, dictionaryFiles )
{
}
string const & BtreeDictionary::ensureInitDone()
{
static string empty;
return empty;
}
void BtreeIndex::openIndex( IndexInfo const & indexInfo,
File::Class & file, Mutex & mutex )
{
indexNodeSize = indexInfo.btreeMaxElements;
rootOffset = indexInfo.rootOffset;
idxFile = &file;
idxFileMutex = &mutex;
rootNodeLoaded = false;
rootNode.clear();
}
vector< WordArticleLink > BtreeIndex::findArticles( wstring const & word, bool ignoreDiacritics )
{
vector< WordArticleLink > result;
try
{
wstring folded = Folding::apply( word );
if( folded.empty() )
folded = Folding::applyWhitespaceOnly( word );
bool exactMatch;
vector< char > leaf;
uint32_t nextLeaf;
char const * leafEnd;
char const * chainOffset = findChainOffsetExactOrPrefix( folded, exactMatch,
leaf, nextLeaf,
leafEnd );
if ( chainOffset && exactMatch )
{
result = readChain( chainOffset );
antialias( word, result, ignoreDiacritics );
}
}
catch( std::exception & e )
{
gdWarning( "Articles searching failed, error: %s\n", e.what() );
result.clear();
}
catch(...)
{
qWarning( "Articles searching failed\n" );
result.clear();
}
return result;
}
class BtreeWordSearchRunnable: public QRunnable
{
BtreeWordSearchRequest & r;
QSemaphore & hasExited;
public:
BtreeWordSearchRunnable( BtreeWordSearchRequest & r_,
QSemaphore & hasExited_ ): r( r_ ),
hasExited( hasExited_ )
{}
~BtreeWordSearchRunnable()
{
hasExited.release();
}
virtual void run();
};
void BtreeWordSearchRunnable::run()
{
r.run();
}
BtreeWordSearchRequest::BtreeWordSearchRequest( BtreeDictionary & dict_,
wstring const & str_,
unsigned minLength_,
int maxSuffixVariation_,
bool allowMiddleMatches_,
unsigned long maxResults_,
bool startRunnable ):
dict( dict_ ), str( str_ ),
maxResults( maxResults_ ),
minLength( minLength_ ),
maxSuffixVariation( maxSuffixVariation_ ),
allowMiddleMatches( allowMiddleMatches_ )
{
if( startRunnable )
{
QThreadPool::globalInstance()->start(
new BtreeWordSearchRunnable( *this, hasExited ) );
}
}
void BtreeWordSearchRequest::findMatches()
{
if ( Qt4x5::AtomicInt::loadAcquire( isCancelled ) )
{
finish();
return;
}
if ( dict.ensureInitDone().size() )
{
setErrorString( QString::fromUtf8( dict.ensureInitDone().c_str() ) );
finish();
return;
}
#if QT_VERSION >= QT_VERSION_CHECK( 5, 0, 0 )
QRegularExpression regexp;
#else
QRegExp regexp;
#endif
bool useWildcards = false;
if( allowMiddleMatches )
useWildcards = ( str.find( '*' ) != wstring::npos ||
str.find( '?' ) != wstring::npos ||
str.find( '[' ) != wstring::npos ||
str.find( ']' ) != wstring::npos );
wstring folded = Folding::apply( str );
int minMatchLength = 0;
if( useWildcards )
{
#if QT_VERSION >= QT_VERSION_CHECK( 5, 0, 0 )
regexp.setPattern( wildcardsToRegexp( gd::toQString( Folding::applyDiacriticsOnly( Folding::applySimpleCaseOnly( str ) ) ) ) );
if( !regexp.isValid() )
regexp.setPattern( QRegularExpression::escape( regexp.pattern() ) );
regexp.setPatternOptions( QRegularExpression::CaseInsensitiveOption );
#else
regexp.setPattern( gd::toQString( Folding::applyDiacriticsOnly( Folding::applySimpleCaseOnly( str ) ) ) );
regexp.setPatternSyntax( QRegExp::WildcardUnix );
regexp.setCaseSensitivity( Qt::CaseInsensitive );
#endif
bool bNoLetters = folded.empty();
wstring foldedWithWildcards;
if( bNoLetters )
foldedWithWildcards = Folding::applyWhitespaceOnly( str );
else
foldedWithWildcards = Folding::apply( str, useWildcards );
// Calculate minimum match length
bool insideSet = false;
bool escaped = false;
for( wstring::size_type x = 0; x < foldedWithWildcards.size(); x++ )
{
wchar ch = foldedWithWildcards[ x ];
if( ch == L'\\' && !escaped )
{
escaped = true;
continue;
}
if( ch == L']' && !escaped )
{
insideSet = false;
continue;
}
if( insideSet )
{
escaped = false;
continue;
}
if( ch == L'[' && !escaped )
{
minMatchLength += 1;
insideSet = true;
continue;
}
if( ch == L'*' && !escaped )
continue;
escaped = false;
minMatchLength += 1;
}
// Fill first match chars
folded.clear();
folded.reserve( foldedWithWildcards.size() );
escaped = false;
for( wstring::size_type x = 0; x < foldedWithWildcards.size(); x++ )
{
wchar ch = foldedWithWildcards[ x ];
if( escaped )
{
if( bNoLetters || ( ch != L'*' && ch != L'?' && ch != L'[' && ch != L']' ) )
folded.push_back( ch );
escaped = false;
continue;
}
if( ch == L'\\' )
{
if( bNoLetters || folded.empty() )
{
escaped = true;
continue;
}
else
break;
}
if( ch == '*' || ch == '?' || ch == '[' || ch == ']' )
break;
folded.push_back( ch );
}
}
else
{
if( folded.empty() )
folded = Folding::applyWhitespaceOnly( str );
}
int initialFoldedSize = folded.size();
int charsLeftToChop = 0;
if ( maxSuffixVariation >= 0 )
{
charsLeftToChop = initialFoldedSize - (int)minLength;
if ( charsLeftToChop < 0 )
charsLeftToChop = 0;
else
if ( charsLeftToChop > maxSuffixVariation )
charsLeftToChop = maxSuffixVariation;
}
try
{
for( ; ; )
{
bool exactMatch;
vector< char > leaf;
uint32_t nextLeaf;
char const * leafEnd;
char const * chainOffset = dict.findChainOffsetExactOrPrefix( folded, exactMatch,
leaf, nextLeaf,
leafEnd );
if ( chainOffset )
for( ; ; )
{
if ( Qt4x5::AtomicInt::loadAcquire( isCancelled ) )
break;
//DPRINTF( "offset = %u, size = %u\n", chainOffset - &leaf.front(), leaf.size() );
vector< WordArticleLink > chain = dict.readChain( chainOffset );
wstring chainHead = Utf8::decode( chain[ 0 ].word );
wstring resultFolded = Folding::apply( chainHead );
if( resultFolded.empty() )
resultFolded = Folding::applyWhitespaceOnly( chainHead );
if ( ( useWildcards && folded.empty() ) ||
( resultFolded.size() >= folded.size()
&& !resultFolded.compare( 0, folded.size(), folded ) ) )
{
// Exact or prefix match
Mutex::Lock _( dataMutex );
for( unsigned x = 0; x < chain.size(); ++x )
{
if( useWildcards )
{
wstring word = Utf8::decode( chain[ x ].prefix + chain[ x ].word );
wstring result = Folding::applyDiacriticsOnly( word );
#if QT_VERSION >= QT_VERSION_CHECK( 5, 0, 0 )
if( result.size() >= (wstring::size_type)minMatchLength )
{
QRegularExpressionMatch match = regexp.match( gd::toQString( result ) );
if( match.hasMatch() && match.capturedStart() == 0 )
{
addMatch( word );
}
}
#else
if( result.size() >= (wstring::size_type)minMatchLength
&& regexp.indexIn( gd::toQString( result ) ) == 0
&& regexp.matchedLength() >= minMatchLength )
{
addMatch( word );
}
#endif
}
else
{
// Skip middle matches, if requested. If suffix variation is specified,
// make sure the string isn't larger than requested.
if ( ( allowMiddleMatches || Folding::apply( Utf8::decode( chain[ x ].prefix ) ).empty() ) &&
( maxSuffixVariation < 0 || (int)resultFolded.size() - initialFoldedSize <= maxSuffixVariation ) )
addMatch( Utf8::decode( chain[ x ].prefix + chain[ x ].word ) );
}
}
if( Qt4x5::AtomicInt::loadAcquire( isCancelled ) )
break;
if ( matches.size() >= maxResults )
{
// For now we actually allow more than maxResults if the last
// chain yield more than one result. That's ok and maybe even more
// desirable.
break;
}
}
else
// Neither exact nor a prefix match, end this
break;
// Fetch new leaf if we're out of chains here
if ( chainOffset >= leafEnd )
{
// We're past the current leaf, fetch the next one
//DPRINTF( "advancing\n" );
if ( nextLeaf )
{
Mutex::Lock _( *dict.idxFileMutex );
dict.readNode( nextLeaf, leaf );
leafEnd = &leaf.front() + leaf.size();
nextLeaf = dict.idxFile->read< uint32_t >();
chainOffset = &leaf.front() + sizeof( uint32_t );
uint32_t leafEntries = *(uint32_t *)&leaf.front();
if ( leafEntries == 0xffffFFFF )
{
//DPRINTF( "bah!\n" );
exit( 1 );
}
}
else
break; // That was the last leaf
}
}
if ( charsLeftToChop && !Qt4x5::AtomicInt::loadAcquire( isCancelled ) )
{
--charsLeftToChop;
folded.resize( folded.size() - 1 );
}
else
break;
}
}
catch( std::exception & e )
{
qWarning( "Index searching failed: \"%s\", error: %s\n",
dict.getName().c_str(), e.what() );
}
catch(...)
{
gdWarning( "Index searching failed: \"%s\"\n", dict.getName().c_str() );
}
}
void BtreeWordSearchRequest::run()
{
if ( Qt4x5::AtomicInt::loadAcquire( isCancelled ) )
{
finish();
return;
}
if ( dict.ensureInitDone().size() )
{
setErrorString( QString::fromUtf8( dict.ensureInitDone().c_str() ) );
finish();
return;
}
findMatches();
finish();
}
BtreeWordSearchRequest::~BtreeWordSearchRequest()
{
isCancelled.ref();
hasExited.acquire();
}
sptr< Dictionary::WordSearchRequest > BtreeDictionary::prefixMatch(
wstring const & str, unsigned long maxResults )
THROW_SPEC( std::exception )
{
return new BtreeWordSearchRequest( *this, str, 0, -1, true, maxResults );
}
sptr< Dictionary::WordSearchRequest > BtreeDictionary::stemmedMatch(
wstring const & str, unsigned minLength, unsigned maxSuffixVariation,
unsigned long maxResults )
THROW_SPEC( std::exception )
{
return new BtreeWordSearchRequest( *this, str, minLength, (int)maxSuffixVariation,
false, maxResults );
}
void BtreeIndex::readNode( uint32_t offset, vector< char > & out )
{
idxFile->seek( offset );
uint32_t uncompressedSize = idxFile->read< uint32_t >();
uint32_t compressedSize = idxFile->read< uint32_t >();
//DPRINTF( "%x,%x\n", uncompressedSize, compressedSize );
out.resize( uncompressedSize );
vector< unsigned char > compressedData( compressedSize );
idxFile->read( &compressedData.front(), compressedData.size() );
#ifdef __BTREE_USE_LZO
lzo_uint decompressedLength = out.size();
if ( lzo1x_decompress( &compressedData.front(), compressedData.size(),
(unsigned char *)&out.front(), &decompressedLength, 0 )
!= LZO_E_OK || decompressedLength != out.size() )
throw exFailedToDecompressNode();
#else
unsigned long decompressedLength = out.size();
if ( uncompress( (unsigned char *)&out.front(),
&decompressedLength,
&compressedData.front(),
compressedData.size() ) != Z_OK ||
decompressedLength != out.size() )
throw exFailedToDecompressNode();
#endif
}
char const * BtreeIndex::findChainOffsetExactOrPrefix( wstring const & target,
bool & exactMatch,
vector< char > & extLeaf,
uint32_t & nextLeaf,
char const * & leafEnd )
{
if ( !idxFile )
throw exIndexWasNotOpened();
Mutex::Lock _( *idxFileMutex );
// Lookup the index by traversing the index btree
vector< wchar > wcharBuffer;
exactMatch = false;
// Read a node
uint32_t currentNodeOffset = rootOffset;
if ( !rootNodeLoaded )
{
// Time to load our root node. We do it only once, at the first request.
readNode( rootOffset, rootNode );
rootNodeLoaded = true;
}
char const * leaf = &rootNode.front();
leafEnd = leaf + rootNode.size();
if( target.empty() )
{
//For empty target string we return first chain in index
for( ; ; )
{
uint32_t leafEntries = *(uint32_t *)leaf;
if ( leafEntries == 0xffffFFFF )
{
// A node
currentNodeOffset = *( (uint32_t *)leaf + 1 );
readNode( currentNodeOffset, extLeaf );
leaf = &extLeaf.front();
leafEnd = leaf + extLeaf.size();
nextLeaf = idxFile->read< uint32_t >();
}
else
{
// A leaf
if( currentNodeOffset == rootOffset )
{
// Only one leaf in index, there's no next leaf
nextLeaf = 0;
}
if( !leafEntries )
return 0;
return leaf + sizeof( uint32_t );
}
}
}
for( ; ; )
{
// Is it a leaf or a node?
uint32_t leafEntries = *(uint32_t *)leaf;
if ( leafEntries == 0xffffFFFF )
{
// A node
//DPRINTF( "=>a node\n" );
uint32_t const * offsets = (uint32_t *)leaf + 1;
char const * ptr = leaf + sizeof( uint32_t ) +
( indexNodeSize + 1 ) * sizeof( uint32_t );
// ptr now points to a span of zero-separated strings, up to leafEnd.
// We find our match using a binary search.
char const * closestString;
int compareResult;
char const * window = ptr;
unsigned windowSize = leafEnd - ptr;
for( ; ; )
{
// We boldly shoot in the middle of the whole mess, and then adjust
// to the beginning of the string that we've hit.
char const * testPoint = window + windowSize/2;
closestString = testPoint;
while( closestString > ptr && closestString[ -1 ] )
--closestString;
size_t wordSize = strlen( closestString );
if ( wcharBuffer.size() <= wordSize )
wcharBuffer.resize( wordSize + 1 );
long result = Utf8::decode( closestString, wordSize, &wcharBuffer.front() );
if ( result < 0 )
throw Utf8::exCantDecode( closestString );
wcharBuffer[ result ] = 0;
//DPRINTF( "Checking against %s\n", closestString );
compareResult = target.compare( &wcharBuffer.front() );
if ( !compareResult )
{
// The target string matches the current one. Finish the search.
break;
}
if ( compareResult < 0 )
{
// The target string is smaller than the current one.
// Go to the left.
windowSize = closestString - window;
if ( !windowSize )
break;
}
else
{
// The target string is larger than the current one.
// Go to the right.
windowSize -= ( closestString - window ) + wordSize + 1;
window = closestString + wordSize + 1;
if ( !windowSize )
break;
}
}
#if 0
DPRINTF( "The winner is %s, compareResult = %d\n", closestString, compareResult );
if ( closestString != ptr )
{
char const * left = closestString -1;
while( left != ptr && left[ -1 ] )
--left;
DPRINTF( "To the left: %s\n", left );
}
else
DPRINTF( "To the lest -- nothing\n" );
char const * right = closestString + strlen( closestString ) + 1;
if ( right != leafEnd )
{
DPRINTF( "To the right: %s\n", right );
}
else
DPRINTF( "To the right -- nothing\n" );
#endif
// Now, whatever the outcome (compareResult) is, we need to find
// entry number for the closestMatch string.
unsigned entry = 0;
for( char const * next = ptr; next != closestString;
next += strlen( next ) + 1, ++entry ) ;
// Ok, now check the outcome
if ( !compareResult )
{
// The target string matches the one found.
// Go to the right, since it's there where we store such results.
currentNodeOffset = offsets[ entry + 1 ];
}
if ( compareResult < 0 )
{
// The target string is smaller than the one found.
// Go to the left.
currentNodeOffset = offsets[ entry ];
}
else
{
// The target string is larger than the one found.
// Go to the right.
currentNodeOffset = offsets[ entry + 1 ];
}
//DPRINTF( "reading node at %x\n", currentNodeOffset );
readNode( currentNodeOffset, extLeaf );
leaf = &extLeaf.front();
leafEnd = leaf + extLeaf.size();
}
else
{
//DPRINTF( "=>a leaf\n" );
// A leaf
// If this leaf is the root, there's no next leaf, it just can't be.
// We do this check because the file's position indicator just won't
// be in the right place for root node anyway, since we precache it.
nextLeaf = ( currentNodeOffset != rootOffset ? idxFile->read< uint32_t >() : 0 );
if ( !leafEntries )
{
// Empty leaf? This may only be possible for entirely empty trees only.
if ( currentNodeOffset != rootOffset )
throw exCorruptedChainData();
else
return 0; // No match
}
// Build an array containing all chain pointers
char const * ptr = leaf + sizeof( uint32_t );
uint32_t chainSize;
vector< char const * > chainOffsets( leafEntries );
{
char const ** nextOffset = &chainOffsets.front();
while( leafEntries-- )
{
*nextOffset++ = ptr;
memcpy( &chainSize, ptr, sizeof( uint32_t ) );
//DPRINTF( "%s + %s\n", ptr + sizeof( uint32_t ), ptr + sizeof( uint32_t ) + strlen( ptr + sizeof( uint32_t ) ) + 1 );
ptr += sizeof( uint32_t ) + chainSize;
}
}
// Now do a binary search in it, aiming to find where our target
// string lands.
char const ** window = &chainOffsets.front();
unsigned windowSize = chainOffsets.size();
for( ; ; )
{
//DPRINTF( "window = %u, ws = %u\n", window - &chainOffsets.front(), windowSize );
char const ** chainToCheck = window + windowSize/2;
ptr = *chainToCheck;
memcpy( &chainSize, ptr, sizeof( uint32_t ) );
ptr += sizeof( uint32_t );
size_t wordSize = strlen( ptr );
if ( wcharBuffer.size() <= wordSize )
wcharBuffer.resize( wordSize + 1 );
//DPRINTF( "checking against word %s, left = %u\n", ptr, leafEntries );
long result = Utf8::decode( ptr, wordSize, &wcharBuffer.front() );
if ( result < 0 )
throw Utf8::exCantDecode( ptr );
wcharBuffer[ result ] = 0;
wstring foldedWord = Folding::apply( &wcharBuffer.front() );
if( foldedWord.empty() )
foldedWord = Folding::applyWhitespaceOnly( &wcharBuffer.front() );
int compareResult = target.compare( foldedWord );
if ( !compareResult )
{
// Exact match -- return and be done
exactMatch = true;
return ptr - sizeof( uint32_t );
}
else
if ( compareResult < 0 )
{
// The target string is smaller than the current one.
// Go to the first half
windowSize /= 2;
if ( !windowSize )
{
// That finishes our search. Since our target string
// landed before the last tested chain, we return a possible
// prefix match against that chain.
return ptr - sizeof( uint32_t );
}
}
else
{
// The target string is larger than the current one.
// Go to the second half
windowSize -= windowSize/2 + 1;
if ( !windowSize )
{
// That finishes our search. Since our target string
// landed after the last tested chain, we return the next
// chain. If there's no next chain in this leaf, this
// would mean the first element in the next leaf.
if ( chainToCheck == &chainOffsets.back() )
{
if ( nextLeaf )
{
readNode( nextLeaf, extLeaf );
leafEnd = &extLeaf.front() + extLeaf.size();
nextLeaf = idxFile->read< uint32_t >();
return &extLeaf.front() + sizeof( uint32_t );
}
else
return 0; // This was the last leaf
}
else
return chainToCheck[ 1 ];
}
window = chainToCheck + 1;
}
}
}
}
}
vector< WordArticleLink > BtreeIndex::readChain( char const * & ptr )
{
uint32_t chainSize;
memcpy( &chainSize, ptr, sizeof( uint32_t ) );
ptr += sizeof( uint32_t );
vector< WordArticleLink > result;
while( chainSize )
{
string str = ptr;
ptr += str.size() + 1;
string prefix = ptr;
ptr += prefix.size() + 1;
uint32_t articleOffset;
memcpy( &articleOffset, ptr, sizeof( uint32_t ) );
ptr += sizeof( uint32_t );
result.push_back( WordArticleLink( str, articleOffset, prefix ) );
if ( chainSize < str.size() + 1 + prefix.size() + 1 + sizeof( uint32_t ) )
throw exCorruptedChainData();
else
chainSize -= str.size() + 1 + prefix.size() + 1 + sizeof( uint32_t );
}
return result;
}
void BtreeIndex::antialias( wstring const & str,
vector< WordArticleLink > & chain,
bool ignoreDiacritics )
{
wstring caseFolded = Folding::applySimpleCaseOnly( gd::normalize( str ) );
if( ignoreDiacritics )
caseFolded = Folding::applyDiacriticsOnly( caseFolded );
for( unsigned x = chain.size(); x--; )
{
// If after applying case folding to each word they wouldn't match, we
// drop the entry.
wstring entry = Folding::applySimpleCaseOnly( gd::normalize( Utf8::decode( chain[ x ].prefix + chain[ x ].word ) ) );
if( ignoreDiacritics )
entry = Folding::applyDiacriticsOnly( entry );
if ( entry != caseFolded )
chain.erase( chain.begin() + x );
else
if ( chain[ x ].prefix.size() ) // If there's a prefix, merge it with the word,
// since it's what dictionaries expect
{
chain[ x ].word.insert( 0, chain[ x ].prefix );
chain[ x ].prefix.clear();
}
}
}
/// A function which recursively creates btree node.
/// The nextIndex iterator is being iterated over and increased when building
/// leaf nodes.
static uint32_t buildBtreeNode( IndexedWords::const_iterator & nextIndex,
size_t indexSize,
File::Class & file, size_t maxElements,
uint32_t & lastLeafLinkOffset )
{
// We compress all the node data. This buffer would hold it.
vector< unsigned char > uncompressedData;
bool isLeaf = indexSize <= maxElements;
if ( isLeaf )
{
// A leaf.
uint32_t totalChainsLength = 0;
IndexedWords::const_iterator nextWord = nextIndex;
for( unsigned x = indexSize; x--; ++nextWord )
{
totalChainsLength += sizeof( uint32_t );
vector< WordArticleLink > const & chain = nextWord->second;
for( unsigned y = 0; y < chain.size(); ++y )
totalChainsLength += chain[ y ].word.size() + 1 + chain[ y ].prefix.size() + 1 + sizeof( uint32_t );
}
uncompressedData.resize( sizeof( uint32_t ) + totalChainsLength );
// First uint32_t indicates that this is a leaf.
*(uint32_t *)&uncompressedData.front() = indexSize;
unsigned char * ptr = &uncompressedData.front() + sizeof( uint32_t );
for( unsigned x = indexSize; x--; ++nextIndex )
{
vector< WordArticleLink > const & chain = nextIndex->second;
unsigned char * saveSizeHere = ptr;
ptr += sizeof( uint32_t );
uint32_t size = 0;
for( unsigned y = 0; y < chain.size(); ++y )
{
memcpy( ptr, chain[ y ].word.c_str(), chain[ y ].word.size() + 1 );
ptr += chain[ y ].word.size() + 1;
memcpy( ptr, chain[ y ].prefix.c_str(), chain[ y ].prefix.size() + 1 );
ptr += chain[ y ].prefix.size() + 1;
memcpy( ptr, &(chain[ y ].articleOffset), sizeof( uint32_t ) );
ptr += sizeof( uint32_t );
size += chain[ y ].word.size() + 1 + chain[ y ].prefix.size() + 1 + sizeof( uint32_t );