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/** @file keymaker.cc
* @brief Build key strings for MSet ordering or collapsing.
*/
/* Copyright (C) 2007,2009 Olly Betts
*
* 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, write to the Free Software
* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include <config.h>
#include "xapian/keymaker.h"
#include "xapian/document.h"
#include <string>
#include <vector>
using namespace std;
namespace Xapian {
KeyMaker::~KeyMaker() { }
string
MultiValueKeyMaker::operator()(const Xapian::Document & doc) const
{
string result;
vector<pair<Xapian::valueno, bool> >::const_iterator i = slots.begin();
// Don't crash if slots is empty.
if (rare(i == slots.end())) return result;
size_t last_not_empty_forwards = 0;
while (true) {
// All values (except for the last if it's sorted forwards) need to
// be adjusted.
//
// FIXME: allow Xapian::BAD_VALUENO to mean "relevance?"
string v = doc.get_value(i->first);
bool reverse_sort = i->second;
if (reverse_sort || !v.empty())
last_not_empty_forwards = result.size();
if (++i == slots.end() && !reverse_sort) {
if (v.empty()) {
// Trim off all the trailing empty forwards values.
result.resize(last_not_empty_forwards);
} else {
// No need to adjust the last value if it's sorted forwards.
result += v;
}
break;
}
if (reverse_sort) {
// For a reverse ordered value, we subtract each byte from '\xff',
// except for '\0' which we convert to "\xff\0". We insert
// "\xff\xff" after the encoded value.
for (string::const_iterator j = v.begin(); j != v.end(); ++j) {
unsigned char ch(*j);
result += char(255 - ch);
if (ch == 0) result += '\0';
}
result.append("\xff\xff", 2);
if (i == slots.end()) break;
last_not_empty_forwards = result.size();
} else {
// For a forward ordered value (unless it's the last value), we
// convert any '\0' to "\0\xff". We insert "\0\0" after the
// encoded value.
string::size_type j = 0, nul;
while ((nul = v.find('\0', j)) != string::npos) {
++nul;
result.append(v, j, nul - j);
result += '\xff';
j = nul;
}
result.append(v, j, string::npos);
if (!v.empty())
last_not_empty_forwards = result.size();
result.append("\0", 2);
}
}
return result;
}
string
MultiValueSorter::operator()(const Xapian::Document & doc) const
{
string result;
vector<pair<Xapian::valueno, bool> >::const_iterator i = slots.begin();
// Don't crash if slots is empty.
if (rare(i == slots.end())) return result;
while (true) {
// All values (except for the last if it's sorted forwards) need to
// be adjusted.
//
// FIXME: allow Xapian::BAD_VALUENO to mean "relevance?"
string v = doc.get_value(i->first);
bool reverse_sort = !i->second;
if (++i == slots.end() && !reverse_sort) {
// No need to adjust the last value if it's sorted forwards.
result += v;
break;
}
if (reverse_sort) {
// For a reverse ordered value, we subtract each byte from '\xff',
// except for '\0' which we convert to "\xff\0". We insert
// "\xff\xff" after the encoded value.
for (string::const_iterator j = v.begin(); j != v.end(); ++j) {
unsigned char ch(*j);
result += char(255 - ch);
if (ch == 0) result += '\0';
}
result.append("\xff\xff", 2);
if (i == slots.end()) break;
} else {
// For a forward ordered value (unless it's the last value), we
// convert any '\0' to "\0\xff". We insert "\0\0" after the
// encoded value.
string::size_type j = 0, nul;
while ((nul = v.find('\0', j)) != string::npos) {
++nul;
result.append(v, j, nul - j);
result += '\xff';
j = nul;
}
result.append(v, j, string::npos);
result.append("\0", 2);
}
}
return result;
}
}
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