8be147d069
Match SQL's LIKE in allowing an empty pattern, which matches only an empty text field. Tests: unit (dev) Signed-off-by: Dejan Mircevski <dejan@scylladb.com>
99 lines
2.8 KiB
C++
99 lines
2.8 KiB
C++
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/*
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* Copyright 2019 ScyllaDB
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*/
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/*
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* This file is part of Scylla.
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*
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* Scylla is free software: you can redistribute it and/or modify
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* it under the terms of the GNU Affero General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* Scylla is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with Scylla. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include "like_matcher.hh"
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#include <boost/locale/encoding.hpp>
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#include <string>
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namespace {
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using std::wstring;
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/// Processes a new pattern character, extending re with the equivalent regex pattern.
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void process_char(wchar_t c, wstring& re, bool& escaping) {
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if (c == L'\\' && !escaping) {
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escaping = true;
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return;
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}
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switch (c) {
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case L'.':
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case L'[':
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case L'\\':
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case L'*':
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case L'^':
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case L'$':
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// These are meant to match verbatim in LIKE, but they'd be special characters in regex --
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// must escape them.
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re.push_back(L'\\');
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re.push_back(c);
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break;
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case L'_':
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case L'%':
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if (escaping) {
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re.push_back(c);
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} else { // LIKE wildcard.
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re.push_back(L'.');
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if (c == L'%') {
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re.push_back(L'*');
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}
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}
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break;
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default:
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re.push_back(c);
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break;
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}
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escaping = false;
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}
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/// Returns a regex string matching the given LIKE pattern.
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wstring regex_from_pattern(bytes_view pattern) {
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if (pattern.empty()) {
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return L"^$"; // Like SQL, empty pattern matches only empty text.
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}
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using namespace boost::locale::conv;
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wstring wpattern = utf_to_utf<wchar_t>(pattern.begin(), pattern.end(), stop);
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if (wpattern.back() == L'\\') {
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// Add an extra backslash, in case that last character is unescaped. (If it is escaped, the
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// extra backslash will be ignored.)
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wpattern += L'\\';
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}
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wstring re;
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re.reserve(wpattern.size() * 2); // Worst case: every element is a special character and must be escaped.
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bool escaping = false;
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for (const wchar_t c : wpattern) {
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process_char(c, re, escaping);
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}
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return re;
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}
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} // anonymous namespace
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like_matcher::like_matcher(bytes_view pattern) :
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_re(boost::make_u32regex(regex_from_pattern(pattern), boost::u32regex::basic | boost::u32regex::optimize)) {
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}
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bool like_matcher::operator()(bytes_view text) const {
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return boost::u32regex_match(text.begin(), text.end(), _re);
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}
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