qstringmatcher.cpp

Go to the documentation of this file.

/****************************************************************************
**
** Copyright (C) 2020 The Qt Company Ltd.
** Copyright (C) 2019 Mail.ru Group.
** Contact: https://www.qt.io/licensing/
**
** This file is part of the QtCore module of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:LGPL$
** Commercial License Usage
** Licensees holding valid commercial Qt licenses may use this file in
** accordance with the commercial license agreement provided with the
** Software or, alternatively, in accordance with the terms contained in
** a written agreement between you and The Qt Company. For licensing terms
** and conditions see https://www.qt.io/terms-conditions. For further
** information use the contact form at https://www.qt.io/contact-us.
**
** GNU Lesser General Public License Usage
** Alternatively, this file may be used under the terms of the GNU Lesser
** General Public License version 3 as published by the Free Software
** Foundation and appearing in the file LICENSE.LGPL3 included in the
** packaging of this file. Please review the following information to
** ensure the GNU Lesser General Public License version 3 requirements
** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
**
** GNU General Public License Usage
** Alternatively, this file may be used under the terms of the GNU
** General Public License version 2.0 or (at your option) the GNU General
** Public license version 3 or any later version approved by the KDE Free
** Qt Foundation. The licenses are as published by the Free Software
** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
** included in the packaging of this file. Please review the following
** information to ensure the GNU General Public License requirements will
** be met: https://www.gnu.org/licenses/gpl-2.0.html and
** https://www.gnu.org/licenses/gpl-3.0.html.
**
** $QT_END_LICENSE$
**
****************************************************************************/
 
#include "qstringmatcher.h"
 
QT_BEGIN_NAMESPACE
 
static void bm_init_skiptable(QStringView needle, uchar *skiptable, Qt::CaseSensitivity cs)
{
    const char16_t *uc = needle.utf16();
    const qsizetype len = needle.size();
    qsizetype l = qMin(len, qsizetype(255));
    memset(skiptable, l, 256 * sizeof(uchar));
    uc += len - l;
    if (cs == Qt::CaseSensitive) {
        while (l--) {
            skiptable[*uc & 0xff] = l;
            ++uc;
        }
    } else {
        const char16_t *start = uc;
        while (l--) {
            skiptable[foldCase(uc, start) & 0xff] = l;
            ++uc;
        }
    }
}
 
static inline qsizetype bm_find(QStringView haystack, qsizetype index, QStringView needle,
                          const uchar *skiptable, Qt::CaseSensitivity cs)
{
    const char16_t *uc = haystack.utf16();
    const qsizetype l = haystack.size();
    const char16_t *puc = needle.utf16();
    const qsizetype pl = needle.size();
 
    if (pl == 0)
        return index > l ? -1 : index;
    const qsizetype pl_minus_one = pl - 1;
 
    const char16_t *current = uc + index + pl_minus_one;
    const char16_t *end = uc + l;
    if (cs == Qt::CaseSensitive) {
        while (current < end) {
            qsizetype skip = skiptable[*current & 0xff];
            if (!skip) {
                // possible match
                while (skip < pl) {
                    if (*(current - skip) != puc[pl_minus_one-skip])
                        break;
                    ++skip;
                }
                if (skip > pl_minus_one) // we have a match
                    return (current - uc) - pl_minus_one;
 
                // in case we don't have a match we are a bit inefficient as we only skip by one
                // when we have the non matching char in the string.
                if (skiptable[*(current - skip) & 0xff] == pl)
                    skip = pl - skip;
                else
                    skip = 1;
            }
            if (current > end - skip)
                break;
            current += skip;
        }
    } else {
        while (current < end) {
            qsizetype skip = skiptable[foldCase(current, uc) & 0xff];
            if (!skip) {
                // possible match
                while (skip < pl) {
                    if (foldCase(current - skip, uc) != foldCase(puc + pl_minus_one - skip, puc))
                        break;
                    ++skip;
                }
                if (skip > pl_minus_one) // we have a match
                    return (current - uc) - pl_minus_one;
                // in case we don't have a match we are a bit inefficient as we only skip by one
                // when we have the non matching char in the string.
                if (skiptable[foldCase(current - skip, uc) & 0xff] == pl)
                    skip = pl - skip;
                else
                    skip = 1;
            }
            if (current > end - skip)
                break;
            current += skip;
        }
    }
    return -1; // not found
}
 
void QStringMatcher::updateSkipTable()
{
    bm_init_skiptable(q_sv, q_skiptable, q_cs);
}
 
QStringMatcher::QStringMatcher(const QString &pattern, Qt::CaseSensitivity cs)
    : d_ptr(nullptr), q_cs(cs), q_pattern(pattern)
{
    q_sv = q_pattern;
    updateSkipTable();
}
 
QStringMatcher::QStringMatcher(QStringView str, Qt::CaseSensitivity cs)
    : d_ptr(nullptr), q_cs(cs), q_sv(str)
{
    updateSkipTable();
}
QStringMatcher::QStringMatcher(const QStringMatcher &other)
    : d_ptr(nullptr)
{
    operator=(other);
}
 
QStringMatcher::~QStringMatcher()
{
    Q_UNUSED(d_ptr);
}
 
QStringMatcher &QStringMatcher::operator=(const QStringMatcher &other)
{
    if (this != &other) {
        q_pattern = other.q_pattern;
        q_cs = other.q_cs;
        q_sv = other.q_sv;
        memcpy(q_skiptable, other.q_skiptable, sizeof(q_skiptable));
    }
    return *this;
}
 
void QStringMatcher::setPattern(const QString &pattern)
{
    q_pattern = pattern;
    q_sv = q_pattern;
    updateSkipTable();
}
 
QString QStringMatcher::pattern() const
{
    if (!q_pattern.isEmpty())
        return q_pattern;
    return q_sv.toString();
}
 
void QStringMatcher::setCaseSensitivity(Qt::CaseSensitivity cs)
{
    if (cs == q_cs)
        return;
    q_cs = cs;
    updateSkipTable();
}
 
qsizetype QStringMatcher::indexIn(QStringView str, qsizetype from) const
{
    if (from < 0)
        from = 0;
    return bm_find(str, from, q_sv, q_skiptable, q_cs);
}
 
qsizetype qFindStringBoyerMoore(
    QStringView haystack, qsizetype haystackOffset,
    QStringView needle, Qt::CaseSensitivity cs)
{
    uchar skiptable[256];
    bm_init_skiptable(needle, skiptable, cs);
    if (haystackOffset < 0)
        haystackOffset = 0;
    return bm_find(haystack, haystackOffset, needle, skiptable, cs);
}
 
QT_END_NAMESPACE