/*
   This file is part of the KDE libraries
   Copyright (c) 2008 Jakub Stachowski <qbast@go2.pl>

   This library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Library General Public
   License as published by the Free Software Foundation; either
   version 2 of the License, or (at your option) any later version.

   This library 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
   Library General Public License for more details.

   You should have received a copy of the GNU Library General Public License
   along with this library; see the file COPYING.LIB.  If not, write to
   the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
   Boston, MA 02110-1301, USA.
*/

#ifndef BUFFERFRAGMENT_H
#define BUFFERFRAGMENT_H

#include "kconfigini_p.h"

#define bf_isspace(str) ((str == ' ') || (str == '\t') || (str == '\r'))

// This class provides wrapper around fragment of existing buffer (array of bytes).
// If underlying buffer gets deleted, all BufferFragment objects referencing it become invalid.
// Use toByteArray() to make deep copy of the buffer fragment.
//
// API is designed to subset of QByteArray methods with some changes:
// - trim() is like QByteArray.trimmed(), but it modifies current object
// - truncateLeft() provides way to cut off beginning of the buffer
// - split() works more like strtok_r than QByteArray.split()
// - truncateLeft() and mid() require position argument to be valid

class KConfigIniBackend::BufferFragment
{

public:

    BufferFragment() : d(nullptr), len(0)
    {
    }

    BufferFragment(char *buf, int size) : d(buf), len(size)
    {
    }

    int length() const
    {
        return len;
    }

    char at(unsigned int i) const
    {
        Q_ASSERT(i < len);
        return d[i];
    }

    void clear()
    {
        len = 0;
    }

    const char *constData() const
    {
        return d;
    }

    char *data() const
    {
        return d;
    }

    void trim()
    {
        while (bf_isspace(*d) && len > 0) {
            d++;
            len--;
        }
        while (len > 0 && bf_isspace(d[len - 1])) {
            len--;
        }
    }

    // similar to strtok_r . On first call variable pointed by start should be set to 0.
    // Each call will update *start to new starting position.
    BufferFragment split(char c, unsigned int *start)
    {
        while (*start < len) {
            int end = indexOf(c, *start);
            if (end == -1) {
                end = len;
            }
            BufferFragment line(d + (*start), end - (*start));
            *start = end + 1;
            return line;
        }
        return BufferFragment();
    }

    bool isEmpty() const
    {
        return !len;
    }

    BufferFragment left(unsigned int size) const
    {
        return BufferFragment(d, qMin(size, len));
    }

    void truncateLeft(unsigned int size)
    {
        Q_ASSERT(size <= len);
        d += size;
        len -= size;
    }

    void truncate(unsigned int pos)
    {
        if (pos < len) {
            len = pos;
        }
    }

    bool isNull() const
    {
        return !d;
    }

    BufferFragment mid(unsigned int pos, int length = -1) const
    {
        Q_ASSERT(pos < len);
        int size = length;
        if (length == -1 || (pos + length) > len) {
            size = len - pos;
        }
        return BufferFragment(d + pos, size);
    }

    bool operator==(const QByteArray &other) const
    {
        return (other.size() == (int)len && memcmp(d, other.constData(), len) == 0);
    }

    bool operator!=(const QByteArray &other) const
    {
        return (other.size() != (int)len || memcmp(d, other.constData(), len) != 0);
    }

    bool operator==(const BufferFragment &other) const
    {
        return other.len == len && !memcmp(d, other.d, len);
    }

    int indexOf(char c, unsigned int from = 0) const
    {
        const char *cursor = d + from - 1;
        const char *end = d + len;
        while (++cursor < end)
            if (*cursor == c) {
                return cursor - d;
            }
        return -1;
    }

    int lastIndexOf(char c) const
    {
        int from = len - 1;
        while (from >= 0)
            if (d[from] == c) {
                return from;
            } else {
                from--;
            }
        return -1;
    }

    QByteArray toByteArray() const
    {
        return QByteArray(d, len);
    }

    // this is faster than toByteArray, but returned QByteArray becomes invalid
    // when buffer for this BufferFragment disappears
    QByteArray toVolatileByteArray() const
    {
        return QByteArray::fromRawData(d, len);
    }

private:
    char *d;
    unsigned int len;
};

uint qHash(const KConfigIniBackend::BufferFragment &fragment)
{
    const uchar *p = reinterpret_cast<const uchar*>(fragment.constData());
    const int len = fragment.length();

    // This algorithm is copied from qhash.cpp (Qt5 version).
    // Sadly this code is not accessible from the outside without going through abstraction
    // layers. Even QByteArray::fromRawData would do an allocation internally...
    uint h = 0;

    for (int i = 0; i < len; ++i) {
        h = 31 * h + p[i];
    }

    return h;
}

#endif
