word-breaker.cc

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/* Copyright (c) 2007, 2008 Yung-chung Lin (henearkrxern@gmail.com)
 * Copyright (c) 2011 Richard Boulton (richard@tartarus.org)
 * Copyright (c) 2011 Brandon Schaefer (brandontschaefer@gmail.com)
 * Copyright (c) 2011,2019,2023 Olly Betts
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * deal in the Software without restriction, including without limitation the
 * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
 * sell copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
 * IN THE SOFTWARE.
 */

#include <config.h>

#include "word-breaker.h"

#include "omassert.h"
#include "xapian/unicode.h"

#include <cstdlib>
#include <string>

using namespace std;

bool
is_ngram_enabled()
{
    const char * p;
    static bool result = ((p = getenv("XAPIAN_CJK_NGRAM")) != NULL && *p);
    return result;
}

// 2E80..2EFF; CJK Radicals Supplement
// 3000..303F; CJK Symbols and Punctuation
// 3040..309F; Hiragana
// 30A0..30FF; Katakana
// 3100..312F; Bopomofo
// 3130..318F; Hangul Compatibility Jamo
// 3190..319F; Kanbun
// 31A0..31BF; Bopomofo Extended
// 31C0..31EF; CJK Strokes
// 31F0..31FF; Katakana Phonetic Extensions
// 3200..32FF; Enclosed CJK Letters and Months
// 3300..33FF; CJK Compatibility
// 3400..4DBF; CJK Unified Ideographs Extension A
// 4DC0..4DFF; Yijing Hexagram Symbols
// 4E00..9FFF; CJK Unified Ideographs
// A700..A71F; Modifier Tone Letters
// AC00..D7AF; Hangul Syllables
// F900..FAFF; CJK Compatibility Ideographs
// FE30..FE4F; CJK Compatibility Forms
// FF00..FFEF; Halfwidth and Fullwidth Forms
// 20000..2A6DF; CJK Unified Ideographs Extension B
// 2F800..2FA1F; CJK Compatibility Ideographs Supplement
bool
is_unbroken_script(unsigned p)
{
    if (p < 0x2E80) return false;
    return ((p >= 0x2E80 && p <= 0x2EFF) ||
            (p >= 0x3000 && p <= 0x9FFF) ||
            (p >= 0xA700 && p <= 0xA71F) ||
            (p >= 0xAC00 && p <= 0xD7AF) ||
            (p >= 0xF900 && p <= 0xFAFF) ||
            (p >= 0xFE30 && p <= 0xFE4F) ||
            (p >= 0xFF00 && p <= 0xFFEF) ||
            (p >= 0x20000 && p <= 0x2A6DF) ||
            (p >= 0x2F800 && p <= 0x2FA1F));
}

void
get_unbroken(Xapian::Utf8Iterator& it)
{
    while (it != Xapian::Utf8Iterator() &&
           is_unbroken_script(*it) &&
           Xapian::Unicode::is_wordchar(*it)) {
        ++it;
    }
}

void
NgramIterator::init()
{
    if (it != Xapian::Utf8Iterator()) {
        unsigned ch = *it;
        if (is_unbroken_script(ch) && Xapian::Unicode::is_wordchar(ch)) {
            Xapian::Unicode::append_utf8(current_token, ch);
            ++it;
        } else {
            current_token.resize(0);
        }
    }
}

NgramIterator&
NgramIterator::operator++()
{
    if (offset == 0) {
        if (it != Xapian::Utf8Iterator()) {
            unsigned ch = *it;
            if (is_unbroken_script(ch) && Xapian::Unicode::is_wordchar(ch)) {
                offset = current_token.size();
                Xapian::Unicode::append_utf8(current_token, ch);
                ++it;
            } else {
                current_token.resize(0);
            }
        } else {
            current_token.resize(0);
        }
    } else {
        current_token.erase(0, offset);
        offset = 0;
    }
    return *this;
}