modules/skshaper/src/SkUnicode_icu.cpp

/*
* Copyright 2020 Google Inc.
*
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#include "include/private/SkTFitsIn.h"
#include "include/private/SkTemplates.h"
#include "modules/skshaper/src/SkUnicode.h"
#include "src/utils/SkUTF.h"
#include <unicode/ubidi.h>
#include <unicode/ubrk.h>
#include <unicode/utext.h>
#include <unicode/utypes.h>
#include <vector>
#include <functional>

using SkUnicodeBidi = std::unique_ptr<UBiDi, SkFunctionWrapper<decltype(ubidi_close), ubidi_close>>;
using ICUUText = std::unique_ptr<UText, SkFunctionWrapper<decltype(utext_close), utext_close>>;
using ICUBreakIterator = std::unique_ptr<UBreakIterator, SkFunctionWrapper<decltype(ubrk_close), ubrk_close>>;

/** Replaces invalid utf-8 sequences with REPLACEMENT CHARACTER U+FFFD. */
static inline SkUnichar utf8_next(const char** ptr, const char* end) {
    SkUnichar val = SkUTF::NextUTF8(ptr, end);
    return val < 0 ? 0xFFFD : val;
}

class SkBidiIterator_icu : public SkBidiIterator {
    SkUnicodeBidi fBidi;
public:
    explicit SkBidiIterator_icu(SkUnicodeBidi bidi) : fBidi(std::move(bidi)) {}
    Position getLength() override { return ubidi_getLength(fBidi.get()); }
    Level getLevelAt(Position pos) override { return ubidi_getLevelAt(fBidi.get(), pos); }

    static std::unique_ptr<SkBidiIterator> makeBidiIterator(const uint16_t utf16[], int utf16Units, Direction dir) {
        UErrorCode status = U_ZERO_ERROR;
        SkUnicodeBidi bidi(ubidi_openSized(utf16Units, 0, &status));
        if (U_FAILURE(status)) {
            SkDEBUGF("Bidi error: %s", u_errorName(status));
            return nullptr;
        }
        SkASSERT(bidi);
        uint8_t bidiLevel = (dir == SkBidiIterator::kLTR) ? UBIDI_LTR : UBIDI_RTL;
        // The required lifetime of utf16 isn't well documented.
        // It appears it isn't used after ubidi_setPara except through ubidi_getText.
        ubidi_setPara(bidi.get(), (const UChar*)utf16, utf16Units, bidiLevel, nullptr, &status);
        if (U_FAILURE(status)) {
            SkDEBUGF("Bidi error: %s", u_errorName(status));
            return nullptr;
        }
        return std::unique_ptr<SkBidiIterator>(new SkBidiIterator_icu(std::move(bidi)));
    }

    // ICU bidi iterator works with utf16 but clients (Flutter for instance) may work with utf8
    // This method allows the clients not to think about all these details
    static std::unique_ptr<SkBidiIterator> makeBidiIterator(const char utf8[], int utf8Units, Direction dir) {
        // Convert utf8 into utf16 since ubidi only accepts utf16
        if (!SkTFitsIn<int32_t>(utf8Units)) {
            SkDEBUGF("Bidi error: text too long");
            return nullptr;
        }

        // Getting the length like this seems to always set U_BUFFER_OVERFLOW_ERROR
        int utf16Units = SkUTF::UTF8ToUTF16(nullptr, 0, utf8, utf8Units);
        if (utf16Units < 0) {
            SkDEBUGF("Bidi error: Invalid utf8 input");
            return nullptr;
        }
        std::unique_ptr<uint16_t[]> utf16(new uint16_t[utf16Units]);
        SkDEBUGCODE(int dstLen =) SkUTF::UTF8ToUTF16(utf16.get(), utf16Units, utf8, utf8Units);
        SkASSERT(dstLen == utf16Units);

        return makeBidiIterator(utf16.get(), utf16Units, dir);
    }

    // This method returns the final results only: a list of bidi regions
    // (this is all SkParagraph really needs; SkShaper however uses the iterator itself)
    static std::vector<Region> getBidiRegions(const char utf8[], int utf8Units, Direction dir) {

        auto bidiIterator = makeBidiIterator(utf8, utf8Units, dir);
        std::vector<Region> bidiRegions;
        const char* start8 = utf8;
        const char* end8 = utf8 + utf8Units;
        SkBidiIterator::Level currentLevel = 0;

        Position pos8 = 0;
        Position pos16 = 0;
        Position end16 = bidiIterator->getLength();
        while (pos16 < end16) {
            auto level = bidiIterator->getLevelAt(pos16);
            if (pos16 == 0) {
                currentLevel = level;
            } else if (level != currentLevel) {
                auto end = start8 - utf8;
                bidiRegions.emplace_back(pos8, end, currentLevel);
                currentLevel = level;
                pos8 = end;
            }
            SkUnichar u = utf8_next(&start8, end8);
            pos16 += SkUTF::ToUTF16(u);
        }
        auto end = start8 - utf8;
        if (end != pos8) {
            bidiRegions.emplace_back(pos8, end, currentLevel);
        }
        return bidiRegions;
    }
};

void SkBidiIterator::ReorderVisual(const Level runLevels[], int levelsCount,
                                   int32_t logicalFromVisual[]) {
    ubidi_reorderVisual(runLevels, levelsCount, logicalFromVisual);
}

class SkUnicode_icu : public SkUnicode {

    static UBreakIteratorType convertType(UBreakType type) {
        switch (type) {
            case UBreakType::kLines: return UBRK_LINE;
            case UBreakType::kGraphemes: return UBRK_CHARACTER;
            case UBreakType::kWords: return UBRK_WORD;
            default:
              SkDEBUGF("Convert error: wrong break type");
              return UBRK_CHARACTER;
        }
    }

    static int convertUtf8ToUtf16(const char* utf8, size_t utf8Units, std::unique_ptr<uint16_t[]>* utf16) {
        int utf16Units = SkUTF::UTF8ToUTF16(nullptr, 0, utf8, utf8Units);
        if (utf16Units < 0) {
            SkDEBUGF("Convert error: Invalid utf8 input");
            return utf16Units;
        }
        *utf16 = std::unique_ptr<uint16_t[]>(new uint16_t[utf16Units]);
        SkDEBUGCODE(int dstLen =) SkUTF::UTF8ToUTF16(utf16->get(), utf16Units, utf8, utf8Units);
        SkASSERT(dstLen == utf16Units);
        return utf16Units;
    }

    static bool extractBidi(const char utf8[], int utf8Units, TextDirection dir, std::vector<BidiRegion>* bidiRegions) {

        // Convert to UTF16 since for now bidi iterator only operates on utf16
        std::unique_ptr<uint16_t[]> utf16;
        auto utf16Units = convertUtf8ToUtf16(utf8, utf8Units, &utf16);
        if (utf16Units < 0) {
            return false;
        }

        // Create bidi iterator
        UErrorCode status = U_ZERO_ERROR;
        SkUnicodeBidi bidi(ubidi_openSized(utf16Units, 0, &status));
        if (U_FAILURE(status)) {
            SkDEBUGF("Bidi error: %s", u_errorName(status));
            return false;
        }
        SkASSERT(bidi);
        uint8_t bidiLevel = (dir == TextDirection::kLTR) ? UBIDI_LTR : UBIDI_RTL;
        // The required lifetime of utf16 isn't well documented.
        // It appears it isn't used after ubidi_setPara except through ubidi_getText.
        ubidi_setPara(bidi.get(), (const UChar*)utf16.get(), utf16Units, bidiLevel, nullptr, &status);
        if (U_FAILURE(status)) {
            SkDEBUGF("Bidi error: %s", u_errorName(status));
            return false;
        }

        // Iterate through bidi regions and the result positions into utf8
        const char* start8 = utf8;
        const char* end8 = utf8 + utf8Units;
        BidiLevel currentLevel = 0;

        Position pos8 = 0;
        Position pos16 = 0;
        Position end16 = ubidi_getLength(bidi.get());
        while (pos16 < end16) {
            auto level = ubidi_getLevelAt(bidi.get(), pos16);
            if (pos16 == 0) {
                currentLevel = level;
            } else if (level != currentLevel) {
                Position end = start8 - utf8;
                bidiRegions->emplace_back(pos8, end, currentLevel);
                currentLevel = level;
                pos8 = end;
            }
            SkUnichar u = utf8_next(&start8, end8);
            pos16 += SkUTF::ToUTF16(u);
        }
        Position end = start8 - utf8;
        if (end != pos8) {
            bidiRegions->emplace_back(pos8, end, currentLevel);
        }
        return true;
    }

    static bool extractWords(uint16_t utf16[], int utf16Units, std::vector<Position>* words) {

        UErrorCode status = U_ZERO_ERROR;

        UBreakIteratorType breakType = convertType(UBreakType::kWords);
        ICUBreakIterator iterator(ubrk_open(breakType, uloc_getDefault(), nullptr, 0, &status));
        if (U_FAILURE(status)) {
            SkDEBUGF("Break error: %s", u_errorName(status));
            return false;
        }
        SkASSERT(iterator);

        UText sUtf16UText = UTEXT_INITIALIZER;
        ICUUText utf16UText(utext_openUChars(&sUtf16UText, (UChar*)utf16, utf16Units, &status));
        if (U_FAILURE(status)) {
            SkDEBUGF("Break error: %s", u_errorName(status));
            return false;
        }

        ubrk_setUText(iterator.get(), utf16UText.get(), &status);
        if (U_FAILURE(status)) {
            SkDEBUGF("Break error: %s", u_errorName(status));
            return false;
        }

        // Get the words
        int32_t pos = ubrk_first(iterator.get());
        while (pos != UBRK_DONE) {
            words->emplace_back(pos);
            pos = ubrk_next(iterator.get());
        }

        return true;
    }

    static bool extractPositions(const char utf8[], int utf8Units, UBreakType type, std::function<void(int, int)> add) {

        UErrorCode status = U_ZERO_ERROR;
        UText sUtf8UText = UTEXT_INITIALIZER;
        ICUUText text(utext_openUTF8(&sUtf8UText, &utf8[0], utf8Units, &status));

        if (U_FAILURE(status)) {
            SkDEBUGF("Break error: %s", u_errorName(status));
            return false;
        }
        SkASSERT(text);

        ICUBreakIterator iterator(ubrk_open(convertType(type), uloc_getDefault(), nullptr, 0, &status));
        if (U_FAILURE(status)) {
            SkDEBUGF("Break error: %s", u_errorName(status));
        }

        ubrk_setUText(iterator.get(), text.get(), &status);
        if (U_FAILURE(status)) {
            SkDEBUGF("Break error: %s", u_errorName(status));
            return false;
        }

        auto iter = iterator.get();
        int32_t pos = ubrk_first(iter);
        while (pos != UBRK_DONE) {
            add(pos, ubrk_getRuleStatus(iter));
            pos = ubrk_next(iter);
        }
        return true;
    }

    static bool extractWhitespaces(const char utf8[], int utf8Units, std::vector<Position>* whitespaces) {

        const char* start = utf8;
        const char* end = utf8 + utf8Units;
        const char* ch = start;
        while (ch < end) {
            auto index = ch - start;
            auto unichar = utf8_next(&ch, end);
            if (u_isWhitespace(unichar)) {
                auto ending = ch - start;
                for (auto k = index; k < ending; ++k) {
                  whitespaces->emplace_back(k);
                }
            }
        }
        return true;
    }

public:
    ~SkUnicode_icu() override { }
    std::unique_ptr<SkBidiIterator> makeBidiIterator(const uint16_t text[], int count,
                                                     SkBidiIterator::Direction dir) override {
        return SkBidiIterator_icu::makeBidiIterator(text, count, dir);
    }
    std::unique_ptr<SkBidiIterator> makeBidiIterator(const char text[], int count,
                                                     SkBidiIterator::Direction dir) override {
        return SkBidiIterator_icu::makeBidiIterator(text, count, dir);
    }

    bool getBidiRegions(const char utf8[], int utf8Units, TextDirection dir, std::vector<BidiRegion>* results) override {
        return extractBidi(utf8, utf8Units, dir, results);
    }

    bool getLineBreaks(const char utf8[], int utf8Units, std::vector<LineBreakBefore>* results) override {

        return extractPositions(utf8, utf8Units, UBreakType::kLines,
            [results](int pos, int status) {
                    results->emplace_back(pos,status == UBRK_LINE_HARD
                                                        ? LineBreakType::kHardLineBreak
                                                        : LineBreakType::kSoftLineBreak);
        });
    }

    bool getWords(const char utf8[], int utf8Units, std::vector<Position>* results) override {

        // Convert to UTF16 since we want the results in utf16
        std::unique_ptr<uint16_t[]> utf16;
        auto utf16Units = convertUtf8ToUtf16(utf8, utf8Units, &utf16);
        if (utf16Units < 0) {
            return false;
        }

        return extractWords(utf16.get(), utf16Units, results);
    }

    bool getGraphemes(const char utf8[], int utf8Units, std::vector<Position>* results) override {

        return extractPositions(utf8, utf8Units, UBreakType::kGraphemes,
            [results](int pos, int status) { results->emplace_back(pos);
        });
    }

    bool getWhitespaces(const char utf8[], int utf8Units, std::vector<Position>* results) override {

        return extractWhitespaces(utf8, utf8Units, results);
    }

    void reorderVisual(const BidiLevel runLevels[], int levelsCount, int32_t logicalFromVisual[]) override {
        ubidi_reorderVisual(runLevels, levelsCount, logicalFromVisual);
    }
};

std::unique_ptr<SkUnicode> SkUnicode::Make() { return std::make_unique<SkUnicode_icu>(); }