libs/minikin/FontUtils.cpp

/*
 * Copyright (C) 2017 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include <stdlib.h>
#include <stdint.h>

#include "FontUtils.h"

#include <log/log.h>

namespace minikin {

static uint16_t readU16(const uint8_t* data, size_t offset) {
    return data[offset] << 8 | data[offset + 1];
}

static uint32_t readU32(const uint8_t* data, size_t offset) {
    return ((uint32_t)data[offset]) << 24 | ((uint32_t)data[offset + 1]) << 16 |
            ((uint32_t)data[offset + 2]) << 8 | ((uint32_t)data[offset + 3]);
}

bool analyzeStyle(const uint8_t* os2_data, size_t os2_size, int* weight, bool* italic) {
    const size_t kUsWeightClassOffset = 4;
    const size_t kFsSelectionOffset = 62;
    const uint16_t kItalicFlag = (1 << 0);
    if (os2_size < kFsSelectionOffset + 2) {
        return false;
    }
    uint16_t weightClass = readU16(os2_data, kUsWeightClassOffset);
    *weight = weightClass / 100;
    uint16_t fsSelection = readU16(os2_data, kFsSelectionOffset);
    *italic = (fsSelection & kItalicFlag) != 0;
    return true;
}

bool analyzeAxes(const uint8_t* fvar_data, size_t fvar_size, std::unordered_set<uint32_t>* axes) {
    const size_t kMajorVersionOffset = 0;
    const size_t kMinorVersionOffset = 2;
    const size_t kOffsetToAxesArrayOffset = 4;
    const size_t kAxisCountOffset = 8;
    const size_t kAxisSizeOffset = 10;

    axes->clear();

    if (fvar_size < kAxisSizeOffset + 2) {
        return false;
    }
    const uint16_t majorVersion = readU16(fvar_data, kMajorVersionOffset);
    const uint16_t minorVersion = readU16(fvar_data, kMinorVersionOffset);
    const uint32_t axisOffset = readU16(fvar_data, kOffsetToAxesArrayOffset);
    const uint32_t axisCount = readU16(fvar_data, kAxisCountOffset);
    const uint32_t axisSize = readU16(fvar_data, kAxisSizeOffset);

    if (majorVersion != 1 || minorVersion != 0 || axisOffset != 0x10 || axisSize != 0x14) {
        return false;  // Unsupported version.
    }
    if (fvar_size < axisOffset + axisSize * axisCount) {
        if (axisOffset > axisSize) {
            android_errorWriteLog(0x534e4554, "77822336");
        }
        return false;  // Invalid table size.
    }
    for (uint32_t i = 0; i < axisCount; ++i) {
        size_t axisRecordOffset = axisOffset + i * axisSize;
        uint32_t tag = readU32(fvar_data, axisRecordOffset);
        axes->insert(tag);
    }
    return true;
}
}  // namespace minikin