libs/jpegrecoverymap/multipictureformat.cpp

/*
 * Copyright 2023 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 <jpegrecoverymap/multipictureformat.h>
#include <jpegrecoverymap/jpegrutils.h>

namespace android::jpegrecoverymap {
size_t calculateMpfSize() {
    return sizeof(kMpfSig) +                 // Signature
            kMpEndianSize +                   // Endianness
            sizeof(uint32_t) +                // Index IFD Offset
            sizeof(uint16_t) +                // Tag count
            kTagSerializedCount * kTagSize +  // 3 tags at 12 bytes each
            sizeof(uint32_t) +                // Attribute IFD offset
            kNumPictures * kMPEntrySize;      // MP Entries for each image
}

sp<DataStruct> generateMpf(int primary_image_size, int primary_image_offset,
        int secondary_image_size, int secondary_image_offset) {
    size_t mpf_size = calculateMpfSize();
    sp<DataStruct> dataStruct = new DataStruct(mpf_size);

    dataStruct->write(static_cast<const void*>(kMpfSig), sizeof(kMpfSig));
#if USE_BIG_ENDIAN
    dataStruct->write(static_cast<const void*>(kMpBigEndian), kMpEndianSize);
#else
    dataStruct->write(static_cast<const void*>(kMpLittleEndian), kMpEndianSize);
#endif

    // Set the Index IFD offset be the position after the endianness value and this offset.
    constexpr uint32_t indexIfdOffset =
            static_cast<uint16_t>(kMpEndianSize + sizeof(kMpfSig));
    dataStruct->write32(Endian_SwapBE32(indexIfdOffset));

    // We will write 3 tags (version, number of images, MP entries).
    dataStruct->write16(Endian_SwapBE16(kTagSerializedCount));

    // Write the version tag.
    dataStruct->write16(Endian_SwapBE16(kVersionTag));
    dataStruct->write16(Endian_SwapBE16(kVersionType));
    dataStruct->write32(Endian_SwapBE32(kVersionCount));
    dataStruct->write(kVersionExpected, kVersionSize);

    // Write the number of images.
    dataStruct->write16(Endian_SwapBE16(kNumberOfImagesTag));
    dataStruct->write16(Endian_SwapBE16(kNumberOfImagesType));
    dataStruct->write32(Endian_SwapBE32(kNumberOfImagesCount));
    dataStruct->write32(Endian_SwapBE32(kNumPictures));

    // Write the MP entries.
    dataStruct->write16(Endian_SwapBE16(kMPEntryTag));
    dataStruct->write16(Endian_SwapBE16(kMPEntryType));
    dataStruct->write32(Endian_SwapBE32(kMPEntrySize * kNumPictures));
    const uint32_t mpEntryOffset =
            static_cast<uint32_t>(dataStruct->getBytesWritten() -  // The bytes written so far
                                  sizeof(kMpfSig) +   // Excluding the MPF signature
                                  sizeof(uint32_t) +  // The 4 bytes for this offset
                                  sizeof(uint32_t));  // The 4 bytes for the attribute IFD offset.
    dataStruct->write32(Endian_SwapBE32(mpEntryOffset));

    // Write the attribute IFD offset (zero because we don't write it).
    dataStruct->write32(0);

    // Write the MP entries for primary image
    dataStruct->write32(
            Endian_SwapBE32(kMPEntryAttributeFormatJpeg | kMPEntryAttributeTypePrimary));
    dataStruct->write32(Endian_SwapBE32(primary_image_size));
    dataStruct->write32(Endian_SwapBE32(primary_image_offset));
    dataStruct->write16(0);
    dataStruct->write16(0);

    // Write the MP entries for secondary image
    dataStruct->write32(Endian_SwapBE32(kMPEntryAttributeFormatJpeg));
    dataStruct->write32(Endian_SwapBE32(secondary_image_size));
    dataStruct->write32(Endian_SwapBE32(secondary_image_offset));
    dataStruct->write16(0);
    dataStruct->write16(0);

    return dataStruct;
}

} // namespace android::jpegrecoverymap