Method truncate

Core/MemoryFile_Win32.cpp:115–172

}

bool MemoryFile::truncate(size_t size, FileLock *fileLock) {
    if (m_isMayflyFD) {
        openIfNeeded();
    }
    if (!m_diskFile.isFileValid()) {
        return false;
    }
    if (size == m_size) {
        return true;
    }
    if (m_readOnly) {
        // truncate readonly file not allow
        return false;
    }

    auto oldSize = m_size;
    m_size = size;
    // round up to (n * pagesize)
    if (m_size < DEFAULT_MMAP_SIZE || (m_size % DEFAULT_MMAP_SIZE != 0)) {
        m_size = ((m_size / DEFAULT_MMAP_SIZE) + 1) * DEFAULT_MMAP_SIZE;
    }

    // Win32 won't ftruncate a file if there's active file mmapping/handle, we have to unmmap/close ahead
    bool needMMapOnFailure = false;
    if (m_ptr) {
        // if we have a valid file mapping before, we should restore it regardless
        needMMapOnFailure = true;
        if (!UnmapViewOfFile(m_ptr)) {
            MMKVError("fail to munmap [%s], %d", m_diskFile.getUTF8Path().c_str(), GetLastError());
        }
        m_ptr = nullptr;
    }
    if (m_fileMapping) {
        CloseHandle(m_fileMapping);
        m_fileMapping = nullptr;
    }

    if (!ftruncate(m_diskFile.getFd(), m_size)) {
        MMKVError("fail to truncate [%s] to size %zu", m_diskFile.getUTF8Path().c_str(), m_size);
        m_size = oldSize;
        if (needMMapOnFailure) {
            mmapOrCleanup(fileLock);
        }
        return false;
    }
    if (m_size > oldSize) {
        if (!zeroFillFile(m_diskFile.getFd(), oldSize, m_size - oldSize)) {
            MMKVError("fail to zeroFile [%s] to size %zu", m_diskFile.getUTF8Path().c_str(), m_size);
            m_size = oldSize;
            if (needMMapOnFailure) {
                mmapOrCleanup(fileLock);
            }
            return false;
        }
    }

    return mmapOrCleanup(fileLock);
}