Function copyFileContent

Core/MemoryFile_Win32.cpp:489–540

}

bool copyFileContent(const MMKVPath_t &srcPath, MMKVFileHandle_t dstFD, bool needTruncate) {
    if (dstFD == INVALID_HANDLE_VALUE) {
        return false;
    }
    bool ret = false;
    File srcFile(srcPath, OpenFlag::ReadOnly);
    if (!srcFile.isFileValid()) {
        return false;
    }
    auto bufferSize = getPageSize();
    auto buffer = (char *) malloc(bufferSize);
    if (!buffer) {
        MMKVError("fail to malloc size %zu, %d(%s)", bufferSize, errno, strerror(errno));
        goto errorOut;
    }
    SetFilePointer(dstFD, 0, 0, FILE_BEGIN);

    // the Win32 platform don't have sendfile()/fcopyfile() equivalent, do it the hard way
    while (true) {
        DWORD sizeRead = 0;
        if (!ReadFile(srcFile.getFd(), buffer, (DWORD) bufferSize, &sizeRead, nullptr)) {
            MMKVError("fail to read %s: %d", srcFile.getUTF8Path().c_str(), GetLastError());
            goto errorOut;
        }

        DWORD sizeWrite = 0;
        if (!WriteFile(dstFD, buffer, sizeRead, &sizeWrite, nullptr)) {
            MMKVError("fail to write fd [%d], %d", dstFD, GetLastError());
            goto errorOut;
        }

        if (sizeRead < bufferSize) {
            break;
        }
    }
    if (needTruncate) {
        size_t dstFileSize = 0;
        getFileSize(dstFD, dstFileSize);
        auto srcFileSize = srcFile.getActualFileSize();
        if ((dstFileSize != srcFileSize) && !ftruncate(dstFD, static_cast<off_t>(srcFileSize))) {
            MMKVError("fail to truncate [%d] to size [%zu]", dstFD, srcFileSize);
            goto errorOut;
        }
    }

    ret = true;
    MMKVInfo("copy content from %s to fd[%d] finish", srcFile.getUTF8Path().c_str(), dstFD);

errorOut:
    free(buffer);
    return ret;
}

// copy to a temp file then rename it
// this is the best we can do on Win32