Function copyFileContent

Core/MemoryFile.cpp:521–576

}

bool copyFileContent(const MMKVPath_t &srcPath, MMKVFileHandle_t dstFD, bool needTruncate) {
    if (dstFD < 0) {
        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;
    }
    lseek(dstFD, 0, SEEK_SET);

    // the POSIX standard don't have sendfile()/fcopyfile() equivalent, do it the hard way
    while (true) {
        auto sizeRead = read(srcFile.getFd(), buffer, bufferSize);
        if (sizeRead < 0) {
            MMKVError("fail to read file [%s], %d(%s)", srcPath.c_str(), errno, strerror(errno));
            goto errorOut;
        }

        size_t totalWrite = 0;
        do {
            auto sizeWrite = write(dstFD, buffer + totalWrite, sizeRead - totalWrite);
            if (sizeWrite < 0) {
                MMKVError("fail to write fd [%d], %d(%s)", dstFD, errno, strerror(errno));
                goto errorOut;
            }
            totalWrite += sizeWrite;
        } while (totalWrite < sizeRead);

        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)) != 0)) {
            MMKVError("fail to truncate [%d] to size [%zu], %d(%s)", dstFD, srcFileSize, errno, strerror(errno));
            goto errorOut;
        }
    }

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

errorOut:
    free(buffer);
    return ret;
}

#endif // !defined(MMKV_ANDROID) && !defined(MMKV_LINUX)