如何解压lz4压缩的操作系统镜像并写入磁盘

Question

我正在尝试使用 pycurl 获取操作系统映像并将解压缩的数据写入磁盘。使用 gzip 很简单，只有使用 lz4 格式时我会遇到问题，似乎 write_lz4(buf) 会解压缩并写入磁盘，只有当我尝试调整分区大小时，才会收到错误：

entries 为 0 字节，但该程序仅支持 128 字节的条目。 相应调整，但分区表可能是垃圾。 警告：分区表头声称分区表的大小 条目为0字节，但该程序仅支持128字节条目。 相应调整，但分区表可能是垃圾。 在内存中创建新的 GPT 条目。 操作已成功完成。 错误：分区不存在

我也可以使用 io.Byitesio 来管理它：

if url.endswith('.lz4'):
    with io.BytesIO() as output_buffer:
        curl.setopt(pycurl.WRITEDATA, output_buffer)
        curl.perform()
        output_buffer.seek(0)
        decompressed_data = lz4.frame.decompress(output_buffer.read())
        disk.write(decompressed_data)

但是这一步似乎没有必要。我尝试了直接方法，但没有成功。这是代码：

def write_to_disk(self, url, dev, proxy=None):

    if os.path.isfile(dev):
        size = os.path.getsize(dev)

    with open(os.path.realpath(dev), 'wb') as disk:
        disk.seek(0)

        def write_gz(buf):
            disk.write(d.decompress(buf))

        def write_lz4(buf):
            disk.write(lz4.decompress(buf))

        try:
            curl = pycurl.Curl()
            curl.setopt(pycurl.URL, url)
            if proxy is not False:
                curl.setopt(pycurl.PROXY, proxy)
            curl.setopt(pycurl.BUFFERSIZE, 1024)
            if url.endswith('.lz4'):
                curl.setopt(pycurl.WRITEFUNCTION, write_lz4)
            elif url.endswith('.gz'):
                d = zlib.decompressobj(zlib.MAX_WBITS | 32)
                curl.setopt(pycurl.WRITEFUNCTION, write_gz)
            curl.perform()

        except pycurl.error:
            return False

    if os.path.isfile(dev):
        disk.seek(size - 1)
        disk.write(b"\0")

    return True

谢谢

Answer 1

我最终实施了以下解决方案：

def write_to_disk(self, url, dev, proxy=None):
    """Fetch compressed OS image, decompress, and write to disk."""

    if not self.is_block_device(os.path.realpath(dev)):
        print(f"{dev} is not a block device")
        return False

    with open(os.path.realpath(dev), 'wb') as disk:
        disk.seek(0)

        try:
            curl = pycurl.Curl()
            curl.setopt(pycurl.URL, url) 
            if proxy is not False:
                curl.setopt(pycurl.PROXY, proxy)
            curl.setopt(pycurl.BUFFERSIZE, 524288)
            if url.endswith('.gz'):
                d = zlib.decompressobj(zlib.MAX_WBITS | 32)
                def write_gz(buf):
                    disk.write(d.decompress(buf))
                curl.setopt(pycurl.WRITEFUNCTION, write_gz)
                curl.perform()

            elif url.endswith('.zst'):
                # Perform the cURL request and store the data in a buffer
                buffer = bytearray()
                curl.setopt(curl.WRITEFUNCTION, buffer.extend)
                curl.perform()

                # Decompress the received data using zstd.decompress() and write it to disk 
                decompressed_data = zstd.decompress(bytes(buffer))
                disk.write(decompressed_data)
            elif url.endswith('.lz4'):
                # Perform the cURL request and store the data in a buffer
                buffer = bytearray()
                curl.setopt(curl.WRITEFUNCTION, buffer.extend)
                curl.perform()
                 
                # Decompress the received data using lz4.frame.decompress() and write it to disk 
                decompressed_data = lz4.frame.decompress(bytes(buffer))
                disk.write(decompressed_data)
            elif url.endswith('.raw'):
                def write_raw(buf):
                    disk.write(buf)
                curl.setopt(pycurl.WRITEFUNCTION, write_raw)
                curl.perform()

        except pycurl.error as e:
            print("PyCURL error:", e)
            return False

    if os.path.isfile(dev):
        size = os.path.getsize(dev)
        disk.seek(size - 1)
        disk.write(b"\0")

    return True