在Golang中编辑ZIP存档

Question

我正在编写一个应用程序，允许用户将匿名数据上传到S3存储桶，以便他们在不向我们提供身份验证数据的情况下试用我们的产品。

这是处理ZIP存档的结构，已被证明是正确的：

type ZipWriter struct {
    buffer *bytes.Buffer
    writer *zip.Writer
}

func FromFile(file io.Reader) (*ZipWriter, error) {

    // First, read all the data from the file; if this fails then return an error
    data, err := ioutil.ReadAll(file)
    if err != nil {
        return nil, fmt.Errorf("Failed to read data from the ZIP archive")
    }

    // Next, put all the data into a buffer and then create a ZIP writer
    // from the buffer and return that writer
    buffer := bytes.NewBuffer(data)
    return &ZipWriter{
        buffer: buffer,
        writer: zip.NewWriter(buffer),
    }, nil
}

// WriteToStream writes the contents of the ZIP archive to the provided stream
func (writer *ZipWriter) WriteToStream(file io.Writer) error {

    // First, attempt to close the ZIP archive writer so that we can avoid
    // double writes to the underlying buffer; if an error occurs then return it
    if err := writer.writer.Close(); err != nil {
        return fmt.Errorf("Failed to close ZIP archive, error: %v", err)
    }

    // Next, write the underlying buffer to the provided stream; if this fails
    // then return an error
    if _, err := writer.buffer.WriteTo(file); err != nil {
        return fmt.Errorf("Failed to write the ZIP data to the stream, error: %v", err)
    }

    return nil
}

使用ZipWriter，我使用FromFile函数加载ZIP文件，然后使用WriteToStream函数将其写入字节数组。之后，我调用以下函数将ZIP归档数据上传到S3中的预签名URL：

// DoRequest does an HTTP request against an endpoint with a given URL, method and access token
func DoRequest(client *http.Client, method string, url string, code string, reader io.Reader) ([]byte, error) {

    // First, create the request with the method, URL, body and access token
    // We don't expect this to fail so ignore the error
    request, _ := http.NewRequest(method, url, reader)
    if !util.IsEmpty(code) {
        request.Header.Set(headers.Accept, echo.MIMEApplicationJSON)
        request.Header.Set(headers.Authorization, fmt.Sprintf("Bearer %s", code))
    } else {
        request.Header.Set(headers.ContentType, "application/zip")
    }

    // Next, do the request; if this fails then return an error
    resp, err := client.Do(request)
    if err != nil {
        return nil, fmt.Errorf("Failed to run the %s request against %s, error: %v", method, url, err)
    } else if resp.StatusCode != http.StatusOK {
        return nil, fmt.Errorf("Failed to run the %s request against %s, response: %v", method, url, resp)
    }

    // Now, read the body from the response; if this fails then return an error
    defer resp.Body.Close()
    body, err := ioutil.ReadAll(resp.Body)
    if err != nil {
        return nil, fmt.Errorf("Failed to read the body associated with the response, error: %v", err)
    }

    // Finally, return the body from the response
    return body, nil
}

所以，整个操作是这样进行的：

file, err := os.Open(location)
if err != nil {
    log.Fatalf("Unable to open ZIP archive located in %s, error: %v", location, err)
}

writer, err := lutils.FromFile(file)
if err != nil {
    log.Fatalf("File located in %s could not be read as a ZIP archive, error: %v", location, err)
}

buffer := new(bytes.Buffer)
if err := writer.WriteToStream(buffer); err != nil {
    log.Fatalf("Failed to write data to the ZIP archive, error: %v", err)
}

if body, err := DoRequest(new(http.Client), http.MethodPut, url, "", buffer); err != nil {
    log.Fatalf("Failed to upload the data to S3, response: %s, error: %v", string(body), err)
}

我遇到的问题是，尽管上传到S3成功，但当下载ZIP存档并提取数据时，找不到任何文件。在调查这个问题时，我想出了一些可能的失败点：

1. FromFile不能正确地从该文件创建ZIP存档；导致存档文件损坏

在更深入地研究了这些可能性之后，我认为问题可能在于如何从归档文件创建ZIP编写器，但我不确定问题是什么。

Answer 1

这里的问题有点像转移视线。正如@CeriseLimón所指出的，在现有ZIP存档上调用NewWriter和Close必然会导致在文件末尾添加一个空存档。在我的用例中，解决方案是打开文件并将其直接写入流，而不是试图将其作为ZIP存档读取。

file, err := os.Open(location)
if err != nil {
    log.Fatalf("Unable to open ZIP archive located in %s, error: %v", location, err)
}

if body, err := DoRequest(new(http.Client), http.MethodPut, url, "", file); err != nil {
    log.Fatalf("Failed to upload the data to S3, response: %s, error: %v", string(body), err)
}