How to Parse HTTP Requests and Responses from a Text File in Go?

Parsing HTTP Requests and Responses from a Text File in Go

Introduction
This question focuses on parsing a text file that contains a stream of HTTP requests and responses into a Go slice of Connection structs. Each Connection struct includes an HTTP request and response.

Problem Outline
Given a text file containing HTTP requests and responses, the task is to parse it into a []Connection slice. The http.ReadRequest function can be used to parse requests. However, there is no built-in function to parse responses.

Implementation
The solution involves the following steps:

1. Buffered Reader Creation:

   buf := bufio.NewReader(r)

   where r is the io.Reader instance representing the text file.

2. Iterative Parsing:

   for {
       req, err := http.ReadRequest(buf)

   a. Use http.ReadRequest to parse the next request in the stream.

   b. Check for EOF (err == io.EOF). If reached, break out of the loop.

   c. If an error occurs, return the parsed stream with the error.

3. Response Parsing:

    resp, err := http.ReadResponse(buf, req)

   • Use http.ReadResponse to parse the response associated with the request.

4. Response Body Handling:

    b := new(bytes.Buffer)
    io.Copy(b, resp.Body)
    resp.Body.Close()
    resp.Body = ioutil.NopCloser(b)

   • Save the response body to a bytes buffer (b).
   • Close the original response body (resp.Body).
   • Replace resp.Body with the bytes buffer.

5. Stream Population:

   stream = append(stream, Connection{Request: req, Response: resp})

   • Create a Connection struct and add it to the stream slice.

6. Loop Termination:

   if err == io.EOF {
       break
   }

   • Exit the loop when http.ReadRequest returns EOF.

7. Example Usage:

   f, err := os.Open("/tmp/test.http")
   stream, err := ReadHTTPFromFile(f)

   • Open the text file and pass it to the ReadHTTPFromFile function.

Conclusion
This method effectively parses HTTP requests and responses from a text file and populates a []Connection slice with the parsed data. It handles response bodies correctly and ensures correct parsing of multiple requests and responses in a pipelined stream.

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