英文:
How do I properly add a checksum header to this?
问题
当我从HTTP服务器开始下载文件时，我想要知道某种文件校验和（例如SHA-256哈希或其他任何形式）。它可以作为HTTP响应头之一进行传输。
我知道HTTP ETag是类似的东西，但我正在学习的是Golang，虽然我已经查阅了一些文档，但我仍然一头雾水。以下是我目前的代码：
package main
import (
"flag"
"fmt"
"log"
"net/http"
"strconv"
)
const (
crlf = "\r\n"
colonspace = ": "
)
func Checksum(h http.Handler) http.Handler {
return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
func HandleFunc(pattern string, handler func(ResponseWriter, *Request))
})
}
// 请不要更改此函数。
func main() {
var listenAddr = flag.String("http", ":8080", "address to listen on for HTTP")
flag.Parse()
http.Handle("/", Checksum(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
w.Header().Set("X-Foo", "bar")
w.Header().Set("Content-Type", "text/plain")
w.Header().Set("Date", "Sun, 08 May 2016 14:04:53 GMT")
msg := "Curiosity is insubordination in its purest form.\n"
w.Header().Set("Content-Length", strconv.Itoa(len(msg)))
fmt.Fprintf(w, msg)
})))
log.Fatal(http.ListenAndServe(*listenAddr, nil))
}
英文:
I'd like to know some kind of file checksum (like SHA-256 hash, or anything else) when I start downloading a file from HTTP server. It could be transferred as one of HTTP response headers.
I know http etag is something similar, I think, but this is Golang which I am new to learning and although I have looked through some documentation, I am still clueless. This is what I have so far:
package main
import (
"flag"
"fmt"
"log"
"net/http"
"strconv"
)
const (
crlf = "\r\n"
colonspace = ": "
)
func Checksum(h http.Handler) http.Handler {
return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
func HandleFunc(pattern string, handler func(ResponseWriter, *Request))
})
}
// Do not change this function.
func main() {
var listenAddr = flag.String("http", ":8080", "address to listen on for HTTP")
flag.Parse()
http.Handle("/", Checksum(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
w.Header().Set("X-Foo", "bar")
w.Header().Set("Content-Type", "text/plain")
w.Header().Set("Date", "Sun, 08 May 2016 14:04:53 GMT")
msg := "Curiosity is insubordination in its purest form.\n"
w.Header().Set("Content-Length", strconv.Itoa(len(msg)))
fmt.Fprintf(w, msg)
})))
log.Fatal(http.ListenAndServe(*listenAddr, nil))
}
答案1
得分: 2
编写一个包装器，用于捕获响应体和状态的 http.ResponseWriter：
type rwWrapper struct {
http.ResponseWriter
buf bytes.Buffer
status int
}
func (w *rwWrapper) Write(p []byte) (int, error) {
return rw.buf.Write(p)
}
func (w *rwWrapper) WriteHeader(status int) {
rw.status = status
}
在处理程序返回后，对响应体进行校验和，设置头部，然后将响应体写入底层的响应写入器：
func Checksum(h http.Handler) http.Handler {
return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
ww := &rwWrapper{ResponseWriter: w, status:200}
h.ServeHTTP(ww, r)
// 在这里计算 ww.buf.Bytes() 的校验和
w.Header().Set("nameOfHeader", checksum)
w.WriteHeader(ww.status)
w.Write(ww.buf.Bytes())
})
}
英文:
Write a wrapper around an http.ResponseWriter to capture the response body and status:
type rwWrapper struct {
http.ResponseWriter
buf bytes.Buffer
status int
}
func (w *rwWrapper) Write(p []byte) (int, error) {
return rw.buf.Write(p)
}
func (w *rwWrapper) WriteHeader(status int) {
rw.status = status
}
After the handler returns, checksum the body, set the header and then write the body to the underlying response writer:
func Checksum(h http.Handler) http.Handler {
return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
ww := &rwWrapper{ResponseWriter: w, status:200}
h.ServeHttp(ww, r)
// compute checksum of ww.buf.Bytes() here
w.Header().Set("nameOfHeader", checksum)
w.WriteHeader(ww.status)
w.Write(ww.buf.Bytes())
})
}
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