Golang文件IO与网络编程结合实践

net/http

package main

import (
    "fmt"
    "io"
    "net/http"
    "os"
    "path/filepath"
    "time"
)

func uploadFile(w http.ResponseWriter, r *http.Request) {
    if r.Method != "POST" {
        http.Error(w, "Only POST method is allowed", http.StatusMethodNotAllowed)
        return
    }

    // 解析 multipart/form-data
    // 10MB 是最大内存缓存，超过部分会写入临时文件
    err := r.ParseMultipartForm(10 << 20) // 10 MB
    if err != nil {
        http.Error(w, fmt.Sprintf("Failed to parse form: %v", err), http.StatusInternalServerError)
        return
    }

    file, header, err := r.FormFile("uploadFile") // "uploadFile" 是表单中文件字段的name
    if err != nil {
        http.Error(w, fmt.Sprintf("Failed to get file from form: %v", err), http.StatusBadRequest)
        return
    }
    defer file.Close()

    // 创建目标文件
    fileName := fmt.Sprintf("%d_%s", time.Now().UnixNano(), filepath.Base(header.Filename))
    dstPath := filepath.Join("./uploads", fileName) // 保存到当前目录的uploads子目录

    // 确保uploads目录存在
    if _, err := os.Stat("./uploads"); os.IsNotExist(err) {
        os.Mkdir("./uploads", 0755)
    }

    dst, err := os.Create(dstPath)
    if err != nil {
        http.Error(w, fmt.Sprintf("Failed to create file on server: %v", err), http.StatusInternalServerError)
        return
    }
    defer dst.Close()

    // 将上传的文件内容拷贝到目标文件
    _, err = io.Copy(dst, file)
    if err != nil {
        http.Error(w, fmt.Sprintf("Failed to save file: %v", err), http.StatusInternalServerError)
        return
    }

    fmt.Fprintf(w, "File uploaded successfully: %s", fileName)
    fmt.Printf("Received file: %s, saved to: %s\n", header.Filename, dstPath)
}

func main() {
    http.HandleFunc("/upload", uploadFile)
    fmt.Println("Server started on :8080, upload endpoint: /upload")
    err := http.ListenAndServe(":8080", nil)
    if err != nil {
        fmt.Printf("Server failed to start: %v\n", err)
    }
}

http.HandleFunc

/upload

uploadFile

uploadFile

r.ParseMultipartForm

r.FormFile

io.Copy

io.Copy

net/http

io.Copy

http.ServeContent

http.ServeFile

func downloadFile(w http.ResponseWriter, r *http.Request) {
    filePath := "./uploads/your_file_name.txt" // 假设要下载的文件
    http.ServeFile(w, r, filePath) // 简单直接地服务文件
    // 或者更灵活地使用 http.ServeContent，可以自定义内容类型、文件名等
    // file, err := os.Open(filePath)
    // if err != nil {
    //     http.Error(w, "File not found.", http.StatusNotFound)
    //     return
    // }
    // defer file.Close()
    // fi, err := file.Stat()
    // if err != nil {
    //     http.Error(w, "File info error.", http.StatusInternalServerError)
    //     return
    // }
    // http.ServeContent(w, r, filepath.Base(filePath), fi.ModTime(), file)
}

http.ServeFile

defer file.Close()

// 异步写入的简化示例（不包含错误恢复和复杂队列）
func asyncWriteFile(data io.Reader, filename string) {
    go func() {
        dst, err := os.Create(filename)
        if err != nil {
            fmt.Printf("Error creating async file: %v\n", err)
            return
        }
        defer dst.Close()

        _, err = io.Copy(dst, data)
        if err != nil {
            fmt.Printf("Error writing async file: %v\n", err)
            // 这里可能需要更复杂的错误处理，例如重试、报警
        }
        fmt.Printf("Async file %s written successfully.\n", filename)
    }()
}

io.TeeReader

Reader

Writer

// 示例：同时写入文件并转发到另一个网络连接
func processStreamAndSave(conn net.Conn, filename string) {
    file, err := os.Create(filename)
    if err != nil {
        fmt.Printf("Error creating file: %v\n", err)
        conn.Close()
        return
    }
    defer file.Close()

    // 创建一个TeeReader，将conn的数据同时写入file
    teeReader := io.TeeReader(conn, file)

    // 假设我们还要把数据转发到另一个网络服务
    // targetConn, err := net.Dial("tcp", "another.service.com:8081")
    // if err != nil { /* handle error */ }
    // defer targetConn.Close()

    // 从teeReader读取数据，这会同时写入file
    // 并且我们还可以将这些数据再写入targetConn
    // _, err = io.Copy(targetConn, teeReader)
    _, err = io.Copy(io.Discard, teeReader) // 如果只是想写入文件，不转发，可以丢弃
    if err != nil {
        fmt.Printf("Error processing stream: %v\n", err)
    }
    fmt.Printf("Stream processed and saved to %s\n", filename)
    conn.Close()
}

pprof