Chunk File Uploading on GoLang

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This is the backend implementation of chunk file upload under golang platform. The backend system is only implemented. The philosophy behind is it attempted to upload everything in a single request. So, with the chunking strategy, they processed fixed-size chunk requests until all of the file parts are uploaded.

File Chunk data are transmitted from the client-side with the headers like content-type, content-range, content expiry etc, and file form data (filename, filetype). Therefore each chunk is processed by the server to get uploaded on the desired condition.

Go lang code

package main

import (
	"chunk-file-upload/controller"
	"github.com/gin-contrib/cors"
	"github.com/gin-gonic/gin"
)

func main() {
	httpRouter := gin.Default()
	httpRouter.Use(cors.New(cors.Config{
		AllowOrigins:     []string{"*"},
		AllowMethods:     []string{"PUT", "PATCH", "GET", "POST", "OPTIONS", "DELETE"},
		AllowHeaders:     []string{"*"},
		AllowCredentials: true,
	}))
	httpRouter.POST("/chunk-upload", controller.ChunkUploadHandler)
	httpRouter.Run(":8080")
}

package controller

import (
	"io"
	"strconv"
	"strings"
	"net/http"
	"os"
	"github.com/gin-gonic/gin"
)

// Input -> add binding model for input
type Input struct {
	Model string `form:"model,omitempty" binding:"required"`
}

// Response -> response for the util scope
type Response struct {
	Success bool   `json:"success"`
	Message string `json:"message"`
	Name    string `json:"name"`
}

func ChunkUploadHandler(c *gin.Context) {
	var f *os.File
	file, uploadFile, err := c.Request.FormFile("file")
	if err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": "content-type should be multipart/formdata"})
		return
	}

	contentRangeHeader := c.Request.Header.Get("Content-Range")
	rangeAndSize := strings.Split(contentRangeHeader, "/")
	rangeParts := strings.Split(rangeAndSize[0], "-")

	rangeMax, err := strconv.Atoi(rangeParts[1])
	if err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": "Missing range in Content-Range header"})
		return
	}

	fileSize, err := strconv.Atoi(rangeAndSize[1])
	if err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": "Missing file size in Content-Range header"})
		return
	}

	if fileSize > 100*1024*1024 {
		c.JSON(http.StatusBadRequest, gin.H{"error": "File size should be less than 100MB"})
		return
	}

	var input Input
	err = c.ShouldBind(&input)
	if err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": "Missing model name in header"})
		return
	}

	tempDir, err := os.UserHomeDir()
	if err != nil {
		c.JSON(http.StatusInternalServerError, gin.H{"error": "Error resolving home directory"})
		return
	}

	if _, err := os.Stat(tempDir + "/" + input.Model); os.IsNotExist(err) {
		err := os.Mkdir(tempDir+"/"+input.Model, 0777)
		if err != nil {
			c.JSON(http.StatusInternalServerError, gin.H{"error": "Error creating temporary directory"})
			return
		}
	}

	if f == nil {
		f, err = os.OpenFile(tempDir+"/"+input.Model+"/"+uploadFile.Filename, os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0644)
		if err != nil {
			c.JSON(http.StatusInternalServerError, gin.H{"error": "Error creating file"})
			return
		}
	}

	if _, err := io.Copy(f, file); err != nil {
		c.JSON(http.StatusInternalServerError, gin.H{"error": "Error writing to a file"})
		return
	}

	f.Close()
	if rangeMax >= fileSize-1 {
		combinedFile := tempDir + "/" + input.Model + "/" + uploadFile.Filename

		uploadingFile, err := os.Open(combinedFile)
		if err != nil {
			c.JSON(http.StatusBadRequest, gin.H{"error": "Failed to upload file "})
			return
		}
		uploadingFile.Close()
		response := &Response{
			Success: true,
			Message: "Uploaded Successfully",
			Name:    uploadFile.Filename,
		}
		c.JSON(http.StatusOK, gin.H{"data": response})
		return
	}
	c.JSON(http.StatusOK, gin.H{"status": "uploading"})
}

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