added range support to continue interrupted download

internal/server/GET_HEAD.go

@@ -2,11 +2,11 @@ package server
 
 import (
 	"fmt"
+	"io"
 	"os"
 	"path"
 	"serveg/internal/html"
 	"serveg/internal/http"
-	"time"
 )
 
 func (conn *TcpConnection) GET_HEAD(req *http.Request) *http.Response {
@@ -68,31 +68,59 @@ func (conn *TcpConnection) serveFile(req *http.Request, filePath string) *http.R
 	}
 	size := finf.Size()
 
-	// time is received with second precision
-	// if not truncate, mtime will always be > ifModifiedSince
-	mtime := finf.ModTime().UTC().Truncate(time.Second)
-
-	ifModifiedSince, errTime := time.Parse(http.HeaderTimeFormat, req.Headers["if-modified-since"])
-	notModified := errTime == nil && !mtime.After(ifModifiedSince)
-	if notModified {
+	// Clients send back the exact last-modified value they received.
+	// Exact match (not "<=") also detects a file replaced by one with older mtime.
+	lastModified := finf.ModTime().UTC().Format(http.HeaderTimeFormat)
+	if req.Headers["if-modified-since"] == lastModified {
 		return conn.http.CreateResponse(http.StatusNotModified, req, false)
 	}
 
-	res := conn.http.CreateResponse(http.StatusOK, req, false)
+	// Range is used to continue interrupted downloads.
+	// If-Range says "send the range only if the file wasn't changed, otherwise send the whole file".
+	rangeHdr := req.Headers["range"]
+	if ifRange, ok := req.Headers["if-range"]; ok && ifRange != lastModified {
+		rangeHdr = ""
+	}
+	start, end, rangeResult := http.ParseRange(rangeHdr, size)
+
+	status := http.StatusOK
+	bodyLen := size
+	switch rangeResult {
+	case http.RangeUnsatisfiable:
+		return conn.createErrorResponse(req, false, http.StatusRequestedRangeNotSatisfiable,
+			fmt.Sprintf("range '%s' is outside of file size %d", rangeHdr, size)).
+			WithHeader("content-range", fmt.Sprintf("bytes */%d", size)).
+			WithHeader("accept-ranges", "bytes")
+	case http.RangeOK:
+		status = http.StatusPartialContent
+		bodyLen = end - start + 1
+		if _, err = f.Seek(start, io.SeekStart); err != nil {
+			return conn.createErrorResponse(req, false, http.StatusInternalServerError, err.Error())
+		}
+	}
+
+	res := conn.http.CreateResponse(status, req, false)
 	fileName := path.Base(filePath)
+	mimeType := http.GetMimeType(fileName)
 
 	if req.Method != "HEAD" {
 		// file will be closed by SendResponse()
 		fileOwnershipTransferred = true
-		res.WithBodyReader(f, size, http.GetMimeType(fileName))
+		res.WithBodyReader(f, bodyLen, mimeType)
+	} else {
+		// WithBodyReader does nothing for HEAD, but clients use HEAD to get file size
+		res.WithHeaderI("content-length", bodyLen).
+			WithHeader("content-type", mimeType)
+	}
+	if rangeResult == http.RangeOK {
+		res.Headers["content-range"] = fmt.Sprintf("bytes %d-%d/%d", start, end, size)
 	}
 	// Tell browser to not use its own caching, remember last-modified
 	// On next request browser will send if-modified-since and let server check if file changed.
 	res.Headers["cache-control"] = "no-cache"
-	res.Headers["last-modified"] = mtime.Format(http.HeaderTimeFormat)
+	res.Headers["last-modified"] = lastModified
 	res.Headers["content-disposition"] = http.ContentDisposition("inline", fileName)
-	//TODO: accept "range" header and return StatusPartialContent
-	// res.Headers["accept-ranges"] = "bytes"
+	res.Headers["accept-ranges"] = "bytes"
 
 	return res
 }

internal/server/PUT_OPTIONS.go

@@ -104,7 +104,7 @@ func (conn *TcpConnection) handleUpload(req *http.Request, filePath string, file
 
 	// OPTIONS
 	if !reqHasBody {
-		uploadSize, err := strconv.ParseUint(req.Headers["x-upload-size"], 10, 64)
+		uploadSize, err := strconv.ParseUint(req.Headers["x-upload-size"], 10, 63)
 		if err != nil {
 			return createResponseMsg(http.StatusBadRequest,
 				"OPTIONS request must have valid header x-upload-size")