added range support to continue interrupted download

internal/server/GET_HEAD.go

@@ -0,0 +1,126 @@
+package server
+
+import (
+	"fmt"
+	"io"
+	"os"
+	"path"
+	"serveg/internal/html"
+	"serveg/internal/http"
+)
+
+func (conn *TcpConnection) GET_HEAD(req *http.Request) *http.Response {
+	path, share, urlStatus := conn.srv.Conf.Share.MapUrl(req.Url)
+	// handle authorization
+	if share != nil {
+		access := checkSharePasswords(share, req)
+		if access < AccessReadOnly {
+			return conn.createErrorResponse(req, false,
+				http.StatusUnauthorized, "reader password required").
+				WithHeader("www-authenticate",
+					`Basic realm="`+share.Url+` (read)", charset="UTF-8"`)
+		}
+	}
+
+	switch urlStatus {
+	case UrlFile:
+		return conn.serveFile(req, path)
+	case UrlDir:
+		return conn.serveDirListing(req, path)
+	case UrlShareNotFound, UrlDoesntExistInShare:
+		return conn.createErrorResponse(req, false, http.StatusNotFound, req.Url)
+	case UrlForbidden:
+		return conn.createErrorResponse(req, false, http.StatusForbidden, req.Url)
+	case UrlIncorrect:
+		return conn.createErrorResponse(req, false, http.StatusBadRequest,
+			"invalid url '"+req.Url+"'")
+	default:
+		panic(fmt.Sprintf("unsupported UrlStatus: %d", int32(urlStatus)))
+	}
+}
+
+func (conn *TcpConnection) serveDirListing(req *http.Request, dirPath string) *http.Response {
+	htmlBytes, err := html.GenDirListingHtml(&conn.log, dirPath,
+		req.Url, conn.srv.Conf.HtmlTitle)
+	if err != nil {
+		return conn.createErrorResponse(req, false, http.StatusInternalServerError, err.Error())
+	}
+
+	return conn.http.CreateResponse(http.StatusOK, req, false).
+		WithBodyBuf(htmlBytes, http.TextHtml)
+}
+
+func (conn *TcpConnection) serveFile(req *http.Request, filePath string) *http.Response {
+	f, err := os.Open(filePath)
+	if err != nil {
+		return conn.createErrorResponse(req, false, http.StatusInternalServerError, err.Error())
+	}
+	var fileOwnershipTransferred bool
+	defer func() {
+		if !fileOwnershipTransferred {
+			_ = f.Close()
+		}
+	}()
+
+	finf, err := f.Stat()
+	if err != nil {
+		return conn.createErrorResponse(req, false, http.StatusInternalServerError, err.Error())
+	}
+	size := finf.Size()
+
+	// 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)
+	}
+
+	// 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, 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"] = lastModified
+	res.Headers["content-disposition"] = http.ContentDisposition("inline", fileName)
+	res.Headers["accept-ranges"] = "bytes"
+
+	return res
+}