implemented http server

internal/http/Response.go

@@ -2,6 +2,7 @@ package http
 
 import (
 	"errors"
+	"fmt"
 	"io"
 	"net"
 	sh "serveg/internal/string_helper"
@@ -14,19 +15,18 @@ type responseBodyType uint8
 
 const (
 	responseBodyEmpty = responseBodyType(iota)
-	responseBodySmall
-	responseBodyBig
+	responseBodyBuf
+	responseBodyReader
 )
 
-const TextPlain = "text/plain; charset=utf-8"
-
 type Response struct {
-	Status    StatusCode
-	Headers   HeadersMap // keys are in lower case
-	omitBody  bool       // don't add body and content-* headers for HEAD request
-	bodyType  responseBodyType
-	bodySmall []byte      // small body is sent in one write() call with headers
-	bodyBig   io.WriterTo // big body, sent as multiple write() calls to socket
+	Status     StatusCode
+	Headers    HeadersMap // keys are in lower case
+	omitBody   bool       // don't add body and content-* headers for HEAD request
+	bodySize   int64
+	bodyType   responseBodyType
+	bodyBuf    []byte    // small body is sent in one write() call with headers
+	bodyReader io.Reader // big body, sent as multiple write() calls to socket
 }
 
 const TimeFormat = "Mon, 02 Jan 2006 15:04:05 GMT"
@@ -46,7 +46,7 @@ func (conn *Connection) CreateResponse(
 		status >= 200 &&
 		status != StatusNoContent &&
 		status != StatusNotModified {
-		// content-length 0 is mandatory for most responses
+		// content-length is mandatory for most responses
 		res.Headers["content-length"] = "0"
 	}
 
@@ -59,7 +59,7 @@ func (conn *Connection) CreateResponse(
 	return res
 }
 
-func (res *Response) AttachBodySmall(body []byte, contentType string) {
+func (res *Response) AttachBodyBuf(body []byte, contentType string) {
 	if res.omitBody {
 		return
 	}
@@ -67,18 +67,21 @@ func (res *Response) AttachBodySmall(body []byte, contentType string) {
 	if res.bodyType != responseBodyEmpty {
 		panic("response already has body")
 	}
-	res.bodyType = responseBodySmall
-	res.bodySmall = body
-	lenStr := strconv.FormatUint(uint64(len(body)), 10)
+	res.bodyType = responseBodyBuf
+	res.bodyBuf = body
+	size := int64(len(body))
+	res.bodySize = size
+	lenStr := strconv.FormatUint(uint64(size), 10)
 	res.Headers["content-length"] = lenStr
 	res.Headers["content-type"] = contentType
 }
-func (res *Response) AttachBodySmallStr(body string, contentType string) {
-	res.AttachBodySmall(sh.UnsafeGetStrBytes(body), contentType)
+func (res *Response) AttachBodyStr(body string, contentType string) {
+	res.AttachBodyBuf(sh.UnsafeGetStrBytes(body), contentType)
 }
 
-func (res *Response) AttachBodyBig(body io.WriterTo,
-	size uint64, contentType string) {
+// body will be closed by SendResponse
+func (res *Response) AttachBodyReader(body io.Reader,
+	size int64, contentType string) {
 
 	if res.omitBody {
 		return
@@ -86,23 +89,31 @@ func (res *Response) AttachBodyBig(body io.WriterTo,
 	if res.bodyType != responseBodyEmpty {
 		panic("response already has body")
 	}
-	res.bodyType = responseBodyBig
-	res.bodyBig = body
-	lenStr := strconv.FormatUint(size, 10)
+	res.bodyType = responseBodyReader
+	res.bodyReader = body
+	res.bodySize = size
+	lenStr := strconv.FormatUint(uint64(size), 10)
 	res.Headers["content-length"] = lenStr
 	res.Headers["content-type"] = contentType
 }
 
 var ErrInvalidHeader = errors.New("http: header key or value contains CR or LF")
 
-func (conn *Connection) SendResponse(res *Response) error {
+func (conn *Connection) SendResponse(res *Response) (err error) {
+	if res.bodyType == responseBodyReader {
+		if closer, ok := res.bodyReader.(io.Closer); ok {
+			// body is owned by the response
+			defer func() {
+				_ = closer.Close()
+			}()
+		}
+	}
+
 	sb := &conn.wbuf
 	sb.Reset()
-
 	// first line
 	// space before \r\n is required by standard
 	sb.AddS("HTTP/1.1 ").AddU(uint64(res.Status)).AddS(" \r\n")
-
 	// headers
 	for k, v := range res.Headers {
 		// prevent response splitting / header injection
@@ -116,35 +127,52 @@ func (conn *Connection) SendResponse(res *Response) error {
 
 	switch res.bodyType {
 	case responseBodyEmpty:
-		// net.Conn.Write follows the io.Writer contract: it returns a non-nil
-		// error whenever n < len(p), so no loop is needed.
-		if _, err := conn.socket.Write(conn.wbuf.Buf); err != nil {
-			return err
-		}
-	case responseBodySmall:
+		_, err = conn.socket.Write(conn.wbuf.Buf)
+	case responseBodyBuf:
 		// write headers and body in one socket.Write() call
-		bbb := net.Buffers{sb.Buf, res.bodySmall}
-		if _, err := bbb.WriteTo(conn.socket); err != nil {
-			return err
+		bufs := net.Buffers{sb.Buf, res.bodyBuf}
+		_, err = bufs.WriteTo(conn.socket)
+	case responseBodyReader:
+		// write headers
+		if _, err = conn.socket.Write(conn.wbuf.Buf); err != nil {
+			return
 		}
-	case responseBodyBig:
-		// write headers, then write big body
-		if _, err := conn.socket.Write(conn.wbuf.Buf); err != nil {
-			return err
-		}
-		if _, err := res.bodyBig.WriteTo(conn.socket); err != nil {
-			return err
+		// Write exactly bodySize bytes from body.
+		// It prevents session corruption if body size changed since
+		// AttachBodyReader was called.
+		remaining := res.bodySize
+		for remaining > 0 {
+			err = conn.socket.SetWriteDeadline(time.Now().Add(conn.timeout))
+			if err != nil {
+				return
+			}
+			// don't increase or slow connections will trigger socket deadline
+			// 256 KB / 30 s ≈ 8.7 KB/s
+			const fileReadChunkSize = 256 * 1024
+			n := min(remaining, fileReadChunkSize)
+			_, err = io.CopyN(conn.socket, res.bodyReader, n)
+			if err != nil {
+				if errors.Is(err, io.EOF) {
+					// Body ended before bodySize bytes.
+					// Returning just io.EOF would look like a client discnnect
+					err = fmt.Errorf("response body is %d bytes shorter"+
+						" than content-length: %w",
+						remaining, io.ErrUnexpectedEOF)
+				}
+				return
+			}
+			remaining -= n
 		}
 	}
-	return nil
+	return
 }
 
-func (conn *Connection) SendErrorResponse(
-	httpErr *HttpError, req *Request, wantsClose bool,
-) error {
+func (conn *Connection) CreateErrorResponse(
+	req *Request, wantsClose bool, httpErr *HttpError,
+) *Response {
 
 	res := conn.CreateResponse(httpErr.Status, req, wantsClose)
 	// attach error message if method allows
-	res.AttachBodySmallStr(httpErr.Error(), TextPlain)
-	return conn.SendResponse(res)
+	res.AttachBodyStr(httpErr.Error(), TextPlain)
+	return res
 }