add by hand http send example

This adds a demonstration of how to use the http nonblocking
send action to the test server.

If you ask for /leaf.jpg from the test server, it will send
"by hand" a 2.4MB jpeg in HTTP, including the headers.  See
the test server sources to see how it is done.

Although it's a file, and a jpeg image, actually the exact
same scheme will work for any data or mime type.

Signed-off-by: Andy Green <andy.green@linaro.org>

test-server/Makefile.am

@@ -109,7 +109,7 @@ libwebsockets_test_ping_CFLAGS= -Wall -Werror -std=gnu99 -pedantic -DINSTALL_DAT
 endif
 endif
 
-EXTRA_DIST=test.html favicon.ico libwebsockets.org-logo.png
+EXTRA_DIST=test.html favicon.ico libwebsockets.org-logo.png leaf.jpg
 
 #
 # cook a random test cert and key

test-server/test-server.c

@@ -28,6 +28,8 @@
 #include <getopt.h>
 #include <string.h>
 #include <sys/time.h>
+#include <sys/stat.h>
+#include <fcntl.h>
 #include <assert.h>
 #ifdef WIN32
 
@@ -104,6 +106,10 @@ static const struct serveable whitelist[] = {
 	{ "/test.html", "text/html" },
 };
 
+struct per_session_data__http {
+	int fd;
+};
+
 /* this protocol server (always the first one) just knows how to do HTTP */
 
 static int callback_http(struct libwebsocket_context *context,
@@ -117,6 +123,10 @@ static int callback_http(struct libwebsocket_context *context,
 #endif
 	char buf[256];
 	int n;
+	unsigned char *p;
+	static unsigned char buffer[8192];
+	struct stat stat_buf;
+	struct per_session_data__http *pss = (struct per_session_data__http *)user;
 #ifdef EXTERNAL_POLL
 	int m;
 	int fd = (int)(long)user;
@@ -125,6 +135,55 @@ static int callback_http(struct libwebsocket_context *context,
 	switch (reason) {
 	case LWS_CALLBACK_HTTP:
 
+		/* check for the "send a big file by hand" example case */
+
+		if (!strcmp((const char *)in, "/leaf.jpg")) {
+
+			/* well, let's demonstrate how to send the hard way */
+
+			p = buffer;
+
+			pss->fd = open(LOCAL_RESOURCE_PATH"/leaf.jpg", O_RDONLY);
+			if (pss->fd < 0)
+				return -1;
+
+			fstat(pss->fd, &stat_buf);
+
+			/*
+			 * we will send a big jpeg file, but it could be
+			 * anything.  Set the Content-Type: appropriately
+			 * so the browser knows what to do with it.
+			 */
+
+			p += sprintf((char *)p,
+				"HTTP/1.0 200 OK\x0d\x0a"
+				"Server: libwebsockets\x0d\x0a"
+				"Content-Type: image-jpeg\x0d\x0a"
+					"Content-Length: %u\x0d\x0a\x0d\x0a",
+					(unsigned int)stat_buf.st_size);
+
+			/*
+			 * send the http headers...
+			 * this won't block since it's the first payload sent
+			 * on the connection since it was established
+			 */
+
+			n = libwebsocket_write(wsi, buffer,
+				   p - buffer, LWS_WRITE_HTTP);
+
+			if (n < 0) {
+				close(pss->fd);
+				return -1;
+			}
+			/*
+			 * book us a LWS_CALLBACK_HTTP_WRITEABLE callback
+			 */
+			libwebsocket_callback_on_writable(context, wsi);
+			break;
+		}
+
+		/* if not, send a file the easy way */
+
 		for (n = 0; n < (sizeof(whitelist) / sizeof(whitelist[0]) - 1); n++)
 			if (in && strcmp((const char *)in, whitelist[n].urlpath) == 0)
 				break;
@@ -132,7 +191,7 @@ static int callback_http(struct libwebsocket_context *context,
 		sprintf(buf, LOCAL_RESOURCE_PATH"%s", whitelist[n].urlpath);
 
 		if (libwebsockets_serve_http_file(context, wsi, buf, whitelist[n].mimetype))
-			return 1; /* through completion or error, close the socket */
+			return -1; /* through completion or error, close the socket */
 
 		/*
 		 * notice that the sending of the file completes asynchronously,
@@ -145,7 +204,37 @@ static int callback_http(struct libwebsocket_context *context,
 	case LWS_CALLBACK_HTTP_FILE_COMPLETION:
 //		lwsl_info("LWS_CALLBACK_HTTP_FILE_COMPLETION seen\n");
 		/* kill the connection after we sent one file */
-		return 1;
+		return -1;
+
+	case LWS_CALLBACK_HTTP_WRITEABLE:
+		/*
+		 * we can send more of whatever it is we were sending
+		 */
+
+		do {
+			n = read(pss->fd, buffer, sizeof buffer);
+			/* problem reading, close conn */
+			if (n < 0)
+				goto bail;
+			/* sent it all, close conn */
+			if (n == 0)
+				goto bail;
+			/*
+			 * because it's HTTP and not websocket, don't need to take
+			 * care about pre and postamble
+			 */
+			n = libwebsocket_write(wsi, buffer, n, LWS_WRITE_HTTP);
+			if (n < 0)
+				/* write failed, close conn */
+				goto bail;
+
+		} while (!lws_send_pipe_choked(wsi));
+		libwebsocket_callback_on_writable(context, wsi);
+		break;
+
+bail:
+		close(pss->fd);
+		return -1;
 
 	/*
 	 * callback for confirming to continue with client IP appear in
@@ -476,7 +565,7 @@ static struct libwebsocket_protocols protocols[] = {
 	{
 		"http-only",		/* name */
 		callback_http,		/* callback */
-		0,			/* per_session_data_size */
+		sizeof (struct per_session_data__http),	/* per_session_data_size */
 		0,			/* max frame size / rx buffer */
 	},
 	{

test-server/test.html

@@ -37,8 +37,9 @@
 The incrementing number is coming from the server and is individual for
 each connection to the server... try opening a second browser window.
 <br/><br/>
-Click the button to send the server a websocket message to
-reset the number.
+The button zeros just this connection's number.
+<br/><br/>
+Click <a href="/leaf.jpg" target="_blank">Here</a> to have the test server send a big picture by http.
 </td></tr></table>
 </section>
 <br>