http: Add support for using persistent connections

Add a new AVOption 'multiple_requests', which indicates if we want
to use persistent connections (ie. Connection: keep-alive).
Signed-off-by: Martin Storsjö <martin@martin.st>

libavformat/http.c

@@ -53,6 +53,7 @@ typedef struct {
     int chunked_post;
     int end_chunked_post;   /**< A flag which indicates if the end of chunked encoding has been sent. */
     int end_header;         /**< A flag which indicates we have finished to read POST reply. */
+    int multiple_requests;  /**< A flag which indicates if we use persistent connections. */
 } HTTPContext;
 
 #define OFFSET(x) offsetof(HTTPContext, x)
@@ -61,6 +62,7 @@ typedef struct {
 static const AVOption options[] = {
 {"chunked_post", "use chunked transfer-encoding for posts", OFFSET(chunked_post), AV_OPT_TYPE_INT, {.dbl = 1}, 0, 1, E },
 {"headers", "custom HTTP headers, can override built in default headers", OFFSET(headers), AV_OPT_TYPE_STRING, { 0 }, 0, 0, D|E },
+{"multiple_requests", "use persistent connections", OFFSET(multiple_requests), AV_OPT_TYPE_INT, {.dbl = 0}, 0, 1, D|E },
 {NULL}
 };
 #define HTTP_CLASS(flavor)\
@@ -382,9 +384,17 @@ static int http_connect(URLContext *h, const char *path, const char *local_path,
     if (!has_header(s->headers, "\r\nRange: ") && !post)
         len += av_strlcatf(headers + len, sizeof(headers) - len,
                            "Range: bytes=%"PRId64"-\r\n", s->off);
-    if (!has_header(s->headers, "\r\nConnection: "))
-        len += av_strlcpy(headers + len, "Connection: close\r\n",
-                          sizeof(headers)-len);
+
+    if (!has_header(s->headers, "\r\nConnection: ")) {
+        if (s->multiple_requests) {
+            len += av_strlcpy(headers + len, "Connection: keep-alive\r\n",
+                              sizeof(headers) - len);
+        } else {
+            len += av_strlcpy(headers + len, "Connection: close\r\n",
+                              sizeof(headers) - len);
+        }
+    }
+
     if (!has_header(s->headers, "\r\nHost: "))
         len += av_strlcatf(headers + len, sizeof(headers) - len,
                            "Host: %s\r\n", hoststr);