http: block while waiting for reconnecting

It makes no sense to return an error after the first reconnect, and then
somehow resume the next time it's called. Usually this will lead to
demuxer errors. Make reconnecting block instead, until it has either
successfully reconnected, or given up.

Also make the wait reasonably interruptible. Since there is no mechanism
for this in the API, polling is the best we can do. This behaves roughly
the same as other interruptible network functions in libavformat.

(The original code would work if it returned AVERROR(EAGAIN) or so,
which would make retry_transfer_wrapper() repeat the read call. But I
think having an explicit loop for this is better anyway.)

I also snuck in a fix for reconnect_at_eof. It has to check for
AVERROR_EOF, not 0.

libavformat/http.c

@@ -117,7 +117,6 @@ typedef struct HTTPContext {
     int reconnect;
     int reconnect_at_eof;
     int reconnect_streamed;
-    int reconnect_delay;
     int reconnect_delay_max;
     int listen;
     char *resource;
@@ -1433,6 +1432,7 @@ static int http_read_stream(URLContext *h, uint8_t *buf, int size)
     HTTPContext *s = h->priv_data;
     int err, new_location, read_ret;
     int64_t seek_ret;
+    int reconnect_delay = 0;
 
     if (!s->hd)
         return AVERROR_EOF;
@@ -1448,25 +1448,26 @@ static int http_read_stream(URLContext *h, uint8_t *buf, int size)
         return http_buf_read_compressed(h, buf, size);
 #endif /* CONFIG_ZLIB */
     read_ret = http_buf_read(h, buf, size);
-    if (   (read_ret  < 0 && s->reconnect        && (!h->is_streamed || s->reconnect_streamed) && s->filesize > 0 && s->off < s->filesize)
-        || (read_ret == 0 && s->reconnect_at_eof && (!h->is_streamed || s->reconnect_streamed))) {
+    while ((read_ret  < 0           && s->reconnect        && (!h->is_streamed || s->reconnect_streamed) && s->filesize > 0 && s->off < s->filesize)
+        || (read_ret == AVERROR_EOF && s->reconnect_at_eof && (!h->is_streamed || s->reconnect_streamed))) {
         uint64_t target = h->is_streamed ? 0 : s->off;
 
-        if (s->reconnect_delay > s->reconnect_delay_max)
+        if (reconnect_delay > s->reconnect_delay_max)
             return AVERROR(EIO);
 
         av_log(h, AV_LOG_INFO, "Will reconnect at %"PRIu64" error=%s.\n", s->off, av_err2str(read_ret));
-        av_usleep(1000U*1000*s->reconnect_delay);
-        s->reconnect_delay = 1 + 2*s->reconnect_delay;
+        err = ff_network_sleep_interruptible(1000U*1000*reconnect_delay, &h->interrupt_callback);
+        if (err != AVERROR(ETIMEDOUT))
+            return err;
+        reconnect_delay = 1 + 2*reconnect_delay;
         seek_ret = http_seek_internal(h, target, SEEK_SET, 1);
-        if (seek_ret != target) {
+        if (seek_ret >= 0 && seek_ret != target) {
             av_log(h, AV_LOG_ERROR, "Failed to reconnect at %"PRIu64".\n", target);
             return read_ret;
         }
 
         read_ret = http_buf_read(h, buf, size);
-    } else
-        s->reconnect_delay = 0;
+    }
 
     return read_ret;
 }

libavformat/network.c

@@ -103,6 +103,24 @@ int ff_network_wait_fd_timeout(int fd, int write, int64_t timeout, AVIOInterrupt
     }
 }
 
+int ff_network_sleep_interruptible(int64_t timeout, AVIOInterruptCB *int_cb)
+{
+    int64_t wait_start = av_gettime_relative();
+
+    while (1) {
+        int64_t time_left;
+
+        if (ff_check_interrupt(int_cb))
+            return AVERROR_EXIT;
+
+        time_left = timeout - (av_gettime_relative() - wait_start);
+        if (time_left <= 0)
+            return AVERROR(ETIMEDOUT);
+
+        av_usleep(FFMIN(time_left, POLLING_TIME * 1000));
+    }
+}
+
 void ff_network_close(void)
 {
 #if HAVE_WINSOCK2_H

libavformat/network.h

@@ -96,6 +96,15 @@ int ff_network_wait_fd(int fd, int write);
  */
 int ff_network_wait_fd_timeout(int fd, int write, int64_t timeout, AVIOInterruptCB *int_cb);
 
+/**
+ * Waits for up to 'timeout' microseconds. If the usert's int_cb is set and
+ * triggered, return before that.
+ * @timeout Timeout in microseconds. Maybe have lower actual precision.
+ * @param int_cb Interrupt callback, is checked regularly.
+ * @return AVERROR(ETIMEDOUT) if timeout expirted, AVERROR_EXIT if interrupted by int_cb
+ */
+int ff_network_sleep_interruptible(int64_t timeout, AVIOInterruptCB *int_cb);
+
 int ff_inet_aton (const char * str, struct in_addr * add);
 
 #if !HAVE_STRUCT_SOCKADDR_STORAGE