Support delivering fragments from the backlog; intended for HLS.
authorSteinar H. Gunderson <sgunderson@bigfoot.com>
Tue, 3 Apr 2018 22:40:33 +0000 (00:40 +0200)
committerSteinar H. Gunderson <sgunderson@bigfoot.com>
Fri, 6 Apr 2018 17:13:56 +0000 (19:13 +0200)
client.cpp
client.h
server.cpp
state.proto

index 4b7bcb7..c2cbcf5 100644 (file)
@@ -66,6 +66,7 @@ Client::Client(const ClientProto &serialized, Stream *stream)
          header_or_short_response(serialized.header_or_short_response()),
          header_or_short_response_bytes_sent(serialized.header_or_short_response_bytes_sent()),
          stream_pos(serialized.stream_pos()),
+         stream_pos_end(serialized.stream_pos_end()),
          bytes_sent(serialized.bytes_sent()),
          bytes_lost(serialized.bytes_lost()),
          num_loss_events(serialized.num_loss_events())
@@ -120,6 +121,7 @@ ClientProto Client::serialize() const
        serialized.set_header_or_short_response(header_or_short_response);
        serialized.set_header_or_short_response_bytes_sent(serialized.header_or_short_response_bytes_sent());
        serialized.set_stream_pos(stream_pos);
+       serialized.set_stream_pos_end(stream_pos_end);
        serialized.set_bytes_sent(bytes_sent);
        serialized.set_bytes_lost(bytes_lost);
        serialized.set_num_loss_events(num_loss_events);
index ed04bc0..f1d14e6 100644 (file)
--- a/client.h
+++ b/client.h
@@ -87,6 +87,10 @@ struct Client {
        // these negative values will be translated to real numbers.
        size_t stream_pos = 0;
 
+       // Position at which to end the stream (one-past-the-end, used for fragments).
+       // -1 means never to end; this is the common case.
+       size_t stream_pos_end = 0;
+
        // Number of bytes we've sent of data. Only relevant for SENDING_DATA.
        size_t bytes_sent = 0;
 
index 1deb087..e01c9f4 100644 (file)
@@ -545,12 +545,20 @@ sending_header_or_short_response_again:
                            0);
                        client->state = Client::SENDING_DATA;
                        goto sending_data;
+               } else if (client->stream_pos_end != Client::STREAM_POS_NO_END) {
+                       // We're sending a fragment, and should have all of it,
+                       // so start sending right away.
+                       assert(client->stream_pos >= 0);
+                       client->state = Client::SENDING_DATA;
+                       goto sending_data;
                } else if (stream->prebuffering_bytes == 0) {
                        // Start sending from the first keyframe we get. In other
                        // words, we won't send any of the backlog, but we'll start
                        // sending immediately as we get the next keyframe block.
                        // Note that this is functionally identical to the next if branch,
                        // except that we save a binary search.
+                       assert(client->stream_pos == size_t(-1));
+                       assert(client->stream_pos_end == size_t(-1));
                        client->stream_pos = stream->bytes_received;
                        client->state = Client::WAITING_FOR_KEYFRAME;
                } else {
@@ -560,6 +568,8 @@ sending_header_or_short_response_again:
                        // so that we are conservative and never add extra latency over just
                        // waiting (assuming CBR or nearly so); otherwise, we could want e.g.
                        // 100 kB prebuffer but end up sending a 10 MB GOP.
+                       assert(client->stream_pos == size_t(-1));
+                       assert(client->stream_pos_end == size_t(-1));
                        deque<size_t>::const_iterator starting_point_it =
                                lower_bound(stream->suitable_starting_points.begin(),
                                            stream->suitable_starting_points.end(),
@@ -611,9 +621,24 @@ sending_data:
                Stream *stream = client->stream;
 
 sending_data_again:
-               size_t bytes_to_send = stream->bytes_received - client->stream_pos;
+               size_t bytes_to_send;
+               if (client->stream_pos_end == size_t(-1)) {
+                        bytes_to_send = stream->bytes_received - client->stream_pos;
+               } else {
+                        bytes_to_send = client->stream_pos_end - client->stream_pos;
+               }
                assert(bytes_to_send <= stream->backlog_size);
                if (bytes_to_send == 0) {
+                       if (client->stream_pos == client->stream_pos_end) {  // We have a definite end, and we're at it.
+                               if (more_requests(client)) {
+                                       // We're done sending the fragment, but should keep on reading new requests.
+                                       goto read_request_again;
+                               } else {
+                                       // We're done sending the fragment, so now close.
+                                       // This is postcondition #1.
+                                       close_client(client);
+                               }
+                       }
                        return;
                }
 
@@ -645,13 +670,17 @@ sending_data_again:
                client->stream_pos += ret;
                client->bytes_sent += ret;
 
-               if (client->stream_pos == stream->bytes_received) {
+               assert(client->stream_pos_end == size_t(-1) || client->stream_pos <= client->stream_pos_end);
+               if (client->stream_pos == client->stream_pos_end) {
+                       goto sending_data_again;  // Will see that bytes_to_send == 0 and end.
+               } else if (client->stream_pos == stream->bytes_received) {
                        // We don't have any more data for this client, so put it to sleep.
                        // This is postcondition #3.
                        stream->put_client_to_sleep(client);
                } else if (more_data && size_t(ret) == bytes_to_send) {
                        goto sending_data_again;
                }
+               // We'll also get here for postcondition #4 (similar to the EAGAIN path above).
                break;
        }
        default:
@@ -797,9 +826,19 @@ void Server::skip_lost_data(Client *client)
        size_t bytes_to_send = stream->bytes_received - client->stream_pos;
        if (bytes_to_send > stream->backlog_size) {
                size_t bytes_lost = bytes_to_send - stream->backlog_size;
-               client->stream_pos = stream->bytes_received - stream->backlog_size;
                client->bytes_lost += bytes_lost;
                ++client->num_loss_events;
+               if (!client->close_after_response) {
+                       assert(client->stream_pos_end != size_t(-1));
+
+                       // We've already sent a Content-length, so we can't just skip data.
+                       // Close the connection immediately and hope the other side
+                       // is able to figure out that there was an error and it needs to skip.
+                       client->close_after_response = true;
+                       client->stream_pos = client->stream_pos_end;
+               } else {
+                       client->stream_pos = stream->bytes_received - stream->backlog_size;
+               }
        }
 }
 
@@ -837,7 +876,36 @@ int Server::parse_request(Client *client)
                client->stream_pos = -2;
                url = url.substr(0, url.size() - 8);
        } else {
-               client->stream_pos = -1;
+               size_t pos = url.find("?frag=");
+               if (pos != string::npos) {
+                       // Parse an endpoint of the type /stream.mp4?frag=1234-5678.
+                       const char *ptr = url.c_str() + pos + 6;
+                       char *endptr;
+                       long long frag_start = strtol(ptr, &endptr, 10);
+                       if (ptr == endptr || frag_start < 0 || frag_start == LLONG_MAX) {
+                               return 400;  // Bad request.
+                       }
+                       if (*endptr != '-') {
+                               return 400;  // Bad request.
+                       }
+                       ptr = endptr + 1;
+
+                       long long frag_end = strtol(ptr, &endptr, 10);
+                       if (ptr == endptr || frag_end < frag_start || frag_end == LLONG_MAX) {
+                               return 400;  // Bad request.
+                       }
+
+                       if (*endptr != '\0') {
+                               return 400;  // Bad request.
+                       }
+
+                       url = url.substr(0, pos);
+                       client->stream_pos = frag_start;
+                       client->stream_pos_end = frag_end;
+               } else {
+                       client->stream_pos = -1;
+                       client->stream_pos_end = -1;
+               }
        }
 
        // Figure out if we're supposed to close the socket after we've delivered the response.
@@ -873,11 +941,26 @@ int Server::parse_request(Client *client)
                return 503;  // Service unavailable.
        }
 
-       // Streams currently never end, so we don't have a content-length,
-       // and can just as well tell the client it's Connection: close
-       // (otherwise, we'd have to implement chunking TE for no good reason).
-       // When we start to support fragments, this will change.
-       client->close_after_response = true;
+       if (client->stream_pos_end == size_t(-1)) {
+               // This stream won't end, so we don't have a content-length,
+               // and can just as well tell the client it's Connection: close
+               // (otherwise, we'd have to implement chunking TE for no good reason).
+               client->close_after_response = true;
+       } else {
+               if (stream->encoding == Stream::STREAM_ENCODING_METACUBE) {
+                       // This doesn't make any sense, and is hard to implement, too.
+                       return 416;  // Range not satisfiable.
+               }
+
+               // Check that we have the requested fragment in our backlog.
+               size_t buffer_end = stream->bytes_received;
+               size_t buffer_start = (buffer_end <= stream->backlog_size) ? 0 : buffer_end - stream->backlog_size;
+
+               if (client->stream_pos_end > buffer_end ||
+                   client->stream_pos < buffer_start) {
+                       return 416;  // Range not satisfiable.
+               }
+       }
 
        client->stream = stream;
        if (setsockopt(client->sock, SOL_SOCKET, SO_MAX_PACING_RATE, &client->stream->pacing_rate, sizeof(client->stream->pacing_rate)) == -1) {
@@ -894,6 +977,11 @@ void Server::construct_header(Client *client)
 {
        Stream *stream = client->stream;
        client->header_or_short_response = stream->http_header;
+       if (client->stream_pos_end != size_t(-1)) {
+               char buf[64];
+               snprintf(buf, sizeof(buf), "Content-length: %zu\r\n", client->stream_pos_end - client->stream_pos);
+               client->header_or_short_response.append(buf);
+       }
        if (client->http_11) {
                assert(client->header_or_short_response.find("HTTP/1.0") == 0);
                client->header_or_short_response[7] = '1';  // Change to HTTP/1.1.
@@ -921,7 +1009,9 @@ void Server::construct_header(Client *client)
        } else {
                assert(false);
        }
-       client->header_or_short_response.append(stream->stream_header);
+       if (client->stream_pos_end == size_t(-1)) {  // Fragments don't contain stream headers.
+               client->header_or_short_response.append(stream->stream_header);
+       }
 
        // Switch states.
        client->state = Client::SENDING_HEADER;
index e6aefb5..7643bbf 100644 (file)
@@ -12,6 +12,7 @@ message ClientProto {
        optional bytes header_or_short_response = 5;
        optional int64 header_or_short_response_bytes_sent = 6;
        optional int64 stream_pos = 7;
+       optional int64 stream_pos_end = 20 [default=-1];
        optional int64 bytes_sent = 10;
        optional int64 bytes_lost = 11;
        optional int64 num_loss_events = 12;