File: stream.cpp

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#include <assert.h>
#include <errno.h>
#include <limits.h>
#include <netinet/in.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <algorithm>
#include <string>
#include <queue>
#include <vector>

#include "log.h"
#include "metacube2.h"
#include "mutexlock.h"
#include "state.pb.h"
#include "stream.h"
#include "util.h"

using namespace std;

Stream::Stream(const string &url, size_t backlog_size, size_t prebuffering_bytes, Encoding encoding, Encoding src_encoding)
	: url(url),
	  encoding(encoding),
	  src_encoding(src_encoding),
	  data_fd(make_tempfile("")),
          backlog_size(backlog_size),
	  prebuffering_bytes(prebuffering_bytes),
	  bytes_received(0),
	  pacing_rate(~0U)
{
	if (data_fd == -1) {
		exit(1);
	}

	pthread_mutex_init(&queued_data_mutex, NULL);
}

Stream::~Stream()
{
	if (data_fd != -1) {
		safe_close(data_fd);
	}
}

Stream::Stream(const StreamProto &serialized, int data_fd)
	: url(serialized.url()),
	  http_header(serialized.http_header()),
	  stream_header(serialized.stream_header()),
	  encoding(Stream::STREAM_ENCODING_RAW),  // Will be changed later.
	  data_fd(data_fd),
	  backlog_size(serialized.backlog_size()),
	  prebuffering_bytes(serialized.prebuffering_bytes()),
	  bytes_received(serialized.bytes_received()),
	  pacing_rate(~0U)
{
	if (data_fd == -1) {
		exit(1);
	}

	for (int i = 0; i < serialized.suitable_starting_point_size(); ++i) {
		ssize_t point = serialized.suitable_starting_point(i);
		if (point == -1) {
			// Can happen when upgrading from before 1.1.3,
			// where this was an optional field with -1 signifying
			// "no such point".
			continue;
		}
		suitable_starting_points.push_back(point);
	}

	pthread_mutex_init(&queued_data_mutex, NULL);
}

StreamProto Stream::serialize()
{
	StreamProto serialized;
	serialized.set_http_header(http_header);
	serialized.set_stream_header(stream_header);
	serialized.add_data_fds(data_fd);
	serialized.set_backlog_size(backlog_size);
	serialized.set_prebuffering_bytes(prebuffering_bytes);
	serialized.set_bytes_received(bytes_received);
	for (size_t i = 0; i < suitable_starting_points.size(); ++i) {
		serialized.add_suitable_starting_point(suitable_starting_points[i]);
	}
	serialized.set_url(url);
	data_fd = -1;
	return serialized;
}
	
void Stream::set_backlog_size(size_t new_size)
{
	if (backlog_size == new_size) {
		return;
	}

	string existing_data;
	if (!read_tempfile_and_close(data_fd, &existing_data)) {
		exit(1);
	}

	// Unwrap the data so it's no longer circular.
	if (bytes_received <= backlog_size) {
		existing_data.resize(bytes_received);
	} else {
		size_t pos = bytes_received % backlog_size;
		existing_data = existing_data.substr(pos, string::npos) +
			existing_data.substr(0, pos);
	}

	// See if we need to discard data.
	if (new_size < existing_data.size()) {
		size_t to_discard = existing_data.size() - new_size;
		existing_data = existing_data.substr(to_discard, string::npos);
	}

	// Create a new, empty data file.
	data_fd = make_tempfile("");
	if (data_fd == -1) {
		exit(1);
	}
	backlog_size = new_size;

	// Now cheat a bit by rewinding, and adding all the old data back.
	bytes_received -= existing_data.size();
	DataElement data_element;
	data_element.data.iov_base = const_cast<char *>(existing_data.data());
	data_element.data.iov_len = existing_data.size();
	data_element.metacube_flags = 0;  // Ignored by add_data_raw().

	vector<DataElement> data_elements;
	data_elements.push_back(data_element);
	add_data_raw(data_elements);
	remove_obsolete_starting_points();
}

void Stream::put_client_to_sleep(Client *client)
{
	sleeping_clients.push_back(client);
}

// Return a new set of iovecs that contains only the first <bytes_wanted> bytes of <data>.
vector<iovec> collect_iovecs(const vector<Stream::DataElement> &data, size_t bytes_wanted)
{
	vector<iovec> ret;
	size_t max_iovecs = min<size_t>(data.size(), IOV_MAX);
	for (size_t i = 0; i < max_iovecs && bytes_wanted > 0; ++i) {
		if (data[i].data.iov_len <= bytes_wanted) {
			// Consume the entire iovec.
			ret.push_back(data[i].data);
			bytes_wanted -= data[i].data.iov_len;
		} else {
			// Take only parts of this iovec.
			iovec iov;
			iov.iov_base = data[i].data.iov_base;
			iov.iov_len = bytes_wanted;
			ret.push_back(iov);
			bytes_wanted = 0;
		}
	}
	return ret;
}

// Return a new set of iovecs that contains all of <data> except the first <bytes_wanted> bytes.
vector<Stream::DataElement> remove_iovecs(const vector<Stream::DataElement> &data, size_t bytes_wanted)
{
	vector<Stream::DataElement> ret;
	size_t i;
	for (i = 0; i < data.size() && bytes_wanted > 0; ++i) {
		if (data[i].data.iov_len <= bytes_wanted) {
			// Consume the entire iovec.
			bytes_wanted -= data[i].data.iov_len;
		} else {
			// Take only parts of this iovec.
			Stream::DataElement data_element;
			data_element.data.iov_base = reinterpret_cast<char *>(data[i].data.iov_base) + bytes_wanted;
			data_element.data.iov_len = data[i].data.iov_len - bytes_wanted;
			data_element.metacube_flags = METACUBE_FLAGS_NOT_SUITABLE_FOR_STREAM_START;
			ret.push_back(data_element);
			bytes_wanted = 0;
		}
	}

	// Add the rest of the iovecs unchanged.
	ret.insert(ret.end(), data.begin() + i, data.end());
	return ret;
}

void Stream::add_data_raw(const vector<DataElement> &orig_data)
{
	vector<DataElement> data = orig_data;
	while (!data.empty()) {
		size_t pos = bytes_received % backlog_size;

		// Collect as many iovecs as we can before we hit the point
		// where the circular buffer wraps around.
		vector<iovec> to_write = collect_iovecs(data, backlog_size - pos);
		ssize_t ret;
		do {
			ret = pwritev(data_fd, to_write.data(), to_write.size(), pos);
		} while (ret == -1 && errno == EINTR);

		if (ret == -1) {
			log_perror("pwritev");
			// Dazed and confused, but trying to continue...
			return;
		}
		bytes_received += ret;

		// Remove the data that was actually written from the set of iovecs.
		data = remove_iovecs(data, ret);
	}
}

void Stream::remove_obsolete_starting_points()
{
	// We could do a binary search here (std::lower_bound), but it seems
	// overkill for removing what's probably only a few points.
	while (!suitable_starting_points.empty() &&
	       bytes_received - suitable_starting_points[0] > backlog_size) {
		suitable_starting_points.pop_front();
	}
}

void Stream::add_data_deferred(const char *data, size_t bytes, uint16_t metacube_flags)
{
	// For regular output, we don't want to send the client twice
	// (it's already sent out together with the HTTP header).
	// However, for Metacube output, we need to send it so that
	// the Cubemap instance in the other end has a chance to update it.
	// It may come twice in its stream, but Cubemap doesn't care.
	if (encoding == Stream::STREAM_ENCODING_RAW &&
	    (metacube_flags & METACUBE_FLAGS_HEADER) != 0) {
		return;
	}

	MutexLock lock(&queued_data_mutex);

	DataElement data_element;
	data_element.metacube_flags = metacube_flags;

	if (encoding == Stream::STREAM_ENCODING_METACUBE) {
		// Add a Metacube block header before the data.
		metacube2_block_header hdr;
		memcpy(hdr.sync, METACUBE2_SYNC, sizeof(hdr.sync));
		hdr.size = htonl(bytes);
		hdr.flags = htons(metacube_flags);
		hdr.csum = htons(metacube2_compute_crc(&hdr));

		data_element.data.iov_base = new char[bytes + sizeof(hdr)];
		data_element.data.iov_len = bytes + sizeof(hdr);

		memcpy(data_element.data.iov_base, &hdr, sizeof(hdr));
		memcpy(reinterpret_cast<char *>(data_element.data.iov_base) + sizeof(hdr), data, bytes);

		queued_data.push_back(data_element);
	} else if (encoding == Stream::STREAM_ENCODING_RAW) {
		// Just add the data itself.
		data_element.data.iov_base = new char[bytes];
		memcpy(data_element.data.iov_base, data, bytes);
		data_element.data.iov_len = bytes;

		queued_data.push_back(data_element);
	} else {
		assert(false);
	}
}

void Stream::process_queued_data()
{
	vector<DataElement> queued_data_copy;

	// Hold the lock for as short as possible, since add_data_raw() can possibly
	// write to disk, which might disturb the input thread.
	{
		MutexLock lock(&queued_data_mutex);
		if (queued_data.empty()) {
			return;
		}

		swap(queued_data, queued_data_copy);
	}

	// Add suitable starting points for the stream, if the queued data
	// contains such starting points. Note that we drop starting points
	// if they're less than 10 kB apart, so that we don't get a huge
	// amount of them for e.g. each and every MPEG-TS 188-byte cell.
	// The 10 kB value is somewhat arbitrary, but at least it should make
	// the RAM cost of saving the position ~0.1% (or less) of the actual
	// data, and 10 kB is a very fine granularity in most streams.
	static const int minimum_start_point_distance = 10240;
	size_t byte_position = bytes_received;
	for (size_t i = 0; i < queued_data_copy.size(); ++i) {
		if ((queued_data_copy[i].metacube_flags & METACUBE_FLAGS_NOT_SUITABLE_FOR_STREAM_START) == 0) {
			size_t num_points = suitable_starting_points.size();
			if (num_points >= 2 &&
			    suitable_starting_points[num_points - 1] - suitable_starting_points[num_points - 2] < minimum_start_point_distance) {
				// p[n-1] - p[n-2] < 10 kB, so drop p[n-1].
				suitable_starting_points.pop_back();
			}
			suitable_starting_points.push_back(byte_position);
		}
		byte_position += queued_data_copy[i].data.iov_len;
	}

	add_data_raw(queued_data_copy);
	remove_obsolete_starting_points();
	for (size_t i = 0; i < queued_data_copy.size(); ++i) {
		char *data = reinterpret_cast<char *>(queued_data_copy[i].data.iov_base);
		delete[] data;
	}

	// We have more data, so wake up all clients.
	if (to_process.empty()) {
		swap(sleeping_clients, to_process);
	} else {
		to_process.insert(to_process.end(), sleeping_clients.begin(), sleeping_clients.end());
		sleeping_clients.clear();
	}
}