X-Git-Url: http://git.tuebingen.mpg.de/?p=paraslash.git;a=blobdiff_plain;f=vss.c;h=023b2c1d3cc8fcc0dcf23f0b5d2fc5c43487012f;hp=b73562f9733a98e1bea760ea109f1a7cf883d426;hb=HEAD;hpb=96c1602f28d5ef601bad10941cf079686fc67dfd

diff --git a/vss.c b/vss.c
index b73562f9..cd55851c 100644
--- a/vss.c
+++ b/vss.c
@@ -1,8 +1,4 @@
-/*
- * Copyright (C) 1997 Andre Noll <maan@tuebingen.mpg.de>
- *
- * Licensed under the GPL v2. For licencing details see COPYING.
- */
+/* Copyright (C) 1997 Andre Noll <maan@tuebingen.mpg.de>, see file COPYING. */
 
 /** \file vss.c The virtual streaming system.
  *
@@ -29,45 +25,25 @@
 #include "string.h"
 #include "afh.h"
 #include "afs.h"
-#include "server.h"
 #include "net.h"
+#include "server.h"
 #include "list.h"
-#include "send.h"
 #include "sched.h"
+#include "send.h"
 #include "vss.h"
 #include "ipc.h"
 #include "fd.h"
 
 extern struct misc_meta_data *mmd;
-
-extern void dccp_send_init(struct sender *);
-extern void http_send_init(struct sender *);
-extern void udp_send_init(struct sender *);
-
-/** The list of supported senders. */
-struct sender senders[] = {
-	{
-		.name = "http",
-		.init = http_send_init,
-	},
-	{
-		.name = "dccp",
-		.init = dccp_send_init,
-	},
-	{
-		.name = "udp",
-		.init = udp_send_init,
-	},
-	{
-		.name = NULL,
-	}
-};
+extern const struct sender udp_sender, dccp_sender, http_sender;
+const struct sender * const senders[] = {
+	&http_sender, &dccp_sender, &udp_sender, NULL};
 
 /** The possible states of the afs socket. */
 enum afs_socket_status {
 	/** Socket is inactive. */
 	AFS_SOCKET_READY,
-	/** Socket fd was included in the write fd set for select(). */
+	/** Socket fd was monitored for writing. */
 	AFS_SOCKET_CHECK_FOR_WRITE,
 	/** vss wrote a request to the socket and waits for reply from afs. */
 	AFS_SOCKET_AFD_PENDING
@@ -172,14 +148,10 @@ struct fec_client {
 	struct fec_group group;
 	/** The current slice. */
 	uint8_t current_slice_num;
-	/** The data to be FEC-encoded (point to a region within the mapped audio file). */
-	const unsigned char **src_data;
+	/** The data to be FEC-encoded.  */
+	unsigned char **src_data;
 	/** Last time an audio  header was sent. */
 	struct timeval next_header_time;
-	/** Used for the last source pointer of an audio file. */
-	unsigned char *extra_src_buf;
-	/** Needed for the last slice of the audio file header. */
-	unsigned char *extra_header_buf;
 	/** Extra slices needed to store largest chunk + header. */
 	int num_extra_slices;
 	/** Contains the FEC-encoded data. */
@@ -264,6 +236,21 @@ static bool need_data_slices(struct fec_client *fc, struct vss_task *vsst)
 	return false;
 }
 
+static int fc_num_data_slices(const struct fec_client *fc)
+{
+	return fc->fcp->data_slices_per_group + fc->num_extra_slices;
+}
+
+static int fc_num_slices(const struct fec_client *fc)
+{
+	return fc->fcp->slices_per_group + fc->num_extra_slices;
+}
+
+static int fc_num_redundant_slices(const struct fec_client *fc)
+{
+	return fc->fcp->slices_per_group - fc->fcp->data_slices_per_group;
+}
+
 static int num_slices(long unsigned bytes, int max_payload, int rs)
 {
 	int ret;
@@ -294,7 +281,7 @@ static void set_group_timing(struct fec_client *fc, struct vss_task *vsst)
 
 static int initialize_fec_client(struct fec_client *fc, struct vss_task *vsst)
 {
-	int k, n, ret;
+	int i, k, n, ret;
 	int hs, ds, rs; /* header/data/redundant slices */
 	struct fec_client_parms *fcp = fc->fcp;
 
@@ -302,7 +289,7 @@ static int initialize_fec_client(struct fec_client *fc, struct vss_task *vsst)
 	if (fcp->init_fec) {
 		/*
 		 * Set the maximum slice size to the Maximum Packet Size if the
-		 * transport protocol allows to determine this value. The user
+		 * transport protocol allows determination of this value. The user
 		 * can specify a slice size up to this value.
 		 */
 		ret = fcp->init_fec(fc->sc);
@@ -314,7 +301,17 @@ static int initialize_fec_client(struct fec_client *fc, struct vss_task *vsst)
 	if (fc->mps <= FEC_HEADER_SIZE)
 		return -ERRNO_TO_PARA_ERROR(EINVAL);
 
-	rs = fc->fcp->slices_per_group - fc->fcp->data_slices_per_group;
+	/* free previous buffers, if any */
+	if (fc->src_data) {
+		k = fc_num_data_slices(fc);
+		for (i = 0; i < k; i++)
+			free(fc->src_data[i]);
+		free(fc->src_data);
+		fc->src_data = NULL;
+	}
+	free(fc->enc_buf);
+
+	rs = fc_num_redundant_slices(fc);
 	ret = num_slices(vsst->header_len, fc->mps - FEC_HEADER_SIZE, rs);
 	if (ret < 0)
 		return ret;
@@ -330,17 +327,18 @@ static int initialize_fec_client(struct fec_client *fc, struct vss_task *vsst)
 	if (k < fc->fcp->data_slices_per_group)
 		k = fc->fcp->data_slices_per_group;
 	fc->num_extra_slices = k - fc->fcp->data_slices_per_group;
-	n = k + rs;
+	n = fc_num_slices(fc);
+	PARA_INFO_LOG("mps: %d, k: %d, n: %d, extra slices: %d\n",
+		fc->mps, k, n, fc->num_extra_slices);
+
 	fec_free(fc->parms);
 	ret = fec_new(k, n, &fc->parms);
 	if (ret < 0)
 		return ret;
-	PARA_INFO_LOG("mps: %d, k: %d, n: %d, extra slices: %d\n",
-		fc->mps, k, n, fc->num_extra_slices);
-	fc->src_data = para_realloc(fc->src_data, k * sizeof(char *));
-	fc->enc_buf = para_realloc(fc->enc_buf, fc->mps);
-	fc->extra_src_buf = para_realloc(fc->extra_src_buf, fc->mps);
-	fc->extra_header_buf = para_realloc(fc->extra_header_buf, fc->mps);
+	fc->src_data = arr_alloc(k, sizeof(char *));
+	for (i = 0; i < k; i++)
+		fc->src_data[i] = alloc(fc->mps);
+	fc->enc_buf = alloc(fc->mps);
 
 	fc->state = FEC_STATE_READY_TO_RUN;
 	fc->next_header_time.tv_sec = 0;
@@ -349,8 +347,8 @@ static int initialize_fec_client(struct fec_client *fc, struct vss_task *vsst)
 	return 1;
 }
 
-static void vss_get_chunk(int chunk_num, struct vss_task *vsst,
-		char **buf, size_t *sz)
+static int vss_get_chunk(int chunk_num, struct vss_task *vsst,
+		char **buf, uint32_t *len)
 {
 	int ret;
 
@@ -365,32 +363,33 @@ static void vss_get_chunk(int chunk_num, struct vss_task *vsst,
 	if (chunk_num == 0 && vsst->header_len > 0) {
 		assert(vsst->header_buf);
 		*buf = vsst->header_buf; /* stripped header */
-		*sz = vsst->header_len;
-		return;
+		*len = vsst->header_len;
+		return 0;
 	}
 	ret = afh_get_chunk(chunk_num, &mmd->afd.afhi,
 		mmd->afd.audio_format_id, vsst->map, vsst->mapsize,
-		(const char **)buf, sz, &vsst->afh_context);
+		(const char **)buf, len, &vsst->afh_context);
 	if (ret < 0) {
-		PARA_WARNING_LOG("could not get chunk %d: %s\n",
-			chunk_num, para_strerror(-ret));
 		*buf = NULL;
-		*sz = 0;
+		*len = 0;
 	}
+	return ret;
 }
 
-static void compute_group_size(struct vss_task *vsst, struct fec_group *g,
+static int compute_group_size(struct vss_task *vsst, struct fec_group *g,
 		int max_bytes)
 {
 	char *buf;
-	size_t len;
-	int i, max_chunks = PARA_MAX(1LU, 150 / tv2ms(vss_chunk_time()));
+	uint32_t len;
+	int ret, i, max_chunks = PARA_MAX(1LU, 150 / tv2ms(vss_chunk_time()));
 
 	if (g->first_chunk == 0) {
 		g->num_chunks = 1;
-		vss_get_chunk(0, vsst, &buf, &len);
+		ret = vss_get_chunk(0, vsst, &buf, &len);
+		if (ret < 0)
+			 return ret;
 		g->bytes = len;
-		return;
+		return 0;
 	}
 
 	g->num_chunks = 0;
@@ -408,14 +407,20 @@ static void compute_group_size(struct vss_task *vsst, struct fec_group *g,
 			break;
 		if (chunk_num >= mmd->afd.afhi.chunks_total) /* eof */
 			break;
-		vss_get_chunk(chunk_num, vsst, &buf, &len);
+		ret = vss_get_chunk(chunk_num, vsst, &buf, &len);
+		if (ret < 0)
+			 return ret;
 		if (g->bytes + len > max_bytes)
 			break;
 		/* Include this chunk */
 		g->bytes += len;
 		g->num_chunks++;
 	}
-	assert(g->num_chunks);
+	if (g->num_chunks == 0)
+		return -E_EOF;
+	PARA_DEBUG_LOG("group #%u: %u chunks, %u bytes total\n", g->num,
+		g->num_chunks, g->bytes);
+	return 1;
 }
 
 /*
@@ -468,8 +473,8 @@ static void compute_group_size(struct vss_task *vsst, struct fec_group *g,
 static int compute_slice_size(struct fec_client *fc, struct vss_task *vsst)
 {
 	struct fec_group *g = &fc->group;
-	int k = fc->fcp->data_slices_per_group + fc->num_extra_slices;
-	int n = fc->fcp->slices_per_group + fc->num_extra_slices;
+	int k = fc_num_data_slices(fc);
+	int n = fc_num_slices(fc);
 	int ret, k1, k2, h, d, min, max, sum;
 	int max_slice_bytes = fc->mps - FEC_HEADER_SIZE;
 	int max_group_bytes;
@@ -477,7 +482,9 @@ static int compute_slice_size(struct fec_client *fc, struct vss_task *vsst)
 	if (!need_audio_header(fc, vsst)) {
 		max_group_bytes = k * max_slice_bytes;
 		g->num_header_slices = 0;
-		compute_group_size(vsst, g, max_group_bytes);
+		ret = compute_group_size(vsst, g, max_group_bytes);
+		if (ret < 0)
+			return ret;
 		g->slice_bytes = DIV_ROUND_UP(g->bytes, k);
 		if (g->slice_bytes == 0)
 			g->slice_bytes = 1;
@@ -493,7 +500,9 @@ static int compute_slice_size(struct fec_client *fc, struct vss_task *vsst)
 	h = vsst->header_len;
 	max_group_bytes = (k - num_slices(h, max_slice_bytes, n - k))
 		* max_slice_bytes;
-	compute_group_size(vsst, g, max_group_bytes);
+	ret = compute_group_size(vsst, g, max_group_bytes);
+	if (ret < 0)
+		return ret;
 	d = g->bytes;
 	if (d == 0) {
 		g->slice_bytes = DIV_ROUND_UP(h, k);
@@ -528,9 +537,8 @@ static int compute_slice_size(struct fec_client *fc, struct vss_task *vsst)
 
 static int setup_next_fec_group(struct fec_client *fc, struct vss_task *vsst)
 {
-	int ret, i, k, n, data_slices;
-	size_t len;
-	char *buf, *p;
+	int ret, i, c;
+	size_t copy, src_copied, slice_copied;
 	struct fec_group *g = &fc->group;
 
 	if (fc->state == FEC_STATE_NONE) {
@@ -554,84 +562,63 @@ static int setup_next_fec_group(struct fec_client *fc, struct vss_task *vsst)
 		g->first_chunk += g->num_chunks;
 		g->num++;
 	}
-	k = fc->fcp->data_slices_per_group + fc->num_extra_slices;
-	n = fc->fcp->slices_per_group + fc->num_extra_slices;
-
 	compute_slice_size(fc, vsst);
 	assert(g->slice_bytes > 0);
-	ret = num_slices(g->bytes, g->slice_bytes, n - k);
-	if (ret < 0)
-		return ret;
-	data_slices = ret;
-	assert(g->num_header_slices + data_slices <= k);
 	fc->current_slice_num = 0;
 	if (g->num == 0)
 		set_group_timing(fc, vsst);
 	/* setup header slices */
-	buf = vsst->header_buf;
-	for (i = 0; i < g->num_header_slices; i++) {
-		uint32_t payload_size;
-		if (buf + g->slice_bytes <= vsst->header_buf + vsst->header_len) {
-			fc->src_data[i] = (const unsigned char *)buf;
-			buf += g->slice_bytes;
-			continue;
-		}
-		/*
-		 * Can not use vss->header_buf for this slice as it
-		 * goes beyond the buffer. This slice will not be fully
-		 * used.
-		 */
-		payload_size = vsst->header_buf + vsst->header_len - buf;
-		memcpy(fc->extra_header_buf, buf, payload_size);
-		if (payload_size < g->slice_bytes)
-			memset(fc->extra_header_buf + payload_size, 0,
-				g->slice_bytes - payload_size);
-		/*
-		 * There might be more than one header slice to fill although
-		 * only the first one will be used. Set all header slices to
-		 * our extra buffer.
-		 */
-		while (i < g->num_header_slices)
-			fc->src_data[i++] = fc->extra_header_buf;
-		break; /* we don't want i to be increased. */
+	for (i = 0, src_copied = 0; i < g->num_header_slices; i++) {
+		copy = PARA_MIN((size_t)g->slice_bytes, vsst->header_len - src_copied);
+		if (copy == 0)
+			break;
+		memcpy(fc->src_data[i], vsst->header_buf + src_copied, copy);
+		if (copy < g->slice_bytes)
+			memset(fc->src_data[i] + copy, 0, g->slice_bytes - copy);
+		src_copied += copy;
 	}
-
 	/*
-	 * Setup data slices. Note that for ogg streams chunk 0 points to a
-	 * buffer on the heap rather than to the mapped audio file.
+	 * There might be more than one header slice to fill although only the
+	 * first one will be used. Zero out any remaining header slices.
 	 */
-	vss_get_chunk(g->first_chunk, vsst, &buf, &len);
-	for (p = buf; i < g->num_header_slices + data_slices; i++) {
-		if (p + g->slice_bytes > buf + g->bytes) {
-			/*
-			 * We must make a copy for this slice since using p
-			 * directly would exceed the buffer.
-			 */
-			uint32_t payload_size = buf + g->bytes - p;
-			assert(payload_size + FEC_HEADER_SIZE <= fc->mps);
-			memcpy(fc->extra_src_buf, p, payload_size);
-			if (payload_size < g->slice_bytes)
-				memset(fc->extra_src_buf + payload_size, 0,
-					g->slice_bytes - payload_size);
-			fc->src_data[i] = fc->extra_src_buf;
-			i++;
-			break;
+	while (i < g->num_header_slices)
+		memset(fc->src_data[i++], 0, g->slice_bytes);
+
+	slice_copied = 0;
+	for (c = g->first_chunk; c < g->first_chunk + g->num_chunks; c++) {
+		char *buf;
+		uint32_t src_len;
+		ret = vss_get_chunk(c, vsst, &buf, &src_len);
+		if (ret < 0)
+			return ret;
+		if (src_len == 0)
+			continue;
+		src_copied = 0;
+		while (src_copied < src_len) {
+			copy = PARA_MIN((size_t)g->slice_bytes - slice_copied,
+				src_len - src_copied);
+			memcpy(fc->src_data[i] + slice_copied,
+				buf + src_copied, copy);
+			src_copied += copy;
+			slice_copied += copy;
+			if (slice_copied == g->slice_bytes) {
+				i++;
+				slice_copied = 0;
+			}
 		}
-		fc->src_data[i] = (const unsigned char *)p;
-		p += g->slice_bytes;
-	}
-	if (i < k) {
-		/* use arbitrary data for all remaining slices */
-		buf = vsst->map;
-		for (; i < k; i++)
-			fc->src_data[i] = (const unsigned char *)buf;
 	}
+	if (i < fc_num_data_slices(fc) && slice_copied < g->slice_bytes)
+		memset(fc->src_data[i] + slice_copied, 0,
+			 g->slice_bytes - slice_copied);
+	/* zero out remaining slices, if any */
+	while (++i < fc_num_data_slices(fc))
+		memset(fc->src_data[i], 0, g->slice_bytes);
 	PARA_DEBUG_LOG("FEC group %u: %u chunks (%u - %u), %u bytes\n",
 		g->num, g->num_chunks, g->first_chunk,
 		g->first_chunk + g->num_chunks - 1, g->bytes
 	);
 	PARA_DEBUG_LOG("slice_bytes: %d, %d header slices, %d data slices\n",
-		g->slice_bytes, g->num_header_slices, data_slices
+		g->slice_bytes, g->num_header_slices, fc_num_data_slices(fc)
 	);
 	return 1;
 }
@@ -651,8 +638,9 @@ static int compute_next_fec_slice(struct fec_client *fc, struct vss_task *vsst)
 		}
 	}
 	write_fec_header(fc, vsst);
-	fec_encode(fc->parms, fc->src_data, fc->enc_buf + FEC_HEADER_SIZE,
-		fc->current_slice_num, fc->group.slice_bytes);
+	fec_encode(fc->parms, (const unsigned char * const*)fc->src_data,
+		fc->enc_buf + FEC_HEADER_SIZE, fc->current_slice_num,
+		fc->group.slice_bytes);
 	return 1;
 }
 
@@ -683,7 +671,7 @@ size_t vss_get_fec_eof_packet(const char **buf)
 struct fec_client *vss_add_fec_client(struct sender_client *sc,
 				      struct fec_client_parms *fcp)
 {
-	struct fec_client *fc = para_calloc(sizeof(*fc));
+	struct fec_client *fc = zalloc(sizeof(*fc));
 
 	fc->sc  = sc;
 	fc->fcp = fcp;
@@ -698,11 +686,15 @@ struct fec_client *vss_add_fec_client(struct sender_client *sc,
  */
 void vss_del_fec_client(struct fec_client *fc)
 {
+	int i;
+
 	list_del(&fc->node);
-	free(fc->src_data);
 	free(fc->enc_buf);
-	free(fc->extra_src_buf);
-	free(fc->extra_header_buf);
+	if (fc->src_data) {
+		for (i = 0; i < fc_num_data_slices(fc); i++)
+			free(fc->src_data[i]);
+		free(fc->src_data);
+	}
 	fec_free(fc->parms);
 	free(fc);
 }
@@ -835,7 +827,7 @@ static void vss_compute_timeout(struct sched *s, struct vss_task *vsst)
 	if (sched_request_barrier(&vsst->data_send_barrier, s) == 1)
 		return;
 	/*
-	 * Compute the select timeout as the minimal time until the next
+	 * Compute the I/O timeout as the minimal time until the next
 	 * chunk/slice is due for any client.
 	 */
 	compute_chunk_time(mmd->chunks_sent, &mmd->afd.afhi.chunk_tv,
@@ -853,7 +845,6 @@ static void vss_compute_timeout(struct sched *s, struct vss_task *vsst)
 
 static void vss_eof(struct vss_task *vsst)
 {
-
 	if (!vsst->map)
 		return;
 	if (mmd->new_vss_status_flags & VSS_NOMORE)
@@ -864,8 +855,8 @@ static void vss_eof(struct vss_task *vsst)
 	para_munmap(vsst->map, vsst->mapsize);
 	vsst->map = NULL;
 	mmd->chunks_sent = 0;
-	//mmd->offset = 0;
 	mmd->afd.afhi.seconds_total = 0;
+	mmd->afd.afhi.chunks_total = 0;
 	mmd->afd.afhi.chunk_tv.tv_sec = 0;
 	mmd->afd.afhi.chunk_tv.tv_usec = 0;
 	free(mmd->afd.afhi.chunk_table);
@@ -901,21 +892,21 @@ static void set_mmd_offset(void)
 	mmd->offset = tv2ms(&offset);
 }
 
-static void vss_pre_select(struct sched *s, void *context)
+static void vss_pre_monitor(struct sched *s, void *context)
 {
 	int i;
 	struct vss_task *vsst = context;
 
 	if (need_to_request_new_audio_file(vsst)) {
 		PARA_DEBUG_LOG("ready and playing, but no audio file\n");
-		para_fd_set(vsst->afs_socket, &s->wfds, &s->max_fileno);
+		sched_monitor_writefd(vsst->afs_socket, s);
 		vsst->afsss = AFS_SOCKET_CHECK_FOR_WRITE;
 	} else
-		para_fd_set(vsst->afs_socket, &s->rfds, &s->max_fileno);
-	for (i = 0; senders[i].name; i++) {
-		if (!senders[i].pre_select)
+		sched_monitor_readfd(vsst->afs_socket, s);
+	FOR_EACH_SENDER(i) {
+		if (!senders[i]->pre_monitor)
 			continue;
-		senders[i].pre_select(&s->max_fileno, &s->rfds, &s->wfds);
+		senders[i]->pre_monitor(s);
 	}
 	vss_compute_timeout(s, vsst);
 }
@@ -955,16 +946,17 @@ static int recv_afs_msg(int afs_socket, int *fd, uint32_t *code, uint32_t *data)
 }
 
 #ifndef MAP_POPULATE
+/** As of 2018, neither FreeBSD-11.2 nor NetBSD-8.0 have MAP_POPULATE. */
 #define MAP_POPULATE 0
 #endif
 
-static void recv_afs_result(struct vss_task *vsst, fd_set *rfds)
+static void recv_afs_result(struct vss_task *vsst, const struct sched *s)
 {
 	int ret, passed_fd, shmid;
 	uint32_t afs_code = 0, afs_data = 0;
 	struct stat statbuf;
 
-	if (!FD_ISSET(vsst->afs_socket, rfds))
+	if (!sched_read_ok(vsst->afs_socket, s))
 		return;
 	ret = recv_afs_msg(vsst->afs_socket, &passed_fd, &afs_code, &afs_data);
 	if (ret == -ERRNO_TO_PARA_ERROR(EAGAIN))
@@ -972,11 +964,17 @@ static void recv_afs_result(struct vss_task *vsst, fd_set *rfds)
 	if (ret < 0)
 		goto err;
 	vsst->afsss = AFS_SOCKET_READY;
-	PARA_DEBUG_LOG("fd: %d, code: %u, shmid: %u\n", passed_fd, afs_code,
-		afs_data);
+	if (afs_code == NO_ADMISSIBLE_FILES) {
+		PARA_NOTICE_LOG("no admissible files\n");
+		ret = 0;
+		goto err;
+	}
 	ret = -E_NOFD;
-	if (afs_code != NEXT_AUDIO_FILE)
+	if (afs_code != NEXT_AUDIO_FILE) {
+		PARA_ERROR_LOG("afs code: %u, expected: %d\n", afs_code,
+			NEXT_AUDIO_FILE);
 		goto err;
+	}
 	if (passed_fd < 0)
 		goto err;
 	shmid = afs_data;
@@ -991,7 +989,7 @@ static void recv_afs_result(struct vss_task *vsst, fd_set *rfds)
 		goto err;
 	}
 	ret = para_mmap(statbuf.st_size, PROT_READ, MAP_PRIVATE | MAP_POPULATE,
-		passed_fd, 0, &vsst->map);
+		passed_fd, &vsst->map);
 	if (ret < 0)
 		goto err;
 	vsst->mapsize = statbuf.st_size;
@@ -1007,26 +1005,26 @@ static void recv_afs_result(struct vss_task *vsst, fd_set *rfds)
 	return;
 err:
 	free(mmd->afd.afhi.chunk_table);
+	mmd->afd.afhi.chunk_table = NULL;
 	if (passed_fd >= 0)
 		close(passed_fd);
-	PARA_ERROR_LOG("%s\n", para_strerror(-ret));
+	if (ret < 0)
+		PARA_ERROR_LOG("%s\n", para_strerror(-ret));
 	mmd->new_vss_status_flags = VSS_NEXT;
 }
 
 /**
- * Main sending function.
- *
- * This function gets called from vss_post_select(). It checks whether the next
- * chunk of data should be pushed out. It obtains a pointer to the data to be
- * sent out as well as its length from mmd->afd.afhi. This information is then
- * passed to each supported sender's send() function as well as to the send()
- * functions of each registered fec client.
+ * If the next chunk needs to be sent, pass a pointer to the chunk data to all
+ * registered fec clients and to each sender's ->send() method.
  */
 static void vss_send(struct vss_task *vsst)
 {
-	int i, fec_active = 0;
+	int i, ret;
+	bool fec_active = false;
 	struct timeval due;
 	struct fec_client *fc, *tmp_fc;
+	char *buf;
+	uint32_t len;
 
 	if (!vsst->map || !vss_playing())
 		return;
@@ -1038,7 +1036,7 @@ static void vss_send(struct vss_task *vsst)
 		if (fc->state == FEC_STATE_DISABLED)
 			continue;
 		if (!next_slice_is_due(fc, NULL)) {
-			fec_active = 1;
+			fec_active = true;
 			continue;
 		}
 		if (compute_next_fec_slice(fc, vsst) <= 0)
@@ -1048,7 +1046,7 @@ static void vss_send(struct vss_task *vsst)
 		fc->current_slice_num++;
 		fc->fcp->send_fec(fc->sc, (char *)fc->enc_buf,
 			fc->group.slice_bytes + FEC_HEADER_SIZE);
-		fec_active = 1;
+		fec_active = true;
 	}
 	if (mmd->current_chunk >= mmd->afd.afhi.chunks_total) { /* eof */
 		if (!fec_active)
@@ -1057,62 +1055,49 @@ static void vss_send(struct vss_task *vsst)
 	}
 	compute_chunk_time(mmd->chunks_sent, &mmd->afd.afhi.chunk_tv,
 		&mmd->stream_start, &due);
-	if (tv_diff(&due, now, NULL) <= 0) {
-		char *buf;
-		size_t len;
-
-		if (!mmd->chunks_sent) {
-			mmd->stream_start = *now;
-			mmd->events++;
-			set_mmd_offset();
-		}
+	if (tv_diff(&due, now, NULL) > 0)
+		return;
+	if (!mmd->chunks_sent) {
+		mmd->stream_start = *now;
+		mmd->events++;
+		set_mmd_offset();
+	}
+	ret = vss_get_chunk(mmd->current_chunk, vsst, &buf, &len);
+	if (ret < 0) {
+		PARA_ERROR_LOG("could not get chunk %lu: %s\n",
+			mmd->current_chunk, para_strerror(-ret));
+	} else {
 		/*
-		 * We call the send function also in case of empty chunks as
-		 * they might have still some data queued which can be sent in
-		 * this case.
+		 * We call ->send() even if len is zero because senders might
+		 * have data queued which can be sent now.
 		 */
-		vss_get_chunk(mmd->current_chunk, vsst, &buf, &len);
-		for (i = 0; senders[i].name; i++) {
-			if (!senders[i].send)
+		FOR_EACH_SENDER(i) {
+			if (!senders[i]->send)
 				continue;
-			senders[i].send(mmd->current_chunk, mmd->chunks_sent,
+			senders[i]->send(mmd->current_chunk, mmd->chunks_sent,
 				buf, len, vsst->header_buf, vsst->header_len);
 		}
-		/*
-		 * Prefault next chunk(s)
-		 *
-		 * If the backing device of the memory-mapped audio file is
-		 * slow and read-ahead is turned off or prevented for some
-		 * reason, e.g. due to memory pressure, it may take much longer
-		 * than the chunk interval to get the next chunk on the wire,
-		 * causing buffer underruns on the client side. Mapping the
-		 * file with MAP_POPULATE seems to help a bit, but it does not
-		 * eliminate the delays completely. Moreover, it is supported
-		 * only on Linux. So we do our own read-ahead here.
-		 */
-		if (mmd->current_chunk > 0) { /* chunk 0 might be on the heap */
-			buf += len;
-			for (i = 0; i < 5 && buf < vsst->map + vsst->mapsize; i++) {
-				__a_unused volatile char x = *buf;
-				buf += 4096;
-			}
-		}
-		mmd->chunks_sent++;
-		mmd->current_chunk++;
 	}
+	mmd->chunks_sent++;
+	mmd->current_chunk++;
 }
 
-static int vss_post_select(struct sched *s, void *context)
+static int vss_post_monitor(struct sched *s, void *context)
 {
 	int ret, i;
 	struct vss_task *vsst = context;
 
+	ret = task_get_notification(vsst->task);
+	if (ret < 0) {
+		afh_free_header(vsst->header_buf, mmd->afd.audio_format_id);
+		return ret;
+	}
 	if (!vsst->map || vss_next() || vss_paused() || vss_repos()) {
 		/* shut down senders and fec clients */
 		struct fec_client *fc, *tmp;
-		for (i = 0; senders[i].name; i++)
-			if (senders[i].shutdown_clients)
-				senders[i].shutdown_clients();
+		FOR_EACH_SENDER(i)
+			if (senders[i]->shutdown_clients)
+				senders[i]->shutdown_clients();
 		list_for_each_entry_safe(fc, tmp, &fec_client_list, node)
 			fc->state = FEC_STATE_NONE;
 		mmd->stream_start.tv_sec = 0;
@@ -1138,8 +1123,8 @@ static int vss_post_select(struct sched *s, void *context)
 		int num = mmd->sender_cmd_data.cmd_num,
 			sender_num = mmd->sender_cmd_data.sender_num;
 
-		if (senders[sender_num].client_cmds[num]) {
-			ret = senders[sender_num].client_cmds[num]
+		if (senders[sender_num]->client_cmds[num]) {
+			ret = senders[sender_num]->client_cmds[num]
 				(&mmd->sender_cmd_data);
 			if (ret < 0)
 				PARA_ERROR_LOG("%s\n", para_strerror(-ret));
@@ -1147,19 +1132,19 @@ static int vss_post_select(struct sched *s, void *context)
 		mmd->sender_cmd_data.cmd_num = -1;
 	}
 	if (vsst->afsss != AFS_SOCKET_CHECK_FOR_WRITE)
-		recv_afs_result(vsst, &s->rfds);
-	else if (FD_ISSET(vsst->afs_socket, &s->wfds)) {
-		PARA_NOTICE_LOG("requesting new fd from afs\n");
+		recv_afs_result(vsst, s);
+	else if (sched_write_ok(vsst->afs_socket, s)) {
+		PARA_INFO_LOG("requesting new fd from afs\n");
 		ret = write_buffer(vsst->afs_socket, "new");
 		if (ret < 0)
 			PARA_CRIT_LOG("%s\n", para_strerror(-ret));
 		else
 			vsst->afsss = AFS_SOCKET_AFD_PENDING;
 	}
-	for (i = 0; senders[i].name; i++) {
-		if (!senders[i].post_select)
+	FOR_EACH_SENDER(i) {
+		if (!senders[i]->post_monitor)
 			continue;
-		senders[i].post_select(&s->rfds, &s->wfds);
+		senders[i]->post_monitor(s);
 	}
 	if ((vss_playing() && !(mmd->vss_status_flags & VSS_PLAYING)) ||
 			(vss_next() && vss_playing()))
@@ -1177,24 +1162,21 @@ static int vss_post_select(struct sched *s, void *context)
  * This also initializes all supported senders and starts streaming
  * if the --autoplay command line flag was given.
  */
-void init_vss_task(int afs_socket, struct sched *s)
+void vss_init(int afs_socket, struct sched *s)
 {
 	static struct vss_task vss_task_struct, *vsst = &vss_task_struct;
 	int i;
-	char *hn = para_hostname(), *home = para_homedir();
 	long unsigned announce_time = OPT_UINT32_VAL(ANNOUNCE_TIME),
 		autoplay_delay = OPT_UINT32_VAL(AUTOPLAY_DELAY);
 	vsst->header_interval.tv_sec = 5; /* should this be configurable? */
 	vsst->afs_socket = afs_socket;
 	ms2tv(announce_time, &vsst->announce_tv);
 	PARA_INFO_LOG("announce timeval: %lums\n", tv2ms(&vsst->announce_tv));
-	INIT_LIST_HEAD(&fec_client_list);
-	for (i = 0; senders[i].name; i++) {
-		PARA_NOTICE_LOG("initializing %s sender\n", senders[i].name);
-		senders[i].init(&senders[i]);
+	init_list_head(&fec_client_list);
+	FOR_EACH_SENDER(i) {
+		PARA_NOTICE_LOG("initializing %s sender\n", senders[i]->name);
+		senders[i]->init();
 	}
-	free(hn);
-	free(home);
 	mmd->sender_cmd_data.cmd_num = -1;
 	if (OPT_GIVEN(AUTOPLAY)) {
 		struct timeval tmp;
@@ -1206,9 +1188,29 @@ void init_vss_task(int afs_socket, struct sched *s)
 			&vsst->data_send_barrier);
 	}
 	vsst->task = task_register(&(struct task_info) {
-		.name = "vss task",
-		.pre_select = vss_pre_select,
-		.post_select = vss_post_select,
+		.name = "vss",
+		.pre_monitor = vss_pre_monitor,
+		.post_monitor = vss_post_monitor,
 		.context = vsst,
 	}, s);
 }
+
+/**
+ * Turn off the virtual streaming system.
+ *
+ * This is only executed on exit. It calls the ->shutdown method of all senders.
+ */
+void vss_shutdown(void)
+{
+	int i;
+	bool is_command_handler = process_is_command_handler();
+
+	FOR_EACH_SENDER(i) {
+		if (!senders[i]->shutdown)
+			continue;
+		if (!is_command_handler)
+			PARA_NOTICE_LOG("shutting down %s sender\n",
+				senders[i]->name);
+		senders[i]->shutdown();
+	}
+}