add ustream, an api for stream buffer management

CMakeLists.txt

@@ -10,7 +10,7 @@ IF(APPLE)
   LINK_DIRECTORIES(/opt/local/lib)
 ENDIF()
 
-SET(SOURCES avl.c avl-cmp.c blob.c blobmsg.c uloop.c usock.c vlist.c)
+SET(SOURCES avl.c avl-cmp.c blob.c blobmsg.c uloop.c usock.c ustream.c ustream-fd.c vlist.c)
 
 ADD_LIBRARY(ubox SHARED ${SOURCES})
 

ustream-fd.c

@@ -0,0 +1,138 @@
+/*
+ * ustream - library for stream buffer management
+ *
+ * Copyright (C) 2012 Felix Fietkau <nbd@openwrt.org>
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include <unistd.h>
+#include <errno.h>
+#include <stdio.h>
+#include "ustream.h"
+
+static void ustream_fd_set_uloop(struct ustream *s)
+{
+	struct ustream_fd *sf = container_of(s, struct ustream_fd, stream);
+	struct ustream_buf *buf;
+	unsigned int flags = ULOOP_EDGE_TRIGGER;
+
+	if (!s->read_blocked && !s->eof)
+		flags |= ULOOP_READ;
+
+	buf = s->w.head;
+	if (buf && s->w.data_bytes && !s->write_error)
+		flags |= ULOOP_WRITE;
+
+	uloop_fd_add(&sf->fd, flags);
+
+	if (flags & ULOOP_READ)
+		sf->fd.cb(&sf->fd, ULOOP_READ);
+}
+
+static void ustream_fd_read_pending(struct ustream_fd *sf, bool *update)
+{
+	struct ustream *s = &sf->stream;
+	int buflen = 0;
+	ssize_t len;
+	char *buf;
+
+	do {
+		buf = ustream_reserve(s, 1, &buflen);
+		if (!buf)
+			break;
+
+		len = read(sf->fd.fd, buf, buflen);
+		if (!len) {
+			sf->fd.eof = true;
+			return;
+		}
+
+		if (len < 0) {
+			if (errno == EINTR)
+				continue;
+
+			if (errno == EAGAIN)
+				return;
+		}
+
+		ustream_fill_read(s, len);
+	} while (1);
+}
+
+static int ustream_fd_write(struct ustream *s, const char *buf, int buflen, bool more)
+{
+	struct ustream_fd *sf = container_of(s, struct ustream_fd, stream);
+	ssize_t len;
+
+	if (!buflen)
+		return 0;
+
+retry:
+	len = write(sf->fd.fd, buf, buflen);
+	if (!len)
+		goto retry;
+
+	if (len < 0) {
+		if (errno == EINTR)
+			goto retry;
+
+		if (errno == EAGAIN || errno == EWOULDBLOCK)
+			return 0;
+	}
+
+	return len;
+}
+
+static void ustream_uloop_cb(struct uloop_fd *fd, unsigned int events)
+{
+	struct ustream_fd *sf = container_of(fd, struct ustream_fd, fd);
+	struct ustream *s = &sf->stream;
+	bool update = false;
+
+	if (events & ULOOP_READ)
+		ustream_fd_read_pending(sf, &update);
+
+	if (events & ULOOP_WRITE) {
+		if (ustream_write_pending(s))
+			ustream_fd_set_uloop(s);
+	}
+
+	if (!s->eof && fd->eof) {
+		s->eof = true;
+		ustream_fd_set_uloop(s);
+		ustream_state_change(s);
+	}
+}
+
+
+static void ustream_fd_free(struct ustream *s)
+{
+	struct ustream_fd *sf = container_of(s, struct ustream_fd, stream);
+
+	uloop_fd_delete(&sf->fd);
+}
+
+void ustream_fd_init(struct ustream_fd *sf, int fd)
+{
+	struct ustream *s = &sf->stream;
+
+	ustream_init_defaults(s);
+
+	sf->fd.fd = fd;
+	sf->fd.cb = ustream_uloop_cb;
+	s->set_read_blocked = ustream_fd_set_uloop;
+	s->write = ustream_fd_write;
+	s->free = ustream_fd_free;
+	ustream_fd_set_uloop(s);
+}

ustream.c

@@ -0,0 +1,500 @@
+/*
+ * ustream - library for stream buffer management
+ *
+ * Copyright (C) 2012 Felix Fietkau <nbd@openwrt.org>
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <stdio.h>
+#include <stdarg.h>
+
+#include "ustream.h"
+
+void ustream_init_buf(struct ustream_buf *buf, int len)
+{
+	if (!len)
+		abort();
+
+	memset(buf, 0, sizeof(*buf));
+	buf->data = buf->tail = buf->head;
+	buf->end = buf->head + len;
+	*buf->head = 0;
+}
+
+static void ustream_add_buf(struct ustream_buf_list *l, struct ustream_buf *buf)
+{
+	if (!l->tail)
+		l->head = buf;
+	else
+		l->tail->next = buf;
+
+	buf->next = NULL;
+	l->tail = buf;
+	if (!l->data_tail)
+		l->data_tail = l->head;
+}
+
+static bool ustream_can_alloc(struct ustream_buf_list *l)
+{
+	if (l->max_buffers <= 0)
+		return true;
+
+	return (l->buffers < l->max_buffers);
+}
+
+static int ustream_alloc_default(struct ustream *s, struct ustream_buf_list *l)
+{
+	struct ustream_buf *buf;
+
+	if (!ustream_can_alloc(l))
+		return -1;
+
+	buf = malloc(sizeof(*buf) + l->buffer_len + s->string_data);
+	ustream_init_buf(buf, l->buffer_len);
+	ustream_add_buf(l, buf);
+
+	return 0;
+}
+
+static void ustream_free_buffers(struct ustream_buf_list *l)
+{
+	struct ustream_buf *buf = l->head;
+
+	while (buf) {
+		struct ustream_buf *next = buf->next;
+
+		free(buf);
+		buf = next;
+	}
+	l->head = NULL;
+	l->tail = NULL;
+	l->data_tail = NULL;
+}
+
+void ustream_free(struct ustream *s)
+{
+	if (s->free)
+		s->free(s);
+
+	uloop_timeout_cancel(&s->state_change);
+	ustream_free_buffers(&s->r);
+	ustream_free_buffers(&s->w);
+	s->write_error = false;
+	s->eof = false;
+	s->read_blocked = 0;
+}
+
+static void ustream_state_change_cb(struct uloop_timeout *t)
+{
+	struct ustream *s = container_of(t, struct ustream, state_change);
+
+	if (s->write_error)
+		ustream_free_buffers(&s->w);
+	s->notify_state(s);
+}
+
+void ustream_init_defaults(struct ustream *s)
+{
+#define DEFAULT_SET(_f, _default)	\
+	do {				\
+		if (!_f)		\
+			_f = _default;	\
+	} while(0)
+
+	DEFAULT_SET(s->r.alloc, ustream_alloc_default);
+	DEFAULT_SET(s->w.alloc, ustream_alloc_default);
+
+	DEFAULT_SET(s->r.min_buffers, 1);
+	DEFAULT_SET(s->r.max_buffers, 1);
+	DEFAULT_SET(s->r.buffer_len, 4096);
+
+	DEFAULT_SET(s->w.min_buffers, 2);
+	DEFAULT_SET(s->w.max_buffers, -1);
+	DEFAULT_SET(s->w.buffer_len, 256);
+
+#undef DEFAULT_SET
+
+	s->state_change.cb = ustream_state_change_cb;
+}
+
+static bool ustream_should_move(struct ustream_buf_list *l, struct ustream_buf *buf, int len)
+{
+	int maxlen;
+	int offset;
+
+	if (buf->data == buf->head)
+		return false;
+
+	maxlen = buf->end - buf->head;
+	offset = buf->data - buf->head;
+
+	if (offset > maxlen / 2)
+		return true;
+
+	if (buf->tail - buf->data < 32 && offset > maxlen / 4)
+		return true;
+
+	if (buf != l->tail || ustream_can_alloc(l))
+		return false;
+
+	return (buf->end - buf->tail < len);
+}
+
+static void ustream_free_buf(struct ustream_buf_list *l, struct ustream_buf *buf)
+{
+	if (buf == l->head)
+		l->head = buf->next;
+
+	if (buf == l->data_tail)
+		l->data_tail = buf->next;
+
+	if (buf == l->tail)
+		l->tail = NULL;
+
+	if (--l->buffers >= l->min_buffers) {
+		free(buf);
+		return;
+	}
+
+	/* recycle */
+	ustream_init_buf(buf, buf->end - buf->head);
+	ustream_add_buf(l, buf);
+}
+
+static void __ustream_set_read_blocked(struct ustream *s, unsigned char val)
+{
+	bool changed = !!s->read_blocked != !!val;
+
+	s->read_blocked = val;
+	if (changed)
+		s->set_read_blocked(s);
+}
+
+void ustream_set_read_blocked(struct ustream *s, bool set)
+{
+	unsigned char val = s->read_blocked & ~READ_BLOCKED_USER;
+
+	if (set)
+		val |= READ_BLOCKED_USER;
+
+	__ustream_set_read_blocked(s, val);
+}
+
+void ustream_consume(struct ustream *s, int len)
+{
+	struct ustream_buf *buf = s->r.head;
+
+	if (!len)
+		return;
+
+	s->r.data_bytes -= len;
+	if (s->r.data_bytes < 0)
+		abort();
+
+	do {
+		struct ustream_buf *next = buf->next;
+		int buf_len = buf->tail - buf->data;
+
+		if (len < buf_len) {
+			buf->data += len;
+			break;
+		}
+
+		len -= buf_len;
+		ustream_free_buf(&s->r, buf);
+		buf = next;
+	} while(len);
+
+	__ustream_set_read_blocked(s, s->read_blocked & ~READ_BLOCKED_FULL);
+}
+
+static void ustream_fixup_string(struct ustream *s, struct ustream_buf *buf)
+{
+	if (!s->string_data)
+		return;
+
+	*buf->tail = 0;
+}
+
+static bool ustream_prepare_buf(struct ustream *s, struct ustream_buf_list *l, int len)
+{
+	struct ustream_buf *buf;
+
+	buf = l->data_tail;
+	if (buf) {
+		if (ustream_should_move(l, buf, len)) {
+			int len = buf->tail - buf->data;
+
+			memmove(buf->head, buf->data, len);
+			buf->data = buf->head;
+			buf->tail = buf->data + len;
+
+			if (l == &s->r)
+				ustream_fixup_string(s, buf);
+		}
+		if (buf->tail != buf->end)
+			return true;
+	}
+
+	if (buf && buf->next) {
+		l->data_tail = buf->next;
+		return true;
+	}
+
+	if (!ustream_can_alloc(l))
+		return false;
+
+	if (l->alloc(s, l) < 0)
+		return false;
+
+	l->data_tail = l->tail;
+	return true;
+}
+
+char *ustream_reserve(struct ustream *s, int len, int *maxlen)
+{
+	struct ustream_buf *buf = s->r.head;
+
+	if (!ustream_prepare_buf(s, &s->r, len)) {
+		__ustream_set_read_blocked(s, s->read_blocked | READ_BLOCKED_FULL);
+		*maxlen = 0;
+		return NULL;
+	}
+
+	buf = s->r.data_tail;
+	*maxlen = buf->end - buf->tail;
+	return buf->tail;
+}
+
+void ustream_fill_read(struct ustream *s, int len)
+{
+	struct ustream_buf *buf = s->r.data_tail;
+	int n = len;
+	int maxlen;
+
+	s->r.data_bytes += len;
+	do {
+		if (!buf)
+			abort();
+
+		maxlen = buf->end - buf->tail;
+		if (len < maxlen)
+			maxlen = len;
+
+		len -= maxlen;
+		buf->tail += maxlen;
+		ustream_fixup_string(s, buf);
+
+		s->r.data_tail = buf;
+		buf = buf->next;
+	} while (len);
+
+	if (s->notify_read)
+		s->notify_read(s, n);
+}
+
+char *ustream_get_read_buf(struct ustream *s, int *buflen)
+{
+	char *data;
+	int len;
+
+	if (s->r.head) {
+		len = s->r.head->tail - s->r.head->data;
+		data = s->r.head->data;
+	} else {
+		len = 0;
+		data = NULL;
+	}
+
+	if (buflen)
+		*buflen = len;
+
+	return data;
+}
+
+static void ustream_write_error(struct ustream *s)
+{
+	s->write_error = true;
+	ustream_state_change(s);
+}
+
+bool ustream_write_pending(struct ustream *s)
+{
+	struct ustream_buf *buf = s->w.head;
+	int wr = 0, len;
+
+	if (s->write_error)
+		return false;
+
+	while (buf) {
+		struct ustream_buf *next = buf->next;
+		int maxlen = buf->tail - buf->data;
+
+		len = s->write(s, buf->data, maxlen, !!buf->next);
+		if (len < 0) {
+			ustream_write_error(s);
+			break;
+		}
+
+		if (len == 0)
+			break;
+
+		wr += len;
+		s->w.data_bytes -= len;
+		if (len < maxlen) {
+			buf->data += len;
+			break;
+		}
+
+		ustream_free_buf(&s->w, buf);
+		buf = next;
+	}
+
+	if (s->notify_write)
+		s->notify_write(s, wr);
+
+	if (s->eof && wr && !s->w.data_bytes)
+		ustream_state_change(s);
+
+	return !s->w.data_bytes;
+}
+
+static int ustream_write_buffered(struct ustream *s, const char *data, int len, int wr)
+{
+	struct ustream_buf_list *l = &s->w;
+	struct ustream_buf *buf;
+	int maxlen;
+
+	while (len) {
+		if (!ustream_prepare_buf(s, &s->w, len))
+			break;
+
+		buf = l->data_tail;
+
+		maxlen = buf->end - buf->tail;
+		if (maxlen > len)
+			maxlen = len;
+
+		memcpy(buf->tail, data, maxlen);
+		buf->tail += maxlen;
+		data += maxlen;
+		len -= maxlen;
+		wr += maxlen;
+		l->data_bytes += maxlen;
+	}
+
+	return wr;
+}
+
+int ustream_write(struct ustream *s, const char *data, int len, bool more)
+{
+	struct ustream_buf_list *l = &s->w;
+	int wr;
+
+	if (s->write_error)
+		return 0;
+
+	if (!l->data_bytes) {
+		wr = s->write(s, data, len, more);
+		if (wr == len)
+			return wr;
+
+		if (wr < 0) {
+			ustream_write_error(s);
+			return wr;
+		}
+
+		data += wr;
+		len -= wr;
+	}
+
+	return ustream_write_buffered(s, data, len, wr);
+}
+
+#define MAX_STACK_BUFLEN	256
+
+int ustream_vprintf(struct ustream *s, const char *format, va_list arg)
+{
+	struct ustream_buf_list *l = &s->w;
+	char *buf;
+	va_list arg2;
+	int wr, maxlen, buflen;
+
+	if (!l->data_bytes) {
+		buf = alloca(MAX_STACK_BUFLEN);
+		va_copy(arg2, arg);
+		maxlen = vsnprintf(buf, MAX_STACK_BUFLEN, format, arg2);
+		va_end(arg2);
+		if (maxlen < MAX_STACK_BUFLEN) {
+			wr = s->write(s, buf, maxlen, false);
+			if (wr < 0) {
+				ustream_write_error(s);
+				return wr;
+			}
+			if (wr == maxlen)
+				return wr;
+
+			buf += wr;
+			maxlen -= wr;
+			return ustream_write_buffered(s, buf, maxlen, wr);
+		} else {
+			buf = malloc(maxlen + 1);
+			wr = vsnprintf(buf, maxlen + 1, format, arg);
+			wr = ustream_write(s, buf, wr, false);
+			free(buf);
+			return wr;
+		}
+	}
+
+	if (!ustream_prepare_buf(s, l, 1))
+		return 0;
+
+	buf = l->data_tail->tail;
+	buflen = l->data_tail->end - buf;
+
+	va_copy(arg2, arg);
+	maxlen = vsnprintf(buf, buflen, format, arg2);
+	va_end(arg2);
+
+	wr = maxlen;
+	if (wr >= buflen)
+		wr = buflen - 1;
+
+	l->data_tail->tail += wr;
+	l->data_bytes += wr;
+	if (maxlen < buflen)
+		return wr;
+
+	buf = malloc(maxlen + 1);
+	maxlen = vsnprintf(buf, maxlen + 1, format, arg);
+	wr = ustream_write_buffered(s, buf + wr, maxlen - wr, wr);
+	free(buf);
+
+	return wr;
+}
+
+int ustream_printf(struct ustream *s, const char *format, ...)
+{
+	va_list arg;
+	int ret;
+
+	va_start(arg, format);
+	ret = ustream_vprintf(s, format, arg);
+	va_end(arg);
+
+	return ret;
+}

ustream.h

@@ -0,0 +1,183 @@
+/*
+ * ustream - library for stream buffer management
+ *
+ * Copyright (C) 2012 Felix Fietkau <nbd@openwrt.org>
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#ifndef __USTREAM_H
+#define __USTREAM_H
+
+#include "uloop.h"
+
+struct ustream;
+struct ustream_buf;
+
+enum read_blocked_reason {
+	READ_BLOCKED_USER = (1 << 0),
+	READ_BLOCKED_FULL = (1 << 1),
+};
+
+struct ustream_buf_list {
+	struct ustream_buf *head;
+	struct ustream_buf *data_tail;
+	struct ustream_buf *tail;
+
+	int (*alloc)(struct ustream *s, struct ustream_buf_list *l);
+
+	int data_bytes;
+
+	int min_buffers;
+	int max_buffers;
+	int buffer_len;
+
+	int buffers;
+};
+
+struct ustream {
+	struct ustream_buf_list r, w;
+	struct uloop_timeout state_change;
+
+	/*
+	 * notify_read:
+	 * called by the ustream core to notify that new data is available
+	 * for reading.
+	 * must not free the ustream from this callback
+	 */
+	void (*notify_read)(struct ustream *s, int bytes_new);
+
+	/*
+	 * notify_write: (optional)
+	 * called by the ustream core to notify that some buffered data has
+	 * been written to the stream.
+	 * must not free the ustream from this callback
+	 */
+	void (*notify_write)(struct ustream *s, int bytes);
+
+	/*
+	 * notify_state:
+	 * called by the ustream implementation to notify that the read
+	 * side of the stream is closed (eof is set) or there was a write
+	 * error (write_error is set).
+	 * will be called again after the write buffer has been emptied when
+	 * the read side has hit EOF.
+	 */
+	void (*notify_state)(struct ustream *s);
+
+	/*
+	 * write:
+	 * must be defined by ustream implementation, accepts new write data.
+	 * 'more' is used to indicate that a subsequent call will provide more
+	 * data (useful for aggregating writes)
+	 * returns the number of bytes accepted, or -1 if no more writes can
+	 * be accepted (link error)
+	 */
+	int (*write)(struct ustream *s, const char *buf, int len, bool more);
+
+	/*
+	 * free: (optional)
+	 * defined by ustream implementation, tears down the ustream and frees data
+	 */
+	void (*free)(struct ustream *s);
+
+	/*
+	 * set_read_blocked: (optional)
+	 * defined by ustream implementation, called when the read_blocked flag
+	 * changes
+	 */
+	void (*set_read_blocked)(struct ustream *s);
+
+	/*
+	 * ustream user should set this if the input stream is expected
+	 * to contain string data. the core will keep all data 0-terminated.
+	 */
+	bool string_data;
+	bool write_error;
+	bool eof, eof_write_done;
+
+	enum read_blocked_reason read_blocked;
+};
+
+struct ustream_fd {
+	struct ustream stream;
+	struct uloop_fd fd;
+};
+
+struct ustream_buf {
+	struct ustream_buf *next;
+
+	char *data;
+	char *tail;
+	char *end;
+
+	char head[];
+};
+
+/* ustream_fd_init: create a file descriptor ustream (uses uloop) */
+void ustream_fd_init(struct ustream_fd *s, int fd);
+
+/* ustream_free: free all buffers and data associated with a ustream */
+void ustream_free(struct ustream *s);
+
+/* ustream_consume: remove data from the head of the read buffer */
+void ustream_consume(struct ustream *s, int len);
+
+/* ustream_write: add data to the write buffer */
+int ustream_write(struct ustream *s, const char *buf, int len, bool more);
+int ustream_printf(struct ustream *s, const char *format, ...);
+int ustream_vprintf(struct ustream *s, const char *format, va_list arg);
+
+/* ustream_get_read_buf: get a pointer to the next read buffer data */
+char *ustream_get_read_buf(struct ustream *s, int *buflen);
+
+/*
+ * ustream_set_read_blocked: set read blocked state
+ *
+ * if set, the ustream will no longer fetch pending data.
+ */
+void ustream_set_read_blocked(struct ustream *s, bool set);
+
+static inline bool ustream_read_blocked(struct ustream *s)
+{
+	return !!(s->read_blocked & READ_BLOCKED_USER);
+}
+
+/*** --- functions only used by ustream implementations --- ***/
+
+/* ustream_init_defaults: fill default callbacks and options */
+void ustream_init_defaults(struct ustream *s);
+
+/*
+ * ustream_reserve: allocate rx buffer space
+ *
+ * len: hint for how much space is needed (not guaranteed to be met)
+ * maxlen: pointer to where the actual buffer size is going to be stored
+ */
+char *ustream_reserve(struct ustream *s, int len, int *maxlen);
+
+/* ustream_fill_read: mark rx buffer space as filled */
+void ustream_fill_read(struct ustream *s, int len);
+
+/*
+ * ustream_write_pending: attempt to write more data from write buffers
+ * returns true if all write buffers have been emptied.
+ */
+bool ustream_write_pending(struct ustream *s);
+
+static inline void ustream_state_change(struct ustream *s)
+{
+	uloop_timeout_set(&s->state_change, 0);
+}
+
+#endif