mds-clipboard.c

/**
 * mds — A micro-display server
 * Copyright © 2014, 2015, 2016, 2017  Mattias Andrée (maandree@kth.se)
 * 
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
#include "mds-clipboard.h"

#include <libmdsserver/macros.h>
#include <libmdsserver/util.h>
#include <libmdsserver/mds-message.h>

#include <errno.h>
#include <inttypes.h>
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#define reconnect_to_display() -1



#define MDS_CLIPBOARD_VARS_VERSION 0



/**
 * This variable should declared by the actual server implementation.
 * It must be configured before `main` is invoked.
 * 
 * This tells the server-base how to behave
 */
server_characteristics_t server_characteristics = {
	.require_privileges = 0,
	.require_display = 1,
	.require_respawn_info = 1,
	.sanity_check_argc = 1,
	.fork_for_safety = 0,
	.danger_is_deadly = 1
};



/**
 * Value of the ‘Message ID’ header for the next message
 */
static uint32_t message_id = 1;

/**
 * Buffer for received messages
 */
static mds_message_t received;

/**
 * Whether the server is connected to the display
 */
static int connected = 1;

/**
 * The size of each clipstack
 */
static size_t clipboard_size[CLIPBOARD_LEVELS] = { 10, 1, 1 };

/**
 * The number of used elements in each clipstack
 */
static size_t clipboard_used[CLIPBOARD_LEVELS] = { 0, 0, 0 };

/**
 * The entries in each clipstack
 */
static clipitem_t *clipboard[CLIPBOARD_LEVELS];



/**
 * Send a full message even if interrupted
 * 
 * @param   message:const char*  The message to send
 * @param   length:size_t        The length of the message
 * @return  :int                 Zero on success, -1 on error
 */
#define full_send(message, length)\
	((full_send)(socket_fd, message, length))


/**
 * This function will be invoked before `initialise_server` (if not re-exec:ing)
 * or before `unmarshal_server` (if re-exec:ing)
 * 
 * @return  Non-zero on error
 */
int __attribute__((const))
preinitialise_server(void)
{
	return 0;
}


/**
 * This function should initialise the server,
 * and it not invoked after a re-exec.
 * 
 * @return  Non-zero on error
 */
int initialise_server(void)
{
	ssize_t i = 0;
	int stage = 0;
	const char* const message =
		"Command: intercept\n"
		"Message ID: 0\n"
		"Length: 33\n"
		"\n"
		"Command: clipboard\n"
		"Client closed\n";

	fail_if (full_send(message, strlen(message)));

	if (is_respawn) {
		const char* const crash_message =
			"Command: clipboard-info\n"
			"Event: crash\n"
			"Message ID: 1\n"
			"\n";

		fail_if (full_send(crash_message, strlen(crash_message)));
		message_id++;
	}

	stage++;
	fail_if (server_initialised() < 0);
	stage++;
	fail_if (mds_message_initialise(&received));

	for (i = 0; i < CLIPBOARD_LEVELS; i++)
		fail_if (xcalloc(clipboard[i], clipboard_size[i], clipitem_t));

	return 0;

fail:
	xperror(*argv);
	if (stage == 0) return 1;
	mds_message_destroy(&received);
	if (stage == 1) return 1;
	while (i--)
		free(clipboard[i]);
	return 1;
}


/**
 * This function will be invoked after `initialise_server` (if not re-exec:ing)
 * or after `unmarshal_server` (if re-exec:ing)
 * 
 * @return  Non-zero on error
 */
int
postinitialise_server(void)
{
	if (connected)
		return 0;

	fail_if (reconnect_to_display());
	connected = 1;
	return 0;
fail:
	mds_message_destroy(&received);
	return 1;
}


/**
 * Calculate the number of bytes that will be stored by `marshal_server`
 * 
 * On failure the program should `abort()` or exit by other means.
 * However it should not be possible for this function to fail.
 * 
 * @return  The number of bytes that will be stored by `marshal_server`
 */
size_t
marshal_server_size(void)
{
	size_t i, j, rc =  2 * sizeof(int) + sizeof(uint32_t) + mds_message_marshal_size(&received);
	clipitem_t clip;
	rc += 2 * CLIPBOARD_LEVELS * sizeof(size_t);
	for (i = 0; i < CLIPBOARD_LEVELS; i++) {
		for (j = 0; j < clipboard_used[i]; j++) {
			clip = clipboard[i][j];
			rc += sizeof(size_t) + sizeof(time_t) + sizeof(long) + sizeof(uint64_t) + sizeof(int);
			rc += clip.length * sizeof(char);
		}
	}
	return rc;
}


/**
 * `memset`, but the compiler does not know that
 */
void *(*volatile mds_clipboard_my_explicit_memset)(void *s, int c, size_t n) = memset;


/**
 * Wipe a memory area and free it
 * 
 * @param  s  The memory area
 * @param  n  The number of bytes to write
 */
static inline void
wipe_and_free(void *s, size_t n)
{
	if (s)
		free(mds_clipboard_my_explicit_memset(s, 0, n));
}


/**
 * Marshal server implementation specific data into a buffer
 * 
 * @param   state_buf  The buffer for the marshalled data
 * @return             Non-zero on error
 */
int
marshal_server(char *state_buf)
{
	size_t i, j;
	clipitem_t clip;

	buf_set_next(state_buf, int, MDS_CLIPBOARD_VARS_VERSION);
	buf_set_next(state_buf, int, connected);
	buf_set_next(state_buf, uint32_t, message_id);
	mds_message_marshal(&received, state_buf);

	/* Removed entires from the clipboard that may not be marshalled. */
	for (i = 0; i < CLIPBOARD_LEVELS; i++) {
		for (j = 0; j < clipboard_used[i]; j++) {
			clip = clipboard[i][j];

			if (clip.autopurge == CLIPITEM_AUTOPURGE_NEVER)
				continue;

			wipe_and_free(clip.content, clip.length * sizeof(char));

			memmove(clipboard[i] + j, clipboard[i] + j + 1, (clipboard_used[i] - j - 1) * sizeof(clipitem_t));
			clipboard_used[i]--;
			j--;
		}
	}

	/* Marshal clipboard. */
	for (i = 0; i < CLIPBOARD_LEVELS; i++) {
		buf_set_next(state_buf, size_t, clipboard_size[i]);
		buf_set_next(state_buf, size_t, clipboard_used[i]);
		for (j = 0; j < clipboard_used[i]; j++) {
			clip = clipboard[i][j];
			buf_set_next(state_buf, size_t, clip.length);
			buf_set_next(state_buf, time_t, clip.dethklok.tv_sec);
			buf_set_next(state_buf, long, clip.dethklok.tv_nsec);
			buf_set_next(state_buf, uint64_t, clip.client);
			buf_set_next(state_buf, int, clip.autopurge);
			memcpy(state_buf, clip.content, clip.length * sizeof(char));
			state_buf += clip.length;
			
			free(clip.content);
		}
		free(clipboard[i]);
	}

	mds_message_destroy(&received);
	return 0;
}


/**
 * Unmarshal server implementation specific data and update the servers state accordingly
 * 
 * On critical failure the program should `abort()` or exit by other means.
 * That is, do not let `reexec_failure_recover` run successfully, if it unrecoverable
 * error has occurred or one severe enough that it is better to simply respawn.
 * 
 * @param   state_buf  The marshalled data that as not been read already
 * @return             Non-zero on error
 */
int
unmarshal_server(char *state_buf)
{
	size_t i, j;
	clipitem_t *clip;

	for (i = 0; i < CLIPBOARD_LEVELS; i++)
		clipboard[i] = NULL;

	/* buf_get_next(state_buf, int, MDS_CLIPBOARD_VARS_VERSION); */
	buf_next(state_buf, int, 1);
	buf_get_next(state_buf, int, connected);
	buf_get_next(state_buf, uint32_t, message_id);
	fail_if (mds_message_unmarshal(&received, state_buf));

	for (i = 0; i < CLIPBOARD_LEVELS; i++) {
		buf_get_next(state_buf, size_t, clipboard_size[i]);
		buf_get_next(state_buf, size_t, clipboard_used[i]);
		fail_if (xcalloc(clipboard[i], clipboard_size[i], clipitem_t));

		for (j = 0; j < clipboard_used[i]; j++) {
			clip = clipboard[i] + j;
			buf_get_next(state_buf, size_t, clip->length);
			buf_get_next(state_buf, time_t, clip->dethklok.tv_sec);
			buf_get_next(state_buf, long, clip->dethklok.tv_nsec);
			buf_get_next(state_buf, uint64_t, clip->client);
			buf_get_next(state_buf, int, clip->autopurge);
			fail_if (xmemdup(clip->content, state_buf, clip->length, char));
			state_buf += clip->length;
		}
	}

	return 0;
fail:
	xperror(*argv);
	mds_message_destroy(&received);
	for (i = 0; i < CLIPBOARD_LEVELS; i++) {
		if (clipboard[i] != NULL) {
			for (j = 0; j < clipboard_used[i]; j++)
				free(clipboard[i][j].content);
			free(clipboard[i]);
		}
	}
	abort();
	return -1;
}


/**
 * Attempt to recover from a re-exec failure that has been
 * detected after the server successfully updated it execution image
 * 
 * @return  Non-zero on error
 */
int __attribute__((const))
reexec_failure_recover(void)
{
	return -1;
}


/**
 * Perform the server's mission
 * 
 * @return  Non-zero on error
 */
int
master_loop(void)
{
	int rc = 1, r;
	size_t i, j;

	while (!reexecing && !terminating) {
		if (danger) {
			danger = 0;
			clipboard_danger();
		}

		if (r = mds_message_read(&received, socket_fd), r == 0)
			if (r = handle_message(), r == 0)
				continue;

		if (r == -2) {
			eprint("corrupt message received, aborting.");
			goto done;
		} else if (errno == EINTR) {
			continue;
		} else {
			fail_if (errno != ECONNRESET);
		}

		eprint("lost connection to server.");
		mds_message_destroy(&received);
		mds_message_initialise(&received);
		connected = 0;
		fail_if (reconnect_to_display());
		connected = 1;
	}

	rc = 0;
	goto done;
 fail:
	xperror(*argv);
 done:
	if (!rc && reexecing)
		return 0;
	mds_message_destroy(&received);
	for (i = 0; i < CLIPBOARD_LEVELS; i++) {
		if (clipboard[i] != NULL) {
			for (j = 0; j < clipboard_used[i]; j++)
				wipe_and_free(clipboard[i][j].content, clipboard[i][j].length);
			free(clipboard[i]);
		}
	}
	return rc;
}


/**
 * Handle the received message
 * 
 * @return  Zero on success, -1 on error
 */
int
handle_message(void)
{
	/* Fetch message headers. */

	const char *recv_client_id = "0:0";
	const char *recv_message_id = NULL;
	const char *recv_length = NULL;
	const char *recv_level = NULL;
	const char *recv_action = NULL;
	const char *recv_size = NULL;
	const char *recv_index = "0";
	const char *recv_time_to_live = "forever";
	const char *recv_client_closed = NULL;
	size_t i;
	int level;

#define __get_header(storage, header)\
	(startswith(received.headers[i], header))\
		storage = received.headers[i] + strlen(header)

	for (i = 0; i < received.header_count; i++) {
		if      __get_header(recv_client_id,     "Client ID: ");
		else if __get_header(recv_message_id,    "Message ID: ");
		else if __get_header(recv_length,        "Length: ");
		else if __get_header(recv_action,        "Action: ");
		else if __get_header(recv_level,         "Level: ");
		else if __get_header(recv_size,          "Size: ");
		else if __get_header(recv_index,         "Index: ");
		else if __get_header(recv_time_to_live,  "Time to live: ");
		else if __get_header(recv_client_closed, "Client closed: ");
	}

#undef __get_header

	/* Validate headers and take appropriate action. */

	if (!recv_message_id)
		return eprint("received message without ID, ignoring, master server is misbehaving."), 0;

	if (recv_client_closed) {
		if (strequals(recv_client_closed, "0:0"))
			return 0;
		return clipboard_death(recv_client_closed);
	}

	if (!recv_action)
		return eprint("received message without any action, ignoring."), 0;
	if (!recv_level)
		return eprint("received message without specified clipboard level, ignoring."), 0;
	level = atoi(recv_level);
	if ((level < 0) || (CLIPBOARD_LEVELS <= level))
		return eprint("received message without invalid clipboard level, ignoring."), 0;
	if (strequals(recv_client_id, "0:0"))
		if (strequals(recv_action, "read") || strequals(recv_action, "get-size"))
			return eprint("received information request from an anonymous client, ignoring."), 0;

	if (strequals(recv_action, "add")) {
		if (recv_length == NULL)
			return eprint("received request for adding a clipboard entry "
			              "but did not receive any content, ignoring."), 0;
		if ((strequals(recv_client_id, "0:0")) && startswith(recv_time_to_live, "until-death"))
			return eprint("received request new clipboard entry with autopurge upon "
			              "client close from an anonymous client, ignoring."), 0;
		return clipboard_add(level, recv_time_to_live, recv_client_id);
	} else if (strequals(recv_action, "read")) {
		return clipboard_read(level, atoz(recv_index), recv_client_id, recv_message_id);
	} else if (strequals(recv_action, "clear")) {
		return clipboard_clear(level);
	} else if (strequals(recv_action, "set-size")) {
		if (recv_size == NULL)
			return eprint("received request for clipboard resizing without a new size, ignoring."), 0;
		return clipboard_set_size(level, atoz(recv_size));
	} else if (strequals(recv_action, "get-size")) {
		return clipboard_get_size(level, recv_client_id, recv_message_id);
	}

	eprint("received message with invalid action, ignoring.");
	return 0;
}


/**
 * Free an entry from the clipboard
 * 
 * @param  entry  The clipboard entry to free
 */
static inline void __attribute__((nonnull))
free_clipboard_entry(clipitem_t *entry)
{
	if (entry->autopurge == CLIPITEM_AUTOPURGE_NEVER)
		free(entry->content);
	else
		wipe_and_free(entry->content, entry->length);
	entry->content = NULL;
}


/**
 * Broadcast notification about an automatic removal of an entry
 * 
 * @param   level  The clipboard level
 * @param   index  The index in the clipstack of the removed entry
 * @return         Zero on success, -1 on error, `errno` will be set accordingly
 */
static int
clipboard_notify_pop(int level, size_t index)
{
	size_t size = clipboard_size[level];
	size_t used = clipboard_used[level];
	char message[10 + 3 * (sizeof(int) + 3 * sizeof(size_t)) +
		     sizeof("Command: clipboard-info\n"
			    "Event: crash\n"
			    "Message ID: \n"
			    "Level: \n"
			    "Popped: \n"
			    "Size: \n"
			    "Used: \n"
			    "\n") / sizeof(char)];

	sprintf(message,
	        "Command: clipboard-info\n"
	        "Event: crash\n"
	        "Message ID: %" PRIu32 "\n"
	        "Level: %i\n"
	        "Popped: %zu\n"
	        "Size: %zu\n"
	        "Used: %zu\n"
	        "\n",
	        message_id, level, index, size, used);

	message_id = message_id == UINT32_MAX ? 0 : (message_id + 1);
	fail_if (full_send(message, strlen(message)) ? -1 : 0);
	return 0;
fail:
	return -1;
}


/**
 * Remove old entries from a clipstack
 * 
 * @param   level      The clipboard level
 * @param   client_id  The ID of the client that has newly closed, `NULL` if none
 * @return             Zero on success, -1 on error
 */
static int
clipboard_purge(int level, const char *client_id)
{
	uint64_t client = client_id ? parse_client_id(client_id) : 0;
	struct timespec now;
	clipitem_t *clip;
	size_t i;

	fail_if (monotone(&now));

	for (i = 0; i < clipboard_used[level]; i++) {
		clip = clipboard[level] + i;
		if ((clip->autopurge & CLIPITEM_AUTOPURGE_UPON_DEATH)) {
			if (clip->client == client)
				goto removed;
		}
		if ((clip->autopurge & CLIPITEM_AUTOPURGE_UPON_CLOCK)) {
			if (clip->dethklok.tv_sec > now.tv_sec)
				goto removed;
			if (clip->dethklok.tv_sec == now.tv_sec)
				if (clip->dethklok.tv_nsec >= now.tv_nsec)
					goto removed;
		}

		continue;
	removed:
		free_clipboard_entry(clipboard[level] + i);
		clipboard_used[level]--;
		fail_if (clipboard_notify_pop(level, i));
		memmove(clipboard[level] + i, clipboard[level] + i + 1, (clipboard_used[level] - i) * sizeof(clipitem_t));
		i--;
	}

	return 0;
fail:
	xperror(*argv);
	return -1;
}


/**
 * Remove expired entries
 * 
 * @return  Zero on success, -1 on error
 */
int
clipboard_danger(void)
{
	int i;
	for (i = 0; i < CLIPBOARD_LEVELS; i++)
		fail_if (clipboard_purge(i, NULL));
	return 0;
fail:
	return -1;
}


/**
 * Remove entries in the clipboard added by a client
 * 
 * @param   recv_client_id  The ID of the client
 * @return                  Zero on success, -1 on error
 */
int
clipboard_death(const char *recv_client_id)
{
	int i;
	for (i = 0; i < CLIPBOARD_LEVELS; i++)
		fail_if (clipboard_purge(i, recv_client_id));
	return 0;
fail:
	return -1;
}


/**
 * Add a new entry to the clipboard
 * 
 * @param   level           The clipboard level
 * @param   time_to_live    When the entry should be removed
 * @param   recv_client_id  The ID of the client
 * @return                  Zero on success, -1 on error
 */
int
clipboard_add(int level, const char *time_to_live, const char *recv_client_id)
{
	int autopurge = CLIPITEM_AUTOPURGE_UPON_CLOCK;
	uint64_t client = parse_client_id(recv_client_id);
	clipitem_t new_clip;
	struct timespec dethklok;

	fail_if (clipboard_purge(level, NULL));

	if (strequals(time_to_live, "forever")) {
		autopurge = CLIPITEM_AUTOPURGE_NEVER;
	} else if (strequals(time_to_live, "until-death")) {
		autopurge = CLIPITEM_AUTOPURGE_UPON_DEATH;
	} else if (startswith(time_to_live, "until-death ")) {
		autopurge = CLIPITEM_AUTOPURGE_UPON_DEATH_OR_CLOCK;
		time_to_live += strlen("until-death ");
	}

	if ((autopurge & CLIPITEM_AUTOPURGE_UPON_CLOCK)) {
		fail_if (monotone(&dethklok));
		dethklok.tv_sec += (time_t)atoll(time_to_live);
		/* It should really be `atol`, but we want to be future-proof. */
		new_clip.dethklok = dethklok;
	} else {
		new_clip.dethklok.tv_sec = 0;
		new_clip.dethklok.tv_nsec = 0;
	}

	new_clip.client = client;
	new_clip.autopurge = autopurge;
	new_clip.length = received.payload_size;

	fail_if (xmemdup(new_clip.content, received.payload, new_clip.length, char));

	if (clipboard_used[level] == clipboard_size[level])
		free_clipboard_entry(clipboard[level] + clipboard_used[level] - 1);
	memmove(clipboard[level] + 1, clipboard[level], (clipboard_used[level] - 1) * sizeof(clipitem_t));
	clipboard[level][0] = new_clip;

	return 0;
fail:
	xperror(*argv);
	return -1;
}


/**
 * Read an entry to the clipboard
 * 
 * @param   level            The clipboard level
 * @param   index            The index of the clipstack element
 * @param   recv_client_id   The ID of the client
 * @param   recv_message_id  The message ID of the received message
 * @return                   Zero on success, -1 on error
 */
int
clipboard_read(int level, size_t index, const char *recv_client_id, const char *recv_message_id)
{
	char *message = NULL;
	clipitem_t *clip = NULL;
	size_t n;

	fail_if (clipboard_purge(level, NULL));

	if (clipboard_used[level] == 0) {
		n = sizeof("To: \n"
			   "In response to: \n"
			   "Message ID: \n"
			   "Origin command: clipboard\n"
			   "\n") / sizeof(char);
		n += strlen(recv_client_id) + strlen(recv_message_id) + 10;

		fail_if (xmalloc(message, n, char));

		sprintf(message,
			"To: %s\n"
			"In response to: %s\n"
			"Message ID: %" PRIu32 "\n"
			"Origin command: clipboard\n"
			"\n",
			recv_client_id, recv_message_id, message_id);

		goto send;
	}

	if (index >= clipboard_used[level])
		index = clipboard_used[level] - 1;

	clip = clipboard[level] + index;

	n = sizeof("To: \n"
	           "In response to: \n"
	           "Message ID: \n"
	           "Origin command: clipboard\n"
	           "Length: \n"
	           "\n") / sizeof(char);
	n += strlen(recv_client_id) + strlen(recv_message_id) + 10 + 3 * sizeof(size_t);

	fail_if (xmalloc(message, n, char));

	sprintf(message,
	        "To: %s\n"
	        "In response to: %s\n"
	        "Message ID: %" PRIu32 "\n"
	        "Origin command: clipboard\n"
	        "Length: %zu\n"
	        "\n",
	        recv_client_id, recv_message_id, message_id, clip->length);

send:
	message_id = message_id == INT32_MAX ? 0 : (message_id + 1);
	fail_if (full_send(message, strlen(message)));
	if (clip)
		fail_if (full_send(clip->content, clip->length));

	free(message);
	return 0;
fail:
	xperror(*argv);
	free(message);
	return errno = 0, -1;
}


/**
 * Clear a clipstack
 * 
 * @param   level  The clipboard level
 * @return         Zero on success, -1 on error
 */
int
clipboard_clear(int level)
{
	size_t i;
	for (i = 0; i < clipboard_used[level]; i++)
		free_clipboard_entry(clipboard[level] + i);
	clipboard_used[level] = 0;
	return 0;
}


/**
 * Resize a clipstack
 * 
 * @param   level  The clipboard level
 * @param   size   The new clipstack size
 * @return         Zero on success, -1 on error
 */
int
clipboard_set_size(int level, size_t size)
{
	size_t i, old_used;
	clipitem_t* old;

	fail_if (clipboard_purge(level, NULL));

	if (size < clipboard_size[level]) {
		old_used = clipboard_used[level];
		if (size < old_used) {
			clipboard_used[level] = size;
			for (i = size; i < old_used; i++)
				free_clipboard_entry(clipboard[level] + i);
		}
	}

	if (size != clipboard_size[level]) {
		old = clipboard[level];
		if (xrealloc(clipboard[level], size, clipitem_t)) {
			clipboard[level] = old;
			fail_if (1);
		}
		clipboard_size[level] = size;
	}

	return 0;
fail:
	xperror(*argv);
	return -1;
}


/**
 * Get the size of a clipstack and how many entries it contains
 * 
 * @param   level            The clipboard level
 * @param   recv_client_id   The ID of the client
 * @param   recv_message_id  The message ID of the received message
 * @return                   Zero on success, -1 on error
 */
int
clipboard_get_size(int level, const char *recv_client_id, const char *recv_message_id)
{
	char *message = NULL;
	size_t n;

	fail_if (clipboard_purge(level, NULL));

	n = sizeof("To: \n"
	           "In response to: \n"
	           "Message ID: \n"
	           "Origin command: clipboard\n"
	           "Size: \n"
	           "Used: \n"
	           "\n") / sizeof(char);
	n += strlen(recv_client_id) + strlen(recv_message_id) + 10 + 2 * 3 * sizeof(size_t);

	fail_if (xmalloc(message, n, char));
	sprintf(message,
	        "To: %s\n"
	        "In response to: %s\n"
	        "Message ID: %" PRIu32 "\n"
	        "Origin command: clipboard\n"
	        "Size: %zu\n"
	        "Used: %zu\n"
	        "\n",
		recv_client_id, recv_message_id, message_id, clipboard_size[level], clipboard_used[level]);

	message_id = message_id == INT32_MAX ? 0 : (message_id + 1);

	fail_if (full_send(message, strlen(message)));

	free(message);
	return 0;
fail:
	xperror(*argv);
	free(message);
	return errno = 0, -1;
}


/**
 * This function is called when a signal that
 * signals that the system to dump state information
 * and statistics has been received
 * 
 * @param  signo  The signal that has been received
 */
void
received_info(int signo)
{
	SIGHANDLER_START;
	clipitem_t clipitem;
	size_t i, j, n;
	struct timespec now;
	if (monotone(&now) < 0)
		iprint("(unable to get current time)");
	else
		iprintf("current time: %ji.%09li", (intmax_t)(now.tv_sec), (long)(now.tv_nsec));
	iprintf("next message ID: %" PRIu32, message_id);
	iprintf("connected: %s", connected ? "yes" : "no");
	for (i = 0; i < CLIPBOARD_LEVELS; i++) {
		n = clipboard_used[i];
		iprintf("clipstack %zu: allocated: %zu", i, clipboard_size[i]);
		iprintf("clipstack %zu: used: %zu", i, n);
		for (j = 0; j < n; j++) {
			clipitem = clipboard[i][j];
			iprintf("clipstack %zu: item %zu:", i, j);
			iprintf("  autopurge: %s",
			        clipitem.autopurge == CLIPITEM_AUTOPURGE_NEVER ? "as needed" :
			        clipitem.autopurge == CLIPITEM_AUTOPURGE_UPON_DEATH ? "upon death or as needed" :
			        clipitem.autopurge == CLIPITEM_AUTOPURGE_UPON_CLOCK ? "timeout or as needed" :
			        clipitem.autopurge == CLIPITEM_AUTOPURGE_UPON_DEATH_OR_CLOCK ? "upon death, timeout or as needed" :
			        "unrecognised rule, something is wrong here!");
			iprintf("  client: %" PRIu32 ":%" PRIu32,
			        (uint32_t)(clipitem.client >> 32),
			        (uint32_t)(clipitem.client));
			if (clipitem.autopurge & CLIPITEM_AUTOPURGE_UPON_CLOCK)
				iprintf("  timeout: %ji.%09li",
				        (intmax_t)(clipitem.dethklok.tv_sec),
				        (long)(clipitem.dethklok.tv_nsec));
			iprintf("  butes: %zu", clipitem.length);
			iprintf("  content (possibily truncated): %.*s",
			        (int)strnlen(clipitem.content, clipitem.length > 50 ? (size_t)50 : clipitem.length),
			        clipitem.content);
		}
	}
	SIGHANDLER_END;
	(void) signo;
}