split out registry from mds-registry

Signed-off-by: Mattias Andrée <maandree@operamail.com>

6 files changed, 512 insertions, 462 deletions

diff --git a/Makefile b/Makefile
index 7a17192..d760f1e 100644
--- a/Makefile
+++ b/Makefile
@@ -20,7 +20,7 @@ OBJ_mds-server_ = mds-server interception-condition client multicast  \
                   queued-interception globals signals interceptors    \
                   sending slavery reexec receiving
 
-OBJ_mds-registry_ = mds-registry util globals reexec
+OBJ_mds-registry_ = mds-registry util globals reexec registry
 
 OBJ_mds-server   = $(foreach O,$(OBJ_mds-server_),obj/mds-server/$(O).o)
 OBJ_mds-registry = $(foreach O,$(OBJ_mds-registry_),obj/mds-registry/$(O).o)
diff --git a/mk/build.mk b/mk/build.mk
index e8bbd0e..364e23e 100644
--- a/mk/build.mk
+++ b/mk/build.mk
@@ -13,7 +13,7 @@ servers: $(foreach S,$(SERVERS),bin/$(S))
 
 # Link large servers.
 
-bin/mds-server: $(OBJ_mds-server) obj/mds-base.o bin/libmdsserver.so
+bin/mds-server: $(OBJ_mds-server) obj/mds-base.o src/mds-server/*.h bin/libmdsserver.so
 	mkdir -p $(shell dirname $@)
 	$(CC) $(C_FLAGS) -o $@ $(LDS) $(LDS_mds-server) $(OBJ_mds-server) obj/mds-base.o
 ifeq ($(DEBUG),y)
@@ -22,7 +22,7 @@ ifeq ($(DEBUG),y)
 endif
 
 
-bin/mds-registry: $(OBJ_mds-registry) obj/mds-base.o bin/libmdsserver.so
+bin/mds-registry: $(OBJ_mds-registry) obj/mds-base.o src/mds-registry/*.h bin/libmdsserver.so
 	mkdir -p $(shell dirname $@)
 	$(CC) $(C_FLAGS) -o $@ $(LDS) $(LDS_mds-registry) $(OBJ_mds-registry) obj/mds-base.o
 
diff --git a/src/mds-registry/mds-registry.c b/src/mds-registry/mds-registry.c
index 089fa53..4264596 100644
--- a/src/mds-registry/mds-registry.c
+++ b/src/mds-registry/mds-registry.c
@@ -19,26 +19,17 @@
 
 #include "util.h"
 #include "globals.h"
-#include "reexec.h"
+#include "registry.h"
 
 #include <libmdsserver/macros.h>
-#include <libmdsserver/util.h>
-#include <libmdsserver/mds-message.h>
-#include <libmdsserver/hash-table.h>
 #include <libmdsserver/hash-help.h>
-#include <libmdsserver/client-list.h>
 
 #include <errno.h>
-#include <inttypes.h>
-#include <string.h>
 #include <stdio.h>
-#include <stdlib.h>
 #define reconnect_to_display() -1 /* TODO */
 
 
 
-
-
 /**
  * This variable should declared by the actual server implementation.
  * It must be configured before `main` is invoked.
@@ -200,418 +191,3 @@ int master_loop(void)
   return rc;
 }
 
-
-/**
- * Handle the received message containing ‘Command: register’-header–value
- * 
- * @return  Zero on success -1 on error or interruption,
- *          errno will be set accordingly
- */
-static int handle_register_message(void)
-{
-  const char* recv_client_id = NULL;
-  const char* recv_message_id = NULL;
-  const char* recv_length = NULL;
-  const char* recv_action = NULL;
-  size_t i, length = 0;
-  
-#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
-	continue;
-      if (recv_client_id && recv_message_id && recv_length && recv_action)
-	break;
-    }
-  
-#undef __get_header
-  
-  
-  if ((recv_client_id == NULL) || (strequals(recv_client_id, "0:0")))
-    {
-      eprint("received message from anonymous sender, ignoring.");
-      return 0;
-    }
-  else if (strchr(recv_client_id, ':') == NULL)
-    {
-      eprint("received message from sender without a colon it its ID, ignoring, invalid ID.");
-      return 0;
-    }
-  else if ((recv_length == NULL) && ((recv_action == NULL) || !strequals(recv_action, "list")))
-    {
-      eprint("received empty message without `Action: list`, ignoring, has no effect.");
-      return 0;
-    }
-  else if (recv_message_id == NULL)
-    {
-      eprint("received message with ID, ignoring, master server is misbehaving.");
-      return 0;
-    }
-  
-  
-  if (recv_length != NULL)
-    length = (size_t)atoll(recv_length);
-  if (recv_action != NULL)
-    recv_action = "add";
-  
-#define __registry_action(action)  registry_action(length, action, recv_client_id, recv_message_id)
-  
-  if      (strequals(recv_action, "add"))     return __registry_action(1);
-  else if (strequals(recv_action, "remove"))  return __registry_action(-1);
-  else if (strequals(recv_action, "wait"))    return __registry_action(0);
-  else if (strequals(recv_action, "list"))    return list_registry(recv_client_id, recv_message_id);
-  else
-    {
-      eprint("received invalid action, ignoring.");
-      return 0;
-    }
-  
-#undef __registry_action
-}
-
-
-/**
- * Handle the received message containing a ‘Client closed’-header
- * 
- * @return  Zero on success -1 on error or interruption,
- *          errno will be set accordingly
- */
-static int handle_close_message(void)
-{
-  /* Servers do not close too often, there is no need to
-     optimise this with another hash table. */
-  
-  size_t i, j, ptr = 0, size = 1;
-  size_t* keys = NULL;
-  size_t* old_keys;
-  
-  fail_if ((errno = pthread_mutex_lock(&reg_mutex)));
-  
-  for (i = 0; i < received.header_count; i++)
-    if (startswith(received.headers[i], "Client closed: "))
-      {
-	uint64_t client = parse_client_id(received.headers[i] + strlen("Client closed: "));
-	hash_entry_t* entry;
-	
-	foreach_hash_table_entry (reg_table, j, entry)
-	  {
-	    client_list_t* list = (client_list_t*)(void*)(entry->value);
-	    client_list_remove(list, client);
-	    if (list->size)
-	      continue;
-	    
-	    fail_if ((keys == NULL) && xmalloc(keys, size, size_t));
-	    if (ptr == size ? growalloc(old_keys, keys, size, size_t) : 0)
-	      goto fail;
-	    keys[ptr++] = entry->key;
-	  }
-      }
-  
-  for (i = 0; i < ptr; i++)
-    {
-      hash_entry_t* entry = hash_table_get_entry(&reg_table, keys[i]);
-      client_list_t* list = (client_list_t*)(void*)(entry->value);
-      char* command = (char*)(void*)(entry->key);
-      
-      hash_table_remove(&reg_table, entry->key);
-      
-      client_list_destroy(list);
-      free(list);
-      free(command);
-    }
-  
-  pthread_mutex_unlock(&reg_mutex);
-  
-  free(keys);
-  return 0;
- pfail:
-  perror(*argv);
- fail:
-  free(keys);
-  return -1;
-}
-
-
-/**
- * Handle the received message
- * 
- * @return  Zero on success -1 on error or interruption,
- *          errno will be set accordingly
- */
-int handle_message(void)
-{
-  size_t i;
-  for (i = 0; i < received.header_count; i++)
-    if (strequals(received.headers[i], "Command: register"))
-      return handle_register_message();
-  return handle_close_message();
-}
-
-
-/**
- * Add a protocol to the registry
- * 
- * @param   has_key      Whether the command is already in the registry
- * @param   command      The command
- * @param   command_key  The address of `command`
- * @param   client       The ID of the client that implements the server-side of the protocol
- * @return               Non-zero on error
- */
-static int registry_action_add(int has_key, char* command, size_t command_key, uint64_t client)
-{
-  if (has_key)
-    {
-      size_t address = hash_table_get(&reg_table, command_key);
-      client_list_t* list = (client_list_t*)(void*)address;
-      if (client_list_add(list, client) < 0)
-	goto pfail;
-    }
-  else
-    {
-      client_list_t* list = malloc(sizeof(client_list_t));
-      void* address = list;
-      if (list == NULL)
-	goto pfail;
-      if ((command = strdup(command)) == NULL)
-	{
-	  free(list);
-	  goto pfail;
-	}
-      command_key = (size_t)(void*)command;
-      if (client_list_create(list, 1) ||
-	  client_list_add(list, client) ||
-	  (hash_table_put(&reg_table, command_key, (size_t)address) == 0))
-	{
-	  client_list_destroy(list);
-	  free(list);
-	  free(command);
-	  goto pfail;
-	}
-    }
-  
-  return 0;
- pfail:
-  perror(*argv);
-  return -1;
-}
-
-
-/**
- * Remove a protocol from the registry
- * 
- * @param   command_key  The address of a string that contains the command
- * @param   client       The ID of the client that implements the server-side of the protocol
- * @return               Non-zero on error
- */
-static void registry_action_remove(size_t command_key, uint64_t client)
-{
-  hash_entry_t* entry = hash_table_get_entry(&reg_table, command_key);
-  size_t address = entry->value;
-  client_list_t* list = (client_list_t*)(void*)address;
-  client_list_remove(list, client);
-  if (list->size == 0)
-    {
-      client_list_destroy(list);
-      free(list);
-      hash_table_remove(&reg_table, command_key);
-      reg_table_free_key(entry->key);
-    }
-}
-
-
-/**
- * Modify the protocol registry or list missing protocols
- * 
- * @param   command      The command
- * @param   action       -1 to remove command, +1 to add commands, 0 to
- *                       wait until the message commnds are registered
- * @param   client       The ID of the client that implements the server-side of the protocol
- * @param   wait_set     Table to fill with missing protocols if `action == 0`
- * @return               Non-zero on error
- */
-static int registry_action_act(char* command, int action, uint64_t client, hash_table_t* wait_set)
-{
-  size_t command_key = (size_t)(void*)command;
-  int has_key = hash_table_contains_key(&reg_table, command_key);
-  
-  if (action == 1)
-    {
-      if (registry_action_add(has_key, command, command_key, client))
-	return -1;
-    }
-  else if ((action == -1) && has_key)
-    registry_action_remove(command_key, client);
-  else if ((action == 0) && !has_key)
-    {
-      if ((command = strdup(command)) == NULL)
-	goto pfail_wait;
-      command_key = (size_t)(void*)command;
-      if (hash_table_put(wait_set, command_key, 1) == 0)
-	if (errno)
-	  {
-	    free(command);
-	    goto pfail_wait;
-	  }
-    }
-  
-  return 0;
- pfail_wait:
-  perror(*argv);
-  hash_table_destroy(wait_set, (free_func*)reg_table_free_key, NULL);
-  free(wait_set);
-  return -1;
-}
-
-
-/**
- * Perform an action over the registry
- * 
- * @param   length           The length of the received message
- * @param   action           -1 to remove command, +1 to add commands, 0 to
- *                           wait until the message commnds are registered
- * @param   recv_client_id   The ID of the client
- * @param   recv_message_id  The ID of the received message
- * @return                   Zero on success -1 on error or interruption,
- *                           errno will be set accordingly
- */
-int registry_action(size_t length, int action, const char* recv_client_id, const char* recv_message_id)
-{
-  char* payload = received.payload;
-  uint64_t client = action ? parse_client_id(recv_client_id) : 0;
-  hash_table_t* wait_set = NULL;
-  size_t begin;
-  
-  if (action == 0)
-    {
-      wait_set = malloc(sizeof(hash_table_t));
-      if (hash_table_create(wait_set))
-	{
-	  hash_table_destroy(wait_set, NULL, NULL);
-	  free(wait_set);
-	  goto pfail;
-	}
-      wait_set->key_comparator = (compare_func*)string_comparator;
-      wait_set->hasher = (hash_func*)string_hash;
-    }
-  
-  if (received.payload_size == length)
-    {
-      if (growalloc(old, received.payload, received.payload_size, char))
-	{
-	  if (wait_set != NULL)
-	    hash_table_destroy(wait_set, NULL, NULL), free(wait_set);
-	  return -1;
-	}
-      else
-	payload = received.payload;
-    }
-  
-  payload[length] = '\n';
-  
-  fail_if ((errno = pthread_mutex_lock(&reg_mutex)));
-  
-  for (begin = 0; begin < length;)
-    {
-      char* end = rawmemchr(payload + begin, '\n');
-      size_t len = (size_t)(end - payload) - begin - 1;
-      char* command = payload + begin;
-      
-      command[len] = '\0';
-      begin += len + 1;
-      
-      if (registry_action_act(command, action, client, wait_set))
-	goto fail_in_mutex;
-    }
-  
-  pthread_mutex_unlock(&reg_mutex);
-  
-  if (action == 0)
-    {
-      /* FIXME */
-    }
-  
-  return 0;
-  
-  
- pfail:
-  perror(*argv);
-  return -1;
- fail_in_mutex:
-  pthread_mutex_unlock(&reg_mutex);
-  return -1;
-}
-
-
-/**
- * Send a list of all registered commands to a client
- * 
- * @param   recv_client_id   The ID of the client
- * @param   recv_message_id  The ID of the received message
- * @return                   Zero on success -1 on error or interruption,
- *                           errno will be set accordingly
- */
-int list_registry(const char* recv_client_id, const char* recv_message_id)
-{
-  size_t ptr = 0, i;
-  hash_entry_t* entry;
-  
-  if (send_buffer_size == 0)
-    {
-      fail_if (xmalloc(send_buffer, 256, char));
-      send_buffer_size = 256;
-    }
-  
-  fail_if ((errno = pthread_mutex_lock(&reg_mutex)));
-  
-  foreach_hash_table_entry (reg_table, i, entry)
-    {
-      size_t key = entry->key;
-      char* command = (char*)(void*)key;
-      size_t len = strlen(command);
-      
-      while (ptr + len + 1 >= send_buffer_size)
-	if (growalloc(old, send_buffer, send_buffer_size, char))
-	  goto fail_in_mutex;
-      
-      memcpy(send_buffer + ptr, command, len * sizeof(char));
-      ptr += len;
-      send_buffer[ptr++] = '\n';
-    }
-  
-  i = strlen(recv_message_id) + strlen(recv_client_id) + 10 + 19;
-  i += strlen("To: %s\nIn response to: %s\nMessage ID: %" PRIi32 "\nLength: %" PRIu64 "\n\n");
-  
-  while (ptr + i >= send_buffer_size)
-    {
-      if (growalloc(old, send_buffer, send_buffer_size, char))
-	goto fail_in_mutex;
-    }
-  
-  sprintf(send_buffer + ptr, "To: %s\nIn response to: %s\nMessage ID: %" PRIi32 "\nLength: %" PRIu64 "\n\n",
-	  recv_message_id, recv_client_id, message_id, ptr);
-  
-  message_id = message_id == INT32_MAX ? 0 : (message_id + 1);
-  
-  pthread_mutex_unlock(&reg_mutex);
-  
-  if (full_send(send_buffer + ptr, strlen(send_buffer + ptr)))
-    return 1;
-  return full_send(send_buffer, ptr);
-  
-  
- fail_in_mutex:
-  pthread_mutex_unlock(&reg_mutex);
-  return -1;
-  
- pfail:
-  perror(*argv);
-  return -1;
-}
-
diff --git a/src/mds-registry/mds-registry.h b/src/mds-registry/mds-registry.h
index 010b5e3..7560aa2 100644
--- a/src/mds-registry/mds-registry.h
+++ b/src/mds-registry/mds-registry.h
@@ -21,40 +21,6 @@
 
 #include "../mds-base.h"
 
-#include <stdint.h>
-
-
-/**
- * Handle the received message
- * 
- * @return  Zero on success -1 on error or interruption,
- *          errno will be set accordingly
- */
-int handle_message(void);
-
-/**
- * Perform an action over the registry
- * 
- * @param   length           The length of the received message
- * @param   action           -1 to remove command, +1 to add commands, 0 to
- *                           wait until the message commnds are registered
- * @param   recv_client_id   The ID of the client
- * @param   recv_message_id  The ID of the received message
- * @return                   Zero on success -1 on error or interruption,
- *                           errno will be set accordingly
- */
-int registry_action(size_t length, int action, const char* recv_client_id, const char* recv_message_id);
-
-/**
- * Send a list of all registered commands to a client
- * 
- * @param   recv_client_id   The ID of the client
- * @param   recv_message_id  The ID of the received message
- * @return                   Zero on success -1 on error or interruption,
- *                           errno will be set accordingly
- */
-int list_registry(const char* recv_client_id, const char* recv_message_id);
-
 
 #endif
 
diff --git a/src/mds-registry/registry.c b/src/mds-registry/registry.c
new file mode 100644
index 0000000..026a5d5
--- /dev/null
+++ b/src/mds-registry/registry.c
@@ -0,0 +1,450 @@
+/**
+ * mds — A micro-display server
+ * Copyright © 2014  Mattias Andrée (maandree@member.fsf.org)
+ * 
+ * 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 "registry.h"
+
+#include "util.h"
+#include "globals.h"
+
+#include "../mds-base.h"
+
+#include <libmdsserver/macros.h>
+#include <libmdsserver/hash-help.h>
+#include <libmdsserver/client-list.h>
+
+#include <errno.h>
+#include <inttypes.h>
+#include <string.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+
+
+/**
+ * Handle the received message containing ‘Command: register’-header–value
+ * 
+ * @return  Zero on success -1 on error or interruption,
+ *          errno will be set accordingly
+ */
+static int handle_register_message(void)
+{
+  const char* recv_client_id = NULL;
+  const char* recv_message_id = NULL;
+  const char* recv_length = NULL;
+  const char* recv_action = NULL;
+  size_t i, length = 0;
+  
+#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
+	continue;
+      if (recv_client_id && recv_message_id && recv_length && recv_action)
+	break;
+    }
+  
+#undef __get_header
+  
+  
+  if ((recv_client_id == NULL) || (strequals(recv_client_id, "0:0")))
+    {
+      eprint("received message from anonymous sender, ignoring.");
+      return 0;
+    }
+  else if (strchr(recv_client_id, ':') == NULL)
+    {
+      eprint("received message from sender without a colon it its ID, ignoring, invalid ID.");
+      return 0;
+    }
+  else if ((recv_length == NULL) && ((recv_action == NULL) || !strequals(recv_action, "list")))
+    {
+      eprint("received empty message without `Action: list`, ignoring, has no effect.");
+      return 0;
+    }
+  else if (recv_message_id == NULL)
+    {
+      eprint("received message with ID, ignoring, master server is misbehaving.");
+      return 0;
+    }
+  
+  
+  if (recv_length != NULL)
+    length = (size_t)atoll(recv_length);
+  if (recv_action != NULL)
+    recv_action = "add";
+  
+#define __registry_action(action)  registry_action(length, action, recv_client_id, recv_message_id)
+  
+  if      (strequals(recv_action, "add"))     return __registry_action(1);
+  else if (strequals(recv_action, "remove"))  return __registry_action(-1);
+  else if (strequals(recv_action, "wait"))    return __registry_action(0);
+  else if (strequals(recv_action, "list"))    return list_registry(recv_client_id, recv_message_id);
+  else
+    {
+      eprint("received invalid action, ignoring.");
+      return 0;
+    }
+  
+#undef __registry_action
+}
+
+
+/**
+ * Handle the received message containing a ‘Client closed’-header
+ * 
+ * @return  Zero on success -1 on error or interruption,
+ *          errno will be set accordingly
+ */
+static int handle_close_message(void)
+{
+  /* Servers do not close too often, there is no need to
+     optimise this with another hash table. */
+  
+  size_t i, j, ptr = 0, size = 1;
+  size_t* keys = NULL;
+  size_t* old_keys;
+  
+  fail_if ((errno = pthread_mutex_lock(&reg_mutex)));
+  
+  for (i = 0; i < received.header_count; i++)
+    if (startswith(received.headers[i], "Client closed: "))
+      {
+	uint64_t client = parse_client_id(received.headers[i] + strlen("Client closed: "));
+	hash_entry_t* entry;
+	
+	foreach_hash_table_entry (reg_table, j, entry)
+	  {
+	    client_list_t* list = (client_list_t*)(void*)(entry->value);
+	    client_list_remove(list, client);
+	    if (list->size)
+	      continue;
+	    
+	    fail_if ((keys == NULL) && xmalloc(keys, size, size_t));
+	    if (ptr == size ? growalloc(old_keys, keys, size, size_t) : 0)
+	      goto fail;
+	    keys[ptr++] = entry->key;
+	  }
+      }
+  
+  for (i = 0; i < ptr; i++)
+    {
+      hash_entry_t* entry = hash_table_get_entry(&reg_table, keys[i]);
+      client_list_t* list = (client_list_t*)(void*)(entry->value);
+      char* command = (char*)(void*)(entry->key);
+      
+      hash_table_remove(&reg_table, entry->key);
+      
+      client_list_destroy(list);
+      free(list);
+      free(command);
+    }
+  
+  pthread_mutex_unlock(&reg_mutex);
+  
+  free(keys);
+  return 0;
+ pfail:
+  perror(*argv);
+ fail:
+  free(keys);
+  return -1;
+}
+
+
+/**
+ * Handle the received message
+ * 
+ * @return  Zero on success -1 on error or interruption,
+ *          errno will be set accordingly
+ */
+int handle_message(void)
+{
+  size_t i;
+  for (i = 0; i < received.header_count; i++)
+    if (strequals(received.headers[i], "Command: register"))
+      return handle_register_message();
+  return handle_close_message();
+}
+
+
+/**
+ * Add a protocol to the registry
+ * 
+ * @param   has_key      Whether the command is already in the registry
+ * @param   command      The command
+ * @param   command_key  The address of `command`
+ * @param   client       The ID of the client that implements the server-side of the protocol
+ * @return               Non-zero on error
+ */
+static int registry_action_add(int has_key, char* command, size_t command_key, uint64_t client)
+{
+  if (has_key)
+    {
+      size_t address = hash_table_get(&reg_table, command_key);
+      client_list_t* list = (client_list_t*)(void*)address;
+      if (client_list_add(list, client) < 0)
+	goto pfail;
+    }
+  else
+    {
+      client_list_t* list = malloc(sizeof(client_list_t));
+      void* address = list;
+      if (list == NULL)
+	goto pfail;
+      if ((command = strdup(command)) == NULL)
+	{
+	  free(list);
+	  goto pfail;
+	}
+      command_key = (size_t)(void*)command;
+      if (client_list_create(list, 1) ||
+	  client_list_add(list, client) ||
+	  (hash_table_put(&reg_table, command_key, (size_t)address) == 0))
+	{
+	  client_list_destroy(list);
+	  free(list);
+	  free(command);
+	  goto pfail;
+	}
+    }
+  
+  return 0;
+ pfail:
+  perror(*argv);
+  return -1;
+}
+
+
+/**
+ * Remove a protocol from the registry
+ * 
+ * @param   command_key  The address of a string that contains the command
+ * @param   client       The ID of the client that implements the server-side of the protocol
+ * @return               Non-zero on error
+ */
+static void registry_action_remove(size_t command_key, uint64_t client)
+{
+  hash_entry_t* entry = hash_table_get_entry(&reg_table, command_key);
+  size_t address = entry->value;
+  client_list_t* list = (client_list_t*)(void*)address;
+  client_list_remove(list, client);
+  if (list->size == 0)
+    {
+      client_list_destroy(list);
+      free(list);
+      hash_table_remove(&reg_table, command_key);
+      reg_table_free_key(entry->key);
+    }
+}
+
+
+/**
+ * Modify the protocol registry or list missing protocols
+ * 
+ * @param   command      The command
+ * @param   action       -1 to remove command, +1 to add commands, 0 to
+ *                       wait until the message commnds are registered
+ * @param   client       The ID of the client that implements the server-side of the protocol
+ * @param   wait_set     Table to fill with missing protocols if `action == 0`
+ * @return               Non-zero on error
+ */
+static int registry_action_act(char* command, int action, uint64_t client, hash_table_t* wait_set)
+{
+  size_t command_key = (size_t)(void*)command;
+  int has_key = hash_table_contains_key(&reg_table, command_key);
+  
+  if (action == 1)
+    {
+      if (registry_action_add(has_key, command, command_key, client))
+	return -1;
+    }
+  else if ((action == -1) && has_key)
+    registry_action_remove(command_key, client);
+  else if ((action == 0) && !has_key)
+    {
+      if ((command = strdup(command)) == NULL)
+	goto pfail_wait;
+      command_key = (size_t)(void*)command;
+      if (hash_table_put(wait_set, command_key, 1) == 0)
+	if (errno)
+	  {
+	    free(command);
+	    goto pfail_wait;
+	  }
+    }
+  
+  return 0;
+ pfail_wait:
+  perror(*argv);
+  hash_table_destroy(wait_set, (free_func*)reg_table_free_key, NULL);
+  free(wait_set);
+  return -1;
+}
+
+
+/**
+ * Perform an action over the registry
+ * 
+ * @param   length           The length of the received message
+ * @param   action           -1 to remove command, +1 to add commands, 0 to
+ *                           wait until the message commnds are registered
+ * @param   recv_client_id   The ID of the client
+ * @param   recv_message_id  The ID of the received message
+ * @return                   Zero on success -1 on error or interruption,
+ *                           errno will be set accordingly
+ */
+int registry_action(size_t length, int action, const char* recv_client_id, const char* recv_message_id)
+{
+  char* payload = received.payload;
+  uint64_t client = action ? parse_client_id(recv_client_id) : 0;
+  hash_table_t* wait_set = NULL;
+  size_t begin;
+  
+  if (action == 0)
+    {
+      wait_set = malloc(sizeof(hash_table_t));
+      if (hash_table_create(wait_set))
+	{
+	  hash_table_destroy(wait_set, NULL, NULL);
+	  free(wait_set);
+	  goto pfail;
+	}
+      wait_set->key_comparator = (compare_func*)string_comparator;
+      wait_set->hasher = (hash_func*)string_hash;
+    }
+  
+  if (received.payload_size == length)
+    {
+      if (growalloc(old, received.payload, received.payload_size, char))
+	{
+	  if (wait_set != NULL)
+	    hash_table_destroy(wait_set, NULL, NULL), free(wait_set);
+	  return -1;
+	}
+      else
+	payload = received.payload;
+    }
+  
+  payload[length] = '\n';
+  
+  fail_if ((errno = pthread_mutex_lock(&reg_mutex)));
+  
+  for (begin = 0; begin < length;)
+    {
+      char* end = rawmemchr(payload + begin, '\n');
+      size_t len = (size_t)(end - payload) - begin - 1;
+      char* command = payload + begin;
+      
+      command[len] = '\0';
+      begin += len + 1;
+      
+      if (registry_action_act(command, action, client, wait_set))
+	goto fail_in_mutex;
+    }
+  
+  pthread_mutex_unlock(&reg_mutex);
+  
+  if (action == 0)
+    {
+      /* FIXME */
+    }
+  
+  return 0;
+  
+  
+ pfail:
+  perror(*argv);
+  return -1;
+ fail_in_mutex:
+  pthread_mutex_unlock(&reg_mutex);
+  return -1;
+}
+
+
+/**
+ * Send a list of all registered commands to a client
+ * 
+ * @param   recv_client_id   The ID of the client
+ * @param   recv_message_id  The ID of the received message
+ * @return                   Zero on success -1 on error or interruption,
+ *                           errno will be set accordingly
+ */
+int list_registry(const char* recv_client_id, const char* recv_message_id)
+{
+  size_t ptr = 0, i;
+  hash_entry_t* entry;
+  
+  if (send_buffer_size == 0)
+    {
+      fail_if (xmalloc(send_buffer, 256, char));
+      send_buffer_size = 256;
+    }
+  
+  fail_if ((errno = pthread_mutex_lock(&reg_mutex)));
+  
+  foreach_hash_table_entry (reg_table, i, entry)
+    {
+      size_t key = entry->key;
+      char* command = (char*)(void*)key;
+      size_t len = strlen(command);
+      
+      while (ptr + len + 1 >= send_buffer_size)
+	if (growalloc(old, send_buffer, send_buffer_size, char))
+	  goto fail_in_mutex;
+      
+      memcpy(send_buffer + ptr, command, len * sizeof(char));
+      ptr += len;
+      send_buffer[ptr++] = '\n';
+    }
+  
+  i = strlen(recv_message_id) + strlen(recv_client_id) + 10 + 19;
+  i += strlen("To: %s\nIn response to: %s\nMessage ID: %" PRIi32 "\nLength: %" PRIu64 "\n\n");
+  
+  while (ptr + i >= send_buffer_size)
+    {
+      if (growalloc(old, send_buffer, send_buffer_size, char))
+	goto fail_in_mutex;
+    }
+  
+  sprintf(send_buffer + ptr, "To: %s\nIn response to: %s\nMessage ID: %" PRIi32 "\nLength: %" PRIu64 "\n\n",
+	  recv_message_id, recv_client_id, message_id, ptr);
+  
+  message_id = message_id == INT32_MAX ? 0 : (message_id + 1);
+  
+  pthread_mutex_unlock(&reg_mutex);
+  
+  if (full_send(send_buffer + ptr, strlen(send_buffer + ptr)))
+    return 1;
+  return full_send(send_buffer, ptr);
+  
+  
+ fail_in_mutex:
+  pthread_mutex_unlock(&reg_mutex);
+  return -1;
+  
+ pfail:
+  perror(*argv);
+  return -1;
+}
+
diff --git a/src/mds-registry/registry.h b/src/mds-registry/registry.h
new file mode 100644
index 0000000..f36749a
--- /dev/null
+++ b/src/mds-registry/registry.h
@@ -0,0 +1,58 @@
+/**
+ * mds — A micro-display server
+ * Copyright © 2014  Mattias Andrée (maandree@member.fsf.org)
+ * 
+ * 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/>.
+ */
+#ifndef MDS_MDS_REGISTRY_REGISTRY_H
+#define MDS_MDS_REGISTRY_REGISTRY_H
+
+
+#include <stddef.h>
+
+
+/**
+ * Handle the received message
+ * 
+ * @return  Zero on success -1 on error or interruption,
+ *          errno will be set accordingly
+ */
+int handle_message(void);
+
+/**
+ * Perform an action over the registry
+ * 
+ * @param   length           The length of the received message
+ * @param   action           -1 to remove command, +1 to add commands, 0 to
+ *                           wait until the message commnds are registered
+ * @param   recv_client_id   The ID of the client
+ * @param   recv_message_id  The ID of the received message
+ * @return                   Zero on success -1 on error or interruption,
+ *                           errno will be set accordingly
+ */
+int registry_action(size_t length, int action, const char* recv_client_id, const char* recv_message_id);
+
+/**
+ * Send a list of all registered commands to a client
+ * 
+ * @param   recv_client_id   The ID of the client
+ * @param   recv_message_id  The ID of the received message
+ * @return                   Zero on success -1 on error or interruption,
+ *                           errno will be set accordingly
+ */
+int list_registry(const char* recv_client_id, const char* recv_message_id);
+
+
+#endif
+