Shared space for variables (instead of letting other channels muck with your own)

(closes issue #11943)
 Reported by: ramonpeek
 Patches: 
       20080208__bug11943__2.diff.txt uploaded by Corydon76 (license 14)
 Tested by: jmls


git-svn-id: http://svn.digium.com/svn/asterisk/trunk@104098 f38db490-d61c-443f-a65b-d21fe96a405b

1 files changed, 163 insertions, 1 deletions

diff --git a/funcs/func_global.c b/funcs/func_global.c
index 1f0053d94..1f88d0017 100644
--- a/funcs/func_global.c
+++ b/funcs/func_global.c
@@ -33,6 +33,27 @@ ASTERISK_FILE_VERSION(__FILE__, "$Revision$")
 
 #include "asterisk/module.h"
 #include "asterisk/pbx.h"
+#include "asterisk/channel.h"
+#include "asterisk/app.h"
+#include "asterisk/manager.h"
+
+static void shared_variable_free(void *data);
+
+static struct ast_datastore_info shared_variable_info = {
+	.type = "SHARED_VARIABLES",
+	.destroy = shared_variable_free,
+};
+
+static void shared_variable_free(void *data)
+{
+	struct varshead *varshead = data;
+	struct ast_var_t *var;
+
+	while ((var = AST_LIST_REMOVE_HEAD(varshead, entries))) {
+		ast_var_delete(var);
+	}
+	ast_free(varshead);
+}
 
 static int global_read(struct ast_channel *chan, const char *cmd, char *data, char *buf, size_t len)
 {
@@ -61,11 +82,151 @@ static struct ast_custom_function global_function = {
 	.write = global_write,
 };
 
+static int shared_read(struct ast_channel *chan, const char *cmd, char *data, char *buf, size_t len)
+{
+	struct ast_datastore *varstore;
+	struct varshead *varshead;
+	struct ast_var_t *var;
+	AST_DECLARE_APP_ARGS(args,
+		AST_APP_ARG(var);
+		AST_APP_ARG(chan);
+	);
+
+	if (ast_strlen_zero(data)) {
+		ast_log(LOG_WARNING, "SHARED() requires an argument: SHARED(<var>[,<chan>])\n");
+		return -1;
+	}
+
+	AST_STANDARD_APP_ARGS(args, data);
+
+	if (!ast_strlen_zero(args.chan)) {
+		char *prefix = alloca(strlen(args.chan) + 2);
+		sprintf(prefix, "%s-", args.chan);
+		if (!(chan = ast_get_channel_by_name_locked(args.chan)) && !(chan = ast_get_channel_by_name_prefix_locked(prefix, strlen(prefix)))) {
+			ast_log(LOG_ERROR, "Channel '%s' not found!  Variable '%s' will be blank.\n", args.chan, args.var);
+			return -1;
+		}
+	} else
+		ast_channel_lock(chan);
+
+	if (!(varstore = ast_channel_datastore_find(chan, &shared_variable_info, NULL)))
+		return -1;
+	varshead = varstore->data;
+	*buf = '\0';
+
+	/* Protected by the channel lock */
+	AST_LIST_TRAVERSE(varshead, var, entries) {
+		if (!strcmp(args.var, ast_var_name(var))) {
+			ast_copy_string(buf, ast_var_value(var), len);
+			break;
+		}
+	}
+
+	return 0;
+}
+
+static int shared_write(struct ast_channel *chan, const char *cmd, char *data, const char *value)
+{
+	struct ast_datastore *varstore;
+	struct varshead *varshead;
+	struct ast_var_t *var;
+	AST_DECLARE_APP_ARGS(args,
+		AST_APP_ARG(var);
+		AST_APP_ARG(chan);
+	);
+
+	if (ast_strlen_zero(data)) {
+		ast_log(LOG_WARNING, "SHARED() requires an argument: SHARED(<var>[,<chan>])\n");
+		return -1;
+	}
+
+	AST_STANDARD_APP_ARGS(args, data);
+
+	if (!ast_strlen_zero(args.chan)) {
+		char *prefix = alloca(strlen(args.chan) + 2);
+		sprintf(prefix, "%s-", args.chan);
+		if (!(chan = ast_get_channel_by_name_locked(args.chan)) && !(chan = ast_get_channel_by_name_prefix_locked(prefix, strlen(prefix)))) {
+			ast_log(LOG_ERROR, "Channel '%s' not found!  Variable '%s' not set to '%s'.\n", args.chan, args.var, value);
+			return -1;
+		}
+	} else
+		ast_channel_lock(chan);
+
+	if (!(varstore = ast_channel_datastore_find(chan, &shared_variable_info, NULL))) {
+		if (!(varstore = ast_channel_datastore_alloc(&shared_variable_info, NULL))) {
+			ast_log(LOG_ERROR, "Unable to allocate new datastore.  Shared variable not set.\n");
+			ast_channel_unlock(chan);
+			return -1;
+		}
+
+		if (!(varshead = ast_calloc(1, sizeof(*varshead)))) {
+			ast_log(LOG_ERROR, "Unable to allocate variable structure.  Shared variable not set.\n");
+			ast_channel_datastore_free(varstore);
+			ast_channel_unlock(chan);
+			return -1;
+		}
+
+		varstore->data = varshead;
+		ast_channel_datastore_add(chan, varstore);
+	}
+	varshead = varstore->data;
+
+	/* Protected by the channel lock */
+	AST_LIST_TRAVERSE(varshead, var, entries) {
+		/* If there's a previous value, remove it */
+		if (!strcmp(args.var, ast_var_name(var))) {
+			AST_LIST_REMOVE(varshead, var, entries);
+			ast_var_delete(var);
+			break;
+		}
+	}
+
+	var = ast_var_assign(args.var, S_OR(value, ""));
+	AST_LIST_INSERT_HEAD(varshead, var, entries);
+	manager_event(EVENT_FLAG_DIALPLAN, "VarSet", 
+		"Channel: %s\r\n"
+		"Variable: SHARED(%s)\r\n"
+		"Value: %s\r\n"
+		"Uniqueid: %s\r\n", 
+		chan ? chan->name : "none", args.var, value, 
+		chan ? chan->uniqueid : "none");
+
+	ast_channel_unlock(chan);
+
+	return 0;
+}
+
+static struct ast_custom_function shared_function = {
+	.name = "SHARED",
+	.synopsis = "Gets or sets the shared variable specified",
+	.syntax = "SHARED(<varname>[,<channel>])",
+	.desc =
+"Implements a shared variable area, in which you may share variables between\n"
+"channels.  If channel is unspecified, defaults to the current channel.  Note\n"
+"that the channel name may be the complete name (i.e. SIP/12-abcd1234) or the\n"
+"prefix only (i.e. SIP/12).\n"
+"\n"
+"The variables used in this space are separate from the general namespace of\n"
+"the channel and thus ${SHARED(foo)} and ${foo} represent two completely\n"
+"different variables, despite sharing the same name.\n"
+"\n"
+"Finally, realize that there is an inherent race between channels operating\n"
+"at the same time, fiddling with each others' internal variables, which is why\n"
+"this special variable namespace exists; it is to remind you that variables in\n"
+"the SHARED namespace may change at any time, without warning.  You should\n"
+"therefore take special care to ensure that when using the SHARED namespace,\n"
+"you retrieve the variable and store it in a regular channel variable before\n"
+"using it in a set of calculations (or you might be surprised by the result).\n",
+	.read = shared_read,
+	.write = shared_write,
+};
+
 static int unload_module(void)
 {
 	int res = 0;
 
 	res |= ast_custom_function_unregister(&global_function);
+	res |= ast_custom_function_unregister(&shared_function);
 
 	return res;
 }
@@ -75,8 +236,9 @@ static int load_module(void)
 	int res = 0;
 
 	res |= ast_custom_function_register(&global_function);
+	res |= ast_custom_function_register(&shared_function);
 
 	return res;
 }
 
-AST_MODULE_INFO_STANDARD(ASTERISK_GPL_KEY, "Global variable dialplan functions");
+AST_MODULE_INFO_STANDARD(ASTERISK_GPL_KEY, "Variable dialplan functions");