func_channel: Add lastcontext and lastexten.

Adds the lastcontext and lastexten channel fields to allow users
to access previous dialplan execution locations.

ASTERISK-29840 #close

Change-Id: Ib455fe300cc8e9a127686896ee2d0bd11e900307

doc/CHANGES-staging/channel_internal_api.txt

+Subject: channel_internal_api
+
+CHANNEL(lastcontext) and CHANNEL(lastexten)
+are now available for use in the dialplan.

funcs/func_channel.c

@@ -234,6 +234,12 @@
 					<enum name="context">
 						<para>R/O returns the context for an outbound channel.</para>
 					</enum>
+					<enum name="lastexten">
+						<para>R/O returns the last unique extension for an outbound channel.</para>
+					</enum>
+					<enum name="lastcontext">
+						<para>R/O returns the last unique context for an outbound channel.</para>
+					</enum>
 					<enum name="channame">
 						<para>R/O returns the channel name for an outbound channel.</para>
 					</enum>
@@ -410,6 +416,10 @@ static int func_channel_read(struct ast_channel *chan, const char *function,
 		locked_copy_string(chan, buf, ast_channel_exten(chan), len);
 	else if (!strcasecmp(data, "context"))
 		locked_copy_string(chan, buf, ast_channel_context(chan), len);
+	else if (!strcasecmp(data, "lastexten"))
+		locked_copy_string(chan, buf, ast_channel_lastexten(chan), len);
+	else if (!strcasecmp(data, "lastcontext"))
+		locked_copy_string(chan, buf, ast_channel_lastcontext(chan), len);
 	else if (!strcasecmp(data, "userfield"))
 		locked_copy_string(chan, buf, ast_channel_userfield(chan), len);
 	else if (!strcasecmp(data, "channame"))

include/asterisk/channel.h

@@ -4164,8 +4164,10 @@ void ast_channel_blockproc_set(struct ast_channel *chan, const char *value);
 const char *ast_channel_data(const struct ast_channel *chan);
 void ast_channel_data_set(struct ast_channel *chan, const char *value);
 
+const char *ast_channel_lastcontext(const struct ast_channel *chan);
 const char *ast_channel_context(const struct ast_channel *chan);
 void ast_channel_context_set(struct ast_channel *chan, const char *value);
+const char *ast_channel_lastexten(const struct ast_channel *chan);
 const char *ast_channel_exten(const struct ast_channel *chan);
 void ast_channel_exten_set(struct ast_channel *chan, const char *value);
 const char *ast_channel_macrocontext(const struct ast_channel *chan);

main/channel_internal_api.c

@@ -206,6 +206,8 @@ struct ast_channel {
 
 	char context[AST_MAX_CONTEXT];			/*!< Dialplan: Current extension context */
 	char exten[AST_MAX_EXTENSION];			/*!< Dialplan: Current extension number */
+	char lastcontext[AST_MAX_CONTEXT];		/*!< Dialplan: Previous extension context */
+	char lastexten[AST_MAX_EXTENSION];		/*!< Dialplan: Previous extension number */
 	char macrocontext[AST_MAX_CONTEXT];		/*!< Macro: Current non-macro context. See app_macro.c */
 	char macroexten[AST_MAX_EXTENSION];		/*!< Macro: Current non-macro extension. See app_macro.c */
 	char unbridged;							/*!< non-zero if the bridge core needs to re-evaluate the current
@@ -345,8 +347,16 @@ const char *ast_channel_context(const struct ast_channel *chan)
 {
 	return chan->context;
 }
+const char *ast_channel_lastcontext(const struct ast_channel *chan)
+{
+	return chan->lastcontext;
+}
 void ast_channel_context_set(struct ast_channel *chan, const char *value)
 {
+	if (!*chan->lastcontext || strcmp(value, chan->context)) {
+		/* only copy to last context when it changes, unless it's empty to begin with */
+		ast_copy_string(chan->lastcontext, chan->context, sizeof(chan->lastcontext));
+	}
 	ast_copy_string(chan->context, value, sizeof(chan->context));
 	ast_channel_snapshot_invalidate_segment(chan, AST_CHANNEL_SNAPSHOT_INVALIDATE_DIALPLAN);
 }
@@ -354,8 +364,16 @@ const char *ast_channel_exten(const struct ast_channel *chan)
 {
 	return chan->exten;
 }
+const char *ast_channel_lastexten(const struct ast_channel *chan)
+{
+	return chan->lastexten;
+}
 void ast_channel_exten_set(struct ast_channel *chan, const char *value)
 {
+	if (!*chan->lastexten || strcmp(value, chan->exten)) {
+		/* only copy to last exten when it changes, unless it's empty to begin with */
+		ast_copy_string(chan->lastexten, chan->exten, sizeof(chan->lastexten));
+	}
 	ast_copy_string(chan->exten, value, sizeof(chan->exten));
 	ast_channel_snapshot_invalidate_segment(chan, AST_CHANNEL_SNAPSHOT_INVALIDATE_DIALPLAN);
 }