Add support for scoping and symbol binding

As a first step towards stand-alone sets, add support for scoping and
binding symbols. This will be used for user-defined constants, as well
as declarations of modifiable (stand-alone) sets once the kernel side
is ready.

Scopes are currently limited to three nesting levels: the global scope,
table block scopes and chain block scopes.

Signed-off-by: Patrick McHardy <kaber@trash.net>

2 files changed, 62 insertions, 2 deletions

diff --git a/src/parser.y b/src/parser.y
index b13e932e..1ca5981b 100644
--- a/src/parser.y
+++ b/src/parser.y
@@ -33,6 +33,7 @@ void parser_init(struct parser_state *state, struct list_head *msgs)
 	memset(state, 0, sizeof(*state));
 	init_list_head(&state->cmds);
 	state->msgs = msgs;
+	state->scopes[0] = scope_init(&state->top_scope, NULL);
 }
 
 static void yyerror(struct location *loc, void *scanner,
@@ -41,6 +42,22 @@ static void yyerror(struct location *loc, void *scanner,
 	erec_queue(error(loc, "%s", s), state->msgs);
 }
 
+static struct scope *current_scope(const struct parser_state *state)
+{
+	return state->scopes[state->scope];
+}
+
+static void open_scope(struct parser_state *state, struct scope *scope)
+{
+	scope_init(scope, current_scope(state));
+	state->scopes[++state->scope] = scope;
+}
+
+static void close_scope(struct parser_state *state)
+{
+	state->scope--;
+}
+
 static void location_init(void *scanner, struct parser_state *state,
 			  struct location *loc)
 {
@@ -474,6 +491,7 @@ add_cmd			:	TABLE		table_spec
 						'{'	table_block	'}'
 			{
 				handle_merge(&$3->handle, &$2);
+				close_scope(state);
 				$$ = cmd_alloc(CMD_ADD, CMD_OBJ_TABLE, &$2, $5);
 			}
 			|	CHAIN		chain_spec
@@ -484,6 +502,7 @@ add_cmd			:	TABLE		table_spec
 						'{'	chain_block	'}'
 			{
 				handle_merge(&$3->handle, &$2);
+				close_scope(state);
 				$$ = cmd_alloc(CMD_ADD, CMD_OBJ_CHAIN, &$2, $5);
 			}
 			|	RULE		ruleid_spec	rule
@@ -530,7 +549,11 @@ flush_cmd		:	TABLE		table_spec
 			}
 			;
 
-table_block_alloc	:	/* empty */	{ $$ = table_alloc(); }
+table_block_alloc	:	/* empty */
+			{
+				$$ = table_alloc();
+				open_scope(state, &$$->scope);
+			}
 			;
 
 table_block		:	/* empty */	{ $$ = $<table>-1; }
@@ -547,11 +570,16 @@ table_line		:	CHAIN		chain_identifier	chain_block_alloc
 	    					'{' 	chain_block	'}'
 	    		{
 				handle_merge(&$3->handle, &$2);
+				close_scope(state);
 				$$ = $3;
 			}
 			;
 
-chain_block_alloc	:	/* empty */	{ $$ = chain_alloc(NULL); }
+chain_block_alloc	:	/* empty */
+			{
+				$$ = chain_alloc(NULL);
+				open_scope(state, &$$->scope);
+			}
 			;
 
 chain_block		:	/* empty */	{ $$ = $<chain>-1; }
diff --git a/src/rule.c b/src/rule.c
index e86c78aa..8efbd887 100644
--- a/src/rule.c
+++ b/src/rule.c
@@ -68,6 +68,38 @@ void rule_print(const struct rule *rule)
 	printf("\n");
 }
 
+struct scope *scope_init(struct scope *scope, const struct scope *parent)
+{
+	scope->parent = parent;
+	init_list_head(&scope->symbols);
+	return scope;
+}
+
+void symbol_bind(struct scope *scope, const char *identifier, struct expr *expr)
+{
+	struct symbol *sym;
+
+	sym = xzalloc(sizeof(*sym));
+	sym->identifier = xstrdup(identifier);
+	sym->expr = expr;
+
+	list_add_tail(&sym->list, &scope->symbols);
+}
+
+struct symbol *symbol_lookup(const struct scope *scope, const char *identifier)
+{
+	struct symbol *sym;
+
+	while (scope != NULL) {
+		list_for_each_entry(sym, &scope->symbols, list) {
+			if (!strcmp(sym->identifier, identifier))
+				return sym;
+		}
+		scope = scope->parent;
+	}
+	return NULL;
+}
+
 struct chain *chain_alloc(const char *name)
 {
 	struct chain *chain;