Add p_parse_*() API for each start rule

assets/parser.c.erb

@@ -924,6 +924,8 @@ static size_t check_reduce(size_t state_id, <%= @grammar.prefix %>token_t token)
  *
  * @param context
  *   Lexer/parser context structure.
+ * @start_state_id
+ *   ID of the state in which to start.
  *
  * @retval P_SUCCESS
  *   The parser successfully matched the input text. The parse result value
@@ -936,7 +938,7 @@ static size_t check_reduce(size_t state_id, <%= @grammar.prefix %>token_t token)
  * @reval P_UNEXPECTED_INPUT
  *   Input text does not match any lexer pattern.
  */
-size_t <%= @grammar.prefix %>parse(<%= @grammar.prefix %>context_t * context)
+static size_t parse_from(<%= @grammar.prefix %>context_t * context, size_t start_state_id)
 {
     <%= @grammar.prefix %>token_info_t token_info;
     <%= @grammar.prefix %>token_t token = INVALID_TOKEN_ID;
@@ -949,6 +951,7 @@ size_t <%= @grammar.prefix %>parse(<%= @grammar.prefix %>context_t * context)
 <% end %>
     state_values_stack_init(&statevalues);
     state_values_stack_push(&statevalues);
+    state_values_stack_index(&statevalues, -1)->state_id = start_state_id;
     size_t result;
     for (;;)
     {
@@ -1101,6 +1104,19 @@ size_t <%= @grammar.prefix %>parse(<%= @grammar.prefix %>context_t * context)
     return result;
 }
 
+size_t <%= @grammar.prefix %>parse(<%= @grammar.prefix %>context_t * context)
+{
+    return parse_from(context, 0u);
+}
+
+<% @grammar.start_rules.each_with_index do |start_rule, i| %>
+
+size_t <%= @grammar.prefix %>parse_<%= start_rule %>(<%= @grammar.prefix %>context_t * context)
+{
+    return parse_from(context, <%= i %>u);
+}
+<% end %>
+
 /**
  * Get the parse result value.
  *

assets/parser.d.erb

@@ -985,6 +985,8 @@ private size_t check_reduce(size_t state_id, <%= @grammar.prefix %>token_t token
  *
  * @param context
  *   Lexer/parser context structure.
+ * @start_state_id
+ *   ID of the state in which to start.
  *
  * @retval P_SUCCESS
  *   The parser successfully matched the input text. The parse result value
@@ -997,11 +999,12 @@ private size_t check_reduce(size_t state_id, <%= @grammar.prefix %>token_t token
  * @reval P_UNEXPECTED_INPUT
  *   Input text does not match any lexer pattern.
  */
-public size_t <%= @grammar.prefix %>parse(<%= @grammar.prefix %>context_t * context)
+private size_t parse_from(<%= @grammar.prefix %>context_t * context, size_t start_state_id)
 {
     <%= @grammar.prefix %>token_info_t token_info;
     <%= @grammar.prefix %>token_t token = INVALID_TOKEN_ID;
     state_value_t[] statevalues = new state_value_t[](1);
+    statevalues[0].state_id = start_state_id;
     size_t reduced_rule_set = INVALID_ID;
 <% if @grammar.ast %>
     void * reduced_parser_node;
@@ -1147,6 +1150,19 @@ public size_t <%= @grammar.prefix %>parse(<%= @grammar.prefix %>context_t * cont
     }
 }
 
+public size_t <%= @grammar.prefix %>parse(<%= @grammar.prefix %>context_t * context)
+{
+    return parse_from(context, 0u);
+}
+
+<% @grammar.start_rules.each_with_index do |start_rule, i| %>
+
+public size_t <%= @grammar.prefix %>parse_<%= start_rule %>(<%= @grammar.prefix %>context_t * context)
+{
+    return parse_from(context, <%= i %>u);
+}
+<% end %>
+
 /**
  * Get the parse result value.
  *

assets/parser.h.erb

@@ -189,6 +189,9 @@ size_t <%= @grammar.prefix %>decode_code_point(uint8_t const * input, size_t inp
 size_t <%= @grammar.prefix %>lex(<%= @grammar.prefix %>context_t * context, <%= @grammar.prefix %>token_info_t * out_token_info);
 
 size_t <%= @grammar.prefix %>parse(<%= @grammar.prefix %>context_t * context);
+<%   @grammar.start_rules.each_with_index do |start_rule, i| %>
+size_t <%= @grammar.prefix %>parse_<%= start_rule %>(<%= @grammar.prefix %>context_t * context);
+<%   end %>
 
 <% if @grammar.ast %>
 <%= @grammar.ast_prefix %><%= @grammar.start_rules[0] %><%= @grammar.ast_suffix %> * <%= @grammar.prefix %>result(<%= @grammar.prefix %>context_t * context);

lib/propane/generator.rb

@@ -71,14 +71,15 @@ class Propane
         end
         tokens_by_name[token.name] = token
       end
-      # Check for user start rules.
-      @grammar.start_rules.each_with_index do |start_rule, i|
+      # Create real start rule(s).
+      real_start_rules = @grammar.start_rules.map do |start_rule|
         unless @grammar.rules.find {|rule| rule.name == start_rule}
           raise Error.new("Start rule `#{start_rule}` not found")
         end
-        # Add "real" start rule.
-        @grammar.rules.unshift(Rule.new("$#{start_rule}", [start_rule, "$EOF"], nil, nil, nil))
+        Rule.new("$#{start_rule}", [start_rule, "$EOF"], nil, nil, nil)
       end
+      # Add real start rules before user-given rules.
+      @grammar.rules = real_start_rules + @grammar.rules
       # Generate and add rules for optional components.
       generate_optional_component_rules!(tokens_by_name)
       # Build rule sets.

lib/propane/grammar.rb

@@ -11,7 +11,7 @@ class Propane
     attr_reader :free_token_node
     attr_reader :modulename
     attr_reader :patterns
-    attr_reader :rules
+    attr_accessor :rules
     attr_reader :start_rules
     attr_reader :tokens
     attr_reader :code_blocks

lib/propane/parser.rb

@@ -16,11 +16,20 @@ class Propane
       @warnings = Set.new
       @errors = Set.new
       @options = options
-      start_item = Item.new(grammar.rules.first, 0)
-      eval_item_sets = Set[ItemSet.new([start_item])]
+      start_items = grammar.rules[0...grammar.start_rules.length].map do |start_rule|
+        Item.new(start_rule, 0)
+      end
+      start_item_sets = start_items.map {|item| ItemSet.new([item])}
+      eval_item_sets = Set[*start_item_sets]
 
       while eval_item_sets.size > 0
-        item_set = eval_item_sets.first
+        item_set =
+          if start_item_sets.size > 0
+            # Ensure we evaluate start_item_sets first in order
+            start_item_sets.slice!(0)
+          else
+            eval_item_sets.first
+          end
         eval_item_sets.delete(item_set)
         unless @item_sets_set.include?(item_set)
           item_set.id = @item_sets.size