Add p_set_input_index()

spec/test_rewind.d

@@ -0,0 +1,101 @@
+import testparser;
+import testutils;
+
+/* Grammar and scenario: see test_rewind.c. */
+
+int[16] nums;
+size_t n_nums;
+uint[16] num_cols;
+size_t n_num_cols;
+
+void record(int value)
+{
+    nums[n_nums++] = value;
+}
+
+size_t mylexfn(p_context_t * context, p_token_info_t * out_token_info)
+{
+    static int remaining;
+    static size_t body_index;
+    static p_position_t body_position;
+
+    for (;;)
+    {
+        size_t result = p_lex(context, out_token_info);
+        if (result != P_SUCCESS)
+        {
+            return result;
+        }
+
+        if (out_token_info.token == TOKEN_repeat)
+        {
+            /* Consume "repeat <count> {" and remember where the body begins. */
+            p_token_info_t count_info;
+            size_t count_result = p_lex(context, &count_info);
+            assert(count_result == P_SUCCESS);
+            assert(count_info.token == TOKEN_num);
+            p_token_info_t brace_info;
+            size_t brace_result = p_lex(context, &brace_info);
+            assert(brace_result == P_SUCCESS);
+            assert(brace_info.token == TOKEN_lbrace);
+            remaining = p_value_get(&count_info.pvalue);
+            body_index = p_input_index(context);
+            body_position = p_position(context);
+            continue;
+        }
+        if (out_token_info.token == TOKEN_rbrace)
+        {
+            /* End of the body. If more expansions remain, rewind the lexer to
+             * the start of the body and re-read it; otherwise fall through to
+             * the input following the '}'. */
+            if (remaining > 1)
+            {
+                remaining--;
+                p_set_input_index(context, body_index);
+                p_set_position(context, body_position);
+                continue;
+            }
+            remaining = 0;
+            continue;
+        }
+        if (out_token_info.token == TOKEN_num)
+        {
+            num_cols[n_num_cols++] = out_token_info.position.col;
+        }
+        return result;
+    }
+}
+
+int main()
+{
+    return 0;
+}
+
+unittest
+{
+    /* "repeat 3 { 10 + 20 } 5 + 5": the body "10 + 20" is expanded three
+     * times (recording 30 each time), followed by "5 + 5" (recording 10). */
+    string input = "repeat 3 { 10 + 20 } 5 + 5";
+    p_context_t * context = p_context_new(input);
+    assert(p_parse(context) == P_SUCCESS);
+    p_context_delete(context);
+
+    assert_eq(4u, n_nums);
+    assert_eq(30, nums[0]);
+    assert_eq(30, nums[1]);
+    assert_eq(30, nums[2]);
+    assert_eq(10, nums[3]);
+
+    /* Each body expansion reported the same columns for its num tokens (12 and
+     * 17), because the text position was rewound along with the byte offset.
+     * The trailing statement's nums are at columns 22 and 26. */
+    assert_eq(8u, n_num_cols);
+    assert_eq(12u, num_cols[0]);
+    assert_eq(17u, num_cols[1]);
+    assert_eq(12u, num_cols[2]);
+    assert_eq(17u, num_cols[3]);
+    assert_eq(12u, num_cols[4]);
+    assert_eq(17u, num_cols[5]);
+    assert_eq(22u, num_cols[6]);
+    assert_eq(26u, num_cols[7]);
+}