Add helper method to read an integer from a buffer

Change-Id: Ifdd2122a3e60cdb11cc9df67570ab5628bfcdeea
Signed-off-by: Arne Schwabe <[email protected]>

src/openvpn/buffer.c

@@ -1443,3 +1443,28 @@ buffer_read_from_file(const char *filename, struct gc_arena *gc)
     fclose(fp);
     return ret;
 }
+
+bool
+buffer_read_int(struct buffer *buf, int *result)
+{
+    *result = 0;
+    bool ret = false;
+
+    while (buf_len(buf))
+    {
+        uint8_t c = *BPTR(buf);
+        if (c >= '0' && c <= '9')
+        {
+            *result = *result * 10;
+            /* lower nibble of ascii digits is their value */
+            *result += (c & 0x0f);
+            buf_advance(buf, 1);
+            ret = true;
+        }
+        else
+        {
+            return ret;
+        }
+    }
+    return ret;
+}

src/openvpn/buffer.h

@@ -1233,4 +1233,14 @@ struct buffer_list *buffer_list_file(const char *fn, int max_line_len);
  */
 struct buffer buffer_read_from_file(const char *filename, struct gc_arena *gc);
 
+/**
+ * will read a decimal integer from a buffer until the next non-decimal
+ * character. If successful the method will return true and the integer
+ * in \c result. The buffer will be advanced to the next character after
+ * the integer
+ *
+ */
+bool
+buffer_read_int(struct buffer *buf, int *result);
+
 #endif /* BUFFER_H */

tests/unit_tests/openvpn/test_buffer.c

@@ -403,6 +403,37 @@ test_env_special_free(void **state)
     assert_true(unit_test_free_called);
 }
 
+static void
+test_buffer_read_int(void **state)
+{
+    struct gc_arena gc = gc_new();
+    struct buffer buf = alloc_buf_gc(1000, &gc);
+
+    buf_printf(&buf, "72732,1234");
+
+    int tmp = -1;
+    assert_true(buffer_read_int(&buf, &tmp));
+    assert_int_equal(tmp, 72732);
+    assert_int_equal(*BPTR(&buf), ',');
+
+    buf_advance(&buf, 1);
+
+    assert_true(buffer_read_int(&buf, &tmp));
+    assert_int_equal(tmp, 1234);
+    assert_int_equal(buf_len(&buf), 0);
+
+    buf = alloc_buf_gc(1000, &gc);
+    buf_printf(&buf, "fo42,7777");
+
+    assert_false(buffer_read_int(&buf, &tmp));
+
+    buf = alloc_buf_gc(1000, &gc);
+    buf_printf(&buf, "");
+    assert_false(buffer_read_int(&buf, &tmp));
+
+    gc_free(&gc);
+}
+
 int
 main(void)
 {
@@ -435,7 +466,8 @@ main(void)
         cmocka_unit_test(test_buffer_free_gc_two),
         cmocka_unit_test(test_buffer_gc_realloc),
         cmocka_unit_test(test_character_class),
-        cmocka_unit_test(test_env_special_free)
+        cmocka_unit_test(test_env_special_free),
+        cmocka_unit_test(test_buffer_read_int),
     };
 
     return cmocka_run_group_tests_name("buffer", tests, NULL, NULL);