3 files changed, 132 insertions, 1 deletions
diff --git a/gcc/rust/parse/rust-cfg-parser.cc b/gcc/rust/parse/rust-cfg-parser.cc
new file mode 100644
index 0000000..a6f34b6
--- /dev/null
+++ b/gcc/rust/parse/rust-cfg-parser.cc
@@ -0,0 +1,75 @@
+#include "rust-cfg-parser.h"
+#include "selftest.h"
+
+namespace Rust {
+bool
+parse_cfg_option (const std::string &input, std::string &key,
+		  std::string &value)
+{
+  key.clear ();
+  value.clear ();
+
+  auto equal = input.find ('=');
+
+  // If there is no equal sign, it means there is no value. Clean up the key
+  // and return
+  if (equal == std::string::npos)
+    {
+      key = input;
+
+      // FIXME: Make sure key is a proper identifier
+
+      return true;
+    }
+
+  key = input.substr (0, equal);
+
+  auto remaining_input = input.substr (equal + 1);
+  if (remaining_input[0] != '"' || remaining_input.back () != '"')
+    return false;
+
+  // Remove the quotes around the value, by advancing one character
+  value = remaining_input.substr (1);
+  // And trimming the rightmost character. This is fine since we've already
+  // checked that both the first and last characters were quotes.
+  value.resize (value.size () - 1);
+
+  // FIXME: We need to sanitize here and make sure that both key and value
+  // are proper identifiers
+
+  return true;
+}
+
+} // namespace Rust
+
+#if CHECKING_P
+
+namespace selftest {
+
+void
+rust_cfg_parser_test (void)
+{
+  std::string key;
+  std::string value;
+
+  ASSERT_TRUE (Rust::parse_cfg_option ("key-no-value", key, value));
+  ASSERT_EQ (key, "key-no-value");
+  ASSERT_TRUE (value.empty ());
+
+  ASSERT_TRUE (Rust::parse_cfg_option ("k=\"v\"", key, value));
+  ASSERT_EQ (key, "k");
+  ASSERT_EQ (value, "v");
+
+  // values should be between double quotes
+  ASSERT_FALSE (Rust::parse_cfg_option ("k=v", key, value));
+
+  // No value is an error if there is an equal sign
+  ASSERT_FALSE (Rust::parse_cfg_option ("k=", key, value));
+
+  // No key is an error
+  ASSERT_FALSE (Rust::parse_cfg_option ("=", key, value));
+  ASSERT_FALSE (Rust::parse_cfg_option ("=value", key, value));
+}
+} // namespace selftest
+
+#endif // CHECKING_P
diff --git a/gcc/rust/parse/rust-cfg-parser.h b/gcc/rust/parse/rust-cfg-parser.h
new file mode 100644
index 0000000..a4b860f
--- /dev/null
+++ b/gcc/rust/parse/rust-cfg-parser.h
@@ -0,0 +1,57 @@
+/* This file is part of GCC.
+
+GCC is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 3, or (at your option)
+any later version.
+
+GCC is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with GCC; see the file COPYING3.  If not see
+<http://www.gnu.org/licenses/>. */
+
+#ifndef RUST_CFG_PARSER_H
+#define RUST_CFG_PARSER_H
+
+#include "config.h"
+#include "system.h"
+#include "coretypes.h"
+
+#include <string>
+
+namespace Rust {
+/**
+ * Parse a `key` or `key="value"` pair given to the `-frust-cfg` compiler
+ * option.
+ *
+ * The format is as follows:
+ *
+ * -frust-cfg=<input>
+ *
+ * cfg_input: identifier | identifier '=' '"' identifier '"'
+ *
+ * @param input User input given to the -frust-cfg option
+ * @param key String in which to store the parsed `key`.
+ * @param value String in which to store the parsed `value` if it exists
+ *
+ * @return false if the given input was invalid, true otherwise
+ */
+bool
+parse_cfg_option (const std::string &input, std::string &key,
+		  std::string &value);
+} // namespace Rust
+
+#if CHECKING_P
+
+namespace selftest {
+extern void
+rust_cfg_parser_test (void);
+} // namespace selftest
+
+#endif // CHECKING_P
+
+#endif // RUST_CFG_PARSER_H
diff --git a/gcc/rust/parse/rust-parse.cc b/gcc/rust/parse/rust-parse.cc
index e78de51..f2c1301 100644
--- a/gcc/rust/parse/rust-parse.cc
+++ b/gcc/rust/parse/rust-parse.cc
@@ -118,5 +118,4 @@ extract_module_path (const AST::AttrVec &inner_attrs,
 
   return path;
 }
-
 } // namespace Rust