Implement support for tokenization of preprocessed C/C++ source

1 files changed, 166 insertions, 0 deletions

diff --git a/build2/cc/lexer.hxx b/build2/cc/lexer.hxx
new file mode 100644
index 0000000..0735b45
--- /dev/null
+++ b/build2/cc/lexer.hxx
@@ -0,0 +1,166 @@
+// file      : build2/cc/lexer.hxx -*- C++ -*-
+// copyright : Copyright (c) 2014-2017 Code Synthesis Ltd
+// license   : MIT; see accompanying LICENSE file
+
+#ifndef BUILD2_CC_LEXER_HXX
+#define BUILD2_CC_LEXER_HXX
+
+#include <libbutl/char-scanner.hxx>
+
+#include <build2/types.hxx>
+#include <build2/utility.hxx>
+
+#include <build2/diagnostics.hxx>
+
+namespace build2
+{
+  namespace cc
+  {
+    // Preprocessor-level tokenization of C/C++ source. In other words, the
+    // sequence of tokens returned is similar to what a real C/C++ compiler
+    // would see from its preprocessor.
+    //
+    // The input is a (partially-)preprocessed translation unit that may still
+    // contain comments, line continuations, and preprocessor directives such
+    // as #line, #pragma, etc. Currently all preprocessor directives are
+    // discarded and no values are saved for literals.
+    //
+    enum class token_type
+    {
+      // NOTE: remember to update operator<<() if changing anything here!
+      //
+      eos,
+
+      dot,         // .
+      semi,        // ;
+      lcbrace,     // {
+      rcbrace,     // }
+      punctuation, // Other punctuation.
+
+      identifier,
+
+      number,      // Number literal.
+      character,   // Char   literal.
+      string,      // String literal.
+
+      other        // Other token.
+    };
+
+    struct token
+    {
+      token_type type;
+      string     value;
+
+      uint64_t line;
+      uint64_t column;
+
+    public:
+      token ()
+          : token (token_type::eos, 0, 0) {}
+
+      token (token_type t, uint64_t l, uint64_t c)
+          : token (t, string (), l, c) {}
+
+      token (token_type t, string v, uint64_t l, uint64_t c)
+          : type (t), value (move (v)), line (l), column (c) {}
+    };
+
+    // Output the token value in a format suitable for diagnostics.
+    //
+    ostream&
+    operator<< (ostream&, const token&);
+
+    class lexer: protected butl::char_scanner
+    {
+    public:
+      lexer (istream& is, const path& name)
+          : char_scanner (is, false), name_ (name), fail ("error", &name_) {}
+
+      const path&
+      name () const {return name_;}
+
+      // Note that it is ok to call next() again after getting eos.
+      //
+      token
+      next ()
+      {
+        token t;
+        next (t, skip_spaces ());
+        return t;
+      }
+
+      // As above but reuse the token to avoid a (potential) memory
+      // allocation. Typical usage:
+      //
+      // for (token t; l.next (t) != token_type::eos; )
+      //   ...
+      //
+      token_type
+      next (token& t)
+      {
+        next (t, skip_spaces ());
+        return t.type;
+      }
+
+    private:
+      void
+      next (token&, xchar);
+
+      void
+      number_literal (token&, xchar);
+
+      void
+      char_literal (token&, xchar);
+
+      void
+      string_literal (token&, xchar);
+
+      void
+      raw_string_literal (token&, xchar);
+
+      void
+      literal_suffix (xchar);
+
+      xchar
+      skip_spaces (bool newline = true);
+
+      // The char_scanner adaptation for newline escape sequence processing.
+      // Enabled by default and is only disabled in the raw string literals.
+      //
+    private:
+      using base = char_scanner;
+
+      xchar
+      get (bool escape = true);
+
+      void
+      get (const xchar& peeked) {base::get (peeked);}
+
+      xchar
+      peek (bool escape = true);
+
+    private:
+      const path name_;
+      fail_mark fail;
+    };
+
+    // Diagnostics plumbing. We assume that any diag stream for which we can
+    // use token as location has its aux data pointing to pointer to path.
+    //
+    inline location
+    get_location (const token& t, const path& p)
+    {
+      return location (&p, t.line, t.column);
+    }
+
+    inline location
+    get_location (const token& t, const void* data)
+    {
+      assert (data != nullptr); // E.g., must be &parser::path_.
+      const path* p (*static_cast<const path* const*> (data));
+      return get_location (t, *p);
+    }
+  }
+}
+
+#endif // BUILD2_CC_LEXER_HXX