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// file : build/lexer -*- C++ -*-
// copyright : Copyright (c) 2014-2015 Code Synthesis Ltd
// license : MIT; see accompanying LICENSE file
#ifndef BUILD_LEXER
#define BUILD_LEXER
#include <string>
#include <iosfwd>
#include <cstdint> // uint64_t
#include <exception>
#include <build/token>
#include <build/diagnostics>
namespace build
{
// Context-dependent lexing mode. In the value mode we don't treat
// certain characters (e.g., +, =) as special so that we can use
// them in the variable values, e.g., 'foo = g++'. In contrast,
// in the variable mode, we restrict certain character (e.g., /)
// from appearing in the name. The pairs mode is just like value
// except that we split names separated by the pair character.
// The pairs mode must be set manually.
//
enum class lexer_mode {normal, value, variable, pairs};
class lexer
{
public:
lexer (std::istream& is, const std::string& name): is_ (is), fail (name) {}
const std::string&
name () const {return fail.name_;}
// Note: sets mode for the next token. If mode is pairs, then
// the second argument specifies the separator character.
//
void
mode (lexer_mode m, char pair_separator = '=')
{
next_mode_ = m;
pair_separator_ = pair_separator;
}
lexer_mode
mode () const {return mode_;}
// Scanner.
//
token
next ();
private:
class xchar
{
public:
typedef std::char_traits<char> traits_type;
typedef traits_type::int_type int_type;
typedef traits_type::char_type char_type;
xchar (int_type v, std::uint64_t l, std::uint64_t c)
: v_ (v), l_ (l), c_ (c) {}
operator char_type () const {return static_cast<char_type> (v_);}
int_type
value () const {return v_;}
std::uint64_t line () const {return l_;}
std::uint64_t column () const {return c_;}
private:
int_type v_;
std::uint64_t l_;
std::uint64_t c_;
};
token
name (xchar, bool separated);
// Return true we have seen any spaces. Skipped empty lines don't
// count. In other words, we are only interested in spaces that
// are on the same line as the following non-space character.
//
bool
skip_spaces ();
xchar
escape ();
// Character interface.
//
private:
xchar
peek ();
xchar
get ();
void
unget (const xchar&);
// Tests.
//
bool
is_eos (const xchar& c) const
{
return c.value () == xchar::traits_type::eof ();
}
// Diagnostics.
//
private:
struct fail_mark_base: build::fail_mark_base<failed>
{
fail_mark_base (const std::string& n): name_ (n) {}
location_prologue
operator() (const xchar&) const;
std::string name_;
};
typedef diag_mark<fail_mark_base> fail_mark;
private:
std::istream& is_;
fail_mark fail;
std::uint64_t l_ {1};
std::uint64_t c_ {1};
bool unget_ {false};
xchar buf_ {0, 0, 0};
bool eos_ {false};
lexer_mode mode_ {lexer_mode::normal};
char pair_separator_;
lexer_mode next_mode_ {lexer_mode::normal}; // Switch to for next token.
lexer_mode prev_mode_; // Return to after current mode expires.
};
}
#endif // BUILD_LEXER
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