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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 <cstddef> // size_t
#include <cstdint> // uint64_t
#include <cassert>
#include <exception>
#include <butl/char-scanner>
#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 alternnative modes must be set manually. The value and
// pairs modes are automatically reset after the end of the line.
// The variable mode is automatically reset after the name token.
//
enum class lexer_mode {normal, variable, value, pairs};
class lexer: protected butl::char_scanner
{
public:
lexer (std::istream& is, const std::string& name)
: char_scanner (is), fail (name) {mode_.push (lexer_mode::normal);}
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 = '=')
{
mode_.push (m);
pair_separator_ = pair_separator;
}
// Expire the current mode early.
//
void
expire_mode () {mode_.pop ();}
lexer_mode
mode () const {return mode_.top ();}
char
pair_separator () const {return pair_separator_;}
// Scanner.
//
token
next ();
private:
token
name (bool separated);
void
single_quote (std::string& lexeme);
// 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 ();
// 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:
fail_mark fail;
// Currently, the maximum mode nesting is 3: {normal, value, variable}.
//
struct mode_stack
{
static const size_t max_size = 3;
void push (lexer_mode m) {assert (n_ != max_size); d_[n_++] = m;}
void pop () {assert (n_ != 0); n_--;}
lexer_mode top () const {return d_[n_ - 1];}
private:
size_t n_ = 0;
lexer_mode d_[max_size];
};
mode_stack mode_;
char pair_separator_;
};
}
#endif // BUILD_LEXER
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