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// file : build/lexer.cxx -*- C++ -*-
// copyright : Copyright (c) 2014-2015 Code Synthesis Tools CC
// license : MIT; see accompanying LICENSE file
#include <build/lexer>
#include <iostream>
using namespace std;
namespace build
{
token lexer::
next ()
{
skip_spaces ();
xchar c (get ());
uint64_t ln (c.line ()), cn (c.column ());
if (is_eos (c))
return token (ln, cn);
switch (c)
{
// NOTE: remember to update name() if adding new punctuations.
//
case '\n':
{
return token (token_punctuation::newline, ln, cn);
}
case ':':
{
return token (token_punctuation::colon, ln, cn);
}
case '{':
{
return token (token_punctuation::lcbrace, ln, cn);
}
case '}':
{
return token (token_punctuation::rcbrace, ln, cn);
}
}
// Otherwise it is a name.
//
return name (c);
}
lexer::xchar lexer::
escape ()
{
xchar c (get ());
if (!is_eos (c))
return c;
cerr << name_ << ':' << c.line () << ':' << c.column () << ": error: " <<
"unterminated escape sequence" << endl;
throw lexer_error ();
}
void lexer::
skip_spaces ()
{
xchar c (peek ());
bool start (c.column () == 1);
for (; !is_eos (c); c = peek ())
{
switch (c)
{
case ' ':
case '\t':
break;
case '\n':
{
// Skip empty lines.
//
if (start)
break;
return;
}
case '#':
{
get ();
// Read until newline or eos.
//
for (c = peek (); !is_eos (c) && c != '\n'; c = peek ())
get ();
continue;
}
case '\\':
{
get ();
if (peek () == '\n')
break;
unget (c);
// Fall through.
}
default:
return; // Not a space.
}
get ();
}
}
token lexer::
name (xchar c)
{
uint64_t ln (c.line ()), cn (c.column ());
string lexeme;
lexeme += (c != '\\' ? c : escape ());
for (c = peek (); !is_eos (c); c = peek ())
{
switch (c)
{
case ' ':
case '\t':
case '\n':
case ':':
case '{':
case '}':
case '#':
{
break;
}
case '\\':
{
get ();
lexeme += escape ();
continue;
}
default:
{
get ();
lexeme += c;
continue;
}
}
break;
}
return token (lexeme, ln, cn);
}
lexer::xchar lexer::
peek ()
{
if (unget_)
return buf_;
else
{
if (eos_)
return xchar (xchar::traits_type::eof (), l_, c_);
else
{
xchar::int_type v (is_.peek ());
if (v == xchar::traits_type::eof ())
eos_ = true;
return xchar (v, l_, c_);
}
}
}
lexer::xchar lexer::
get ()
{
if (unget_)
{
unget_ = false;
return buf_;
}
else
{
// When is_.get () returns eof, the failbit is also set (stupid,
// isn't?) which may trigger an exception. To work around this
// we will call peek() first and only call get() if it is not
// eof. But we can only call peek() on eof once; any subsequent
// calls will spoil the failbit (even more stupid).
//
xchar c (peek ());
if (!is_eos (c))
{
is_.get ();
if (c == '\n')
{
l_++;
c_ = 1;
}
else
c_++;
}
return c;
}
}
void lexer::
unget (const xchar& c)
{
// Because iostream::unget cannot work once eos is reached,
// we have to provide our own implementation.
//
buf_ = c;
unget_ = true;
}
}
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