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// Copyright Toru Niina 2017.
// Distributed under the MIT License.
#ifndef TOML11_COMBINATOR_HPP
#define TOML11_COMBINATOR_HPP
#include <cassert>
#include <cctype>
#include <cstdio>
#include <array>
#include <iomanip>
#include <iterator>
#include <limits>
#include <type_traits>
#include "region.hpp"
#include "result.hpp"
#include "traits.hpp"
#include "utility.hpp"
// they scans characters and returns region if it matches to the condition.
// when they fail, it does not change the location.
// in lexer.hpp, these are used.
namespace toml
{
namespace detail
{
// to output character as an error message.
inline std::string show_char(const char c)
{
// It suppresses an error that occurs only in Debug mode of MSVC++ on Windows.
// I'm not completely sure but they check the value of char to be in the
// range [0, 256) and some of the COMPLETELY VALID utf-8 character sometimes
// has negative value (if char has sign). So here it re-interprets c as
// unsigned char through pointer. In general, converting pointer to a
// pointer that has different type cause UB, but `(signed|unsigned)?char`
// are one of the exceptions. Converting pointer only to char and std::byte
// (c++17) are valid.
if(std::isgraph(*reinterpret_cast<unsigned char const*>(std::addressof(c))))
{
return std::string(1, c);
}
else
{
std::array<char, 5> buf;
buf.fill('\0');
const auto r = std::snprintf(
buf.data(), buf.size(), "0x%02x", static_cast<int>(c) & 0xFF);
(void) r; // Unused variable warning
assert(r == static_cast<int>(buf.size()) - 1);
return std::string(buf.data());
}
}
template<char C>
struct character
{
static constexpr char target = C;
static result<region, none_t>
invoke(location& loc)
{
if(loc.iter() == loc.end()) {return none();}
const auto first = loc.iter();
const char c = *(loc.iter());
if(c != target)
{
return none();
}
loc.advance(); // update location
return ok(region(loc, first, loc.iter()));
}
};
template<char C>
constexpr char character<C>::target;
// closed interval [Low, Up]. both Low and Up are included.
template<char Low, char Up>
struct in_range
{
// assuming ascii part of UTF-8...
static_assert(Low <= Up, "lower bound should be less than upper bound.");
static constexpr char upper = Up;
static constexpr char lower = Low;
static result<region, none_t>
invoke(location& loc)
{
if(loc.iter() == loc.end()) {return none();}
const auto first = loc.iter();
const char c = *(loc.iter());
if(c < lower || upper < c)
{
return none();
}
loc.advance();
return ok(region(loc, first, loc.iter()));
}
};
template<char L, char U> constexpr char in_range<L, U>::upper;
template<char L, char U> constexpr char in_range<L, U>::lower;
// keep iterator if `Combinator` matches. otherwise, increment `iter` by 1 char.
// for detecting invalid characters, like control sequences in toml string.
template<typename Combinator>
struct exclude
{
static result<region, none_t>
invoke(location& loc)
{
if(loc.iter() == loc.end()) {return none();}
auto first = loc.iter();
auto rslt = Combinator::invoke(loc);
if(rslt.is_ok())
{
loc.reset(first);
return none();
}
loc.reset(std::next(first)); // XXX maybe loc.advance() is okay but...
return ok(region(loc, first, loc.iter()));
}
};
// increment `iter`, if matches. otherwise, just return empty string.
template<typename Combinator>
struct maybe
{
static result<region, none_t>
invoke(location& loc)
{
const auto rslt = Combinator::invoke(loc);
if(rslt.is_ok())
{
return rslt;
}
return ok(region(loc));
}
};
template<typename ... Ts>
struct sequence;
template<typename Head, typename ... Tail>
struct sequence<Head, Tail...>
{
static result<region, none_t>
invoke(location& loc)
{
const auto first = loc.iter();
auto rslt = Head::invoke(loc);
if(rslt.is_err())
{
loc.reset(first);
return none();
}
return sequence<Tail...>::invoke(loc, std::move(rslt.unwrap()), first);
}
// called from the above function only, recursively.
template<typename Iterator>
static result<region, none_t>
invoke(location& loc, region reg, Iterator first)
{
const auto rslt = Head::invoke(loc);
if(rslt.is_err())
{
loc.reset(first);
return none();
}
reg += rslt.unwrap(); // concat regions
return sequence<Tail...>::invoke(loc, std::move(reg), first);
}
};
template<typename Head>
struct sequence<Head>
{
// would be called from sequence<T ...>::invoke only.
template<typename Iterator>
static result<region, none_t>
invoke(location& loc, region reg, Iterator first)
{
const auto rslt = Head::invoke(loc);
if(rslt.is_err())
{
loc.reset(first);
return none();
}
reg += rslt.unwrap(); // concat regions
return ok(reg);
}
};
template<typename ... Ts>
struct either;
template<typename Head, typename ... Tail>
struct either<Head, Tail...>
{
static result<region, none_t>
invoke(location& loc)
{
const auto rslt = Head::invoke(loc);
if(rslt.is_ok()) {return rslt;}
return either<Tail...>::invoke(loc);
}
};
template<typename Head>
struct either<Head>
{
static result<region, none_t>
invoke(location& loc)
{
return Head::invoke(loc);
}
};
template<typename T, typename N>
struct repeat;
template<std::size_t N> struct exactly{};
template<std::size_t N> struct at_least{};
struct unlimited{};
template<typename T, std::size_t N>
struct repeat<T, exactly<N>>
{
static result<region, none_t>
invoke(location& loc)
{
region retval(loc);
const auto first = loc.iter();
for(std::size_t i=0; i<N; ++i)
{
auto rslt = T::invoke(loc);
if(rslt.is_err())
{
loc.reset(first);
return none();
}
retval += rslt.unwrap();
}
return ok(std::move(retval));
}
};
template<typename T, std::size_t N>
struct repeat<T, at_least<N>>
{
static result<region, none_t>
invoke(location& loc)
{
region retval(loc);
const auto first = loc.iter();
for(std::size_t i=0; i<N; ++i)
{
auto rslt = T::invoke(loc);
if(rslt.is_err())
{
loc.reset(first);
return none();
}
retval += rslt.unwrap();
}
while(true)
{
auto rslt = T::invoke(loc);
if(rslt.is_err())
{
return ok(std::move(retval));
}
retval += rslt.unwrap();
}
}
};
template<typename T>
struct repeat<T, unlimited>
{
static result<region, none_t>
invoke(location& loc)
{
region retval(loc);
while(true)
{
auto rslt = T::invoke(loc);
if(rslt.is_err())
{
return ok(std::move(retval));
}
retval += rslt.unwrap();
}
}
};
} // detail
} // toml
#endif// TOML11_COMBINATOR_HPP
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