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libcruft-util/format.hpp

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/*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
* Copyright 2017 Danny Robson <danny@nerdcruft.net>
*/
#ifndef CRUFT_UTIL_FORMAT_HPP
#define CRUFT_UTIL_FORMAT_HPP
#include "view.hpp"
#include <algorithm>
#include <cmath>
#include <cstddef>
#include <iomanip>
#include <iterator>
#include <sstream>
#include <vector>
namespace util::format {
/// denotes the stated data type of one specifier
enum class type_t {
/// an internal type that indicates a span of literal text to copy
/// from the format specifier string
LITERAL,
/// a type that has implemented an ostream operator
USER,
/// a literal '%' symbol
ESCAPE,
/// numeric types
SIGNED,
UNSIGNED,
REAL,
/// a C style string, or equivalent C++ type (std::string,
/// std::string_view, util::view, etc, ...)
STRING,
/// a single character
CHAR,
/// a raw pointer (rather than value that needs to be dereferenced)
POINTER,
/// number of characters written
COUNT
};
/// formatting information for a single specifier.
///
/// TODO: investigate using a proper tagged union to compress the data size
struct specifier {
/// the sub-region of the format specifier that we parsed for this
/// information. probably only useful for the LITERAL type as we just
/// copy the view into the output buffer directly.
util::view<const char*> fmt = util::view<const char*> {nullptr};
int parameter = -1;
struct {
bool plus = false;
bool minus = false;
bool space = false;
bool zero = false;
bool hash = false;
} flags;
int width = -1;
int precision = -1;
int length = -1;
type_t type = type_t::USER;
bool upper = false;
int base = 10;
enum {
FIXED,
SCIENTIFIC,
DEFAULT,
HEX,
} representation = DEFAULT;
};
struct parsed;
template <typename ...Args> class bound;
template <typename ...Args> class stored;
/// a sequence of parsed specifiers that can be used to render some
/// collection parameters in the future.
struct parsed {
std::vector<specifier> m_specifiers;
auto begin (void) const { return std::begin (m_specifiers); }
auto end (void) const { return std::end (m_specifiers); }
/// records a complete collection of parameters for rendering in the
/// future. the caller must maintain the 'parsed' object for the
/// lifetime of the return value.
template <typename ...Args>
bound<Args...>
operator () (const Args &...args) &;
/// records a complete collection of parameters for rendering in the
/// future. takes ownership of the specifiers so there is no lifetime
/// requirement.
template <typename ...Args>
stored<Args...>
operator () (const Args &...args) &&;
};
/// parameter collection for a non-owning sequence of specifiers
template <typename ...ValueT>
class bound {
public:
bound (const parsed &_parsed, const ValueT &...args):
m_parsed {_parsed},
m_values {args...}
{ ; }
auto specifiers (void) const
{ return util::make_view (m_parsed.m_specifiers); }
template <size_t Index>
auto
get (void) const& { return std::get<Index> (m_values); }
private:
const parsed &m_parsed;
std::tuple<const ValueT&...> m_values;
};
/// parameter collection for an owning squence of specifiers.
template <typename ...ValueT>
class stored {
public:
stored (std::vector<specifier> &&_specifiers, const ValueT &...args):
m_specifiers {std::move (_specifiers)},
m_values {args...}
{ ; }
auto
specifiers (void) const&
{
return util::make_view (m_specifiers);
}
template <size_t Index>
const auto&
get (void) const& { return std::get<Index> (m_values); }
private:
std::vector<specifier> m_specifiers;
std::tuple<const ValueT&...> m_values;
};
template <typename ...Args>
bound<Args...>
parsed::operator () (const Args &...args) &
{ return bound { *this, args... }; }
template <typename ...Args>
stored<Args...>
parsed::operator () (const Args &...args) &&
{
return stored { std::move (m_specifiers), args... };
}
/// parses a format string in the style of std::printf
///
/// if the format specifier is invalid the function will throw an error at
/// runtime. specifically does not make allowances for constexpr
/// validation.
parsed printf (util::view<const char*>);
/// parses a format specifier in the style of PEP3101 (with the notable
/// exception of named parameters).
///
/// in the event of a parsing error the function will throw. makes no
/// attempt to cater for constexpr validation.
parsed python (util::view<const char*>);
/// parses a printf format string and binds parameters for rendering.
template <typename ...Args>
auto
printf (util::view<const char*> fmt, const Args &...args)
{
return printf (fmt) (args...);
}
/// parses a python format string and binds parameters for rendering.
template <typename ...Args>
auto
python (util::view<const char*> fmt, const Args &...args)
{
return python (fmt) (args...);
}
template <typename ValueT>
struct value {
static std::ostream&
write (std::ostream &os, specifier spec, const ValueT &val)
{
os << std::resetiosflags (~std::ios_base::fmtflags{});
switch (spec.type) {
case type_t::REAL:
if (!std::is_floating_point_v<ValueT>)
throw std::runtime_error ("expected real value");
break;
case type_t::UNSIGNED:
if (!std::is_unsigned_v<ValueT>)
throw std::runtime_error ("expected unsigned value");
break;
case type_t::SIGNED:
if (!std::is_signed_v<ValueT>)
throw std::runtime_error ("expected signed value");
break;
case type_t::STRING:
if (!std::is_same_v<ValueT, util::view<const char*>> && !std::is_same_v<ValueT, std::string>)
throw std::runtime_error ("expected string value");
break;
case type_t::POINTER:
if (!std::is_pointer_v<ValueT> && !std::is_integral_v<ValueT>)
throw std::runtime_error ("expected pointer value");
break;
case type_t::CHAR:
if (!std::is_same_v<ValueT, char> &&
!std::is_same_v<ValueT, wchar_t> &&
!std::is_same_v<ValueT, char16_t> &&
!std::is_same_v<ValueT, char32_t> &&
!std::is_same_v<ValueT, signed char> &&
!std::is_same_v<ValueT, unsigned char>)
throw std::runtime_error ("expected character value");
break;
case type_t::COUNT:
if (!std::is_pointer_v<ValueT> && !std::is_reference_v<ValueT>)
if (!std::is_integral_v<std::remove_pointer_t<std::remove_reference_t<ValueT>>>)
throw std::runtime_error ("expected pointer/reference to integral");
break;
case type_t::USER:
break;
case type_t::ESCAPE:
case type_t::LITERAL:
break;
}
// easy case where we just throw it to ostream
if (spec.type == type_t::USER)
return os << val;
if (spec.length > 0 && sizeof (val) != spec.length)
throw std::runtime_error ("mismatched argument size");
const bool uses_space = std::is_arithmetic_v<ValueT> && spec.flags.space && !spec.flags.plus;
if (uses_space)
os << ' ';
if (spec.flags.plus)
os << std::showpos;
if (spec.flags.minus)
os << std::left;
if (spec.flags.zero)
os << std::setfill ('0');
if (spec.base >= 0) {
switch (spec.base) {
case 10: os << std::dec; break;
case 16: os << std::hex; break;
case 8: os << std::oct; break;
default:
throw std::runtime_error ("unhandled numeric base");
}
}
if (spec.precision >= 0) {
os << std::setprecision (spec.precision);
}
if (spec.width >= 0)
os << std::setw (spec.width - (uses_space ? 1 : 0));
if (spec.upper)
os << std::uppercase;
if (spec.type == type_t::UNSIGNED || spec.type == type_t::SIGNED)
if (spec.flags.hash)
os << std::showbase;
if (spec.type == type_t::REAL)
if (spec.flags.hash)
os << std::showpoint;
if (spec.type == type_t::REAL) {
switch (spec.representation) {
case specifier::FIXED: os << std::fixed; break;
case specifier::SCIENTIFIC: os << std::scientific; break;
case specifier::DEFAULT: os << std::defaultfloat; break;
case specifier::HEX: os << std::hexfloat; break;
}
}
if constexpr (std::is_integral_v<ValueT>) {
if (spec.type == type_t::POINTER) {
if (!val)
return os << "(nil)";
return os << reinterpret_cast<const void*> (val);
}
}
if constexpr (std::is_floating_point_v<ValueT>) {
if (spec.type == type_t::REAL) {
if (std::isnan (val))
return os << (spec.upper ? "NAN" : "nan");
if (std::isinf (val))
return os << (spec.upper ? "INF" : "inf");
}
}
if constexpr (std::is_integral_v<ValueT>) {
if (spec.type == type_t::SIGNED || spec.type == type_t::UNSIGNED) {
// explicitly handle the zero width case as blank because
// there's no easy way to do this using iomanip.
if (spec.precision == 0 && !val) {
return os;
}
}
}
if constexpr (std::is_same_v<util::view<const char*>, ValueT>) {
if (spec.precision >= 0) {
std::copy_n (
std::begin (val),
util::min (spec.precision, static_cast<int> (val.size ())),
std::ostream_iterator<char> (os)
);
return os;
}
}
// the final output calls. we need to use unary plus so that
// chars get promoted to ints for correct stream rendering when
// the intention is to output a number.
if constexpr (std::is_fundamental_v<ValueT>) {
if (spec.type == type_t::CHAR)
return os << val;
if constexpr (!std::is_null_pointer_v<ValueT>)
if (spec.type != type_t::USER)
return os << +val;
}
return os << val;
}
};
template <typename ValueT>
struct value<const ValueT*> {
static std::ostream&
write (std::ostream &os, specifier spec, const ValueT *val)
{
if (spec.type != type_t::POINTER && spec.type != type_t::USER)
throw std::runtime_error ("expected pointer specification");
if (!val)
return os << "(nil)";
return os << reinterpret_cast<const void*> (val);
}
};
template <typename ValueT>
struct value<ValueT*> {
static std::ostream&
write (std::ostream &os, specifier spec, ValueT *val) {
return value<const ValueT*>::write (os, spec, val);
}
};
template <>
struct value<std::nullptr_t> {
static std::ostream&
write (std::ostream &os, specifier s, const std::nullptr_t &val)
{
if (s.type != type_t::POINTER || s.type == type_t::USER)
throw std::runtime_error ("expected pointer specifier");
return value<const void*>::write (os, s, val);
}
};
template <size_t N>
struct value<const char[N]> {
static std::ostream&
write (std::ostream &os, specifier spec, const char (&val)[N]) {
if (spec.type == type_t::STRING || spec.type == type_t::USER)
return value<util::view<const char*>>::write (os, spec, util::view<const char*> (val));
throw std::runtime_error ("invalid data type");
}
};
template <size_t N>
struct value<char[N]> {
static std::ostream&
write (std::ostream &os, specifier spec, const char (&val)[N]) {
return value<util::view<const char*>>::write (os, spec, util::view<const char*> (val));
}
};
template <>
struct value<char*> {
static std::ostream&
write (std::ostream &os, specifier spec, char *val) {
if (!val)
return os << "(nil)";
if (spec.type == type_t::STRING || spec.type == type_t::USER)
return value<util::view<const char*>>::write (os, spec, util::view<const char*> { val, val + strlen (val) });
if (spec.type == type_t::POINTER)
return value<const void*>::write (os, spec, val);
throw std::runtime_error ("invalid data type");
}
};
template <>
struct value<const char*> {
static std::ostream&
write (std::ostream &os, specifier spec, const char *val) {
if (!val)
return os << "(nil)";
if (spec.type == type_t::STRING || spec.type == type_t::USER)
return value<util::view<const char*>>::write (os, spec, util::view<const char*> { val, val + strlen (val) });
if (spec.type == type_t::POINTER)
return value<const void*>::write (os, spec, val);
throw std::runtime_error ("invalid data type");
}
};
template <>
struct value<const std::string&> {
static std::ostream&
write (std::ostream &os, specifier spec, const std::string &val) {
return value<util::view<const char*>>::write (
os, spec, util::view<const char*> (val.data (), val.data () + val.size ())
);
}
};
template <>
struct value<std::string&> {
static std::ostream&
write (std::ostream &os, specifier spec, std::string &val) {
return value<const std::string&>::write (os, spec, val);
}
};
/// renders an LITERAL specifiers followed by one parameter, then
/// recurses for any following specifiers.
///
/// \tparam Index the index of the next parameter to render
/// \tparam SpecifierT a forward iterator container
/// \tparam DataT a tuple-like object template class
/// \tparam Args a paramater pack of all parameter types
///
/// \param os the ostream that we render to
/// \param specifiers the sequence of all specifiers to be rendered
/// \param data a tuple-like object containing references to all parameters
template <int Index, typename SpecifiersT, template <typename...> class HolderT, typename ...DataT>
static std::ostream&
write (std::ostream &os, const SpecifiersT &specifiers, const HolderT<DataT...> &data)
{
for (auto cursor = std::cbegin (specifiers); cursor != std::cend (specifiers); ++cursor) {
const auto &s = *cursor;
if (s.type == type_t::LITERAL) {
std::copy (std::begin (s.fmt), std::end (s.fmt), std::ostream_iterator<char> (os));
continue;
}
if (s.type == type_t::ESCAPE) {
os << '%';
continue;
}
if constexpr (Index < sizeof... (DataT)) {
using value_t = std::tuple_element_t<Index,std::tuple<DataT...>>;
value<value_t>::write (os, s, data.template get<Index> ());
return write<Index+1> (os, util::make_view (cursor+1,specifiers.end ()), data);
} else {
throw std::runtime_error ("insufficient data parameters");
}
}
return os;
}
/// dispatches rendering of formats with associated parameters
template <
typename ...Args
>
std::ostream&
operator<< (std::ostream &os, const bound<Args...> &val)
{
return write<0> (os, val.specifiers (), val);
}
/// dispatches rendering of formats with associated parameters
template <
typename ...Args
>
std::ostream&
operator<< (std::ostream &os, const stored<Args...> &val)
{
return write<0> (os, val.specifiers (), val);
}
template <typename ...Args>
std::string
to_string (const bound<Args...> &fmt)
{
std::ostringstream os;
os << fmt;
return os.str ();
}
template <typename ...Args>
std::string
to_string (const stored<Args...> &fmt)
{
std::ostringstream os;
os << fmt;
return os.str ();
}
}
#endif
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