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C++

/**
* ini_config.hpp - Evaluate INI configs at compile-time for efficient use at run-time.
* Written by Clyne Sullivan.
* https://github.com/tcsullivan/ini-config
*/
#ifndef TCSULLIVAN_INI_CONFIG_HPP
#define TCSULLIVAN_INI_CONFIG_HPP
// Uncomment below to run std::forward_iterator check
//#define TCSULLIVAN_INI_CONFIG_CHECK_FORWARD_ITERATOR
#ifdef TCSULLIVAN_INI_CONFIG_CHECK_FORWARD_ITERATOR
#include <iterator> // std::forward_iterator
#endif
namespace ini_config {
/**
* A minimal container for a given string literal, used to allow string
* literals to be passed as template parameters.
*/
template<typename T = char, unsigned long int N = 0>
struct string_container {
using char_type = T;
char_type data[N];
constexpr string_container(const char_type (&s)[N]) noexcept {
auto dst = data;
for (auto src = s; src != s + N; ++src)
*dst++ = *src;
}
constexpr operator const char_type *() const noexcept {
return data;
}
constexpr auto size() const noexcept {
return N;
}
consteval auto begin() const noexcept {
return data;
}
consteval auto end() const noexcept {
return data + N;
}
};
template<auto Input>
class ini_config
{
// Private implementation stuff must be defined first.
// Jump to the public section below for the available interface.
using char_type = typename decltype(Input)::char_type;
consteval static bool isgraph(char_type c) noexcept {
return c > ' ' && c != 0x7F;
}
consteval static bool iseol(char_type c) noexcept {
return c == '\n' || c == '\0';
}
consteval static bool iscomment(char_type c) noexcept {
return c == ';' || c == '#';
}
constexpr static bool stringmatch(const char_type *a, const char_type *b) noexcept {
while (*a == *b && (*a != '\0' || *b != '\0'))
++a, ++b;
return *a == *b && *a == '\0';
}
consteval static const char_type *nextline(const char_type *in) noexcept {
while (!iseol(*in))
++in;
return in + 1;
}
consteval static unsigned int verify_and_size() {
unsigned int sizechars = 0;
auto line = Input.begin();
do {
auto p = line;
// Remove beginning whitespace
for (; !iseol(*p) && !isgraph(*p); ++p);
if (iseol(*p) || iscomment(*p))
continue;
// Check for section header
if (*p == '[') {
do {
++sizechars;
} while (*++p != ']');
++sizechars; // Null terminator
continue;
}
// This is the key (and whitespace until =)
for (bool keyend = false; !iseol(*p); ++p) {
if (*p == '=')
break;
if (!keyend) {
if (!isgraph(*p))
keyend = true;
else
++sizechars;
} else {
if (isgraph(*p))
throw "Invalid key!";
}
}
if (*p != '=')
throw "Invalid key!";
++p;
// Next is the value
auto oldsizechars = sizechars;
for (bool valuestart = false; !iseol(*p); ++p) {
if (!valuestart && isgraph(*p))
valuestart = true;
if (valuestart)
++sizechars;
}
if (oldsizechars == sizechars)
throw "No value!";
// All good, add two bytes for key/value terminators
sizechars += 2;
} while ((line = nextline(line)) != Input.end());
return sizechars;
}
consteval static unsigned int kvpcount() noexcept {
unsigned int count = 0;
auto line = Input.begin();
do {
auto p = line;
// Remove beginning whitespace
for (; !iseol(*p) && !isgraph(*p); ++p);
if (iseol(*p) || iscomment(*p) || *p == '[')
continue;
count++; // Must be a key-value pair
} while ((line = nextline(line)) != Input.end());
return count;
}
char_type kvp_buffer[verify_and_size() + 1] = {};
consteval void fill_kvp_buffer() noexcept {
auto bptr = kvp_buffer;
auto line = Input.begin();
do {
auto p = line;
// Remove beginning whitespace
for (; !iseol(*p) && !isgraph(*p); ++p);
if (iseol(*p) || iscomment(*p))
continue;
if (*p == '[') {
do {
*bptr++ = *p++;
} while (*p != ']');
*bptr++ = '\0';
continue;
}
// This is the key (and whitespace until =)
for (bool keyend = false; !iseol(*p); ++p) {
if (*p == '=')
break;
if (!keyend) {
if (!isgraph(*p))
keyend = true;
else
*bptr++ = *p;
}
}
++p;
*bptr++ = '\0';
// Next is the value
for (bool valuestart = false; !iseol(*p); ++p) {
if (!valuestart && isgraph(*p))
valuestart = true;
if (valuestart)
*bptr++ = *p;
}
*bptr++ = '\0';
} while ((line = nextline(line)) != Input.end());
*bptr = '\0';
}
public:
struct kvp {
const char_type *section = nullptr;
const char_type *first = nullptr;
const char_type *second = nullptr;
};
class iterator {
const char_type *m_pos = nullptr;
kvp m_current = {};
constexpr const auto& get_next() noexcept {
if (*m_pos == '\0') {
// At the end
if (m_current.first != nullptr)
m_current.first = nullptr;
} else {
// Enter new section(s) if necessary
while (*m_pos == '[') {
m_current.section = m_pos + 1;
while (*m_pos++ != '\0');
}
m_current.first = m_pos;
while (*m_pos++ != '\0');
m_current.second = m_pos;
while (*m_pos++ != '\0');
}
return m_current;
}
public:
using difference_type = long int;
using value_type = kvp;
// Parameter is a location within kvp_buffer
constexpr iterator(const char_type *pos) noexcept
: m_pos(pos)
{
while (*m_pos == '[') {
m_current.section = m_pos + 1;
while (*m_pos++ != '\0');
}
get_next();
}
constexpr iterator() = default;
constexpr const auto& operator*() const noexcept {
return m_current;
}
constexpr const auto *operator->() const noexcept {
return &m_current;
}
constexpr auto& operator++() noexcept {
get_next();
return *this;
}
constexpr auto operator++(int) noexcept {
auto copy = *this;
get_next();
return copy;
}
constexpr auto operator<=>(const iterator& other) const noexcept {
return m_pos <=> other.m_pos;
}
constexpr bool operator==(const iterator& other) const noexcept {
return m_pos == other.m_pos && m_current.first == other.m_current.first;
}
};
consteval ini_config() noexcept
#ifdef TCSULLIVAN_INI_CONFIG_CHECK_FORWARD_ITERATOR
requires(std::forward_iterator<iterator>)
#endif
{
fill_kvp_buffer();
}
/**
* Returns the number of key-value pairs.
*/
consteval auto size() const noexcept {
return kvpcount();
}
constexpr auto begin() const noexcept {
return iterator(kvp_buffer);
}
/**
* Returns beginning iterator for the given section.
*/
constexpr auto begin(const char_type *section) const noexcept {
for (auto it = begin(); it != end(); ++it) {
if (it->section != nullptr && stringmatch(it->section, section))
return it;
}
return end();
}
constexpr auto end() const noexcept {
return iterator(kvp_buffer + sizeof(kvp_buffer) / sizeof(char_type) - 1);
}
/**
* Returns end iterator for the given section.
*/
constexpr auto end(const char_type *section) const noexcept {
for (auto it = begin(); it != end(); ++it) {
if (it->section != nullptr && stringmatch(it->section, section)) {
for (++it; it != end() && stringmatch(it->section, section); ++it);
return it;
}
}
return end();
}
class section_view {
iterator m_begin;
iterator m_end;
public:
constexpr section_view(const ini_config& ini, const char_type *section)
: m_begin(ini.begin(section)), m_end(ini.end(section)) {}
constexpr auto begin() const noexcept {
return m_begin;
}
constexpr auto end() const noexcept {
return m_end;
}
};
/**
* Creates a 'view' for the given section (use with ranged for).
*/
constexpr auto section(const char_type *s) const noexcept {
return section_view(*this, s);
}
/**
* Finds and returns the pair with the given key.
* Returns an empty string on failure.
*/
constexpr auto get(const char_type *key) const noexcept {
for (auto kvp : *this) {
if (stringmatch(kvp.first, key))
return kvp.second;
}
return "";
}
/**
* Finds and returns the pair with the given key, in the given section.
* Returns an empty string on failure.
*/
constexpr auto get(const char_type *sec, const char_type *key) const noexcept {
for (auto kvp : section(sec)) {
if (stringmatch(kvp.first, key))
return kvp.second;
}
return "";
}
/**
* Array-style access to values. Searches all sections.
* Returns an empty string on failure.
*/
constexpr auto operator[](const char_type *key) const noexcept {
return get(key);
}
};
} // namespace ini_config
/**
* _ini suffix definition.
*/
template <ini_config::string_container Input>
constexpr auto operator ""_ini()
{
return ini_config::ini_config<Input>();
}
#endif // TCSULLIVAN_INI_CONFIG_HPP