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enum.hpp
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enum.hpp
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#ifndef _C4_ENUM_HPP_
#define _C4_ENUM_HPP_
#include "c4/error.hpp"
#include <string.h>
/** @file enum.hpp utilities for enums: convert to/from string
*/
namespace c4 {
C4_SUPPRESS_WARNING_GCC_CLANG_WITH_PUSH("-Wold-style-cast")
//! taken from http://stackoverflow.com/questions/15586163/c11-type-trait-to-differentiate-between-enum-class-and-regular-enum
template<typename Enum>
using is_scoped_enum = std::integral_constant<bool, std::is_enum<Enum>::value && !std::is_convertible<Enum, int>::value>;
//-----------------------------------------------------------------------------
//-----------------------------------------------------------------------------
//-----------------------------------------------------------------------------
typedef enum {
EOFFS_NONE = 0, ///< no offset
EOFFS_CLS = 1, ///< get the enum offset for the class name. @see eoffs_cls()
EOFFS_PFX = 2, ///< get the enum offset for the enum prefix. @see eoffs_pfx()
_EOFFS_LAST ///< reserved
} EnumOffsetType;
//-----------------------------------------------------------------------------
//-----------------------------------------------------------------------------
//-----------------------------------------------------------------------------
/** A simple (proxy) container for the value-name pairs of an enum type.
* Uses linear search for finds; this could be improved for time-critical
* code. */
template<class Enum>
class EnumSymbols
{
public:
struct Sym
{
Enum value;
const char *name;
bool cmp(const char *s) const;
bool cmp(const char *s, size_t len) const;
const char *name_offs(EnumOffsetType t) const;
};
using const_iterator = Sym const*;
public:
template<size_t N>
EnumSymbols(Sym const (&p)[N]) : m_symbols(p), m_num(N) {}
size_t size() const { return m_num; }
bool empty() const { return m_num == 0; }
Sym const* get(Enum v) const { auto p = find(v); C4_CHECK_MSG(p != nullptr, "could not find symbol=%zd", (std::ptrdiff_t)v); return p; }
Sym const* get(const char *s) const { auto p = find(s); C4_CHECK_MSG(p != nullptr, "could not find symbol \"%s\"", s); return p; }
Sym const* get(const char *s, size_t len) const { auto p = find(s, len); C4_CHECK_MSG(p != nullptr, "could not find symbol \"%.*s\"", len, s); return p; }
Sym const* find(Enum v) const;
Sym const* find(const char *s) const;
Sym const* find(const char *s, size_t len) const;
Sym const& operator[] (size_t i) const { C4_CHECK(i < m_num); return m_symbols[i]; }
Sym const* begin() const { return m_symbols; }
Sym const* end () const { return m_symbols + m_num; }
private:
Sym const* m_symbols;
size_t const m_num;
};
//-----------------------------------------------------------------------------
/** return an EnumSymbols object for the enum type T
*
* @warning SPECIALIZE! This needs to be specialized for each enum
* type. Failure to provide a specialization will cause a linker
* error. */
template<class Enum>
EnumSymbols<Enum> const esyms();
/** return the offset for an enum symbol class. For example,
* eoffs_cls<MyEnumClass>() would be 13=strlen("MyEnumClass::").
*
* With this function you can announce that the full prefix (including
* an eventual enclosing class or C++11 enum class) is of a certain
* length.
*
* @warning Needs to be specialized for each enum class type that
* wants to use this. When no specialization is given, will return
* 0. */
template<class Enum>
size_t eoffs_cls()
{
return 0;
}
/** return the offset for an enum symbol prefix. This includes
* eoffs_cls(). With this function you can announce that the full
* prefix (including an eventual enclosing class or C++11 enum class
* plus the string prefix) is of a certain length.
*
* @warning Needs to be specialized for each enum class type that
* wants to use this. When no specialization is given, will return
* 0. */
template<class Enum>
size_t eoffs_pfx()
{
return 0;
}
template<class Enum>
size_t eoffs(EnumOffsetType which)
{
switch(which)
{
case EOFFS_NONE:
return 0;
case EOFFS_CLS:
return eoffs_cls<Enum>();
case EOFFS_PFX:
{
size_t pfx = eoffs_pfx<Enum>();
return pfx > 0 ? pfx : eoffs_cls<Enum>();
}
default:
C4_ERROR("unknown offset type %d", (int)which);
}
}
//-----------------------------------------------------------------------------
/** get the enum value corresponding to a c-string */
#ifdef __clang__
# pragma clang diagnostic push
#elif defined(__GNUC__)
# pragma GCC diagnostic push
# if __GNUC__ >= 6
# pragma GCC diagnostic ignored "-Wnull-dereference"
# endif
#endif
template<class Enum>
Enum str2e(const char* str)
{
auto pairs = esyms<Enum>();
auto *p = pairs.get(str);
C4_CHECK_MSG(p != nullptr, "no valid enum pair name for '%s'", str);
return p->value;
}
/** get the c-string corresponding to an enum value */
template<class Enum>
const char* e2str(Enum e)
{
auto es = esyms<Enum>();
auto *p = es.get(e);
C4_CHECK_MSG(p != nullptr, "no valid enum pair name");
return p->name;
}
/** like e2str(), but add an offset. */
template<class Enum>
const char* e2stroffs(Enum e, EnumOffsetType ot=EOFFS_PFX)
{
const char *s = e2str<Enum>(e) + eoffs<Enum>(ot);
return s;
}
#ifdef __clang__
# pragma clang diagnostic pop
#elif defined(__GNUC__)
# pragma GCC diagnostic pop
#endif
//-----------------------------------------------------------------------------
/** Find a symbol by value. Returns nullptr when none is found */
template<class Enum>
typename EnumSymbols<Enum>::Sym const* EnumSymbols<Enum>::find(Enum v) const
{
for(Sym const* p = this->m_symbols, *e = p+this->m_num; p < e; ++p)
if(p->value == v)
return p;
return nullptr;
}
/** Find a symbol by name. Returns nullptr when none is found */
template<class Enum>
typename EnumSymbols<Enum>::Sym const* EnumSymbols<Enum>::find(const char *s) const
{
for(Sym const* p = this->m_symbols, *e = p+this->m_num; p < e; ++p)
if(p->cmp(s))
return p;
return nullptr;
}
/** Find a symbol by name. Returns nullptr when none is found */
template<class Enum>
typename EnumSymbols<Enum>::Sym const* EnumSymbols<Enum>::find(const char *s, size_t len) const
{
for(Sym const* p = this->m_symbols, *e = p+this->m_num; p < e; ++p)
if(p->cmp(s, len))
return p;
return nullptr;
}
//-----------------------------------------------------------------------------
template<class Enum>
bool EnumSymbols<Enum>::Sym::cmp(const char *s) const
{
if(strcmp(name, s) == 0)
return true;
for(int i = 1; i < _EOFFS_LAST; ++i)
{
auto o = eoffs<Enum>((EnumOffsetType)i);
if(o > 0)
if(strcmp(name + o, s) == 0)
return true;
}
return false;
}
template<class Enum>
bool EnumSymbols<Enum>::Sym::cmp(const char *s, size_t len) const
{
if(strncmp(name, s, len) == 0)
return true;
size_t nlen = 0;
for(int i = 1; i <_EOFFS_LAST; ++i)
{
auto o = eoffs<Enum>((EnumOffsetType)i);
if(o > 0)
{
if(!nlen)
{
nlen = strlen(name);
}
C4_ASSERT(o < nlen);
size_t rem = nlen - o;
auto m = len > rem ? len : rem;
if(len >= m && strncmp(name + o, s, m) == 0)
return true;
}
}
return false;
}
//-----------------------------------------------------------------------------
template<class Enum>
const char* EnumSymbols<Enum>::Sym::name_offs(EnumOffsetType t) const
{
C4_ASSERT(eoffs<Enum>(t) < strlen(name));
return name + eoffs<Enum>(t);
}
C4_SUPPRESS_WARNING_GCC_CLANG_POP
} // namespace c4
#endif // _C4_ENUM_HPP_