Roland Conybeare
5d49dc5a9b
subrepo: subdir: "xo-object" merged: "d830632a" upstream: origin: "git@github.com:Rconybea/xo-object.git" branch: "main" commit: "d830632a" git-subrepo: version: "0.4.9" origin: "???" commit: "???"
128 lines
4.3 KiB
C++
128 lines
4.3 KiB
C++
/** @file object.hpp
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*
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* Author: Roland Conybeare
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**/
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#pragma once
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#include "xo/reflect/Object.hpp"
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#include <cstdint>
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namespace xo {
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namespace obj {
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enum class otag : std::uint16_t {
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vt_invalid = -1,
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vt_sentinel = 0x00,
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vt_boolean = 0x01,
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vt_char = 0x02,
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vt_i32 = 0x03,
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vt_f32 = 0x04,
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vt_i64 = 0x08,
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vt_f64 = 0x09,
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vt_list = 0x0a,
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vt_object = 0x10,
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};
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class cons;
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/** @class object
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*
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* @brief dynamically tyyped object; support for schematica
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**/
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class object {
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public:
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using Object = xo::reflect::Object;
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/** number of pointer bits stolen for type tag **/
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static constexpr int c_tag_bits = 16;
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/** number of pointer bits remaining after hi tag bits stolen **/
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static constexpr int c_ptr_bits = 64 - c_tag_bits;
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static constexpr std::uint64_t c_ptr_mask = (0UL - 1) >> c_tag_bits;
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public:
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object() = default;
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otag tag() const noexcept { return reinterpret_cast<vtag>(value_ >> c_ptr_bits); }
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std::uint64_t masked_value() const noexcept { return value_ & c_ptr_mask; }
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std::int32_t as_int32(std::int32_t sentinel = 0) const noexcept {
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if (tag() == vtag::vt_i32) {
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return masked_value();
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} else {
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return sentinel;
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}
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}
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float as_float32(float sentinel = std::numeric_limits<float>::quiet_NaN()) const noexcept {
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if (tag() == vtag::vt_f64) {
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return masked_value();
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} else {
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return sentinel;
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}
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}
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std::int64_t as_int64(int64_t sentinel = 0) const noexcept {
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if (tag() == vtag::vt_i64) {
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return * reinterpret_cast<std::int64_t *>(masked_value());
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} else {
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return sentinel;
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}
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}
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double as_float64(double sentinel = std::numeric_limits<double>::quiet_NaN()) const noexcept {
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if (tag() == vtag::vt_f64) {
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return * reinterpret_cast<double *>(masked_value());
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} else {
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return sentinel;
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}
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}
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Object * as_object() const noexcept {
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if (tag() == vtag::vt_object) {
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return reinterpret_cast<Object *>(masked_value());
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} else {
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return nullptr;
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}
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}
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private:
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/**
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* Rely on being able to steal the 16 most-significant
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* bits from a 64-bit pointer
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*
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* @code
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* <- 16 -> <---------- 48 ---------->
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* +--------+--------------------------+
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* | tag | |
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* +--------+--------------------------+
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* @endcode
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*
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* tag values given by @ref otag
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*
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* 0x00 -> sentinel. sentinel value. not accessible from schematica
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* 0x01 -> boolean. truth value in least-significant bit
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* 0x02 -> char. ascii character in least-significant 8 bits
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* 0x03 -> int. integer in least-significant 32 bits
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* 0x04 -> float. 32-bit float in least-significant 32 bitsg
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*
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* 0x05..0x07 reserved
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*
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* 0x08 -> long. ptr refers to 64-bit integer
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* 0x09 -> double. ptr refers to 64-bit floating-point value
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* 0x0a -> zstring. ptr refers to length-prefixed null-terminated cstring.
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* 0x0b -> symbol. ptr refers to interned (unique'd) symbol
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* 0x0c -> cons. ptr refers to 128-bit cons-cell (or is nullptr, representing nil)
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*
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* 0x0d..0x0f reserved
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*
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* 0x10 -> Object. ptr to refcounted xo::obj::Object
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* see xo-reflect/ Object.hpp
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**/
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std::uint64_t value_ = 0;
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};
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} /*namespace obj*/
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} /*namespace xo*/
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/** end object.hpp **/
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