Roland Conybeare
ec639ebb4b
Helps streamline DX1Collector in xo-gc/. Want both forward and verify entry points for the same representation.
119 lines
3.6 KiB
C++
119 lines
3.6 KiB
C++
/** @file DUniqueString.cpp
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*
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* @author Roland Conybeare, Jan 2026
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**/
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#include "DUniqueString.hpp"
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#include "DString.hpp"
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#include <xo/arena/padding.hpp>
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#include <xo/indentlog/scope.hpp>
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#include <cstring>
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namespace xo {
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using xo::mm::padding;
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using xo::facet::typeseq;
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namespace scm {
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int
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DUniqueString::compare(const DUniqueString & lhs, const DUniqueString & rhs)
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{
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if (&lhs == &rhs)
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return 0;
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return DString::compare(*(lhs._text()), *(rhs._text()));
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}
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DString *
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DUniqueString::_text() const noexcept
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{
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// location of paired DString is chosen
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// by allocator (DArena, probably).
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//
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// In general allocator alignment more conservative
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// than C++ alignment
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//
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// Remmebr also: although DUniqueString has zero members,
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// C++ requires it to behave asif size at least 1 byte
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// for iterator consistency
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// (e.g. because c++ would support iterating over
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// std::vector<EmptyStruct>)
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//
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size_t offset = padding::with_padding(sizeof(*this));
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assert(offset > 0);
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return (DString *)(((std::byte *)this) + offset);
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}
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bool
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DUniqueString::pretty(const ppindentinfo & ppii) const
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{
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return _text()->pretty(ppii);
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}
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DUniqueString *
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DUniqueString::from_view(obj<AAllocator> mm,
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std::string_view sv)
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{
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scope log(XO_DEBUG(false));
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/** fine point: choosing to allocate DUniqueString ahead of DString,
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* so it comes first in bump allocator
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**/
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void * mem = mm.super_alloc(typeseq::id<DUniqueString>(),
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sizeof(DUniqueString));
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DUniqueString * result = new (mem) DUniqueString();
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/** allocated in memory immediate following @p result.
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* This optimization saves us one pointer (8 bytes) in DUniqueString
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* itself, plus one allocation header (8 bytes) for 16 bytes total
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**/
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DString * text = DString::from_view_suballoc(mm, sv);
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log && log(xtag("result", result), xtag("result.text", result->_text()), xtag("text", text));
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assert(text);
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assert(text == result->_text());
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/** must finish super-allocation before next alloc **/
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mm.sub_alloc(0, true);
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return result;
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}
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DUniqueString *
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DUniqueString::gco_shallow_move(obj<AGCObjectVisitor> gc) noexcept
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{
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// well-posed, but not expected to be used.
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//
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// Not using gc.std_move_for() here because compiler doesn't know
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// actual alloc size of a DUniqueString instance
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assert(false);
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DUniqueString * copy = (DUniqueString *)gc.alloc_copy((std::byte *)this);
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if (copy) {
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// Copy assignment not implemented in general
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// *copy = *this;
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// in this case *copy already has the same size as *this
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assert(size() <= capacity());
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strncpy(copy->_text()->data(),
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this->_text()->chars(),
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this->size());
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}
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return copy;
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}
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void
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DUniqueString::visit_gco_children(VisitReason, obj<AGCObjectVisitor>) noexcept
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{
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// no-op -- childless!
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}
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} /*namespace scm*/
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} /*namespace xo*/
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/* end DUniqueString.cpp */
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