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Library: implement access to storage and subscript

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...not sure if this approach works out OK,
since we can not make a safe downcast to a size known at runtime
This commit is contained in:
Fischlurch 2024-05-28 18:07:08 +02:00
parent f6e4358259
commit 27b36f0679
3 changed files with 63 additions and 11 deletions
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5
src/lib/several-builder.hpp
View file

@ -46,8 +46,11 @@
#include "lib/several.hpp"
#include "include/logging.h"
#include <utility>
#include <vector>
using std::vector;
using std::move;
@ -75,7 +78,7 @@ namespace lib {
Several<I>
build()
{
UNIMPLEMENTED ("materialise into Several-Container");
return move (*this);
}
};

44
src/lib/several.hpp
View file

@ -57,6 +57,9 @@ namespace lib {
Manager manager;
size_t spread;
template<class I>
auto access();
};
template<class I, size_t bytes>
@ -65,8 +68,27 @@ namespace lib {
{
alignas(I)
std::byte storage[bytes];
I&
subscript (size_t idx)
{
std::byte* elm = storage;
size_t off = idx * spread;
elm += off;
return * std::launder (reinterpret_cast<I*> (elm));
}
};
/** @internal perform an unsafe down-cast to access the storage area */
template<class I>
auto
Bucket::access()
{
using Storage = ArrayBucket<I, sizeof(I)>;
return static_cast<Storage&> (*this);
}
}//(End)implementation details
@ -80,7 +102,7 @@ namespace lib {
*/
template<class I>
class Several
: util::MoveOnly
: util::MoveAssign
{
protected:
size_t size_{0};
@ -91,20 +113,24 @@ namespace lib {
size_t
size() const
{
UNIMPLEMENTED ("determine storage size");
return size_;
}
bool
empty() const
{
return not (size_ and data_);
}
I&
operator[] (size_t i)
operator[] (size_t idx)
{
UNIMPLEMENTED ("subscript");
REQUIRE (data_);
return data_->access<I>().subscript (idx);
}
I&
back()
{
UNIMPLEMENTED ("storage access");
}
I& front() { return operator[] (size_-1); }
I& back() { return operator[] (0); }
using iterator = I*;
using const_iterator = I const*;

25
wiki/thinkPad.ichthyo.mm
View file

@ -81846,15 +81846,38 @@ Date:&#160;&#160;&#160;Thu Apr 20 18:53:17 2023 +0200<br/>
<node BACKGROUND_COLOR="#eee5c3" COLOR="#990000" CREATED="1716907249314" ID="ID_1711986050" MODIFIED="1716907418033" TEXT="Bucket">
<node CREATED="1716907252393" ID="ID_198747165" MODIFIED="1716907259884" TEXT="der Descriptor"/>
<node CREATED="1716907260424" ID="ID_1362772717" MODIFIED="1716907268555" TEXT="liegt am Anfang der Element-Storage"/>
<node CREATED="1716912140198" ID="ID_9984568" MODIFIED="1716912197368" TEXT="erm&#xf6;glicht beliebigen Down-cast auf gegebene Storage-Gr&#xf6;&#xdf;e">
<linktarget COLOR="#a9b4c1" DESTINATION="ID_9984568" ENDARROW="Default" ENDINCLINATION="97;4;" ID="Arrow_ID_396222637" SOURCE="ID_581123494" STARTARROW="None" STARTINCLINATION="0;-15;"/>
</node>
</node>
<node BACKGROUND_COLOR="#eee5c3" COLOR="#990000" CREATED="1716906944780" ID="ID_1643896091" MODIFIED="1716907418033" TEXT="ArrayBucket&lt;I,bytes&gt;">
<node CREATED="1716907277198" ID="ID_104268426" MODIFIED="1716907281769" TEXT="Subklasse von Bucket"/>
<node CREATED="1716907312241" ID="ID_835337350" MODIFIED="1716907333394" TEXT="umspannt das Storage-Array"/>
<node CREATED="1716907356091" ID="ID_1876919425" MODIFIED="1716907403909" TEXT="enth&#xe4;lt den subscript-Code"/>
<node COLOR="#338800" CREATED="1716907356091" ID="ID_1876919425" MODIFIED="1716912200686" TEXT="enth&#xe4;lt den subscript-Code">
<icon BUILTIN="button_ok"/>
<node BACKGROUND_COLOR="#f8f1cb" COLOR="#a50125" CREATED="1716912163674" ID="ID_581123494" MODIFIED="1716912308218" TEXT="mu&#xdf; hier einen offenen Downcast machen">
<richcontent TYPE="NOTE"><html>
<head>
</head>
<body>
<p>
...weil ich den Zieltyp zum Cast nicht dynamisch konstruieren kann
</p>
</body>
</html>
</richcontent>
<arrowlink DESTINATION="ID_9984568" ENDARROW="Default" ENDINCLINATION="97;4;" ID="Arrow_ID_396222637" STARTARROW="None" STARTINCLINATION="0;-15;"/>
<icon BUILTIN="messagebox_warning"/>
</node>
</node>
</node>
</node>
<node CREATED="1716909012702" ID="ID_1876994172" MODIFIED="1716909016713" TEXT="const-correctness">
<node CREATED="1716909019405" ID="ID_1406909807" MODIFIED="1716909042294" TEXT="ein const Several&lt;X&gt; ist ein Several&lt;const X&gt;"/>
</node>
</node>
</node>
<node BACKGROUND_COLOR="#eee5c3" COLOR="#990000" CREATED="1715625082614" ID="ID_1575150785" MODIFIED="1715625089779" TEXT="SeveralBuilder_test">
<icon BUILTIN="flag-yellow"/>
<node BACKGROUND_COLOR="#eee5c3" COLOR="#990000" CREATED="1716857382440" ID="ID_46730448" MODIFIED="1716857402102" TEXT="simpleUsage">