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xo-arena: annex padding from xo-alloc2

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This commit is contained in:
Roland Conybeare 2026-01-06 00:08:50 -05:00
commit 49ee32cb30
3 changed files with 4 additions and 66 deletions
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60
include/xo/alloc2/padding.hpp
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@ -1,60 +0,0 @@
/** @file padding.hpp
*
* @author Roland Conybeare, Dec 2025
**/
#pragma once
#include <memory>
#include <cstdint>
namespace xo {
namespace mm {
struct padding {
/** word size for alignment**/
static constexpr std::size_t c_alloc_alignment = sizeof(std::uintptr_t);
static inline std::size_t is_aligned(std::size_t n,
std::size_t align = c_alloc_alignment) {
return n % align == 0;
}
/** how much to add to @p z to get a multiple of
* @ref c_alloc_alignment
**/
static inline std::size_t alloc_padding(std::size_t z,
std::size_t align = c_alloc_alignment)
{
/* round up to multiple of c_bpw, but map 0 -> 0
* (table assuming c_bpw==8)
*
* z%c_bpw dz
* ------------
* 0 0
* 1 7
* 2 6
* .. ..
* 7 1
*/
std::size_t dz = (align - (z % align)) % align;
return dz;
}
/** @p z rounded up to an exact multiple
* of @ref c_alloc_alignment
**/
static inline
std::size_t with_padding(std::size_t z,
std::size_t align = c_alloc_alignment)
{
return z + alloc_padding(z, align);
}
};
} /*namespace mm*/
} /*namespace xo*/
/* end padding.hpp */