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- #pragma once
-
- #include "gp_config.hpp"
-
- #include "gp/algorithms/modifiers.hpp"
- #include "gp/algorithms/tmp_manip.hpp"
- #include "gp/utils/allocators/dummy.hpp"
- #include "gp/containers/array.hpp"
- #include "gp/containers/buffer.hpp"
- #include "gp/math/integral.hpp"
- #include "gp/utils/allocators/allocator.hpp"
-
- #include <type_traits>
-
-
- namespace gp{
- /**
- * @brief An allocator that uses the buddy algorithm to divide the space into allocatable memory.
- *
- * This is not resilient to memory fragmentation, but the smallest memory unit should always be allocatable unless the memory is actually full.
- *
- * @tparam max_msb The log2 rounded up of the maximum space you expect to address in bytes
- * @tparam align The smallest size of memory you expect the allocator to allocate
- */
- template<size_t max_msb = 24, size_t align = 8>
- class buddy : public allocator {
-
- /**
- * @brief an allocation tree node, made into an easily packable struct
- */
- struct twig {
- bool used : 1;
- bool used_children : 1;
- twig(uint8_t src) noexcept {
- used = 1 & src;
- used_children = 2 & src;
- }
-
- operator uint8_t() noexcept {
- return 1 * used + 2 * used_children;
- }
- };
-
- /**
- * @brief a structure to pack 4 twig within
- */
- struct bundle {
- uint8_t a : 2;
- uint8_t b : 2;
- uint8_t c : 2;
- uint8_t d : 2;
-
- bundle() noexcept {
- a = 0; b = 0; c = 0; d = 0;
- }
- };
-
- /**
- * @brief a meta allocator to allocate the memory used and deallocate it later
- */
- gp::optional<gp::reference_wrapper<allocator>> allocator_v;
-
- /**
- * @brief The actual buffer where data is stored
- *
- */
- gp::buffer<char> data;
- const size_t max_depth;
- const size_t twig_explore_length;
-
- /**
- * @brief The depth of the tree required to allocate
- */
- static constexpr size_t max_theoric_depth = max_msb - gp::math::msb(align);
-
- /**
- * @brief The actual number of twigs to support the specified depth
- */
- static constexpr size_t required_twigs = (1 << (max_theoric_depth + 1)) - 1;
-
- /**
- * @brief ((max allocatable size - min allocatable size) ** 2 - 1) / 4 twigs in a bundle
- **/
- static constexpr size_t span_size = required_twigs / 4 + (required_twigs % 4 != 0);
-
- /**
- * @brief The array of twigs (in bundles) aka the metadata
- */
- gp::array<bundle, span_size> stack;
-
- /**
- * This code has been manually checked and will always return.
- * If you find a case where it doesn't, please file an issue.
- **/
- #pragma clang diagnostic push
- #pragma clang diagnostic ignored "-Wreturn-type"
- #pragma GCC diagnostic push
- #pragma GCC diagnostic ignored "-Wreturn-type"
- /**
- * @brief Get the value of the twig at the specified index
- *
- * @param idx
- * @return twig A copy of the specified twig
- */
- twig get_twig(size_t idx) const noexcept {
- auto far = idx / 4;
- auto local = idx % 4;
- switch(local) {
- case 0:
- return stack[far].a;
- case 1:
- return stack[far].b;
- case 2:
- return stack[far].c;
- case 3:
- return stack[far].d;
- }
- }
- #pragma GCC diagnostic pop
- #pragma clang diagnostic pop
-
- /**
- * @brief Set the twig at the specified index to the value of the heredescribed twig
- *
- * @param idx
- * @param v
- */
- void set_twig(size_t idx, twig v) noexcept {
- auto far = idx / 4;
- auto local = idx % 4;
- auto& group = stack[far];
-
- switch(local) {
- case 0:
- group.a = v;
- return;
- case 1:
- group.b = v;
- return;
- case 2:
- group.c = v;
- return;
- case 3:
- group.d = v;
- return;
- }
- }
-
- /**
- * @brief Deduces the depth to explore to allocate the specified size
- *
- * @param sz
- * @return size_t
- */
- constexpr size_t size_to_depth(size_t sz) noexcept {
- size_t pow2 = gp::math::msb(sz) - gp::math::msb(align);
- return gp::clamp(
- (size_t)0 ,
- max_depth - pow2,
- max_depth
- );
- }
-
- /**
- * @brief Deduces the size from the specified depth
- *
- * @param depth
- * @return size_t
- */
- constexpr size_t depth_to_size(size_t depth) noexcept {
- return 1 << (max_depth - depth + gp::math::msb(align));
- }
-
- /**
- * @brief Get the left child index from the specified index
- *
- * @param index
- * @return size_t
- */
- constexpr size_t get_left(size_t index) const noexcept {
- return ((index + 1) << 1) - 1;
- }
-
- /**
- * @brief Get the right child index from the specified index
- *
- * @param index
- * @return size_t
- */
- constexpr size_t get_right(size_t index) const noexcept{
- return ((index + 1) << 1);
- }
-
- /**
- * @brief Recursively applies a function to the children of a given node
- *
- * @param index the starting node
- * @param func the function to apply downwards
- */
- template<typename function>
- void all_under(size_t index, function func) {
- size_t left = get_left(index);
- size_t right = get_right(index);
- all_under(left, func);
- all_under(right, func);
- func(left);
- func(right);
- }
-
-
- /**
- * @brief Recursively applies a function to the chain of parents of the given node
- *
- * @param index the starting node
- * @param func the function to apply upwards
- */
- template<typename function>
- void all_over(size_t index, function func) {
- if(index != 0) {
- size_t parent = ((index + 1) >> 1) - 1;
- func(parent);
- if(parent != 0)
- all_over(parent, func);
- }
- }
-
- /**
- * @brief Recursively checks if any child matches a given predicate
- *
- * @param index The parent
- * @param func The predicate
- * @return true if the predicate matched once
- * @return false if the predicate never matched
- */
- template<typename function>
- bool is_any_child(size_t index, function func) const {
- size_t left = get_left(index);
- size_t right = get_right(index);
- if(left < twig_explore_length && right < twig_explore_length) {
- if(func(left)) return true;
- if(func(right)) return true;
- if(is_any_child(left, func)) return true;
- if(is_any_child(right, func)) return true;
- }
- return false;
- }
-
- /**
- * @brief a constant used to specify that no twig has been found
- */
- static constexpr size_t no_twig = -1;
-
- /**
- * @brief Finds a twig that represent free memory
- *
- * It's free real estate!
- *
- * @param depth the depth to allocate
- * @param root the root to look from
- * @param explored the current depth we sit at
- * @return size_t
- */
- size_t find_free_twig(size_t depth, size_t root = 0, size_t explored = 0) const {
- auto v = get_twig(root);
- if(depth == explored) {
- if(v.used || v.used_children)
- {
- return no_twig;
- } else {
- return root;
- }
- } else {
- if(v.used)
- {
- return no_twig;
- }
- ++explored;
- auto ret = find_free_twig(depth, get_right(root), explored);
- if(ret != no_twig)
- {
- return ret;
- }
- ret = find_free_twig(depth, get_left(root), explored);
- if(ret != no_twig)
- {
- return ret;
- }
- }
- return no_twig;
- }
-
- /**
- * @brief Recursively looks for the highest filled nodewith the given offset
- *
- * @param offset The offset to look for
- * @param root the root to look from
- * @param explored the explored depth
- * @return size_t
- */
- size_t find_used_twig(size_t offset, size_t root = 0, size_t explored = 0) {
- auto v = get_twig(root);
- if(v.used && offset == 0)
- {
- return root;
- }
- ++explored;
- if(explored > max_depth) return no_twig;
- size_t cut = (1 << (max_depth + gp::math::log2(align))) >> explored;
- if(offset >= cut)
- {
- return find_used_twig(offset-cut, get_right(root), explored);
- } else {
- return find_used_twig(offset, get_left(root), explored);
- }
- }
-
-
- static bool empty_node(const buddy* me, size_t node) {
- gp_config::assertion(node < me->twig_explore_length, "bad emptyness test");
- auto p = me->get_twig(node);
- return !(
- p.used | p.used_children
- );
- }
- public:
- /**
- * @brief Construct a new empty buddy object
- */
- buddy()
- : data(gp::buffer<char>(nullptr,nullptr))
- , max_depth(0)
- , twig_explore_length(1 << max_depth)
- {}
-
- /**
- * @brief Construct a new buddy object from another allocator
- *
- * @param sz the size to allocate
- * @param allocator_p the source of the allocated memory
- */
- buddy(size_t sz, allocator& allocator_p)
- : allocator_v(allocator_p)
- , data(nullptr,nullptr)
- , max_depth(gp::math::msb(sz)-gp::math::msb(align))
- , twig_explore_length(1 << max_depth)
- {
- if(sz!=0 && (sz & (sz - 1)) == 0)
- {
- auto v=allocator_v.value().get().allocate(sz);
- if(v!=nullptr)
- {
- if((reinterpret_cast<intptr_t>(v) % align) ==0)
- {
- data=gp::buffer<char>(reinterpret_cast<char*>(v),reinterpret_cast<char*>(v)+sz);
- }
- else
- {
- allocator_v.value().get().deallocate(v);
- }
- }
- }
- }
-
- /**
- * @brief Construct a new buddy object from a memory location
- *
- * @param pos the location of the memory to manage
- * @param sz the size of the span to manage
- */
- buddy(char* pos, size_t sz)
- : data(pos,pos+sz)
- , max_depth(gp::math::msb(sz)-gp::math::msb(align))
- , twig_explore_length(1 << max_depth)
- {
- }
-
- /**
- * @brief Allocates memory
- *
- * @param sz The size of memory to allocate
- * @return void* the allocated memory OR nullptr
- */
- virtual void* allocate(size_t sz)
- {
- auto depth = size_to_depth(sz);
- auto index = find_free_twig(depth);
- if(index == no_twig)
- {
- return nullptr;
- }
-
- auto pot = reinterpret_cast<char*>(
- (index - (1 << depth) + 1)*depth_to_size(depth)
- + reinterpret_cast<intptr_t>(&*data.begin())
- );
-
- if(!data.contains(pot)) {
- return nullptr;
- }
-
- all_over(index, [&](size_t idx){
- auto t = get_twig(idx);
- t.used_children = true;
- set_twig(idx, t);
- });
-
- auto t = get_twig(index);
- t.used = true;
- set_twig(index, t);
- return pot;
- }
-
- /**
- * @brief Tries to reallocate (UNIMPLEMENTED)
- *
- * @return false
- */
- virtual bool try_reallocate(void*, size_t) {
- return false;
- }
-
- /**
- * @brief Tries to deallocate the given memory
- *
- * @param ptr the pointer to the memory to deallocate
- * @return true if everything went fine
- * @return false if deallocation failed
- */
- virtual bool deallocate(void* ptr)
- {
- if(data.contains((char*)ptr))
- {
- size_t integral_offset = reinterpret_cast<intptr_t>(ptr) - reinterpret_cast<intptr_t>(&*data.begin());
- auto index = find_used_twig(integral_offset);
- if(index == no_twig)
- {
- return false;
- }
- twig v = get_twig(index);
- v.used = false;
- v.used_children = false;
- set_twig(index, v);
- all_over(index, [&](size_t idx){
- auto l = get_twig(get_left(idx));
- auto r = get_twig(get_right(idx));
- // And now for the tricky bit:
- // Sets the "used_children" bit if any of the collected twigs has a bit set
- set_twig(idx, 2*(l.used | l.used_children | r.used | r.used_children));
- });
-
- return true;
- }
- return false;
- }
-
- /**
- * @brief Checks if anything is still allocated in
- *
- * @return true if the allocator is completely empty
- * @return false if anything is still allocated in there
- */
- bool empty() const noexcept {
- const buddy* addr = (buddy*)this;
- const auto prepred = not_fn(&buddy::empty_node);
- const auto pred = bind_front(prepred, addr);
- return empty_node(addr, 0) && !is_any_child(0, pred);
- }
-
- /**
- * @brief Destroy the buddy object, will wrink out the space if it was created with an allocator
- */
- virtual ~buddy()
- {
- if(allocator_v.has_value())
- {
- allocator_v.value().get().deallocate(data.begin().data);
- }
- }
- };
- }
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