X-Git-Url: https://git.sesse.net/?a=blobdiff_plain;f=raylib_pi4_test%2Frmem.h;fp=raylib_pi4_test%2Frmem.h;h=dbf417fe610d6c458c3194425aaf3e40922f29c6;hb=31f58d05d3587ed024ef7860d130ff86d4a84d90;hp=0000000000000000000000000000000000000000;hpb=a2ec9011ca7e900cf758dd43ab6856749f25d84d;p=pistorm

diff --git a/raylib_pi4_test/rmem.h b/raylib_pi4_test/rmem.h
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+++ b/raylib_pi4_test/rmem.h
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+/**********************************************************************************************
+*
+*   rmem - raylib memory pool and objects pool
+*
+*   A quick, efficient, and minimal free list and arena-based allocator
+*
+*   PURPOSE:
+*     - A quicker, efficient memory allocator alternative to 'malloc' and friends.
+*     - Reduce the possibilities of memory leaks for beginner developers using Raylib.
+*     - Being able to flexibly range check memory if necessary.
+*
+*   CONFIGURATION:
+*
+*   #define RMEM_IMPLEMENTATION
+*       Generates the implementation of the library into the included file.
+*       If not defined, the library is in header only mode and can be included in other headers
+*       or source files without problems. But only ONE file should hold the implementation.
+*
+*
+*   LICENSE: zlib/libpng
+*
+*   Copyright (c) 2019 Kevin 'Assyrianic' Yonan (@assyrianic) and reviewed by Ramon Santamaria (@raysan5)
+*
+*   This software is provided "as-is", without any express or implied warranty. In no event
+*   will the authors be held liable for any damages arising from the use of this software.
+*
+*   Permission is granted to anyone to use this software for any purpose, including commercial
+*   applications, and to alter it and redistribute it freely, subject to the following restrictions:
+*
+*     1. The origin of this software must not be misrepresented; you must not claim that you
+*     wrote the original software. If you use this software in a product, an acknowledgment
+*     in the product documentation would be appreciated but is not required.
+*
+*     2. Altered source versions must be plainly marked as such, and must not be misrepresented
+*     as being the original software.
+*
+*     3. This notice may not be removed or altered from any source distribution.
+*
+**********************************************************************************************/
+
+#ifndef RMEM_H
+#define RMEM_H
+
+#include <inttypes.h>
+#include <stdbool.h>
+
+//----------------------------------------------------------------------------------
+// Defines and Macros
+//----------------------------------------------------------------------------------
+#if defined(_WIN32) && defined(BUILD_LIBTYPE_SHARED)
+    #define RMEMAPI __declspec(dllexport)         // We are building library as a Win32 shared library (.dll)
+#elif defined(_WIN32) && defined(USE_LIBTYPE_SHARED)
+    #define RMEMAPI __declspec(dllimport)         // We are using library as a Win32 shared library (.dll)
+#else
+    #define RMEMAPI   // We are building or using library as a static library (or Linux shared library)
+#endif
+
+#define RMEM_VERSION    "v1.3"    // changelog at bottom of header.
+
+//----------------------------------------------------------------------------------
+// Types and Structures Definition
+//----------------------------------------------------------------------------------
+
+// Memory Pool
+typedef struct MemNode MemNode;
+struct MemNode {
+    size_t size;
+    MemNode *next, *prev;
+};
+
+// Freelist implementation
+typedef struct AllocList {
+    MemNode *head, *tail;
+    size_t len;
+} AllocList;
+
+// Arena allocator.
+typedef struct Arena {
+    uintptr_t mem, offs;
+    size_t size;
+} Arena;
+
+
+enum {
+    MEMPOOL_BUCKET_SIZE = 8,
+    MEMPOOL_BUCKET_BITS = (sizeof(uintptr_t) >> 1) + 1,
+    MEM_SPLIT_THRESHOLD = sizeof(uintptr_t) * 4
+};
+
+typedef struct MemPool {
+    AllocList large, buckets[MEMPOOL_BUCKET_SIZE];
+    Arena arena;
+} MemPool;
+
+
+// Object Pool
+typedef struct ObjPool {
+    uintptr_t mem, offs;
+    size_t objSize, freeBlocks, memSize;
+} ObjPool;
+
+
+// Double-Ended Stack aka Deque
+typedef struct BiStack {
+    uintptr_t mem, front, back;
+    size_t size;
+} BiStack;
+
+
+#if defined(__cplusplus)
+extern "C" {            // Prevents name mangling of functions
+#endif
+
+//------------------------------------------------------------------------------------
+// Functions Declaration - Memory Pool
+//------------------------------------------------------------------------------------
+RMEMAPI MemPool CreateMemPool(size_t bytes);
+RMEMAPI MemPool CreateMemPoolFromBuffer(void *buf, size_t bytes);
+RMEMAPI void DestroyMemPool(MemPool *mempool);
+
+RMEMAPI void *MemPoolAlloc(MemPool *mempool, size_t bytes);
+RMEMAPI void *MemPoolRealloc(MemPool *mempool, void *ptr, size_t bytes);
+RMEMAPI void MemPoolFree(MemPool *mempool, void *ptr);
+RMEMAPI void MemPoolCleanUp(MemPool *mempool, void **ptrref);
+RMEMAPI void MemPoolReset(MemPool *mempool);
+RMEMAPI size_t GetMemPoolFreeMemory(const MemPool mempool);
+
+//------------------------------------------------------------------------------------
+// Functions Declaration - Object Pool
+//------------------------------------------------------------------------------------
+RMEMAPI ObjPool CreateObjPool(size_t objsize, size_t len);
+RMEMAPI ObjPool CreateObjPoolFromBuffer(void *buf, size_t objsize, size_t len);
+RMEMAPI void DestroyObjPool(ObjPool *objpool);
+
+RMEMAPI void *ObjPoolAlloc(ObjPool *objpool);
+RMEMAPI void ObjPoolFree(ObjPool *objpool, void *ptr);
+RMEMAPI void ObjPoolCleanUp(ObjPool *objpool, void **ptrref);
+
+//------------------------------------------------------------------------------------
+// Functions Declaration - Double-Ended Stack
+//------------------------------------------------------------------------------------
+RMEMAPI BiStack CreateBiStack(size_t len);
+RMEMAPI BiStack CreateBiStackFromBuffer(void *buf, size_t len);
+RMEMAPI void DestroyBiStack(BiStack *destack);
+
+RMEMAPI void *BiStackAllocFront(BiStack *destack, size_t len);
+RMEMAPI void *BiStackAllocBack(BiStack *destack, size_t len);
+
+RMEMAPI void BiStackResetFront(BiStack *destack);
+RMEMAPI void BiStackResetBack(BiStack *destack);
+RMEMAPI void BiStackResetAll(BiStack *destack);
+
+RMEMAPI intptr_t BiStackMargins(BiStack destack);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif // RMEM_H
+
+/***********************************************************************************
+*
+*   RMEM IMPLEMENTATION
+*
+************************************************************************************/
+
+#if defined(RMEM_IMPLEMENTATION)
+
+#include <stdio.h>          // Required for:
+#include <stdlib.h>         // Required for:
+#include <string.h>         // Required for:
+
+//----------------------------------------------------------------------------------
+// Defines and Macros
+//----------------------------------------------------------------------------------
+
+// Make sure restrict type qualifier for pointers is defined
+// NOTE: Not supported by C++, it is a C only keyword
+#if defined(_WIN32) || defined(_WIN64) || defined(__CYGWIN__) || defined(_MSC_VER)
+    #ifndef restrict
+        #define restrict __restrict
+    #endif
+#endif
+
+//----------------------------------------------------------------------------------
+// Global Variables Definition
+//----------------------------------------------------------------------------------
+// ...
+
+//----------------------------------------------------------------------------------
+// Module specific Functions Declaration
+//----------------------------------------------------------------------------------
+static inline size_t __AlignSize(const size_t size, const size_t align)
+{
+    return (size + (align - 1)) & -align;
+}
+
+static MemNode *__SplitMemNode(MemNode *const node, const size_t bytes)
+{
+    uintptr_t n = ( uintptr_t )node;
+    MemNode *const r = ( MemNode* )(n + (node->size - bytes));
+    node->size -= bytes;
+    r->size = bytes;
+    return r;
+}
+
+static void __InsertMemNodeBefore(AllocList *const list, MemNode *const insert, MemNode *const curr)
+{
+    insert->next = curr;
+    if (curr->prev==NULL) list->head = insert;
+    else
+    {
+        insert->prev = curr->prev;
+        curr->prev->next = insert;
+    }
+    curr->prev = insert;
+}
+
+static void __ReplaceMemNode(MemNode *const old, MemNode *const replace)
+{
+    replace->prev = old->prev;
+    replace->next = old->next;
+    if( old->prev != NULL )
+        old->prev->next = replace;
+    if( old->next != NULL )
+        old->next->prev = replace;
+}
+
+
+static MemNode *__RemoveMemNode(AllocList *const list, MemNode *const node)
+{
+    if (node->prev != NULL) node->prev->next = node->next;
+    else
+    {
+        list->head = node->next;
+        if (list->head != NULL) list->head->prev = NULL;
+        else list->tail = NULL;
+    }
+
+    if (node->next != NULL) node->next->prev = node->prev;
+    else
+    {
+        list->tail = node->prev;
+        if (list->tail != NULL) list->tail->next = NULL;
+        else list->head = NULL;
+    }
+    list->len--;
+    return node;
+}
+
+static MemNode *__FindMemNode(AllocList *const list, const size_t bytes)
+{
+    for (MemNode *node = list->head; node != NULL; node = node->next)
+    {
+        if (node->size < bytes) continue;
+        // close in size - reduce fragmentation by not splitting.
+        else if (node->size <= bytes + MEM_SPLIT_THRESHOLD) return __RemoveMemNode(list, node);
+        else return __SplitMemNode(node, bytes);
+    }
+    return NULL;
+}
+
+static void __InsertMemNode(MemPool *const mempool, AllocList *const list, MemNode *const node, const bool is_bucket)
+{
+    if (list->head == NULL)
+    {
+        list->head = node;
+        list->len++;
+    }
+    else
+    {
+        for (MemNode *iter = list->head; iter != NULL; iter = iter->next)
+        {
+            if (( uintptr_t )iter == mempool->arena.offs)
+            {
+                mempool->arena.offs += iter->size;
+                __RemoveMemNode(list, iter);
+                iter = list->head;
+            }
+            const uintptr_t inode = ( uintptr_t )node;
+            const uintptr_t iiter = ( uintptr_t )iter;
+            const uintptr_t iter_end = iiter + iter->size;
+            const uintptr_t node_end = inode + node->size;
+            if (iter==node) return;
+            else if (iter < node)
+            {
+                // node was coalesced prior.
+                if (iter_end > inode) return;
+                else if (iter_end==inode && !is_bucket)
+                {
+                    // if we can coalesce, do so.
+                    iter->size += node->size;
+                    return;
+                }
+            }
+            else if (iter > node)
+            {
+                // Address sort, lowest to highest aka ascending order.
+                if (iiter < node_end) return;
+                else if (iter==list->head && !is_bucket)
+                {
+                    if (iter_end==inode) iter->size += node->size;
+                    else if (node_end==iiter)
+                    {
+                        node->size += list->head->size;
+                        node->next = list->head->next;
+                        node->prev = NULL;
+                        list->head = node;
+                    }
+                    else
+                    {
+                        node->next = iter;
+                        node->prev = NULL;
+                        iter->prev = node;
+                        list->head = node;
+                        list->len++;
+                    }
+                    return;
+                }
+                else if (iter_end==inode && !is_bucket)
+                {
+                    // if we can coalesce, do so.
+                    iter->size += node->size;
+                    return;
+                }
+                else
+                {
+                    __InsertMemNodeBefore(list, iter, node);
+                    list->len++;
+                    return;
+                }
+            }
+        }
+    }
+}
+
+//----------------------------------------------------------------------------------
+// Module Functions Definition - Memory Pool
+//----------------------------------------------------------------------------------
+
+MemPool CreateMemPool(const size_t size)
+{
+    MemPool mempool = { 0 };
+
+    if (size == 0) return mempool;
+    else
+    {
+        // Align the mempool size to at least the size of an alloc node.
+        uint8_t *const restrict buf = malloc(size*sizeof *buf);
+        if (buf==NULL) return mempool;
+        else
+        {
+            mempool.arena.size = size;
+            mempool.arena.mem = ( uintptr_t )buf;
+            mempool.arena.offs = mempool.arena.mem + mempool.arena.size;
+            return mempool;
+        }
+    }
+}
+
+MemPool CreateMemPoolFromBuffer(void *const restrict buf, const size_t size)
+{
+    MemPool mempool = { 0 };
+    if ((size == 0) || (buf == NULL) || (size <= sizeof(MemNode))) return mempool;
+    else
+    {
+        mempool.arena.size = size;
+        mempool.arena.mem = ( uintptr_t )buf;
+        mempool.arena.offs = mempool.arena.mem + mempool.arena.size;
+        return mempool;
+    }
+}
+
+void DestroyMemPool(MemPool *const restrict mempool)
+{
+    if (mempool->arena.mem == 0) return;
+    else
+    {
+        void *const restrict ptr = ( void* )mempool->arena.mem;
+        free(ptr);
+        *mempool = (MemPool){ 0 };
+    }
+}
+
+void *MemPoolAlloc(MemPool *const mempool, const size_t size)
+{
+    if ((size == 0) || (size > mempool->arena.size)) return NULL;
+    else
+    {
+        MemNode *new_mem = NULL;
+        const size_t ALLOC_SIZE = __AlignSize(size + sizeof *new_mem, sizeof(intptr_t));
+        const size_t BUCKET_SLOT = (ALLOC_SIZE >> MEMPOOL_BUCKET_BITS) - 1;
+
+        // If the size is small enough, let's check if our buckets has a fitting memory block.
+        if (BUCKET_SLOT < MEMPOOL_BUCKET_SIZE)
+        {
+            new_mem = __FindMemNode(&mempool->buckets[BUCKET_SLOT], ALLOC_SIZE);
+        }
+        else if (mempool->large.head != NULL)
+        {
+            new_mem = __FindMemNode(&mempool->large, ALLOC_SIZE);
+        }
+
+        if (new_mem == NULL)
+        {
+            // not enough memory to support the size!
+            if ((mempool->arena.offs - ALLOC_SIZE) < mempool->arena.mem) return NULL;
+            else
+            {
+                // Couldn't allocate from a freelist, allocate from available mempool.
+                // Subtract allocation size from the mempool.
+                mempool->arena.offs -= ALLOC_SIZE;
+
+                // Use the available mempool space as the new node.
+                new_mem = ( MemNode* )mempool->arena.offs;
+                new_mem->size = ALLOC_SIZE;
+            }
+        }
+
+        // Visual of the allocation block.
+        // --------------
+        // | mem size   | lowest addr of block
+        // | next node  | 12 byte (32-bit) header
+        // | prev node  | 24 byte (64-bit) header
+        // |------------|
+        // |   alloc'd  |
+        // |   memory   |
+        // |   space    | highest addr of block
+        // --------------
+        new_mem->next = new_mem->prev = NULL;
+        uint8_t *const restrict final_mem = ( uint8_t* )new_mem + sizeof *new_mem;
+        return memset(final_mem, 0, new_mem->size - sizeof *new_mem);
+    }
+}
+
+void *MemPoolRealloc(MemPool *const restrict mempool, void *const ptr, const size_t size)
+{
+    if (size > mempool->arena.size) return NULL;
+    // NULL ptr should make this work like regular Allocation.
+    else if (ptr == NULL) return MemPoolAlloc(mempool, size);
+    else if ((uintptr_t)ptr - sizeof(MemNode) < mempool->arena.mem) return NULL;
+    else
+    {
+        MemNode *const node = ( MemNode* )(( uint8_t* )ptr - sizeof *node);
+        const size_t NODE_SIZE = sizeof *node;
+        uint8_t *const resized_block = MemPoolAlloc(mempool, size);
+        if (resized_block == NULL) return NULL;
+        else
+        {
+            MemNode *const resized = ( MemNode* )(resized_block - sizeof *resized);
+            memmove(resized_block, ptr, (node->size > resized->size)? (resized->size - NODE_SIZE) : (node->size - NODE_SIZE));
+            MemPoolFree(mempool, ptr);
+            return resized_block;
+        }
+    }
+}
+
+void MemPoolFree(MemPool *const restrict mempool, void *const ptr)
+{
+    const uintptr_t p = ( uintptr_t )ptr;
+    if ((ptr == NULL) || (p - sizeof(MemNode) < mempool->arena.mem)) return;
+    else
+    {
+        // Behind the actual pointer data is the allocation info.
+        const uintptr_t block = p - sizeof(MemNode);
+        MemNode *const mem_node = ( MemNode* )block;
+        const size_t BUCKET_SLOT = (mem_node->size >> MEMPOOL_BUCKET_BITS) - 1;
+
+        // Make sure the pointer data is valid.
+        if ((block < mempool->arena.offs) ||
+            ((block - mempool->arena.mem) > mempool->arena.size) ||
+            (mem_node->size == 0) ||
+            (mem_node->size > mempool->arena.size)) return;
+        // If the mem_node is right at the arena offs, then merge it back to the arena.
+        else if (block == mempool->arena.offs)
+        {
+            mempool->arena.offs += mem_node->size;
+        }
+        else
+        {
+            // try to place it into bucket or large freelist.
+            struct AllocList *const l = (BUCKET_SLOT < MEMPOOL_BUCKET_SIZE) ? &mempool->buckets[BUCKET_SLOT] : &mempool->large;
+            __InsertMemNode(mempool, l, mem_node, (BUCKET_SLOT < MEMPOOL_BUCKET_SIZE));
+        }
+    }
+}
+
+void MemPoolCleanUp(MemPool *const restrict mempool, void **const ptrref)
+{
+    if ((ptrref == NULL) || (*ptrref == NULL)) return;
+    else
+    {
+        MemPoolFree(mempool, *ptrref);
+        *ptrref = NULL;
+    }
+}
+
+size_t GetMemPoolFreeMemory(const MemPool mempool)
+{
+    size_t total_remaining = mempool.arena.offs - mempool.arena.mem;
+
+    for (MemNode *n=mempool.large.head; n != NULL; n = n->next) total_remaining += n->size;
+
+    for (size_t i=0; i<MEMPOOL_BUCKET_SIZE; i++) for (MemNode *n = mempool.buckets[i].head; n != NULL; n = n->next) total_remaining += n->size;
+
+    return total_remaining;
+}
+
+void MemPoolReset(MemPool *const mempool)
+{
+    mempool->large.head = mempool->large.tail = NULL;
+    mempool->large.len = 0;
+    for (size_t i = 0; i < MEMPOOL_BUCKET_SIZE; i++)
+    {
+        mempool->buckets[i].head = mempool->buckets[i].tail = NULL;
+        mempool->buckets[i].len = 0;
+    }
+    mempool->arena.offs = mempool->arena.mem + mempool->arena.size;
+}
+
+//----------------------------------------------------------------------------------
+// Module Functions Definition - Object Pool
+//----------------------------------------------------------------------------------
+
+ObjPool CreateObjPool(const size_t objsize, const size_t len)
+{
+    ObjPool objpool = { 0 };
+    if ((len == 0) || (objsize == 0)) return objpool;
+    else
+    {
+        const size_t aligned_size = __AlignSize(objsize, sizeof(size_t));
+        uint8_t *const restrict buf = calloc(len, aligned_size);
+        if (buf == NULL) return objpool;
+        objpool.objSize = aligned_size;
+        objpool.memSize = objpool.freeBlocks = len;
+        objpool.mem = ( uintptr_t )buf;
+
+        for (size_t i=0; i<objpool.freeBlocks; i++)
+        {
+            size_t *const restrict index = ( size_t* )(objpool.mem + (i*aligned_size));
+            *index = i + 1;
+        }
+
+        objpool.offs = objpool.mem;
+        return objpool;
+    }
+}
+
+ObjPool CreateObjPoolFromBuffer(void *const restrict buf, const size_t objsize, const size_t len)
+{
+    ObjPool objpool = { 0 };
+
+    // If the object size isn't large enough to align to a size_t, then we can't use it.
+    const size_t aligned_size = __AlignSize(objsize, sizeof(size_t));
+    if ((buf == NULL) || (len == 0) || (objsize < sizeof(size_t)) || (objsize*len != aligned_size*len)) return objpool;
+    else
+    {
+        objpool.objSize = aligned_size;
+        objpool.memSize = objpool.freeBlocks = len;
+        objpool.mem = (uintptr_t)buf;
+
+        for (size_t i=0; i<objpool.freeBlocks; i++)
+        {
+            size_t *const restrict index = ( size_t* )(objpool.mem + (i*aligned_size));
+            *index = i + 1;
+        }
+
+        objpool.offs = objpool.mem;
+        return objpool;
+    }
+}
+
+void DestroyObjPool(ObjPool *const restrict objpool)
+{
+    if (objpool->mem == 0) return;
+    else
+    {
+        void *const restrict ptr = ( void* )objpool->mem;
+        free(ptr);
+        *objpool = (ObjPool){0};
+    }
+}
+
+void *ObjPoolAlloc(ObjPool *const objpool)
+{
+    if (objpool->freeBlocks > 0)
+    {
+        // For first allocation, head points to the very first index.
+        // Head = &pool[0];
+        // ret = Head == ret = &pool[0];
+        size_t *const restrict block = ( size_t* )objpool->offs;
+        objpool->freeBlocks--;
+
+        // after allocating, we set head to the address of the index that *Head holds.
+        // Head = &pool[*Head * pool.objsize];
+        objpool->offs = (objpool->freeBlocks != 0)? objpool->mem + (*block*objpool->objSize) : 0;
+        return memset(block, 0, objpool->objSize);
+    }
+    else return NULL;
+}
+
+void ObjPoolFree(ObjPool *const restrict objpool, void *const ptr)
+{
+    uintptr_t block = (uintptr_t)ptr;
+    if ((ptr == NULL) || (block < objpool->mem) || (block > objpool->mem + objpool->memSize*objpool->objSize)) return;
+    else
+    {
+        // When we free our pointer, we recycle the pointer space to store the previous index and then we push it as our new head.
+        // *p = index of Head in relation to the buffer;
+        // Head = p;
+        size_t *const restrict index = ( size_t* )block;
+        *index = (objpool->offs != 0)? (objpool->offs - objpool->mem)/objpool->objSize : objpool->memSize;
+        objpool->offs = block;
+        objpool->freeBlocks++;
+    }
+}
+
+void ObjPoolCleanUp(ObjPool *const restrict objpool, void **const restrict ptrref)
+{
+    if (ptrref == NULL) return;
+    else
+    {
+        ObjPoolFree(objpool, *ptrref);
+        *ptrref = NULL;
+    }
+}
+
+
+//----------------------------------------------------------------------------------
+// Module Functions Definition - Double-Ended Stack
+//----------------------------------------------------------------------------------
+BiStack CreateBiStack(const size_t len)
+{
+    BiStack destack = { 0 };
+    if (len == 0) return destack;
+
+    uint8_t *const buf = malloc(len*sizeof *buf);
+    if (buf==NULL) return destack;
+    destack.size = len;
+    destack.mem = ( uintptr_t )buf;
+    destack.front = destack.mem;
+    destack.back = destack.mem + len;
+    return destack;
+}
+
+BiStack CreateBiStackFromBuffer(void *const buf, const size_t len)
+{
+    BiStack destack = { 0 };
+    if (len == 0 || buf == NULL) return destack;
+    else
+    {
+        destack.size = len;
+        destack.mem = destack.front = ( uintptr_t )buf;
+        destack.back = destack.mem + len;
+        return destack;
+    }
+}
+
+void DestroyBiStack(BiStack *const restrict destack)
+{
+    if (destack->mem == 0) return;
+    else
+    {
+        uint8_t *const restrict buf = ( uint8_t* )destack->mem;
+        free(buf);
+        *destack = (BiStack){0};
+    }
+}
+
+void *BiStackAllocFront(BiStack *const restrict destack, const size_t len)
+{
+    if (destack->mem == 0) return NULL;
+    else
+    {
+        const size_t ALIGNED_LEN = __AlignSize(len, sizeof(uintptr_t));
+        // front end arena is too high!
+        if (destack->front + ALIGNED_LEN >= destack->back) return NULL;
+        else
+        {
+            uint8_t *const restrict ptr = ( uint8_t* )destack->front;
+            destack->front += ALIGNED_LEN;
+            return ptr;
+        }
+    }
+}
+
+void *BiStackAllocBack(BiStack *const restrict destack, const size_t len)
+{
+    if (destack->mem == 0) return NULL;
+    else
+    {
+        const size_t ALIGNED_LEN = __AlignSize(len, sizeof(uintptr_t));
+        // back end arena is too low
+        if (destack->back - ALIGNED_LEN <= destack->front) return NULL;
+        else
+        {
+            destack->back -= ALIGNED_LEN;
+            uint8_t *const restrict ptr = ( uint8_t* )destack->back;
+            return ptr;
+        }
+    }
+}
+
+void BiStackResetFront(BiStack *const destack)
+{
+    if (destack->mem == 0) return;
+    else destack->front = destack->mem;
+}
+
+void BiStackResetBack(BiStack *const destack)
+{
+    if (destack->mem == 0) return;
+    else destack->back = destack->mem + destack->size;
+}
+
+void BiStackResetAll(BiStack *const destack)
+{
+    BiStackResetBack(destack);
+    BiStackResetFront(destack);
+}
+
+inline intptr_t BiStackMargins(const BiStack destack)
+{
+    return destack.back - destack.front;
+}
+
+#endif  // RMEM_IMPLEMENTATION
+
+/*******
+ * Changelog
+ * v1.0: First Creation.
+ * v1.1: bug patches for the mempool and addition of object pool.
+ * v1.2: addition of bidirectional arena.
+ * v1.3:
+    * optimizations of allocators.
+    * renamed 'Stack' to 'Arena'.
+    * replaced certain define constants with an anonymous enum.
+    * refactored MemPool to no longer require active or deferred defragging.
+ ********/