From b3bd3df103a5a75d267b2b79e85558768b1dc4bb Mon Sep 17 00:00:00 2001
From: "@syxhe" <https://t.me/syxhe>
Date: Sun, 23 Mar 2025 22:11:15 -0500
Subject: Fix a whole bunch of shit, create an arena implementation

---
 src/arena.c | 183 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 183 insertions(+)
 create mode 100644 src/arena.c

(limited to 'src/arena.c')

diff --git a/src/arena.c b/src/arena.c
new file mode 100644
index 0000000..d340f3a
--- /dev/null
+++ b/src/arena.c
@@ -0,0 +1,183 @@
+#include "arena.h"
+#include "shared.h"
+
+#include <stddef.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <errno.h>
+#include <error.h>
+
+typedef struct an {
+    void *membase;
+    void *memcur;
+    size_t allocated;
+    size_t used;
+
+    struct an *next;
+} arenanode;
+
+typedef struct arena {
+    arenanode *start;
+    arenanode *current;
+
+    // For keeping track of the largest possible thing that can be allocated to one node
+    size_t node_memspace;
+} arena;
+
+int arenanode_init(arenanode **an, size_t bytes) {
+    (*an) = xcalloc(1, sizeof(**an));
+    if(!(*an))
+        return -1;
+
+    (*an)->allocated = bytes;
+    (*an)->used = 0;
+    (*an)->next = NULL;
+    
+    void *mem = xcalloc(bytes, 1);
+    if(!mem) {
+        free((*an));
+        (*an) = NULL;
+        return -1;
+    }
+
+    (*an)->membase = mem;
+    (*an)->memcur = mem;
+
+    return 0;
+}
+
+int arena_init(arena **a, size_t bytes) {
+    if(!ISPOWOF2(MEM_ALIGN_BYTES))
+        XALLOC_EXIT("<arena_init> \"MEM_ALIGN_BYTES\" is not a power of 2. Refusing to create a new arena");
+
+    (*a) = xcalloc(1, sizeof(**a));
+    if(!(*a))
+        return -1;
+    (*a)->start = NULL;
+    (*a)->current = NULL;
+    (*a)->node_memspace = bytes;
+
+    arenanode *base;
+    if(arenanode_init(&base, bytes) < 0) {
+        free(*a);
+        (*a) = NULL;
+        return -1;
+    }
+
+    (*a)->start = base;
+    (*a)->current = base;
+
+    return 0;
+}
+
+void* arena_alloc(arena * const arena, size_t bytes) {
+    if(!arena) {
+        errno = EINVAL;
+        return NULL;
+    }
+    if(bytes > arena->node_memspace) {
+        errno = ENOMEM;
+        return NULL;
+    }
+    if(!ISPOWOF2(MEM_ALIGN_BYTES))
+        XALLOC_EXIT("<arena_alloc> \"MEM_ALIGN_BYTES\" is not a power of 2. Refusing to allocate any memory");
+
+    if(bytes > ((arena->current)->allocated - (arena->current)->used)) {
+        arenanode *new;
+        if(arenanode_init(&new, arena->node_memspace) < 0)
+            return NULL;
+
+        arena->current->next = new;
+        arena->current = new;
+    }
+
+    size_t alignment = MEM_ALIGN(bytes);
+    size_t offset = bytes + alignment;
+
+    void *mem = arena->current->memcur;
+    arena->current->memcur = (void*)(((uint8_t*)arena->current->memcur) + offset); 
+
+    arena->current->used += offset;
+
+    return mem;
+
+        // Note: This implementation assumes that malloc provides already-aligned memory. If it
+        // doesn't, that sucks and blows everything up
+}
+
+int arena_free(arena **arena) {
+    if(!arena) {
+        errno = EINVAL;
+        return -1;
+    }
+    if(!(*arena)) {
+        errno = EINVAL;
+        return -1;
+    }
+
+    (*arena)->current = (*arena)->start;
+    for(arenanode *n; (*arena)->current != NULL;) {
+        n = (*arena)->current->next;
+        
+        free((*arena)->current->membase);
+        free((*arena)->current);
+
+        (*arena)->current = n;
+    }
+    free((*arena));
+    (*arena) = NULL; 
+
+    return 0;
+}
+
+int arena_clear(arena **arena) {
+    if(!arena) {
+        errno = EINVAL;
+        return -1;
+    }
+    if(!(*arena)) {
+        errno = EINVAL;
+        return -1;
+    }
+
+    size_t bytes = (*arena)->node_memspace;
+    
+    int ret = 0;
+    if((ret = arena_free(arena)) < 0)
+        return ret;
+    return arena_init(arena, bytes);
+}
+
+
+
+// Simple Arena is an arena that can't expand whenever allocating memory, meaning what you originally allocated is what you get
+
+typedef arena simplearena;
+
+int simplearena_init(simplearena **a, size_t bytes) {
+    return arena_init(a, bytes);
+}
+
+void* simplearena_alloc(simplearena * const a, size_t bytes) {
+    // The criteria to allocate new memory in arena_alloc is 'bytes > ((a->current)->allocated - (a->current)->used)', so if this
+    // is true, just return NULL & set errno
+
+    if(!a) {
+        errno = EINVAL;
+        return NULL;
+    }
+    if(bytes > ((a->current)->allocated - (a->current)->used)) {
+        errno = ENOMEM;
+        return NULL;
+    }
+
+    return arena_alloc(a, bytes);
+}
+
+int simplearena_free(simplearena **a) {
+    return arena_free(a);
+}
+
+int simplearena_clear(simplearena **a) {
+    return arena_clear(a);
+}
\ No newline at end of file
-- 
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