diff -r 44986c0e2b05 -r d92a59f5d261 src/mempool.c
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/mempool.c	Wed Jun 28 20:07:52 2023 +0200
@@ -0,0 +1,232 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
+ *
+ * Copyright 2021 Mike Becker, Olaf Wintermann All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ *   1. Redistributions of source code must retain the above copyright
+ *      notice, this list of conditions and the following disclaimer.
+ *
+ *   2. Redistributions in binary form must reproduce the above copyright
+ *      notice, this list of conditions and the following disclaimer in the
+ *      documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "cx/mempool.h"
+#include "cx/utils.h"
+#include <string.h>
+
+struct cx_mempool_memory_s {
+    /** The destructor. */
+    cx_destructor_func destructor;
+    /** The actual memory. */
+    char c[];
+};
+
+static void *cx_mempool_malloc(
+        void *p,
+        size_t n
+) {
+    struct cx_mempool_s *pool = p;
+
+    if (pool->size >= pool->capacity) {
+        size_t newcap = pool->capacity - (pool->capacity % 16) + 16;
+        struct cx_mempool_memory_s **newdata = realloc(pool->data, newcap*sizeof(struct cx_mempool_memory_s*));
+        if (newdata == NULL) {
+            return NULL;
+        }
+        pool->data = newdata;
+        pool->capacity = newcap;
+    }
+
+    struct cx_mempool_memory_s *mem = malloc(sizeof(cx_destructor_func) + n);
+    if (mem == NULL) {
+        return NULL;
+    }
+
+    mem->destructor = pool->auto_destr;
+    pool->data[pool->size] = mem;
+    pool->size++;
+
+    return mem->c;
+}
+
+static void *cx_mempool_calloc(
+        void *p,
+        size_t nelem,
+        size_t elsize
+) {
+    size_t msz;
+    if (cx_szmul(nelem, elsize, &msz)) {
+        return NULL;
+    }
+    void *ptr = cx_mempool_malloc(p, msz);
+    if (ptr == NULL) {
+        return NULL;
+    }
+    memset(ptr, 0, nelem * elsize);
+    return ptr;
+}
+
+static void *cx_mempool_realloc(
+        void *p,
+        void *ptr,
+        size_t n
+) {
+    struct cx_mempool_s *pool = p;
+
+    struct cx_mempool_memory_s *mem, *newm;
+    mem = (struct cx_mempool_memory_s*)(((char *) ptr) - sizeof(cx_destructor_func));
+    newm = realloc(mem, n + sizeof(cx_destructor_func));
+
+    if (newm == NULL) {
+        return NULL;
+    }
+    if (mem != newm) {
+        cx_for_n(i, pool->size) {
+            if (pool->data[i] == mem) {
+                pool->data[i] = newm;
+                return ((char*)newm) + sizeof(cx_destructor_func);
+            }
+        }
+        abort();
+    } else {
+        return ptr;
+    }
+}
+
+static void cx_mempool_free(
+        void *p,
+        void *ptr
+) {
+    struct cx_mempool_s *pool = p;
+
+    struct cx_mempool_memory_s *mem = (struct cx_mempool_memory_s *)
+            ((char *) ptr - sizeof(cx_destructor_func));
+
+    cx_for_n(i, pool->size) {
+        if (mem == pool->data[i]) {
+            if (mem->destructor) {
+                mem->destructor(mem->c);
+            }
+            free(mem);
+            size_t last_index = pool->size - 1;
+            if (i != last_index) {
+                pool->data[i] = pool->data[last_index];
+                pool->data[last_index] = NULL;
+            }
+            pool->size--;
+            return;
+        }
+    }
+    abort();
+}
+
+void cxMempoolDestroy(CxMempool *pool) {
+    struct cx_mempool_memory_s *mem;
+    cx_for_n(i, pool->size) {
+        mem = pool->data[i];
+        if (mem->destructor) {
+            mem->destructor(mem->c);
+        }
+        free(mem);
+    }
+    free(pool->data);
+    free((void*) pool->allocator);
+    free(pool);
+}
+
+void cxMempoolSetDestructor(
+        void *ptr,
+        cx_destructor_func func
+) {
+    *(cx_destructor_func *) ((char *) ptr - sizeof(cx_destructor_func)) = func;
+}
+
+struct cx_mempool_foreign_mem_s {
+    cx_destructor_func destr;
+    void* mem;
+};
+
+static void cx_mempool_destr_foreign_mem(void* ptr) {
+    struct cx_mempool_foreign_mem_s *fm = ptr;
+    fm->destr(fm->mem);
+}
+
+int cxMempoolRegister(
+        CxMempool *pool,
+        void *memory,
+        cx_destructor_func destr
+) {
+    struct cx_mempool_foreign_mem_s *fm = cx_mempool_malloc(
+            pool,
+            sizeof(struct cx_mempool_foreign_mem_s)
+    );
+    if (fm == NULL) return 1;
+
+    fm->mem = memory;
+    fm->destr = destr;
+    *(cx_destructor_func *) ((char *) fm - sizeof(cx_destructor_func)) = cx_mempool_destr_foreign_mem;
+
+    return 0;
+}
+
+static cx_allocator_class cx_mempool_allocator_class = {
+        cx_mempool_malloc,
+        cx_mempool_realloc,
+        cx_mempool_calloc,
+        cx_mempool_free
+};
+
+CxMempool *cxMempoolCreate(
+        size_t capacity,
+        cx_destructor_func destr
+) {
+    size_t poolsize;
+    if (cx_szmul(capacity, sizeof(struct cx_mempool_memory_s*), &poolsize)) {
+        return NULL;
+    }
+
+    struct cx_mempool_s *pool =
+            malloc(sizeof(struct cx_mempool_s));
+    if (pool == NULL) {
+        return NULL;
+    }
+
+    CxAllocator *provided_allocator = malloc(sizeof(CxAllocator));
+    if (provided_allocator == NULL) {
+        free(pool);
+        return NULL;
+    }
+    provided_allocator->cl = &cx_mempool_allocator_class;
+    provided_allocator->data = pool;
+
+    pool->allocator = provided_allocator;
+
+    pool->data = malloc(poolsize);
+    if (pool->data == NULL) {
+        free(provided_allocator);
+        free(pool);
+        return NULL;
+    }
+
+    pool->size = 0;
+    pool->capacity = capacity;
+    pool->auto_destr = destr;
+
+    return (CxMempool *) pool;
+}