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/*
 * 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 <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) {
        for (size_t i = 0; i < pool->size; i++) {
            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
) {
    if (!ptr) return;
    struct cx_mempool_s *pool = p;

    struct cx_mempool_memory_s *mem = (struct cx_mempool_memory_s *)
            ((char *) ptr - sizeof(cx_destructor_func));

    for (size_t i = 0; i < pool->size; i++) {
        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;
    for (size_t i = 0; i < pool->size; i++) {
        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;
}