src/mempool.c

/*
 * 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>
#include <errno.h>

struct cx_mempool_memory_s {
    /** The destructor. */
    cx_destructor_func destructor;
    /** The actual memory. */
    char c[];
};

static int cx_mempool_ensure_capacity(
        struct cx_mempool_s *pool,
        size_t needed_capacity
) {
    if (needed_capacity <= pool->capacity) return 0;
    size_t newcap = pool->capacity >= 1000 ?
        pool->capacity + 1000 : pool->capacity * 2;
    size_t newmsize;
    if (pool->capacity > newcap || cx_szmul(newcap,
            sizeof(struct cx_mempool_memory_s*), &newmsize)) {
        errno = EOVERFLOW;
        return 1;
    }
    struct cx_mempool_memory_s **newdata = cxRealloc(
        cxDefaultAllocator, pool->data, newmsize);
    if (newdata == NULL) return 1;
    pool->data = newdata;
    pool->capacity = newcap;
    return 0;
}

static void *cx_mempool_malloc(
        void *p,
        size_t n
) {
    struct cx_mempool_s *pool = p;

    if (cx_mempool_ensure_capacity(pool, pool->size + 1)) {
        return NULL;
    }

    struct cx_mempool_memory_s *mem = cxMalloc(
        cxDefaultAllocator, 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)) {
        errno = EOVERFLOW;
        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 = cxRealloc(cxDefaultAllocator, 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(); // LCOV_EXCL_LINE
    } 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);
            }
            cxFree(cxDefaultAllocator, 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(); // LCOV_EXCL_LINE
}

void cxMempoolFree(CxMempool *pool) {
    if (pool == NULL) return;
    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);
        }
        cxFree(cxDefaultAllocator, mem);
    }
    cxFree(cxDefaultAllocator, pool->data);
    cxFree(cxDefaultAllocator, (void*) pool->allocator);
    cxFree(cxDefaultAllocator, pool);
}

void cxMempoolSetDestructor(
        void *ptr,
        cx_destructor_func func
) {
    *(cx_destructor_func *) ((char *) ptr - sizeof(cx_destructor_func)) = func;
}

void cxMempoolRemoveDestructor(void *ptr) {
    *(cx_destructor_func *) ((char *) ptr - sizeof(cx_destructor_func)) = NULL;
}

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)) {
        errno = EOVERFLOW;
        return NULL;
    }

    struct cx_mempool_s *pool =
            cxMalloc(cxDefaultAllocator, sizeof(struct cx_mempool_s));
    if (pool == NULL) return NULL;

    CxAllocator *provided_allocator = cxMalloc(cxDefaultAllocator, sizeof(CxAllocator));
    if (provided_allocator == NULL) { // LCOV_EXCL_START
        cxFree(cxDefaultAllocator, pool);
        return NULL;
    } // LCOV_EXCL_STOP
    provided_allocator->cl = &cx_mempool_allocator_class;
    provided_allocator->data = pool;

    pool->allocator = provided_allocator;

    pool->data = cxMalloc(cxDefaultAllocator, poolsize);
    if (pool->data == NULL) { // LCOV_EXCL_START
        cxFree(cxDefaultAllocator, provided_allocator);
        cxFree(cxDefaultAllocator, pool);
        return NULL;
    } // LCOV_EXCL_STOP

    pool->size = 0;
    pool->capacity = capacity;
    pool->auto_destr = destr;

    return pool;
}

static void cx_mempool_free_transferred_allocator(void *al) {
    cxFree(cxDefaultAllocator, al);
}

int cxMempoolTransfer(
        CxMempool *source,
        CxMempool *dest
) {
    // safety check
    if (source == dest) return 1;

    // ensure enough capacity in the destination pool
    if (cx_mempool_ensure_capacity(dest, dest->size + source->size + 1)) {
        return 1; // LCOV_EXCL_LINE
    }

    // allocate a replacement allocator for the source pool
    CxAllocator *new_source_allocator = cxMalloc(cxDefaultAllocator, sizeof(CxAllocator));
    if (new_source_allocator == NULL) { // LCOV_EXCL_START
        return 1;
    } // LCOV_EXCL_STOP
    new_source_allocator->cl = &cx_mempool_allocator_class;
    new_source_allocator->data = source;

    // transfer all the data
    memcpy(&dest->data[dest->size], source->data, sizeof(source->data[0])*source->size);
    dest->size += source->size;

    // register the old allocator with the new pool
    // we have to remove const-ness for this, but that's okay here
    CxAllocator *transferred_allocator = (CxAllocator*) source->allocator;
    transferred_allocator->data = dest;
    cxMempoolRegister(dest, transferred_allocator, cx_mempool_free_transferred_allocator);

    // prepare the source pool for re-use
    source->allocator = new_source_allocator;
    memset(source->data, 0, source->size * sizeof(source->data[0]));
    source->size = 0;

    return 0;
}

int cxMempoolTransferObject(
        CxMempool *source,
        CxMempool *dest,
        const void *obj
) {
    // safety check
    if (source == dest) return 1;

    // first, make sure that the dest pool can take the object
    if (cx_mempool_ensure_capacity(dest, dest->size + 1)) {
        return 1; // LCOV_EXCL_LINE
    }
    // search for the object
    for (size_t i = 0; i < source->size; i++) {
        struct cx_mempool_memory_s *mem = source->data[i];
        if (mem->c == obj) {
            // remove from the source pool
            size_t last_index = source->size - 1;
            if (i != last_index) {
                source->data[i] = source->data[last_index];
                source->data[last_index] = NULL;
            }
            source->size--;
            // add to the target pool
            dest->data[dest->size++] = mem;
            return 0;
        }
    }
    // not found
    return 1;
}