/**
 * \file mlt_pool.c
 * \brief memory pooling functionality
 * \see mlt_pool_s
 *
 * Copyright (C) 2003-2026 Meltytech, LLC
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 */

#include "mlt_deque.h"
#include "mlt_log.h"
#include "mlt_properties.h"

#include <pthread.h>
#include <stdlib.h>
#include <string.h>

// Not nice - memalign is defined here apparently?
#ifdef linux
#include <malloc.h>
#endif

// Macros to re-assign system functions.
#ifdef _WIN32
#define mlt_free _aligned_free
#define mlt_alloc(X) _aligned_malloc((X), 16)
#define mlt_realloc(X, Y) _aligned_realloc((X), (Y), 16)
#else
#define mlt_free free
#ifdef linux
#define mlt_alloc(X) memalign(16, (X))
#else
#define mlt_alloc(X) malloc((X))
#endif
#define mlt_realloc realloc
#endif

// We now require a compile-time define to use mlt_pool.
#ifndef USE_MLT_POOL
#define USE_MLT_POOL 1
#endif

#if !USE_MLT_POOL

void mlt_pool_init() {}
void *mlt_pool_alloc(int size)
{
    return mlt_alloc(size);
}
void *mlt_pool_realloc(void *ptr, int size)
{
    return mlt_realloc(ptr, size);
}
void mlt_pool_release(void *release)
{
    return mlt_free(release);
}
void mlt_pool_purge() {}
void mlt_pool_close() {}
void mlt_pool_stat() {}

#else

/** global singleton for tracking pools */

static mlt_properties pools = NULL;

/** \brief Pool (memory) class
 */

typedef struct mlt_pool_s
{
    pthread_mutex_t lock; ///< lock to prevent race conditions
    mlt_deque stack;      ///< a stack of addresses to memory blocks
    int size;             ///< the size of the memory block as a power of 2
    int count;            ///< the number of blocks in the pool
} * mlt_pool;

/** \brief private to mlt_pool_s, for tracking items to release
 *
 * Aligned to 16 byte in case we toss buffers to external assembly
 * optimized libraries (sse/altivec).
 */

// In the future with C23 we should be able to use alignas
// typedef struct alignas(16) mlt_release_s
#ifdef _MSC_VER
typedef struct __declspec(align(16)) mlt_release_s
#else
typedef struct __attribute__((aligned(16))) mlt_release_s
#endif
{
    mlt_pool pool;
    int references;
} * mlt_release;

/** Create a pool.
 *
 * \private \memberof mlt_pool_s
 * \param size the size of the memory blocks to hold as some power of two
 * \return a new pool object
 */

static mlt_pool pool_init(int size)
{
    // Create the pool
    mlt_pool self = calloc(1, sizeof(struct mlt_pool_s));

    // Initialise it
    if (self != NULL) {
        // Initialise the mutex
        pthread_mutex_init(&self->lock, NULL);

        // Create the stack
        self->stack = mlt_deque_init();

        // Assign the size
        self->size = size;
    }

    // Return it
    return self;
}

/** Get an item from the pool.
 *
 * \private \memberof mlt_pool_s
 * \param self a pool
 * \return an opaque pointer
 */

static void *pool_fetch(mlt_pool self)
{
    // We will generate a release object
    void *ptr = NULL;

    // Sanity check
    if (self != NULL) {
        // Lock the pool
        pthread_mutex_lock(&self->lock);

        // Check if the stack is empty
        if (mlt_deque_count(self->stack) != 0) {
            // Pop the top of the stack
            ptr = mlt_deque_pop_back(self->stack);

            // Assign the reference
            mlt_release release = (void *) ((char *) ptr - sizeof(struct mlt_release_s));
            release->references = 1;
        } else {
            // We need to generate a release item
            mlt_release release = mlt_alloc(self->size);

            // If out of memory, log it, reclaim memory, and try again.
            if (!release && self->size > 0) {
                mlt_log_fatal(NULL, "[mlt_pool] out of memory\n");
                mlt_pool_purge();
                release = mlt_alloc(self->size);
            }

            // Initialise it
            if (release != NULL) {
                // Increment the number of items allocated to this pool
                self->count++;

                // Assign the pool
                release->pool = self;

                // Assign the reference
                release->references = 1;

                // Determine the ptr
                // The memory is not leaked - it's returned via ptr
                ptr = (char *) release + sizeof(struct mlt_release_s);
            }
            // cppcheck-suppress memleak
        }

        // Unlock the pool
        pthread_mutex_unlock(&self->lock);
    }

    // Return the generated release object
    return ptr;
}

/** Return an item to the pool.
 *
 * \private \memberof mlt_pool_s
 * \param ptr an opaque pointer
 */

static void pool_return(void *ptr)
{
    // Sanity checks
    if (ptr != NULL) {
        // Get the release pointer
        mlt_release that = (void *) ((char *) ptr - sizeof(struct mlt_release_s));

        // Get the pool
        mlt_pool self = that->pool;

        if (self != NULL) {
            // Lock the pool
            pthread_mutex_lock(&self->lock);

            // Push it back onto the stack
            mlt_deque_push_back(self->stack, ptr);

            // Unlock the pool
            pthread_mutex_unlock(&self->lock);

            return;
        }

        // Free the release itself
        mlt_free((char *) ptr - sizeof(struct mlt_release_s));
    }
}

/** Destroy a pool.
 *
 * \private \memberof mlt_pool_s
 * \param self a pool
 */

static void pool_close(mlt_pool self)
{
    if (self != NULL) {
        // We need to free up all items in the pool
        void *release = NULL;

        // Iterate through the stack until depleted
        while ((release = mlt_deque_pop_back(self->stack)) != NULL) {
            // We'll free this item now
            mlt_free((char *) release - sizeof(struct mlt_release_s));
        }

        // We can now close the stack
        mlt_deque_close(self->stack);

        // Destroy the mutex
        pthread_mutex_destroy(&self->lock);

        // Close the pool
        free(self);
    }
}

/** Initialise the global pool.
 *
 * \public \memberof mlt_pool_s
 */

void mlt_pool_init()
{
    // Loop variable used to create the pools
    int i = 0;

    // Create the pools
    pools = mlt_properties_new();

    // Create the pools
    for (i = 8; i < 31; i++) {
        // Each properties item needs a name
        char name[32];

        // Construct a pool
        mlt_pool pool = pool_init(1 << i);

        // Generate a name
        sprintf(name, "%d", i);

        // Register with properties
        mlt_properties_set_data(pools, name, pool, 0, (mlt_destructor) pool_close, NULL);
    }
}

/** Allocate size bytes from the pool.
 *
 * \public \memberof mlt_pool_s
 * \param size the number of bytes
 */

void *mlt_pool_alloc(int size)
{
    // This will be used to obtain the pool to use
    mlt_pool pool = NULL;

    // Determines the index of the pool to use
    int index = 8;

    // Minimum size pooled is 256 bytes
    size += sizeof(struct mlt_release_s);
    while ((1 << index) < size)
        index++;

    // Now get the pool at the index
    pool = mlt_properties_get_data_at(pools, index - 8, NULL);

    // Now get the real item
    return pool_fetch(pool);
}

/** Allocate size bytes from the pool.
 *
 * \public \memberof mlt_pool_s
 * \param ptr an opaque pointer - can be in the pool or a new block to allocate
 * \param size the number of bytes
 */

void *mlt_pool_realloc(void *ptr, int size)
{
    // Result to return
    void *result = NULL;

    // Check if we actually have an address
    if (ptr != NULL) {
        // Get the release pointer
        mlt_release that = (void *) ((char *) ptr - sizeof(struct mlt_release_s));

        // If the current pool this ptr belongs to is big enough
        if (size > that->pool->size - sizeof(struct mlt_release_s)) {
            // Allocate
            result = mlt_pool_alloc(size);

            // Copy
            memcpy(result, ptr, that->pool->size - sizeof(struct mlt_release_s));

            // Release
            mlt_pool_release(ptr);
        } else {
            // Nothing to do
            result = ptr;
        }
    } else {
        // Simply allocate
        result = mlt_pool_alloc(size);
    }

    return result;
}

/** Purge unused items in the pool.
 *
 * A form of garbage collection.
 * \public \memberof mlt_pool_s
 */

void mlt_pool_purge()
{
    int i = 0;

    // For each pool
    for (i = 0; i < mlt_properties_count(pools); i++) {
        // Get the pool
        mlt_pool self = mlt_properties_get_data_at(pools, i, NULL);

        // Pointer to unused memory
        void *release = NULL;

        // Lock the pool
        pthread_mutex_lock(&self->lock);

        // We'll free all unused items now
        while ((release = mlt_deque_pop_back(self->stack)) != NULL) {
            mlt_free((char *) release - sizeof(struct mlt_release_s));
            self->count--;
        }

        // Unlock the pool
        pthread_mutex_unlock(&self->lock);
    }
}

/** Release the allocated memory.
 *
 * \public \memberof mlt_pool_s
 * \param release an opaque pointer of a block in the pool
 */

void mlt_pool_release(void *release)
{
    // Return to the pool
    pool_return(release);
}

/** Close the pool.
 *
 * \public \memberof mlt_pool_s
 */

void mlt_pool_close()
{
#ifdef _MLT_POOL_CHECKS_
    mlt_pool_stat();
#endif

    // Close the properties
    mlt_properties_close(pools);
}

void mlt_pool_stat()
{
    // Stats dump
    uint64_t allocated = 0, used = 0, s;
    int i = 0, c = mlt_properties_count(pools);

    mlt_log(NULL, MLT_LOG_VERBOSE, "%s: count %d\n", __FUNCTION__, c);

    for (i = 0; i < c; i++) {
        mlt_pool pool = mlt_properties_get_data_at(pools, i, NULL);
        if (pool->count)
            mlt_log_verbose(NULL,
                            "%s: size %d allocated %d returned %d %c\n",
                            __FUNCTION__,
                            pool->size,
                            pool->count,
                            mlt_deque_count(pool->stack),
                            pool->count != mlt_deque_count(pool->stack) ? '*' : ' ');
        s = pool->size;
        s *= pool->count;
        allocated += s;
        s = pool->count - mlt_deque_count(pool->stack);
        s *= pool->size;
        used += s;
    }

    mlt_log_verbose(NULL,
                    "%s: allocated %" PRIu64 " bytes, used %" PRIu64 " bytes \n",
                    __FUNCTION__,
                    allocated,
                    used);
}

#endif // NO_MLT_POOL
