/* Manage sets of pixel buffers on an image.
 *
 * 30/10/06
 *	- from window.c
 * 2/2/07
 * 	- speed up the search, use our own lock (thanks Christian)
 * 5/2/07
 * 	- split to many buffer lists per image
 * 11/2/07
 * 	- split to a buffer hash per thread
 * 	- reuse buffer mallocs when we can
 * 20/2/07
 * 	- add VipsBufferCacheList and we can avoid some hash ops on
 * 	  done/undone
 * 5/3/10
 * 	- move invalid stuff to region
 * 	- move link maintenance to im_demand_hint
 * 21/9/11
 * 	- switch to vips_tracked_malloc()
 * 18/12/13
 * 	- keep a few buffers in reserve per image, stops malloc/free
 * 	  cycling when sharing is repeatedly discovered
 * 6/6/16
 * 	- free buffers on image close as well as thread exit, so main thread
 * 	  buffers don't clog up the system
 * 13/10/16
 * 	- better solution: don't keep a buffercache for non-workers
 */

/*

	This file is part of VIPS.

	VIPS 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 of the License, or
	(at your option) any later version.

	This program 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 program; if not, write to the Free Software
	Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
	02110-1301  USA

 */

/*

	These files are distributed with VIPS - http://www.vips.ecs.soton.ac.uk

 */

/*
#define DEBUG_VERBOSE
#define DEBUG_CREATE
#define DEBUG
 */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif /*HAVE_CONFIG_H*/
#include <glib/gi18n-lib.h>

#include <stdio.h>
#include <stdlib.h>

#include <vips/vips.h>
#include <vips/internal.h>
#include <vips/thread.h>

#ifdef DEBUG
/* Track all buffers here for debugging.
 */
static GSList *vips__buffer_all = NULL;
#endif /*DEBUG*/

#ifdef DEBUG_CREATE
static GSList *vips__buffer_cache_all = NULL;
#endif /*DEBUG_CREATE*/

/* The maximum numbers of buffers we hold in reserve per image.
 */
static const int buffer_cache_max_reserve = 2;

/* Workers have a BufferThread (and BufferCache) in a GPrivate they have
 * exclusive access to.
 */
static GPrivate *buffer_thread_key = NULL;

void
vips_buffer_print(VipsBuffer *buffer)
{
	printf("VipsBuffer: %p ref_count = %d, ", buffer, buffer->ref_count);
	printf("im = %p, ", buffer->im);
	printf("area.left = %d, ", buffer->area.left);
	printf("area.top = %d, ", buffer->area.top);
	printf("area.width = %d, ", buffer->area.width);
	printf("area.height = %d, ", buffer->area.height);
	printf("done = %d, ", buffer->done);
	printf("cache = %p, ", buffer->cache);
	printf("buf = %p, ", buffer->buf);
	printf("bsize = %zd\n", buffer->bsize);
}

#ifdef DEBUG
static void *
vips_buffer_dump(VipsBuffer *buffer, size_t *reserve, size_t *alive)
{
	vips_buffer_print(buffer);

	g_assert(buffer->im);
	g_assert(buffer->buf);

	if (!buffer->cache &&
		!buffer->done) {
		/* Global buffer, not linked to any cache.
		 */
		printf("global buffer %p, %.3g MB\n",
			buffer, buffer->bsize / (1024 * 1024.0));
		*alive += buffer->bsize;
	}

	else if (buffer->cache &&
		buffer->done &&
		!vips_rect_isempty(&buffer->area) &&
		g_slist_find(buffer->cache->buffers, buffer)) {
		/* Published on a thread.
		 */
		printf("thread buffer %p, %.3g MB\n",
			buffer, buffer->bsize / (1024 * 1024.0));
		*alive += buffer->bsize;
	}

	else if (buffer->ref_count == 0 &&
		buffer->cache &&
		!buffer->done &&
		vips_rect_isempty(&buffer->area) &&
		g_slist_find(buffer->cache->reserve, buffer))
		/* Held in reserve.
		 */
		*reserve += buffer->bsize;

	else
		printf("buffer craziness!\n");

	return NULL;
}
#endif /*DEBUG*/

#ifdef DEBUG_CREATE
static void *
vips_buffer_cache_dump(VipsBufferCache *cache, void *a, void *b)
{
	printf("VipsBufferCache: %p\n", cache);
	printf("\t%d buffers\n", g_slist_length(cache->buffers));
	printf("\tthread %p\n", cache->thread);
	printf("\timage %p\n", cache->im);
	printf("\tbuffer_thread %p\n", cache->buffer_thread);
	printf("\t%d in reserve\n", g_slist_length(cache->reserve));

	return NULL;
}
#endif /*DEBUG_CREATE*/

void
vips_buffer_dump_all(void)
{
#ifdef DEBUG
	if (vips__buffer_all) {
		size_t reserve;
		size_t alive;

		printf("buffers:\n");

		reserve = 0;
		alive = 0;
		vips_slist_map2(vips__buffer_all,
			(VipsSListMap2Fn) vips_buffer_dump, &reserve, &alive);
		printf("%.3g MB alive\n", alive / (1024 * 1024.0));
		printf("%.3g MB in reserve\n", reserve / (1024 * 1024.0));
	}

#ifdef DEBUG_CREATE
	if (vips__buffer_cache_all) {
		printf("buffers: %d buffer cache still alive\n",
			g_slist_length(vips__buffer_cache_all));
		vips_slist_map2(vips__buffer_cache_all,
			(VipsSListMap2Fn) vips_buffer_cache_dump, NULL, NULL);
		printf("g_thread_self() == %p\n", g_thread_self());
	}
#endif /*DEBUG_CREATE*/
#endif /*DEBUG*/
}

static void
vips_buffer_free(VipsBuffer *buffer)
{
	VIPS_FREEF(vips_tracked_aligned_free, buffer->buf);
	buffer->bsize = 0;
	g_free(buffer);

#ifdef DEBUG
	g_mutex_lock(vips__global_lock);

	g_assert(g_slist_find(vips__buffer_all, buffer));
	vips__buffer_all = g_slist_remove(vips__buffer_all, buffer);

	g_mutex_unlock(vips__global_lock);
#endif /*DEBUG*/

#ifdef DEBUG_VERBOSE
	printf("vips_buffer_free: freeing buffer %p\n", buffer);
#endif /*DEBUG_VERBOSE*/
}

static void
buffer_thread_free(VipsBufferThread *buffer_thread)
{
	VIPS_FREEF(g_hash_table_destroy, buffer_thread->hash);
	VIPS_FREE(buffer_thread);
}

/* Run for GDestroyNotify on the VipsBufferThread hash.
 */
static void
buffer_cache_free(VipsBufferCache *cache)
{
	GSList *p;

#ifdef DEBUG_CREATE
	g_mutex_lock(vips__global_lock);
	vips__buffer_cache_all =
		g_slist_remove(vips__buffer_cache_all, cache);
	g_mutex_unlock(vips__global_lock);

	printf("buffer_cache_free: freeing cache %p on thread %p\n",
		cache, g_thread_self());
	printf("\t(%d caches left)\n",
		g_slist_length(vips__buffer_cache_all));
#endif /*DEBUG_CREATE*/

	/* Need to mark undone so we don't try and take them off this cache on
	 * unref.
	 */
	for (p = cache->buffers; p; p = p->next) {
		VipsBuffer *buffer = (VipsBuffer *) p->data;

		g_assert(buffer->done);
		g_assert(buffer->cache == cache);

		buffer->done = FALSE;
		buffer->cache = NULL;
	}
	VIPS_FREEF(g_slist_free, cache->buffers);

	for (p = cache->reserve; p; p = p->next) {
		VipsBuffer *buffer = (VipsBuffer *) p->data;

		vips_buffer_free(buffer);
	}
	VIPS_FREEF(g_slist_free, cache->reserve);

	g_free(cache);
}

static VipsBufferCache *
buffer_cache_new(VipsBufferThread *buffer_thread, VipsImage *im)
{
	VipsBufferCache *cache;

	cache = g_new(VipsBufferCache, 1);
	cache->buffers = NULL;
	cache->thread = g_thread_self();
	cache->im = im;
	cache->buffer_thread = buffer_thread;
	cache->reserve = NULL;
	cache->n_reserve = 0;

#ifdef DEBUG_CREATE
	g_mutex_lock(vips__global_lock);
	vips__buffer_cache_all =
		g_slist_prepend(vips__buffer_cache_all, cache);
	g_mutex_unlock(vips__global_lock);

	printf("buffer_cache_new: new cache %p for thread %p on image %p\n",
		cache, g_thread_self(), im);
	printf("\t(%d caches now)\n",
		g_slist_length(vips__buffer_cache_all));
#endif /*DEBUG_CREATE*/

	return cache;
}

static VipsBufferThread *
buffer_thread_new(void)
{
	VipsBufferThread *buffer_thread;

	buffer_thread = g_new(VipsBufferThread, 1);
	buffer_thread->hash = g_hash_table_new_full(
		g_direct_hash, g_direct_equal,
		NULL, (GDestroyNotify) buffer_cache_free);
	buffer_thread->thread = g_thread_self();

	return buffer_thread;
}

/* Get our private VipsBufferThread. NULL for non-worker threads.
 */
static VipsBufferThread *
buffer_thread_get(void)
{
	VipsBufferThread *buffer_thread;

	if (vips_thread_isvips()) {
		/* Our threads get a set of private buffers, since we know we
		 * will be calling vips_thread_shutdown() on thread
		 * termination.
		 */
		if (!(buffer_thread = g_private_get(buffer_thread_key))) {
			buffer_thread = buffer_thread_new();
			g_private_set(buffer_thread_key, buffer_thread);
		}

		g_assert(buffer_thread->thread == g_thread_self());
	}
	else
		/* Non-vips threads don't have one.
		 */
		buffer_thread = NULL;

	return buffer_thread;
}

/* Get the VipsBufferCache for this image, or NULL for a non-worker.
 */
static VipsBufferCache *
buffer_cache_get(VipsImage *im)
{
	VipsBufferThread *buffer_thread;
	VipsBufferCache *cache;

	if ((buffer_thread = buffer_thread_get())) {
		if (!(cache = (VipsBufferCache *)
					g_hash_table_lookup(buffer_thread->hash, im))) {
			cache = buffer_cache_new(buffer_thread, im);
			g_hash_table_insert(buffer_thread->hash, im, cache);
		}

		g_assert(cache->thread == g_thread_self());
	}
	else
		cache = NULL;

	return cache;
}

/* Pixels have been calculated: publish for other parts of this thread to see.
 */
void
vips_buffer_done(VipsBuffer *buffer)
{
	VipsImage *im = buffer->im;
	VipsBufferCache *cache;

	if (!buffer->done &&
		(cache = buffer_cache_get(im))) {
		g_assert(!g_slist_find(cache->buffers, buffer));
		g_assert(!buffer->cache);

		buffer->done = TRUE;
		buffer->cache = cache;

		cache->buffers = g_slist_prepend(cache->buffers, buffer);

#ifdef DEBUG_VERBOSE
		printf("vips_buffer_done: thread %p adding buffer %p to cache %p\n",
			g_thread_self(), buffer, cache);
		vips_buffer_print(buffer);
#endif /*DEBUG_VERBOSE*/
	}
}

/* Take off the public 'done' list. Make sure it has no calculated pixels in.
 */
void
vips_buffer_undone(VipsBuffer *buffer)
{
	if (buffer->done) {
		VipsBufferCache *cache = buffer->cache;

#ifdef DEBUG_VERBOSE
		printf("vips_buffer_undone: thread %p removing "
			   "buffer %p from cache %p\n",
			g_thread_self(), buffer, cache);
#endif /*DEBUG_VERBOSE*/

		g_assert(cache->thread == g_thread_self());
		g_assert(cache->buffer_thread->thread == cache->thread);
		g_assert(g_slist_find(cache->buffers, buffer));
		g_assert(buffer_thread_get());
		g_assert(cache->buffer_thread == buffer_thread_get());

		cache->buffers = g_slist_remove(cache->buffers, buffer);
		buffer->done = FALSE;

#ifdef DEBUG_VERBOSE
		printf("vips_buffer_undone: %d buffers left\n",
			g_slist_length(cache->buffers));
#endif /*DEBUG_VERBOSE*/
	}

	buffer->cache = NULL;
	buffer->area.width = 0;
	buffer->area.height = 0;
}

void
vips_buffer_unref(VipsBuffer *buffer)
{
#ifdef DEBUG_VERBOSE
	printf("** vips_buffer_unref: left = %d, top = %d, "
		   "width = %d, height = %d (%p)\n",
		buffer->area.left, buffer->area.top,
		buffer->area.width, buffer->area.height,
		buffer);
#endif /*DEBUG_VERBOSE*/

	g_assert(buffer->ref_count > 0);

	buffer->ref_count -= 1;

	if (buffer->ref_count == 0) {
		VipsBufferCache *cache;

#ifdef DEBUG_VERBOSE
		if (!buffer->done)
			printf("vips_buffer_unref: buffer was not done\n");
#endif /*DEBUG_VERBOSE*/

		vips_buffer_undone(buffer);

		/* Place on this thread's reserve list for reuse.
		 */
		if ((cache = buffer_cache_get(buffer->im)) &&
			cache->n_reserve < buffer_cache_max_reserve) {
			g_assert(!buffer->cache);

			cache->reserve =
				g_slist_prepend(cache->reserve, buffer);
			cache->n_reserve += 1;

			buffer->cache = cache;
			buffer->area.width = 0;
			buffer->area.height = 0;
		}
		else
			vips_buffer_free(buffer);
	}
}

static int
buffer_move(VipsBuffer *buffer, VipsRect *area)
{
	VipsImage *im = buffer->im;
	size_t new_bsize;
	size_t align;

	g_assert(buffer->ref_count == 1);

	vips_buffer_undone(buffer);
	g_assert(!buffer->done);

	buffer->area = *area;

	new_bsize = (size_t) VIPS_IMAGE_SIZEOF_PEL(im) *
		area->width * area->height;

	/* Need to pad buffer size to be aligned-up to
	 * 64 bytes for the vips_reduce{h,v} highway path.
	 */
#ifdef HAVE_HWY
	if (im->BandFmt == VIPS_FORMAT_UCHAR) {
		new_bsize += /*HWY_ALIGNMENT*/ 64 - 1;
		align = /*HWY_ALIGNMENT*/ 64;
	}
	else
#endif /*HAVE_HWY*/
		align = 16;

	if (buffer->bsize < new_bsize ||
		!buffer->buf) {
		buffer->bsize = new_bsize;
		VIPS_FREEF(vips_tracked_aligned_free, buffer->buf);
		if (!(buffer->buf = vips_tracked_aligned_alloc(buffer->bsize, align)))
			return -1;
	}

	return 0;
}

/* Make a new buffer.
 */
VipsBuffer *
vips_buffer_new(VipsImage *im, VipsRect *area)
{
	VipsBufferCache *cache;
	VipsBuffer *buffer;

	if ((cache = buffer_cache_get(im)) &&
		cache->reserve) {
		buffer = (VipsBuffer *) cache->reserve->data;
		cache->reserve = g_slist_remove(cache->reserve, buffer);
		cache->n_reserve -= 1;

		g_assert(buffer->im == im);
		g_assert(buffer->done == FALSE);
		g_assert(buffer->cache);

		buffer->ref_count = 1;
		buffer->done = FALSE;
		buffer->cache = NULL;
	}
	else {
		buffer = g_new0(VipsBuffer, 1);
		buffer->ref_count = 1;
		buffer->im = im;
		buffer->done = FALSE;
		buffer->cache = NULL;
		buffer->buf = NULL;
		buffer->bsize = 0;

#ifdef DEBUG
		g_mutex_lock(vips__global_lock);
		vips__buffer_all =
			g_slist_prepend(vips__buffer_all, buffer);
		g_mutex_unlock(vips__global_lock);
#endif /*DEBUG*/
	}

	if (buffer_move(buffer, area)) {
		vips_buffer_free(buffer);
		return NULL;
	}

	return buffer;
}

/* Find an existing buffer that encloses area and return a ref. Or NULL for no
 * existing buffer.
 */
static VipsBuffer *
buffer_find(VipsImage *im, VipsRect *r)
{
	VipsBufferCache *cache;
	VipsBuffer *buffer;
	GSList *p;
	VipsRect *area;

	if (!(cache = buffer_cache_get(im)))
		return NULL;

	/* This needs to be quick :-( don't use
	 * vips_slist_map2()/vips_rect_includesrect(), do the search
	 * inline.
	 *
	 * FIXME we return the first enclosing buffer, perhaps we should
	 * search for the largest?
	 */
	for (p = cache->buffers; p; p = p->next) {
		buffer = (VipsBuffer *) p->data;
		area = &buffer->area;

		if (area->left <= r->left &&
			area->top <= r->top &&
			area->left + area->width >= r->left + r->width &&
			area->top + area->height >= r->top + r->height) {
			buffer->ref_count += 1;

#ifdef DEBUG_VERBOSE
			printf("buffer_find: left = %d, top = %d, "
				   "width = %d, height = %d, count = %d (%p)\n",
				buffer->area.left, buffer->area.top,
				buffer->area.width, buffer->area.height,
				buffer->ref_count,
				buffer);
#endif /*DEBUG_VERBOSE*/

			return buffer;
		}
	}

	return NULL;
}

/* Return a ref to a buffer that encloses area. The buffer we return might be
 * done.
 */
VipsBuffer *
vips_buffer_ref(VipsImage *im, VipsRect *area)
{
	VipsBuffer *buffer;

	if ((buffer = buffer_find(im, area)))
		return buffer;
	else
		return vips_buffer_new(im, area);
}

/* Unref old, ref new, in a single operation. Reuse stuff if we can. The
 * buffer we return might or might not be done.
 */
VipsBuffer *
vips_buffer_unref_ref(VipsBuffer *old_buffer, VipsImage *im, VipsRect *area)
{
	VipsBuffer *buffer;

	g_assert(!old_buffer ||
		old_buffer->im == im);

	/* Is the current buffer OK?
	 */
	if (old_buffer &&
		vips_rect_includesrect(&old_buffer->area, area))
		return old_buffer;

	/* Does the new area already have a buffer?
	 */
	if ((buffer = buffer_find(im, area))) {
		VIPS_FREEF(vips_buffer_unref, old_buffer);
		return buffer;
	}

	/* Is the current buffer unshared? We can just move it.
	 */
	if (old_buffer &&
		old_buffer->ref_count == 1) {
		if (buffer_move(old_buffer, area)) {
			vips_buffer_unref(old_buffer);
			return NULL;
		}

		return old_buffer;
	}

	/* Fallback ... unref the old one, make a new one.
	 */
	VIPS_FREEF(vips_buffer_unref, old_buffer);
	if (!(buffer = vips_buffer_new(im, area)))
		return NULL;

	return buffer;
}

static void
buffer_thread_destroy_notify(VipsBufferThread *buffer_thread)
{
	/* We only come here if vips_thread_shutdown() was not called for this
	 * thread. Do our best to clean up.
	 *
	 * GPrivate has stopped working by this point in destruction, be
	 * careful not to touch that.
	 */
	buffer_thread_free(buffer_thread);
}

/* Init the buffer cache system. This is called during vips_init.
 */
void
vips__buffer_init(void)
{
	static GPrivate private =
		G_PRIVATE_INIT((GDestroyNotify) buffer_thread_destroy_notify);

	buffer_thread_key = &private;

	if (buffer_cache_max_reserve < 1)
		printf("vips__buffer_init: buffer reserve disabled\n");

#ifdef DEBUG
	printf("vips__buffer_init: DEBUG enabled\n");
#endif /*DEBUG*/

#ifdef DEBUG_CREATE
	printf("vips__buffer_init: DEBUG_CREATE enabled\n");
#endif /*DEBUG_CREATE*/
}

void
vips__buffer_shutdown(void)
{
	VipsBufferThread *buffer_thread;

	if ((buffer_thread = g_private_get(buffer_thread_key))) {
		buffer_thread_free(buffer_thread);
		g_private_set(buffer_thread_key, NULL);
	}
}
