/* Copyright (C) 1998 Aladdin Enterprises.  All rights reserved.
  
  This file is part of GNU Ghostscript.
  
  GNU Ghostscript is distributed in the hope that it will be useful, but
  WITHOUT ANY WARRANTY.  No author or distributor accepts responsibility
  to anyone for the consequences of using it or for whether it serves any
  particular purpose or works at all, unless he says so in writing.  Refer
  to the GNU General Public License for full details.
  
  Everyone is granted permission to copy, modify and redistribute GNU
  Ghostscript, but only under the conditions described in the GNU General
  Public License.  A copy of this license is supposed to have been given
  to you along with GNU Ghostscript so you can know your rights and
  responsibilities.  It should be in a file named COPYING.  Among other
  things, the copyright notice and this notice must be preserved on all
  copies.
  
  Aladdin Enterprises supports the work of the GNU Project, but is not
  affiliated with the Free Software Foundation or the GNU Project.  GNU
  Ghostscript, as distributed by Aladdin Enterprises, does not require any
  GNU software to build or run it.
*/

/*$Id: gxpageq.c $ */
/* Page queue implementation */

/* Initial version 2/1/98 by John Desrosiers (soho@crl.com) */

#include "gx.h"
#include "gxdevice.h"
#include "gxclist.h"
#include "gxpageq.h"
#include "gserrors.h"

/* ------------------- Global Data ----------------------- */
/* Structure descriptor for GC */
private_st_gx_page_queue_entry();
private_st_gx_page_queue();

/* ------------ Forward Decl's --------------------------- */
private gx_page_queue_entry *	/* removed entry, 0 if none avail */
                    gx_page_queue_remove_first(P1(
						     gx_page_queue * queue	/* page queue to retrieve from */
					       ));


/* --------------------Procedures------------------------- */

/* Allocate a page queue. */
gx_page_queue *
gx_page_queue_alloc(gs_memory_t *mem)
{
    return gs_alloc_struct(mem, gx_page_queue, &st_gx_page_queue,
			   "gx_page_queue_alloc");
}

/* ------- page_queue_entry alloc/free --------- */
/* Allocate & init a gx_page_queue_entry */
gx_page_queue_entry *		/* rets ptr to allocated object, 0 if VM error */
gx_page_queue_entry_alloc(
			     gx_page_queue * queue	/* queue that entry is being alloc'd for */
)
{
    gx_page_queue_entry *entry
    = gs_alloc_struct(queue->memory, gx_page_queue_entry,
		      &st_gx_page_queue_entry, "gx_page_queue_entry_alloc");

    if (entry != 0) {
	entry->next = 0;
	entry->queue = queue;
    }
    return entry;
}

/* Free a gx_page_queue_entry allocated w/gx_page_queue_entry_alloc */
void
gx_page_queue_entry_free(
			    gx_page_queue_entry * entry		/* entry to free up */
)
{
    gs_free_object(entry->queue->memory, entry, "gx_page_queue_entry_free");
}

/* -------- page_queue init/dnit ---------- */
/* Initialize a gx_page_queue object */
int				/* -ve error code, or 0 */
gx_page_queue_init(
		      gx_page_queue * queue,	/* page queue to init */
		      gs_memory_t * memory	/* allocator for dynamic memory */
)
{
    queue->memory = memory;
    queue->monitor = gx_monitor_alloc(memory);	/* alloc monitor to serialize */
    queue->entry_count = 0;
    queue->dequeue_in_progress = false;
    queue->render_req_sema = gx_semaphore_alloc(memory);
    queue->enable_render_done_signal = false;
    queue->render_done_sema = gx_semaphore_alloc(memory);
    queue->first_in = queue->last_in = 0;
    queue->reserve_entry = gx_page_queue_entry_alloc(queue);

    if (queue->monitor && queue->render_req_sema && queue->render_done_sema
	&& queue->reserve_entry)
	return 0;
    else {
	gx_page_queue_dnit(queue);
	return gs_error_VMerror;
    }
}

/* Dnitialize a gx_page_queue object */
void
gx_page_queue_dnit(
		      gx_page_queue * queue	/* page queue to dnit */
)
{
    /* Deallocate any left-over queue entries */
    gx_page_queue_entry *entry;

    while ((entry = gx_page_queue_remove_first(queue)) != 0)
	gx_page_queue_entry_free(entry);

    /* Free dynamic objects */
    if (queue->monitor) {
	gx_monitor_free(queue->monitor);
	queue->monitor = 0;
    }
    if (queue->render_req_sema) {
	gx_semaphore_free(queue->render_req_sema);
	queue->render_req_sema = 0;
    }
    if (queue->render_done_sema) {
	gx_semaphore_free(queue->render_done_sema);
	queue->render_done_sema = 0;
    }
    if (queue->reserve_entry) {
	gx_page_queue_entry_free(queue->reserve_entry);
	queue->reserve_entry = 0;
    }
}

/* -------- low-level queue add/remove ---------- */
/* Retrieve & remove firstin queue entry */
private gx_page_queue_entry *	/* removed entry, 0 if none avail */
gx_page_queue_remove_first(
			      gx_page_queue * queue	/* page queue to retrieve from */
)
{
    gx_page_queue_entry *entry = 0;	/* assume failure */

    /* Enter monitor */
    gx_monitor_enter(queue->monitor);

    /* Get the goods */
    if (queue->entry_count) {
	entry = queue->first_in;
	queue->first_in = entry->next;
	if (queue->last_in == entry)
	    queue->last_in = 0;
	--queue->entry_count;
    }
    /* exit monitor */
    gx_monitor_leave(queue->monitor);

    return entry;
}

/* Add entry to queue at end */
private void
gx_page_queue_add_last(
			  gx_page_queue_entry * entry	/* entry to add */
)
{
    gx_page_queue *queue = entry->queue;

    /* Enter monitor */
    gx_monitor_enter(queue->monitor);

    /* Add the goods */
    entry->next = 0;
    if (queue->last_in != 0)
	queue->last_in->next = entry;
    queue->last_in = entry;
    if (queue->first_in == 0)
	queue->first_in = entry;
    ++queue->entry_count;

    /* exit monitor */
    gx_monitor_leave(queue->monitor);
}

/* --------- low-level synchronization ---------- */
/* Wait for a single page to finish rendering (if any pending) */
int				/* rets 0 if no pages were waiting for rendering, 1 if actually waited */
gx_page_queue_wait_one_page(
			       gx_page_queue * queue	/* queue to wait on */
)
{
    int code;

    gx_monitor_enter(queue->monitor);
    if (!queue->entry_count && !queue->dequeue_in_progress) {
	code = 0;
	gx_monitor_leave(queue->monitor);
    } else {
	/* request acknowledgement on render done */
	queue->enable_render_done_signal = true;

	/* exit monitor & wait for acknowlegement */
	gx_monitor_leave(queue->monitor);
	gx_semaphore_wait(queue->render_done_sema);
	code = 1;
    }
    return code;
}

/* Wait for page queue to become empty */
void
gx_page_queue_wait_until_empty(
				  gx_page_queue * queue		/* page queue to wait on */
)
{
    while (gx_page_queue_wait_one_page(queue));
}

/* -----------  Synchronized page_queue get/put routines ------ */
/* Add an entry to page queue for rendering w/sync to renderer */
void
gx_page_queue_enqueue(
			 gx_page_queue_entry * entry	/* entry to add */
)
{
    gx_page_queue *queue = entry->queue;

    /* Add the goods to queue, & signal it */
    gx_page_queue_add_last(entry);
    gx_semaphore_signal(queue->render_req_sema);
}

/* Add page to a page queue */
/* Even if an error is returned, entry will have been added to queue! */
int				/* rets 0 ok, gs_error_VMerror if error */
gx_page_queue_add_page(
			  gx_page_queue * queue,	/* page queue to add to */
			  gx_page_queue_action_t action,	/* action code to queue */
			  const gx_band_page_info * page_info,	/* bandinfo incl. bandlist (or 0) */
			  int page_count	/* see comments in gdevprna.c */
)
{
    int code = 0;

    /* Allocate a new page queue entry */
    gx_page_queue_entry *entry
    = gx_page_queue_entry_alloc(queue);

    if (!entry) {
	/* Use reserve page queue entry */
	gx_monitor_enter(queue->monitor);	/* not strictly necessary */
	entry = queue->reserve_entry;
	queue->reserve_entry = 0;
	gx_monitor_leave(queue->monitor);
    }
    /* Fill in page queue entry with info from device */
    entry->action = action;
    if (page_info != 0)
	entry->page_info = *page_info;
    entry->num_copies = page_count;

    /* Stick onto page queue & signal */
    gx_page_queue_enqueue(entry);

    /* If a new reserve entry is needed, wait till enough mem is avail */
    while (!queue->reserve_entry) {
	queue->reserve_entry = gx_page_queue_entry_alloc(queue);
	if (!queue->reserve_entry && !gx_page_queue_wait_one_page(queue)) {
	    /* Should never happen: all pages rendered & still can't get memory: give up! */
	    code = gs_note_error(gs_error_Fatal);
	    break;
	}
    }
    return code;
}

/* Wait for & get next page queue entry */
gx_page_queue_entry *		/* removed entry */
gx_page_queue_start_dequeue(
			       gx_page_queue * queue	/* page queue to retrieve from */
)
{
    gx_semaphore_wait(queue->render_req_sema);
    queue->dequeue_in_progress = true;
    return gx_page_queue_remove_first(queue);
}

/* After rendering page gotten w/gx_page_queue_dequeue, call this to ack */
void
gx_page_queue_finish_dequeue(
				gx_page_queue_entry * entry	/* entry that was retrieved to delete */
)
{
    gx_page_queue *queue = entry->queue;

    gx_monitor_enter(queue->monitor);
    if (queue->enable_render_done_signal) {
	queue->enable_render_done_signal = false;
	gx_semaphore_signal(queue->render_done_sema);
    }
    queue->dequeue_in_progress = false;

    /* Delete the previously-allocated entry, do inside monitor in case */
    /* this is the reserve entry & is the only memory in the universe; */
    /* in that case gx_page_queue_add_page won't be looking for this */
    /* until the monitor is exited. */
    gx_page_queue_entry_free(entry);

    gx_monitor_leave(queue->monitor);
}
