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/*************************************************************************
* Copyright (C) 2008 Tavian Barnes <tavianator@gmail.com> *
* *
* This file is part of The Dimension Library. *
* *
* The Dimension 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 3 of the *
* License, or (at your option) any later version. *
* *
* The Dimension 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 program. If not, see *
* <http://www.gnu.org/licenses/>. *
*************************************************************************/
#include "dimension.h"
#include <pthread.h>
#include <stdlib.h> /* For malloc(), free() */
/* Allocate a new canvas, of width x and height y. If any intermediary step
fails, free all acquired memory to avoid leaks. */
dmnsn_canvas *
dmnsn_new_canvas(unsigned int x, unsigned int y)
{
unsigned int i, j, k, l;
/* Allocate the dmnsn_canvas struct */
dmnsn_canvas *canvas = malloc(sizeof(dmnsn_canvas));
if (canvas) {
/* Set the width and height */
canvas->x = x;
canvas->y = y;
/* Allocate the pixels */
canvas->pixels = malloc(sizeof(dmnsn_color)*x*y);
if (!canvas->pixels) {
free(canvas);
return NULL;
}
/* Allocate the rwlocks */
canvas->rwlocks = malloc(sizeof(pthread_rwlock_t)*x*y);
if (!canvas->rwlocks) {
free(canvas->pixels);
free(canvas);
return NULL;
}
/* Initialize the rwlocks */
for (i = 0; i < x; ++i) {
for (j = 0; j < y; ++j) {
if (pthread_rwlock_init(&canvas->rwlocks[j*x + i], NULL) != 0) {
/* pthread_rwlock_init failed. Destroy the locks we've already made,
free the canvas, and return NULL. We leak memory if destruction
fails (i.e. someone is somehow using an rwlock already). */
for (l = 0; l < j; ++l) {
for (k = 0; k < x; ++k) {
if (pthread_rwlock_destroy(&canvas->rwlocks[l*x + k]) != 0) {
/* Low severity, because leaked locks won't actually hurt us */
dmnsn_error(DMNSN_SEVERITY_LOW,
"Leaking rwlocks in failed allocation.");
}
}
}
for (k = 0; k < i; ++k) {
if (pthread_rwlock_destroy(&canvas->rwlocks[j*x + k]) != 0) {
dmnsn_error(DMNSN_SEVERITY_LOW,
"Leaking rwlocks in failed allocation.");
}
}
free(canvas->rwlocks);
free(canvas->pixels);
free(canvas);
return NULL;
}
}
}
}
return canvas;
}
/* Delete a dmnsn_canvas allocated with dmnsn_new_canvas */
void
dmnsn_delete_canvas(dmnsn_canvas *canvas)
{
unsigned int i, j;
if (canvas) {
/* Destroy the rwlocks */
for (i = 0; i < canvas->x; ++i) {
for (j = 0; j < canvas->y; ++j) {
if (pthread_rwlock_destroy(&canvas->rwlocks[j*canvas->x + i]) != 0) {
dmnsn_error(DMNSN_SEVERITY_LOW,
"Leaking rwlocks in deallocation.");
}
}
}
/* Free the locks, pixels, and canvas */
free(canvas->rwlocks);
free(canvas->pixels);
free(canvas);
}
}
/* Get a pixel at (x,y) thread-safely, using dmnsn_rdlock_pixel. */
dmnsn_color
dmnsn_get_pixel(const dmnsn_canvas *canvas, unsigned int x, unsigned int y)
{
dmnsn_color color;
dmnsn_rdlock_pixel(canvas, x, y);
color = canvas->pixels[y*canvas->x + x];
dmnsn_unlock_pixel(canvas, x, y);
return color;
}
/* Set a pixel at (x,y) thread-safely, using dmnsn_wrlock_pixel. */
void
dmnsn_set_pixel(dmnsn_canvas *canvas,
unsigned int x, unsigned int y, dmnsn_color color)
{
dmnsn_wrlock_pixel(canvas, x, y);
canvas->pixels[y*canvas->x + x] = color;
dmnsn_unlock_pixel(canvas, x, y);
}
/* Acquire a read-lock for a pixel */
void
dmnsn_rdlock_pixel(const dmnsn_canvas *canvas, unsigned int x, unsigned int y)
{
if (pthread_rwlock_rdlock(&canvas->rwlocks[y*canvas->x + x]) != 0) {
/* Medium severity, because undefined behaviour is pretty likely if our
reads and writes aren't synced */
dmnsn_error(DMNSN_SEVERITY_MEDIUM,
"Couldn't acquire read-lock for pixel.");
}
}
/* Acquire a write-lock for a pixel */
void
dmnsn_wrlock_pixel(dmnsn_canvas *canvas, unsigned int x, unsigned int y)
{
if (pthread_rwlock_wrlock(&canvas->rwlocks[y*canvas->x + x]) != 0) {
/* Medium severity, because undefined behaviour is pretty likely if our
reads and writes aren't synced */
dmnsn_error(DMNSN_SEVERITY_MEDIUM,
"Couldn't acquire write-lock for pixel.");
}
}
/* Unlock a pixel */
void
dmnsn_unlock_pixel(const dmnsn_canvas *canvas, unsigned int x, unsigned int y)
{
if (pthread_rwlock_unlock(&canvas->rwlocks[y*canvas->x + x]) != 0) {
/* Medium severity, because if the pixel is locked, we're likely to hang
the next time we try to read or write it */
dmnsn_error(DMNSN_SEVERITY_MEDIUM, "Couldn't unlock pixel.");
}
}
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