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ex_threads2.c
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ex_threads2.c
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/*
* Example program for the Allegro library, by Peter Wang.
*
* In this example, threads render to their own memory buffers, while the
* main thread handles events and drawing (copying from the memory buffers
* to the display).
*
* Click on an image to pause its thread.
*/
#include <math.h>
#include <allegro5/allegro.h>
#include "common.c"
/* feel free to bump these up */
#define NUM_THREADS 9
#define IMAGES_PER_ROW 3
/* size of each fractal image */
#define W 120
#define H 120
typedef struct ThreadInfo {
ALLEGRO_BITMAP *bitmap;
ALLEGRO_MUTEX *mutex;
ALLEGRO_COND *cond;
bool is_paused;
int random_seed;
double target_x, target_y;
} ThreadInfo;
typedef struct Viewport {
double centre_x;
double centre_y;
double x_extent;
double y_extent;
double zoom;
} Viewport;
static ThreadInfo thread_info[NUM_THREADS];
unsigned char sin_lut[256];
static double cabs2(double re, double im)
{
return re*re + im*im;
}
static int mandel(double cre, double cim, int MAX_ITER)
{
const float Z_MAX2 = 4.0;
double zre = cre, zim = cim;
int iter;
for (iter = 0; iter < MAX_ITER; iter++) {
double z1re, z1im;
z1re = zre * zre - zim * zim;
z1im = 2 * zre * zim;
z1re += cre;
z1im += cim;
if (cabs2(z1re, z1im) > Z_MAX2) {
return iter + 1; /* outside set */
}
zre = z1re;
zim = z1im;
}
return 0; /* inside set */
}
/* local_rand:
* Simple rand() replacement with guaranteed randomness in the lower 16 bits.
* We just need a RNG with a thread-safe interface.
*/
static int local_rand(int *seed)
{
const int LOCAL_RAND_MAX = 0xFFFF;
*seed = (*seed + 1) * 1103515245 + 12345;
return ((*seed >> 16) & LOCAL_RAND_MAX);
}
static void random_palette(unsigned char palette[256][3], int *seed)
{
unsigned char rmax = 128 + local_rand(seed) % 128;
unsigned char gmax = 128 + local_rand(seed) % 128;
unsigned char bmax = 128 + local_rand(seed) % 128;
int i;
for (i = 0; i < 256; i++) {
palette[i][0] = rmax * i / 256;
palette[i][1] = gmax * i / 256;
palette[i][2] = bmax * i / 256;
}
}
static void draw_mandel_line(ALLEGRO_BITMAP *bitmap, const Viewport *viewport,
unsigned char palette[256][3], const int y)
{
ALLEGRO_LOCKED_REGION *lr;
unsigned char *rgb;
double xlower, ylower;
double xscale, yscale;
double im;
double re;
int w, h;
int x;
int n = 512 / pow(2, viewport->zoom);
w = al_get_bitmap_width(bitmap);
h = al_get_bitmap_height(bitmap);
if (!(lr = al_lock_bitmap_region(bitmap, 0, y, w, 1, ALLEGRO_PIXEL_FORMAT_ANY_24_NO_ALPHA,
ALLEGRO_LOCK_WRITEONLY))) {
abort_example("draw_mandel_line: al_lock_bitmap_region failed\n");
}
xlower = viewport->centre_x - viewport->x_extent / 2.0 * viewport->zoom;
ylower = viewport->centre_y - viewport->y_extent / 2.0 * viewport->zoom;
xscale = viewport->x_extent / w * viewport->zoom;
yscale = viewport->y_extent / h * viewport->zoom;
re = xlower;
im = ylower + y * yscale;
rgb = lr->data;
for (x = 0; x < w; x++) {
int i = mandel(re, im, n);
int v = sin_lut[(int)(i * 64 / n)];
rgb[0] = palette[v][0];
rgb[1] = palette[v][1];
rgb[2] = palette[v][2];
rgb += 3;
re += xscale;
}
al_unlock_bitmap(bitmap);
}
static void *thread_func(ALLEGRO_THREAD *thr, void *arg)
{
ThreadInfo *info = (ThreadInfo *) arg;
Viewport viewport;
unsigned char palette[256][3];
int y, h;
y = 0;
h = al_get_bitmap_height(info->bitmap);
viewport.centre_x = info->target_x;
viewport.centre_y = info->target_y;
viewport.x_extent = 3.0;
viewport.y_extent = 3.0;
viewport.zoom = 1.0;
info->target_x = 0;
info->target_y = 0;
while (!al_get_thread_should_stop(thr)) {
al_lock_mutex(info->mutex);
while (info->is_paused) {
al_wait_cond(info->cond, info->mutex);
/* We might be awoken because the program is terminating. */
if (al_get_thread_should_stop(thr)) {
break;
}
}
if (!info->is_paused) {
if (y == 0) {
random_palette(palette, &info->random_seed);
}
draw_mandel_line(info->bitmap, &viewport, palette, y);
y++;
if (y >= h) {
double z = viewport.zoom;
y = 0;
viewport.centre_x += z * viewport.x_extent * info->target_x;
viewport.centre_y += z * viewport.y_extent * info->target_y;
info->target_x = 0;
info->target_y = 0;
viewport.zoom *= 0.99;
}
}
al_unlock_mutex(info->mutex);
al_rest(0);
}
return NULL;
}
static void show_images(void)
{
int x = 0;
int y = 0;
int i;
al_set_blender(ALLEGRO_ADD, ALLEGRO_ONE, ALLEGRO_ZERO);
for (i = 0; i < NUM_THREADS; i++) {
/* for lots of threads, this is not good enough */
al_lock_mutex(thread_info[i].mutex);
al_draw_bitmap(thread_info[i].bitmap, x * W, y * H, 0);
al_unlock_mutex(thread_info[i].mutex);
x++;
if (x == IMAGES_PER_ROW) {
x = 0;
y++;
}
}
al_flip_display();
}
static void set_target(int n, double x, double y)
{
thread_info[n].target_x = x;
thread_info[n].target_y = y;
}
static void toggle_pausedness(int n)
{
ThreadInfo *info = &thread_info[n];
al_lock_mutex(info->mutex);
info->is_paused = !info->is_paused;
al_broadcast_cond(info->cond);
al_unlock_mutex(info->mutex);
}
int main(int argc, char **argv)
{
ALLEGRO_THREAD *thread[NUM_THREADS];
ALLEGRO_DISPLAY *display;
ALLEGRO_TIMER *timer;
ALLEGRO_EVENT_QUEUE *queue;
ALLEGRO_EVENT event;
bool need_draw;
int i;
(void)argc;
(void)argv;
for (i = 0; i < 256; i++) {
sin_lut[i] = 128 + (int) (127.0 * sin(i / 8.0));
}
if (!al_init()) {
abort_example("Could not init Allegro.\n");
}
al_install_keyboard();
al_install_mouse();
display = al_create_display(W * IMAGES_PER_ROW,
H * NUM_THREADS / IMAGES_PER_ROW);
if (!display) {
abort_example("Error creating display\n");
}
timer = al_create_timer(1.0/3);
if (!timer) {
abort_example("Error creating timer\n");
}
queue = al_create_event_queue();
if (!queue) {
abort_example("Error creating event queue\n");
}
al_register_event_source(queue, al_get_display_event_source(display));
al_register_event_source(queue, al_get_keyboard_event_source());
al_register_event_source(queue, al_get_mouse_event_source());
al_register_event_source(queue, al_get_timer_event_source(timer));
/* Note:
* Right now, A5 video displays can only be accessed from the thread which
* created them (at least for OpenGL). To lift this restriction, we could
* keep track of the current OpenGL context for each thread and make all
* functions accessing the display check for it.. not sure it's worth the
* additional complexity though.
*/
al_set_new_bitmap_format(ALLEGRO_PIXEL_FORMAT_RGB_888);
al_set_new_bitmap_flags(ALLEGRO_MEMORY_BITMAP);
for (i = 0; i < NUM_THREADS; i++) {
thread_info[i].bitmap = al_create_bitmap(W, H);
if (!thread_info[i].bitmap) {
goto Error;
}
thread_info[i].mutex = al_create_mutex();
if (!thread_info[i].mutex) {
goto Error;
}
thread_info[i].cond = al_create_cond();
if (!thread_info[i].cond) {
goto Error;
}
thread_info[i].is_paused = false;
thread_info[i].random_seed = i;
thread[i] = al_create_thread(thread_func, &thread_info[i]);
if (!thread[i]) {
goto Error;
}
}
set_target(0, -0.56062033041600878303, -0.56064322926933807256);
set_target(1, -0.57798076669230014080, -0.63449861991138123418);
set_target(2, 0.36676836392830602929, -0.59081385302214906030);
set_target(3, -1.48319283039401317303, -0.00000000200514696273);
set_target(4, -0.74052910500707636032, 0.18340899525730713915);
set_target(5, 0.25437906525768350097, -0.00046678223345789554);
set_target(6, -0.56062033041600878303, 0.56064322926933807256);
set_target(7, -0.57798076669230014080, 0.63449861991138123418);
set_target(8, 0.36676836392830602929, 0.59081385302214906030);
for (i = 0; i < NUM_THREADS; i++) {
al_start_thread(thread[i]);
}
al_start_timer(timer);
need_draw = true;
while (true) {
if (need_draw && al_is_event_queue_empty(queue)) {
show_images();
need_draw = false;
}
al_wait_for_event(queue, &event);
if (event.type == ALLEGRO_EVENT_TIMER) {
need_draw = true;
}
else if (event.type == ALLEGRO_EVENT_MOUSE_BUTTON_DOWN) {
int n = (event.mouse.y / H) * IMAGES_PER_ROW + (event.mouse.x / W);
if (n < NUM_THREADS) {
double x = event.mouse.x - (event.mouse.x / W) * W;
double y = event.mouse.y - (event.mouse.y / H) * H;
/* Center to the mouse click position. */
if (thread_info[n].is_paused) {
thread_info[n].target_x = x / W - 0.5;
thread_info[n].target_y = y / H - 0.5;
}
toggle_pausedness(n);
}
}
else if (event.type == ALLEGRO_EVENT_DISPLAY_EXPOSE) {
need_draw = true;
}
else if (event.type == ALLEGRO_EVENT_DISPLAY_CLOSE) {
break;
}
else if (event.type == ALLEGRO_EVENT_KEY_DOWN) {
if (event.keyboard.keycode == ALLEGRO_KEY_ESCAPE) {
break;
}
need_draw = true;
}
}
for (i = 0; i < NUM_THREADS; i++) {
/* Set the flag to stop the thread. The thread might be waiting on a
* condition variable, so signal the condition to force it to wake up.
*/
al_set_thread_should_stop(thread[i]);
al_lock_mutex(thread_info[i].mutex);
al_broadcast_cond(thread_info[i].cond);
al_unlock_mutex(thread_info[i].mutex);
/* al_destroy_thread() implicitly joins the thread, so this call is not
* strictly necessary.
*/
al_join_thread(thread[i], NULL);
al_destroy_thread(thread[i]);
}
al_destroy_event_queue(queue);
al_destroy_timer(timer);
al_destroy_display(display);
return 0;
Error:
return 1;
}
/* vim: set sts=3 sw=3 et: */