Add thread sharing for producer(webcam) and consumer(rendering) threads

C/src/thread_sharing.c

@@ -0,0 +1,98 @@
+#include "ascii.h"
+#include "capture.h"
+#include "thread_sharing.h"
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <sys/mman.h>
+
+// Producer thread for capturing frames
+void *capture_thread(void *arg) {
+  shared_frame_t *sf = arg;
+  webcam_t cam = {.fd = -1, .buffer = MAP_FAILED};
+
+  // Intialialize webcam into the thread context
+  if (webcam_init(&cam, "/dev/video0", sf->width, sf->height) < 0) {
+    perror("webcam_init in capture thread");
+    sf->stop = 1;
+    return NULL;
+  }
+
+  int write_idx = 0;
+
+  while (!sf->stop) {
+    if (webcam_wait_frame(&cam, 100) < 0) {
+      continue;
+    }
+
+    // Capture into inactive frame buffer slot
+    if (webcam_capture_frame(&cam, sf->buf[write_idx]) < 0) {
+      break;
+    }
+    webcam_requeue_buffer(&cam);
+
+    pthread_mutex_lock(&sf->lock);
+    sf->ready_idx = write_idx;
+    sf->has_frame = 1;
+    pthread_cond_signal(&sf->cond); // wake render thread
+    pthread_mutex_unlock(&sf->lock);
+
+    write_idx ^= 1; // XOR, swap buffers
+  }
+
+  webcam_cleanup(&cam);
+  return NULL;
+}
+
+// Producer thread for rendering
+void *render_thread(void *arg) {
+  shared_frame_t *sf = arg;
+
+  // Allocate dynamic buffers
+  size_t out_size = ascii_out_size(sf->ascii_w, sf->ascii_h, sf->opts.color);
+  char *out_buf = malloc(out_size);
+  uint8_t *local_rgb =
+      sf->opts.color ? malloc(sf->width * sf->height * 3) : NULL;
+
+  if (!out_buf) {
+    perror("render_thread malloc");
+    return NULL;
+  }
+
+  pthread_mutex_lock(&sf->lock);
+  while (!sf->stop) {
+    while (!sf->has_frame && !sf->stop) {
+      pthread_cond_wait(&sf->cond, &sf->lock); // sleep
+    }
+    if (sf->stop)
+      break;
+
+    int read_idx = sf->ready_idx;
+    sf->has_frame = 0;
+
+    pthread_mutex_unlock(&sf->lock);
+
+    // Process frame outside locked state
+    int len = grayscale_to_ascii(sf->buf[read_idx], local_rgb, sf->width,
+                                 sf->height, sf->ascii_w, sf->ascii_h, out_buf,
+                                 out_size, &sf->opts);
+
+    if (len > 0) {
+      write(STDOUT_FILENO, "\033[H", 3); // cursor to top-left
+      write(STDOUT_FILENO, out_buf, (size_t)len);
+    }
+
+    pthread_mutex_lock(&sf->lock);
+  }
+
+  pthread_mutex_unlock(&sf->lock);
+
+  // Cleanup memory
+  free(out_buf);
+  if (local_rgb) {
+    free(local_rgb);
+  }
+
+  return NULL;
+}