Send cv::Mat with FIFO

code/C++/FIFO_w_OpenCV/reader.cpp

@@ -0,0 +1,73 @@
+#include <fcntl.h>
+#include <poll.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/select.h>
+#include <sys/stat.h>
+#include <unistd.h>
+
+#include <opencv2/opencv.hpp>
+
+#define FIFO_NAME "cvMat"
+#define MAX_BUF 150 * 150 * 4
+
+using namespace cv;
+
+int main() {
+  unsigned int timeout_seconds = 2;
+
+  while (true) {
+    int fd = open(FIFO_NAME, O_RDONLY | O_NONBLOCK);
+    if (fd < 0) {
+      perror("open");
+      return EXIT_FAILURE;
+    }
+
+    struct pollfd waiter = {.fd = fd, .events = POLLIN};
+
+    while (true) {
+      bool stop = false;
+
+      int poll_result = poll(&waiter, 1, timeout_seconds * 1000);
+      switch (poll_result) {
+      case 0:
+        puts("No data from fifo");
+        break;
+
+      case 1:
+        if (waiter.revents & POLLIN) {
+          std::vector<uchar> buff;
+          char tempBuff[256];
+          ssize_t bytesRead;
+
+          while ((bytesRead = read(fd, tempBuff, sizeof(tempBuff))) > 0) buff.insert(buff.end(), tempBuff, tempBuff + bytesRead);
+          printf("Received: %d\n", buff.size());
+
+          Mat img(cv::Size(810, 1080), CV_8UC3, buff.data());
+          cv::imwrite("received.jpg", img);
+        } else if (waiter.revents & POLLERR) {
+          puts("Got a POLLERR");
+          return EXIT_FAILURE;
+        } else if (waiter.revents & POLLHUP) {
+          stop = true; // Writer closed its end
+          break;
+        }
+        break;
+
+      default:
+        perror("poll error");
+        return EXIT_FAILURE;
+      }
+
+      if (stop) break;
+    }
+
+    if (close(fd) < 0) {
+      perror("close");
+      return EXIT_FAILURE;
+    }
+  }
+
+  return EXIT_SUCCESS;
+}