From b31bcf598b7129d97c5817dce25791748bc2534a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Franti=C5=A1ek=20Boh=C3=A1=C4=8Dek?=
 <fandabohacek@gmail.com>
Date: Mon, 14 Jun 2021 21:33:37 +0200
Subject: [PATCH] feat: add nonblocking io functions

---
 image-viewer/include/nonblocking_io.h | 14 +++++
 image-viewer/src/nonblocking_io.c     | 86 +++++++++++++++++++++++++++
 2 files changed, 100 insertions(+)
 create mode 100644 image-viewer/include/nonblocking_io.h
 create mode 100644 image-viewer/src/nonblocking_io.c

diff --git a/image-viewer/include/nonblocking_io.h b/image-viewer/include/nonblocking_io.h
new file mode 100644
index 0000000..31913a4
--- /dev/null
+++ b/image-viewer/include/nonblocking_io.h
@@ -0,0 +1,14 @@
+#ifndef _NONBLOCKING_IO_H
+#define _NONBLOCKING_IO_H
+
+#include <stdbool.h>
+#include <stdint.h>
+#include <unistd.h>
+#include <termios.h>
+
+int file_set_nonblocking(int file, struct termios *old);
+int file_set_blocking(int file, struct termios *old);
+int file_read_nonblocking(int file, size_t max_size, uint8_t *data);
+bool file_write_nonblocking(int file, size_t size, uint8_t *data, int max_delay);
+
+#endif //_NONBLOCKING_IO_H
diff --git a/image-viewer/src/nonblocking_io.c b/image-viewer/src/nonblocking_io.c
new file mode 100644
index 0000000..4cc4761
--- /dev/null
+++ b/image-viewer/src/nonblocking_io.c
@@ -0,0 +1,86 @@
+#include "nonblocking_io.h"
+#include "time_measure.h"
+#include <stdint.h>
+#include <asm-generic/errno-base.h>
+#include <asm-generic/errno.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <termios.h>
+#include <unistd.h>
+#include <errno.h>
+
+int file_set_blocking(int file, struct termios *old) {
+  int oldfl;
+  oldfl = fcntl(file, F_GETFL);
+  if (oldfl == -1) {
+    return oldfl;
+  }
+
+  if(tcsetattr(file, TCSANOW, old) == -1) {
+    return -1;
+  }
+
+  return fcntl(file, F_SETFL, oldfl & ~O_NONBLOCK);
+}
+
+int file_set_nonblocking(int file, struct termios *old)
+{
+  fcntl(file, F_SETFL, O_NONBLOCK);
+
+  struct termios attrs;
+  if (tcgetattr(file, &attrs) < 0) {
+    return -1;
+  }
+
+  if (old != NULL) {
+    tcgetattr(file, old);
+  }
+
+  cfmakeraw(&attrs);
+
+  tcsetattr(file, TCSANOW, &attrs);
+  return 1;
+}
+
+int file_read_nonblocking(int file, size_t max_size, uint8_t *data)
+{
+  int read_bytes = read(file, data, max_size);
+
+  int error = errno;
+  if (read_bytes == -1 && error == EAGAIN) {
+    read_bytes = 0; // Do not treat EAGAIN as an error.
+  } else {
+    errno = error;
+  }
+
+  return read_bytes;
+}
+
+bool file_write_nonblocking(int file, size_t size, uint8_t *data, int max_delay) {
+  int written = 0;
+  bool correct = true;
+
+  TimeMeasure measure = tmeasure_start();
+
+  while (written < size && !tmeasure_exceededmilli(&measure, max_delay)) {
+    int status = write(file, data + written, size - written);
+
+    if (status == -1) {
+      int error = errno;
+
+      if (error != EAGAIN) {
+        errno = error;
+        correct = false;
+        break;
+      }
+    } else {
+      written += status;
+    }
+  }
+
+  if (correct && written < size) {
+    errno = ETIMEDOUT;
+  }
+
+  return correct;
+}
-- 
2.49.0