init commit

3sem/cnts/contest4/01.c

@@ -0,0 +1,59 @@
+#include <stdio.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <limits.h>
+#include <errno.h>
+#include <stdlib.h>
+
+enum
+{
+    PEN_CHAR_BIT = 12
+};
+
+int
+safe_write(int fd, void *buf, size_t count)
+{
+    errno = 0;
+    size_t bytes_written = 0;
+    while (bytes_written < count) {
+        ssize_t res = write(fd, buf + bytes_written, count - bytes_written);
+
+        if (res < 0) {
+            if (errno == EINTR) {
+                errno = 0;
+                continue;
+            }
+
+            fprintf(stderr, "Error writing to file descriptor %d\n", fd);
+            close(fd);
+            exit(1); // TODO: по-хорошему заменить на внешний обработчик ошибок
+        }
+
+        bytes_written += res;
+    }
+
+    return bytes_written;
+}
+
+int
+main(int argc, char **argv)
+{
+    int fdout = open(argv[1], O_WRONLY | O_CREAT | O_TRUNC, 0600);
+    if (fdout == -1) {
+        return 1;
+    }
+
+    unsigned char res[4];
+    unsigned tmp;
+    while (scanf("%u", &tmp) == 1) {
+        res[0] = (tmp & (0x0F << (CHAR_BIT + PEN_CHAR_BIT))) >> (CHAR_BIT + PEN_CHAR_BIT);
+        res[1] = (tmp & (0xFF << PEN_CHAR_BIT)) >> PEN_CHAR_BIT;
+        res[2] = (tmp & (0x0F << CHAR_BIT)) >> CHAR_BIT;
+        res[3] = tmp & 0xFF;
+        safe_write(fdout, res, sizeof(res));
+    }
+
+    close(fdout);
+
+    return 0;
+}