init commit

3sem/cnts/contest4/04-test.c

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+#include <errno.h>
+#include <fcntl.h>
+#include <limits.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+typedef struct Node
+{
+    int32_t key;
+    int32_t left_idx;
+    int32_t right_idx;
+} Node;
+
+int
+convert_num_to_sys(char num[])
+{
+    unsigned res = 0;
+    for (int i = 0; i < sizeof(res); ++i) {
+        unsigned cur = (unsigned char) num[sizeof(res) - i - 1];
+        res ^= (cur << (CHAR_BIT * i));
+    }
+    return (int) res;
+}
+
+int
+read_int(int fd)
+{
+    int res = 0;
+    char buf[sizeof(res)];
+    int pos = 0;
+    while (pos != sizeof(res)) {
+        ssize_t off = read(fd, buf + pos, sizeof(res) - pos);
+        if (off == -1) {
+            printf("Error, can't read from file\n");
+            exit(1);
+        }
+        pos += off;
+    }
+    res = convert_num_to_sys(buf);
+    return res;
+}
+
+Node
+read_node(int fd)
+{
+    Node new_node;
+    new_node.key = read_int(fd);
+    new_node.right_idx = read_int(fd);
+    new_node.left_idx = read_int(fd);
+    return new_node;
+}
+
+void
+dfs(Node head, int fd)
+{
+    if (head.left_idx != 0) {
+        if (lseek(fd, head.left_idx * sizeof(Node), SEEK_SET) == -1) {
+            printf("Error? can't seek throw file\n");
+            exit(1);
+        }
+        Node left_node = read_node(fd);
+        dfs(left_node, fd);
+    }
+    printf("%d\n", head.key);
+    if (head.right_idx != 0) {
+        if (lseek(fd, head.right_idx * sizeof(Node), SEEK_SET) == -1) {
+            printf("Error? can't seek throw file\n");
+            exit(1);
+        }
+        Node right_node = read_node(fd);
+        dfs(right_node, fd);
+    }
+}
+
+int
+main(int argc, char *argv[])
+{
+    if (argc < 2) {
+        printf("Error: Not enough argumens\n");
+        exit(1);
+    }
+    int fd = open(argv[1], O_RDONLY, 0600);
+    if (fd < 0) {
+        printf("Error: Can't open file\n");
+        exit(1);
+    }
+    struct stat st;
+    if (stat(argv[1], &st) == -1) {
+        printf("Error, can't get info about file\n");
+        exit(1);
+    }
+    if (st.st_size == 0) {
+        return 0;
+    }
+    Node head = read_node(fd);
+    dfs(head, fd);
+    close(fd);
+}