init commit

3sem/cnts/contest4/03-test.c

@@ -0,0 +1,93 @@
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <limits.h>
+#include <errno.h>
+
+ssize_t
+my_write(int fd, void *buf, size_t count)
+{
+    size_t count_1 = 0;
+    ssize_t count_2;
+    while (count_1 != count) {
+        count_2 = write(fd, buf, count - count_1);
+        if (count_2 == -1) {
+            return -1;
+        } else if (count_2 == 0) {
+            return (ssize_t) count_1;
+        } else {
+            count_1 += (size_t) count_2;
+        }
+    }
+    return (ssize_t) count_1;
+}
+
+ssize_t
+my_read(int fd, void *buf, size_t count)
+{
+    size_t count_1 = 0;
+    ssize_t count_2;
+    while (count_1 != count) {
+        count_2 = read(fd, buf, count - count_1);
+        if (count_2 == -1) {
+            return -1;
+        } else if (count_2 == 0) {
+            return (ssize_t) count_1;
+        } else {
+            count_1 += (size_t) count_2;
+        }
+    }
+    return (ssize_t) count_1;
+}
+
+int
+main(int argc, char **argv)
+{
+    if (argc < 2) {
+        return 1;
+    }
+
+    int fd;
+    if ((fd = open(argv[1], O_RDWR)) == -1) {
+        return 1;
+    }
+
+    long long num, min, shift = 0;
+
+    if (my_read(fd, &min, sizeof(min)) < sizeof(min)) {
+        if (errno) {
+            close(fd);
+            return 1;
+        }
+        close(fd);
+        return 0;
+    }
+
+    for (int i = (int) sizeof(num); my_read(fd, &num, sizeof(min)) == sizeof(min); i += (int) sizeof(num)) {
+        if (num < min) {
+            min = num;
+            shift = i;
+        }
+    }
+
+    lseek(fd, shift, 0);
+    if (errno) {
+        close(fd);
+        return 1;
+    }
+
+    if (min != LLONG_MIN) {
+        min = -min;
+    }
+
+    if (my_write(fd, &min, sizeof(min)) != sizeof(min)) {
+        close(fd);
+        return 1;
+    }
+
+    close(fd);
+    if (errno) {
+        return 1;
+    }
+}