init commit

3sem/exam/raid4.c

@@ -0,0 +1,33 @@
+#include <unistd.h>
+#include <fcntl.h>
+
+enum
+{
+    BlockSize = 16,
+}
+
+int fds[5];
+void
+Write_Raid4(int num, char *buf)
+{
+    unsigned char tmp1[BlockSize];
+    unsigned char tmp2[BlockSize];
+    int num_disk = num % 4;
+
+    lseek(fd[num_disk], num * BlockSize);
+    lseek(fd[4], num * BlockSize);
+    read(fd[num_disk], tmp1, BlockSize);
+    read(fd[4], tmp2, BlockSize);
+
+    for (int i = 0; i < BlockSize; ++i) {
+        tmp2[i] ^= tmp1[i];
+        tmp2[i] ^= buf[i];
+    }
+
+    lseek(fd[num_disk], num * BlockSize);
+    lseek(fd[4], num * BlockSize);
+    write(fd[num_disk], buf, BlockSize);
+    write(fd[4], tmp2, BlockSize);
+
+    return;
+}