study

Author: wenjun1055

14.12.c

@@ -0,0 +1,57 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <fcntl.h>
+#include <sys/mman.h>
+
+#define FILE_MODE (S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH)
+
+int main(int argc, char *argv[])
+{
+    int             fdin, fdout;
+    void            *src, *dst;
+    struct stat     statbuf;
+
+    if (3 != argc) {
+        printf("usage: %s <fromfile> <tofile>\n", argv[0]);
+        exit(-1);
+    }
+
+    if ((fdin = open(argv[1], O_RDONLY)) < 0) {
+        printf("can't open %s for reading\n", argv[1]);
+        exit(-1);
+    }
+
+    if ((fdout = open(argv[2], O_RDWR | O_CREAT | O_TRUNC, FILE_MODE)) < 0) {
+        printf("can't create %s for writing\n", argv[2]);
+        exit(-1);
+    }
+
+    if (fstat(fdin, &statbuf) < 0) {
+        printf("fstat error\n");
+        exit(-1);
+    }
+
+    if (lseek(fdout, statbuf.st_size - 1, SEEK_SET) == -1) {
+        printf("lseek error\n");
+        exit(-1);
+    }
+
+    if (write(fdout, "", 1) != 1) {
+        printf("lseek error\n");
+        exit(-1);
+    }
+
+    if ((src = mmap(0, statbuf.st_size, PORT_READ, MAP_SHARED, fdin, 0)) == MAP_FAILED) {
+        printf("mmap error for input\n");
+        exit(-1);
+    }
+    
+    if ((dst = mmap(0, statbuf.st_size, PORT_READ | PORT_WRITE, MAP_SHARED, fdout, 0)) == MAP_FAILED) {
+        printf("mmap error for output\n");
+        exit(-1);
+    }
+
+    memcpy(dst, src, statbuf.st_size);
+
+    return 0;
+}