better mmap example

[mirrors/Programs.git] / c / mmap / mmap.c

diff --git a/c/mmap/mmap.c b/c/mmap/mmap.c
index b2b19209693adcb955bb53bebd1d1ce3135be2c6..69d566699550aa2df3c71b147e987316dc95262e 100644 (file)
--- a/c/mmap/mmap.c
+++ b/c/mmap/mmap.c
@@ -1,28 +1,26 @@
+//#define _GNU_SOURCE
+
 #include <stdio.h>
-#include <fcntl.h>
-#include <sys/mman.h>
-#include <sys/stat.h>
 #include <sys/types.h>
+#include <sys/stat.h>
+#include <sys/mman.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <string.h>
 
-unsigned char *fmmap(FILE *fd) {
-       struct stat sb;
-
-       if(!fd) perror("");
-       fd = fileno(fd);
-       fstat((int)fd, &sb);
-       return mmap(0, sb.st_size, PROT_READ, MAP_PRIVATE, (int)fd, 0);
-}
+#define MEM_PATH "hello.bin"
+#define MEM_SIZE 1048576
 
 int main() {
-       FILE *fd;
-       unsigned char *mm;
-
-       fd = fopen("mmap.c", "r");
-       mm = fmmap(fd);
+       int fd;
+       fd = open(MEM_PATH, O_RDWR | O_SYNC | O_CREAT | O_CLOEXEC, S_IRUSR | S_IWUSR);
+       ftruncate(fd, MEM_SIZE);
 
-       perror("Status");
-       puts(mm);
+       void *mem;
+       mem = mmap(NULL, MEM_SIZE, PROT_READ | PROT_WRITE, MAP_SHARED , fd, 0);
+       close(fd);
 
-       //munmap(mm, 10);
-       fclose(fd);
+       char hello[] = "Hello!";
+       memcpy(mem, hello, sizeof(hello));
+       msync(mem, sizeof(hello), MS_SYNC);
 }