[libc] Add mmap API

components/libc/mmap/posix_mmap.c

@@ -0,0 +1,81 @@
+/*
+ * File      : posix_mmap.c
+ * This file is part of RT-Thread RTOS
+ * COPYRIGHT (C) 2017, RT-Thread Development Team
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License along
+ *  with this program; if not, write to the Free Software Foundation, Inc.,
+ *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Change Logs:
+ * Date           Author       Notes
+ * 2017/11/30     Bernard      The first version.
+ */
+
+#include <stdint.h>
+#include <stdio.h>
+
+#include <rtthread.h>
+#include <dfs_posix.h>
+
+#include <sys/mman.h>
+
+void *mmap(void *addr, size_t length, int prot, int flags,
+    int fd, off_t offset)
+{
+    uint8_t *mem;
+
+    if (addr)
+    {
+        mem = addr;
+    }
+    else mem = (uint8_t *)malloc(length);
+
+    if (mem)
+    {
+        off_t cur;
+        size_t read_bytes;
+
+        cur = lseek(fd, 0, SEEK_SET);
+
+        lseek(fd, offset, SEEK_SET);
+        read_bytes = read(fd, addr, length);
+        if (read_bytes != length)
+        {
+            if (addr == RT_NULL)
+            {
+                /* read failed */
+                free(mem);
+                mem = RT_NULL;
+            }
+        }
+        lseek(fd, cur, SEEK_SET);
+
+        return mem;
+    }
+
+    errno = ENOMEM;
+
+    return MAP_FAILED;
+}
+
+int munmap(void *addr, size_t length)
+{
+    if (addr)
+    {
+        free(addr);
+        return 0;
+    }
+
+    return -1;
+}