--- a/src/dmres.c	Mon Mar 02 20:00:08 2015 +0200
+++ b/src/dmres.c	Mon Mar 02 20:10:36 2015 +0200
@@ -247,7 +247,7 @@
 }
 
 
-static size_t dm_stdio_fwrite(void *ptr, size_t size, size_t nmemb, DMResource * f)
+static size_t dm_stdio_fwrite(const void *ptr, size_t size, size_t nmemb, DMResource * f)
 {
     size_t ret = fwrite(ptr, size, nmemb, f->fh);
     f->error = dmGetErrno();
@@ -633,7 +633,7 @@
 }
 
 
-static size_t dm_mem_fwrite(void *buf, size_t size, size_t nmemb, DMResource * f)
+static size_t dm_mem_fwrite(const void *buf, size_t size, size_t nmemb, DMResource * f)
 {
     size_t length = (size * nmemb);
 
@@ -928,7 +928,7 @@
     return f->fops->fread(ptr, size, nmemb, f);
 }
 
-size_t dmfwrite(void *ptr, size_t size, size_t nmemb, DMResource * f)
+size_t dmfwrite(const void *ptr, size_t size, size_t nmemb, DMResource * f)
 {
     f->atime = time(NULL);
     return f->fops->fwrite(ptr, size, nmemb, f);

--- a/src/dmres.h	Mon Mar 02 20:00:08 2015 +0200
+++ b/src/dmres.h	Mon Mar 02 20:10:36 2015 +0200
@@ -122,7 +122,7 @@
     int     (*fgetc)(DMResource *);
     int     (*fputc)(int, DMResource *);
     size_t  (*fread)(void *, const size_t, const size_t, DMResource *);
-    size_t  (*fwrite)(void *, const size_t, const size_t, DMResource *);
+    size_t  (*fwrite)(const void *, const size_t, const size_t, DMResource *);
 
     int     (*fopen)(DMResource *);
     void    (*fclose)(DMResource *);
@@ -168,7 +168,7 @@
 int          dmfgetc(DMResource *);
 int          dmfputc(int, DMResource *);
 size_t       dmfread(void *, const size_t, const size_t, DMResource *);
-size_t       dmfwrite(void *, const size_t, const size_t, DMResource *);
+size_t       dmfwrite(const void *, const size_t, const size_t, DMResource *);
 char *       dmfgets(char *s, int size, DMResource * f);