diff --git a/src/memfs.c b/src/memfs.c
new file mode 100644
index 000000000..21ea1ad49
--- /dev/null
+++ b/src/memfs.c
@@ -0,0 +1,201 @@
+/*
+ * (C) Copyright 2005- ECMWF.
+ *
+ * This software is licensed under the terms of the Apache Licence Version 2.0
+ * which can be obtained at http://www.apache.org/licenses/LICENSE-2.0.
+ *
+ * In applying this licence, ECMWF does not waive the privileges and immunities granted to it by
+ * virtue of its status as an intergovernmental organisation nor does it submit to any jurisdiction.
+ */
+
+
+#include "eccodes_config.h"
+#ifdef ECCODES_HAVE_FMEMOPEN
+#define _GNU_SOURCE
+#endif
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <errno.h>
+#include <string.h>
+#include "eccodes_windef.h"
+
+struct entry {
+    const char* path;
+    const unsigned char* content;
+    size_t length;
+};
+
+/* The code will be added below: */
+/* Start generated code */
+/* <MARKER> */
+/* End generated code */
+
+#if !defined(ECCODES_HAVE_FMEMOPEN)
+
+#if defined(ECCODES_HAVE_FUNOPEN)
+typedef struct mem_file {
+    const char* buffer;
+    size_t size;
+    size_t pos;
+} mem_file;
+
+static int read_mem(void *data, char * buf, int len) {
+    mem_file* f = (mem_file*)data;
+    int n = len;
+
+    if(f->pos + n > f->size) {
+        n = f->size - f->pos;
+    }
+
+    memcpy(buf, f->buffer + f->pos, n);
+
+    f->pos += n;
+    return n;
+}
+
+static int write_mem(void* data, const char* buf, int len) {
+    mem_file* f = (mem_file*)data;
+    return -1;
+}
+
+static fpos_t seek_mem(void *data, fpos_t pos, int whence) {
+    mem_file* f = (mem_file*)data;
+    long newpos = 0;
+
+    switch (whence) {
+    case SEEK_SET:
+        newpos = (long)pos;
+        break;
+
+    case SEEK_CUR:
+        newpos = (long)f->pos + (long)pos;
+        break;
+
+    case SEEK_END:
+        newpos = (long)f->size -  (long)pos;
+        break;
+
+    default:
+        return -1;
+        break;
+  }
+
+  if(newpos < 0) { newpos = 0; }
+  if(newpos > f->size) { newpos = f->size; }
+
+  f->pos = newpos;
+  return newpos;
+}
+
+static int close_mem(void *data) {
+    mem_file* f = (mem_file*)data;
+    free(f);
+    return 0;
+}
+
+static FILE* fmemopen(const char* buffer, size_t size, const char* mode){
+    mem_file* f = (mem_file*)calloc(sizeof(mem_file), 1);
+    if(!f) return NULL;
+
+    f->buffer = buffer;
+    f->size = size;
+
+    return funopen(f, &read_mem, &write_mem, &seek_mem, &close_mem);
+}
+
+#else /* defined(ECCODES_HAVE_FUNOPEN) */
+
+#if defined(ECCODES_ON_WINDOWS)
+
+#include <io.h>
+#include <fcntl.h>
+#include <windows.h>
+
+static FILE *fmemopen(void* buffer, size_t size, const char* mode) {
+    char path[MAX_PATH - 13];
+    if (!GetTempPath(sizeof(path), path))
+        return NULL;
+
+    char filename[MAX_PATH + 1];
+    if (!GetTempFileName(path, "eccodes", 0, filename))
+        return NULL;
+
+    HANDLE h = CreateFile(filename,
+                          GENERIC_READ | GENERIC_WRITE,
+                          0,
+                          NULL,
+                          OPEN_ALWAYS,
+                          FILE_ATTRIBUTE_TEMPORARY | FILE_FLAG_DELETE_ON_CLOSE,
+                          NULL);
+
+    if (h == INVALID_HANDLE_VALUE)
+        return NULL;
+
+    int fd = _open_osfhandle((intptr_t)h, _O_RDWR);
+    if (fd < 0) {
+        CloseHandle(h);
+        return NULL;
+    }
+
+    FILE* f = _fdopen(fd, "w+");
+    if (!f) {
+        _close(fd);
+        return NULL;
+    }
+
+    fwrite(buffer, size, 1, f);
+    rewind(f);
+    return f;
+}
+
+#else /* defined(ECCODES_ON_WINDOWS) */
+#include <stdio.h>
+/* On old unix systems */
+
+static FILE *fmemopen(void* buffer, size_t size, const char* mode) {
+
+    FILE* f = tmpfile();
+    if (!f) {
+        return NULL;
+    }
+
+    fwrite(buffer, size, 1, f);
+    rewind(f);
+    return f;
+}
+
+#endif /* defined(ECCODES_ON_WINDOWS) */
+
+#endif /* defined(ECCODES_HAVE_FUNOPEN) */
+#endif /* !defined(ECCODES_HAVE_FMEMOPEN) */
+
+static size_t entries_count = sizeof(entries)/sizeof(entries[0]);
+
+static const unsigned char* find(const char* path, size_t* length) {
+    size_t i;
+
+    for(i = 0; i < entries_count; i++) {
+        if(strcmp(path, entries[i].path) == 0) {
+            /*printf("Found in MEMFS %s\\n", path);*/
+            *length = entries[i].length;
+            return entries[i].content;
+        }
+    }
+
+    return NULL;
+}
+
+int codes_memfs_exists(const char* path) {
+    size_t dummy;
+    return find(path, &dummy) != NULL;
+}
+
+FILE* codes_memfs_open(const char* path) {
+    size_t size;
+    const unsigned char* mem = find(path, &size);
+    if(!mem) {
+        return NULL;
+    }
+    return fmemopen((void*)mem, size, "r");
+}