Add a StatefulMemcpy which can be used to safely and iteratively copy blocks of memory.

src/platform/vboot_reference/common/utility_stub.c

 /* Copyright (c) 2010 The Chromium OS Authors. All rights reserved.
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  *
  * Stub implementations of utility functions which call their linux-specific
  * equivalents.
  */
 
 #include "utility.h"
 
 #include <stdio.h>
 #include <stdlib.h>
-#include <string.h>
 
 void* Malloc(size_t size) {
   void* p = malloc(size);
   if (!p) {
     /* Fatal Error. We must abort. */
     abort();
   }
   return p;
 }
 
 void Free(void* ptr) {
   free(ptr);
 }
 
 void* Memcpy(void* dest, const void* src, size_t n) {
   return memcpy(dest, src, n);
 }
 
+void* Memset(void* dest, const uint8_t c, size_t n) {
+  while (n--) {
+    *((uint8_t*)dest) = c;
+  }
+  return dest;
+}
+
 int SafeMemcmp(const void* s1, const void* s2, size_t n) {
   int match = 1;
   const unsigned char* us1 = s1;
   const unsigned char* us2 = s2;
   while (n--) {
     if (*us1++ != *us2++)
       match = 0;
     else
       match = 1;
   }
 
   return match;
 }
+
+void* StatefulMemcpy(MemcpyState* state, void* dst, int len) {
+  void* saved_ptr;
+  if (len > state->remaining_len) {
+    state->remaining_len = -1;
+    return NULL;
+  }
+  saved_ptr = state->remaining_buf;
+  Memcpy(dst, saved_ptr, len);
+  state->remaining_buf += len;
+  state->remaining_len -= len;
+  return dst;
+}