StatefulMem* functions should be library functions.

We want the BIOS to implement the stub functions, but that shouldn't include
our StatefulMem* functions.

Also, we ensure that we don't accidently use native linux functions instead
of the stub functions.

Review URL: http://codereview.chromium.org/2255006

vboot_firmware/lib/include/stateful_util.h

@@ -0,0 +1,55 @@
+/* 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.
+ */
+
+/* Helper functions/wrappers for memory allocations, manipulation and
+ * comparison.
+ */
+
+#ifndef VBOOT_FIRMWARE_LIB_UTILITY_H_
+#define VBOOT_FIRMWARE_LIB_UTILITY_H_
+
+#include <stdint.h>
+#include <string.h>
+
+#include "utility.h"
+
+/* Track remaining data to be read in a buffer. */
+typedef struct MemcpyState {
+  void* remaining_buf;
+  uint64_t remaining_len;  /* Remaining length of the buffer. */
+  uint8_t overrun;  /* Flag set to 1 when an overrun occurs. */
+} MemcpyState;
+
+/* Copy [len] bytes into [dst] only if there's enough data to read according
+ * to [state].
+ * On success, return [dst] and update [state].
+ * On failure, return NULL, set remaining len in state to -1.
+ *
+ * Useful for iterating through a binary blob to populate a struct. After the
+ * first failure (buffer overrun), successive calls will always fail.
+ */
+void* StatefulMemcpy(MemcpyState* state, void* dst, uint64_t len);
+
+/* Like StatefulMemcpy() but copies in the opposite direction, populating
+ * data from [src] into the buffer encapsulated in state [state].
+ * On success, return [src] and update [state].
+ * On failure, return NULL, set remaining_len in state to -1.
+ *
+ * Useful for iterating through a structure to populate a binary blob. After the
+ * first failure (buffer overrun), successive calls will always fail.
+ */
+const void* StatefulMemcpy_r(MemcpyState* state, const void* src, uint64_t len);
+
+/* Like StatefulMemcpy_r() but fills a portion of the encapsulated buffer with
+ * a constant value.
+ * On success, return a meaningless but non-NULL pointer and updates [state].
+ * On failure, return NULL, set remaining_len in state to -1.
+ *
+ * After the first failure (buffer overrun), successive calls will always fail.
+ */
+const void* StatefulMemset_r(MemcpyState* state, const uint8_t val,
+                             uint64_t len);
+
+#endif  /* VBOOT_FIRMWARE_LIB_UTILITY_H_ */