Refactor OEMCrypto Engine

Merge from widevine repo of http://go/wvgerrit/23280

This CL moves some of the oemcrypto mock classes into their own
files.  There are no real code changes.

Change-Id: I4e4a6a01d8e75051bc0eb2a5d58361c438c7f41b

libwvdrmengine/oemcrypto/mock/src/oemcrypto_nonce_table.cpp

@@ -0,0 +1,67 @@
+// Copyright 2013 Google Inc. All Rights Reserved.
+//
+//  Mock implementation of OEMCrypto APIs
+//
+#include "oemcrypto_nonce_table.h"
+
+namespace wvoec_mock {
+
+void NonceTable::AddNonce(uint32_t nonce) {
+  int new_slot = -1;
+  int oldest_slot = -1;
+
+  // Flush any nonces that have been checked but not flushed.
+  // After flush, nonces will be either valid or invalid.
+  Flush();
+
+  for (int i = 0; i < kTableSize; ++i) {
+    // Increase age of all valid nonces.
+    if (kNTStateValid == state_[i]) {
+      ++age_[i];
+      if (-1 == oldest_slot) {
+        oldest_slot = i;
+      } else {
+        if (age_[i] > age_[oldest_slot]) {
+          oldest_slot = i;
+        }
+      }
+    } else {
+      if (-1 == new_slot) {
+        age_[i] = 0;
+        nonces_[i] = nonce;
+        state_[i] = kNTStateValid;
+        new_slot = i;
+      }
+    }
+  }
+  if (-1 == new_slot) {
+    // reuse oldest
+    // assert (oldest_slot != -1)
+    int i = oldest_slot;
+    age_[i] = 0;
+    nonces_[i] = nonce;
+    state_[i] = kNTStateValid;
+  }
+}
+
+bool NonceTable::CheckNonce(uint32_t nonce) {
+  for (int i = 0; i < kTableSize; ++i) {
+    if (kNTStateInvalid != state_[i]) {
+      if (nonce == nonces_[i]) {
+        state_[i] = kNTStateFlushPending;
+        return true;
+      }
+    }
+  }
+  return false;
+}
+
+void NonceTable::Flush() {
+  for (int i = 0; i < kTableSize; ++i) {
+    if (kNTStateFlushPending == state_[i]) {
+      state_[i] = kNTStateInvalid;
+    }
+  }
+}
+
+}  // namespace wvoec_mock