add MemoryReader
When dumping log messages, we want to deconstruct an
arbitrary memory region into semantically meaningful
parts. E.g. protocol::Command header, protocol::AsciiMessage
header, message tag, message data.
MemoryReader aids in this deconstruction. A MemoryReader
refers to an un-owned memory region, and provides convenient
ways to:
a) read a trivially-copyable object out the memory region, and
b) read |n| bytes out of the memory region.
In both cases, MemoryReader verifies that the requested read
operation does not exceed the number of available bytes.
Bug: 32256071
Test: ./runtests.sh (on angler)
Change-Id: I8ca77aceff7204756fe225149178f34dd584c757
diff --git a/memory_reader.cpp b/memory_reader.cpp
new file mode 100644
index 0000000..0883c75
--- /dev/null
+++ b/memory_reader.cpp
@@ -0,0 +1,34 @@
+/*
+ * Copyright (C) 2016 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "wifilogd/memory_reader.h"
+
+namespace android {
+namespace wifilogd {
+
+const uint8_t* MemoryReader::GetBytesOrDie(size_t n_bytes) {
+ CHECK(head_);
+ CHECK(n_bytes <= n_bytes_avail_);
+
+ const uint8_t* old_head = head_;
+ head_ += n_bytes;
+ n_bytes_avail_ -= n_bytes;
+
+ return old_head;
+}
+
+} // namespace wifilogd
+} // namespace android